1) Cells that respond to signals are usually called
- A) responders.
- B) receivers.
- C) targets.
- D) contacts.
- E) junctions.
Answer: C
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Knowledge
2) Which is NOT a basic method of cell-to-cell communication?
- A) cytoplasmic transfer of signals
- B) contact-dependent signals
- C) diffused chemical signals
- D) nerve and blood-transported signals
- E) mechanical signals
Answer: E
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Knowledge
3) The most significant difference between a paracrine and an autocrine is
- A) the cell that releases it.
- B) the cell that responds to it.
- C) the method of transport.
- D) the route of transport.
- E) There are no differences—they are the same.
Answer: B
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Knowledge
4) Neurotransmitters and neurohormones both
- A) are released by neurons.
- B) affect only cells with a specific receptor.
- C) travel in the blood to their target cell.
- D) are released by neurons and affect only cells with specific receptors.
- E) are produced by all cells.
Answer: D
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Knowledge
5) Why do some normal cells fail to respond to a chemical signal?
- A) Chemical signals are only delivered to specific cells.
- B) Some cells lack the necessary receptors.
- C) Some cells are completely without receptors.
- D) Some cells are completely without ligands.
- E) Signal chemicals often break down before reaching a distant target.
Answer: B
Section: Signal Pathways
Learning Outcome: 6.1
Bloom’s Taxonomy: Comprehension
6) Receptor molecules on the surface of a cell
- A) determine that cell’s response.
- B) may allow a particular ligand to bind.
- C) bind to all ligands.
- D) determine that cell’s response and may allow a particular ligand to bind.
- E) determine that cell’s response and bind to all ligands.
Answer: D
Section: Signal Pathways
Learning Outcome: 6.2
Bloom’s Taxonomy: Knowledge
7) Receptor molecules are located
- A) only in the outer cell membrane.
- B) only in the cytosol.
- C) only in the nucleus.
- D) only on the cell surface.
- E) in all of these places.
Answer: E
Section: Signal Pathways
Learning Outcome: 6.2, 6.3
Bloom’s Taxonomy: Knowledge
8) Down-regulation may allow a target cell to
- A) only increase its number of receptors for a ligand.
- B) only decrease its number of receptors for a ligand.
- C) only increase its binding affinity for a ligand.
- D) decrease the receptors’ binding affinity and increase its number of receptors.
Answer: B
Section: Modulation of Signal Pathways
Learning Outcome: 6.9
Bloom’s Taxonomy: Knowledge
9) Inositol triphosphate
- A) is a water-insoluble messenger molecule.
- B) binds to the calcium channel of the endoplasmic recticulum.
- C) is involved in the release of calcium into the cytosol.
- D) is a second messenger that is involved in the release of calcium into the cytosol.
- E) uses all of the mechanisms.
Answer: D
Section: Signal Pathways
Learning Outcome: 6.5
Bloom’s Taxonomy: Knowledge
10) Lipophilic hormones
- A) bind to receptors on the surface of the cell.
- B) function by way of a second messenger system.
- C) cannot diffuse through the cell membrane.
- D) bind to receptors inside the cytoplasm or nucleus.
- E) function by activating cAMP.
Answer: D
Section: Signal Pathways
Learning Outcome: 6.2
Bloom’s Taxonomy: Knowledge
11) When adenylyl cyclase is activated,
- A) calcium ions are released from intracellular stores.
- B) cAMP is formed.
- C) cAMP is broken down.
- D) protein kinases are metabolized.
- E) steroids are produced.
Answer: B
Section: Signal Pathways
Learning Outcome: 6.6
Bloom’s Taxonomy: Knowledge
12) Second messenger molecules directly
- A) change the regulation of ion channels.
- B) increase intracellular calcium concentration.
- C) change enzyme activity.
- D) change regulation of gene expression.
- E) All of the answers are correct.
Answer: E
Section: Signal Pathways
Learning Outcome: 6.5
Bloom’s Taxonomy: Knowledge
13) Cyclic AMP activates
- A) a G protein.
- B) adenylyl cyclase.
- C) protein hormones.
- D) protein kinase A.
- E) hormone receptors.
Answer: D
Section: Signal Pathways
Learning Outcome: 6.5
Bloom’s Taxonomy: Knowledge
14) Diacylglycerol is produced from
- A) cyclic AMP.
- B) phospholipase C.
- C) a G protein.
- D) protein kinase A.
- E) phosphatidylinositol bisphosphate.
Answer: E
Section: Signal Pathways
Learning Outcome: 6.5
Bloom’s Taxonomy: Knowledge
15) Usually, cytokine binding activates
- A) JAK kinase.
- B) tyrosine kinase.
- C) intrinsic transducers.
- D) calmodulin kinase.
- E) citrulline kinase.
Answer: A
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Knowledge
16) What by-product results during the production of nitric oxide?
- A) arginine
- B) citrulline
- C) nitric oxide synthase
- D) carbon monoxide
- E) carbon dioxide
Answer: B
Section: Novel Signal Molecules
Learning Outcome: 6.7
Bloom’s Taxonomy: Knowledge
17) An integrating center
- A) is the disturbance or change that sets the pathway in motion.
- B) is an electrical and/or chemical signal that travels to the effector.
- C) evaluates incoming signals and compares it with the setpoint.
- D) is the minimum stimulus that must be achieved to set the reflect response in motion.
Answer: C
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.11
Bloom’s Taxonomy: Knowledge
18) Which of the following are considered differences between endocrine and neural control systems?
- A) specificity
- B) nature of the signal
- C) speed
- D) duration of action
- E) All of the answers are correct.
Answer: E
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.12
Bloom’s Taxonomy: Knowledge
Match the term with its description:
- threshold
- effector
- integrating center
- setpoint
- sensory receptor
19) the desired target value for a parameter
Answer: D
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.11
Bloom’s Taxonomy: Knowledge
20) receives information about the regulated variable and initiates a response
Answer: C
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.11
Bloom’s Taxonomy: Knowledge
21) the minimum stimulus to trigger a response
Answer: A
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.11
Bloom’s Taxonomy: Knowledge
22) the organ or gland that performs the change
Answer: B
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.11
Bloom’s Taxonomy: Knowledge
23) continuously monitors its environment for a specific variable
Answer: E
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.11
Bloom’s Taxonomy: Knowledge
24) Peripheral cells sensitive to the presence of hormones are called ________.
Answer: targets
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.11
Bloom’s Taxonomy: Knowledge
25) A few gases are known to act as signal molecules, including ________, ________, and ________.
Answer: nitric oxide, carbon monoxide, hydrogen sulfide
Section: Novel Signal Molecules
Learning Outcome: 6.7
Bloom’s Taxonomy: Knowledge
26) Before nitric oxide was identified, its action was observed in ________ and it was given the name ________.
Answer: endothelial cells (blood vessel lining), endothelial-derived relaxing factor (EDRF)
Section: Novel Signal Molecules
Learning Outcome: 6.7
Bloom’s Taxonomy: Knowledge
27) ________ can be caused by alterations in receptors or by problems with G protein or second messenger pathways.
Answer: Diseases
Section: Signal Pathways
Learning Outcome: 6.5
Bloom’s Taxonomy: Knowledge
28) Lipid signal molecules that act in a paracrine fashion and combine with G-protein coupled receptors include ________ and ________.
Answer: eicosanoids, sphingolipids
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Knowledge
29) ________ is a process by which an extracellular signal molecule, called the ________, activates a membrane receptor that in turn alters intracellular molecules, called the ________, to create a response.
Answer: Signal transduction, first messenger, second messenger
Section: Signal Pathways
Learning Outcome: 6.5
Bloom’s Taxonomy: Comprehension
30) A gap junction forms when opposing membrane-spanning proteins called ________ on two adjacent cells unite, creating a protein channel that is capable of opening and closing.
Answer: connexins
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Knowledge
31) A chemical that is secreted by a cell to act on cells in its immediate vicinity is called a(n) ________.
Answer: paracrine
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Knowledge
32) If the signal molecule acts on the cell that secreted it, the chemical is called a(n) ________.
Answer: autocrine
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Knowledge
33) All molecules secreted by nerve cells (neuromodulators, neurotransmitters, and neurohormones) are known as ________.
Answer: neurocrines
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Knowledge
34) ________ are molecules that bind to the receptor in such a way that they block the normal ligand from binding and turning the receptor on. As a result, the signal pathway remains inactive.
Answer: Antagonists (or Competitive inhibitors)
Section: Novel Signal Molecules
Learning Outcome: 6.6
Bloom’s Taxonomy: Knowledge
35) If the concentration of an endocrine ligand decreases, the target cell may insert more receptors into the cell membrane in an attempt to keep its response at a normal level, in a process known as ________.
Answer: up-regulation
Section: Novel Signal Molecules
Learning Outcome: 6.6
Bloom’s Taxonomy: Comprehension
36) The nervous system has a role in preserving the “fitness” of the ________.
Answer: Internal Environment
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.11
Bloom’s Taxonomy: Knowledge
37) The ________ link membrane receptors to either ion channels or to membrane enzymes located on the cytoplasmic face of the membrane.
Answer: G proteins
Section: Signal Pathways
Learning Outcome: 6.5
Bloom’s Taxonomy: Knowledge
38) Many second messenger systems activate ________, enzymes that transfer a phosphate group from ATP to a protein. The phosphorylation of proteins sets off a series of intracellular events that lead to the ultimate cellular response.
Answer: protein kinases
Section: Signal Pathways
Learning Outcome: 6.5
Bloom’s Taxonomy: Knowledge
39) Explain how epinephrine can cause intestinal blood vessels to constrict and cause skeletal muscle blood vessels to dilate.
Answer: Epinephrine can bind to different isoforms of the adrenergic receptor. Epinephrine binds to the alpha receptor on the intestinal blood vessels and beta receptors on the skeletal muscle blood vessels (see Fig. 6.14).
Section: Modulation of Signal Pathways
Learning Outcome: 6.8
Bloom’s Taxonomy: Comprehension
40) To maintain ________, the body uses a combination of simple diffusion across small distances; wide spread distribution of molecules through the circulatory system and rapid, specific delivery of messages by the nervous system.
Answer: homeostasis
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Knowledge
41) Most long-distance communication between cells takes place through the ________ and ________ systems with their combination of chemical and electrical signals.
Answer: nervous, endocrine
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Comprehension
42) An intracellular signal molecule that translates a signal from a neurotransmitter or hormone into an intracellular response is called a ________.
Answer: second messenger
Section: Signal Pathways
Learning Outcome: 6.3
Bloom’s Taxonomy: Comprehension
43) The secretion of the hormone insulin in response to changes in blood glucose level is an example of a(n) ________ reflex.
Answer: simple endocrine
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.11
Bloom’s Taxonomy: Knowledge
44) Homeostatic regulation usually involves a(n) ________ that is sensitive to a particular stimulus (variable) and a(n) ________ whose activity has an effect on the same stimulus.
Answer: receptor, effector
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.11
Bloom’s Taxonomy: Knowledge
45) When epinephrine combines with alpha adrenergic receptors on smooth muscle in intestinal blood vessels, the blood vessels ________; however, when epinephrine binds to beta-2 adrenergic receptors on certain skeletal muscle blood vessels, the vessels ________.
Answer: constrict, dilate
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.10
Bloom’s Taxonomy: Knowledge
46) Compare and contrast the four basic methods of cell-to-cell communication.
Answer: The cells can:
- transfer signal molecules to adjacent cells through gap junctions
- use contact-dependent signals, which rely on interactions between cell surface molecules on different cells
- use locally acting chemicals, called paracrines, autocrines, or neuromodulators
- use long-distance means, which rely on combinations of electrical and chemical signals
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Comprehension
47) Explain the two forms of down-regulation.
Answer: Either the number of receptors decreases or desensitization in which the binding affinity of the receptors for the ligand decreases. In both cases the result is a lessened response of the target cell even though the concentration of the signal molecule remains high.
Section: Signal Pathways
Learning Outcome: 6.9
Bloom’s Taxonomy: Comprehension
48) In your own words restate and explain Cannon’s four postulates for maintaining homeostasis.
Answer: This is discussed in the “Cannon’s Postulates Describe Regulated Variables and Control Systems” section of the chapter.
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.10
Bloom’s Taxonomy: Comprehension
49) What is the half-life of a signal?
Answer: the time required for a signal to lose half its activity
Section: Novel Signal Molecules
Learning Outcome: 6.6
Bloom’s Taxonomy: Knowledge
50) What is an orphan receptor?
Answer: a receptor that has no known ligand
Section: Novel Signal Molecules
Learning Outcome: 6.7
Bloom’s Taxonomy: Knowledge
51) The intracellular effector in chemical signaling is often
- A) a hormone.
- B) a membrane receptor molecule.
- C) ATP.
- D) a protein kinase.
- E) cholesterol.
Answer: D
Section: Signal Pathways
Learning Outcome: 6.5
Bloom’s Taxonomy: Comprehension
52) The most important factor determining which type of receptor a signal molecule will bind to is
- A) the lipid solubility of the ligand.
- B) the size of the ligand.
- C) the size of the receptor molecule.
- D) the location of the receptor molecule.
Answer: A
Section: Signal Pathways
Learning Outcome: 6.2, 6.3
Bloom’s Taxonomy: Comprehension
53) An ion widely important in intracellular signaling is
- A) sodium.
- B) potassium.
- C) calcium.
- D) chloride.
- E) cobalt.
Answer: C
Section: Novel Signal Molecules
Learning Outcome: 6.6
Bloom’s Taxonomy: Comprehension
54) When calcium becomes available inside a cell, it comes from
- A) extracellular fluid only.
- B) intracellular storage only.
- C) extracellular fluid and intracellular storage.
- D) It is always available as a major cytosol cation.
Answer: C
Section: Novel Signal Molecules
Learning Outcome: 6.6
Bloom’s Taxonomy: Comprehension
55) One intracellular calcium-binding protein is
- A) calmodulin.
- B) calcitonin.
- C) calcitriol.
- D) IP3.
- E) nitric oxide.
Answer: A
Section: Novel Signal Molecules
Learning Outcome: 6.6
Bloom’s Taxonomy: Comprehension
56) Signal molecule receptors exhibit
- A) specificity only.
- B) competition only.
- C) saturation only.
- D) competition and saturation only.
- E) specificity, competition, and saturation.
Answer: E
Section: Modulation of Signal Pathways
Learning Outcome: 6.8
Bloom’s Taxonomy: Comprehension
57) The binding of lipophilic messengers, such as steroid hormones, to their receptors triggers
- A) adenylyl cyclase activation.
- B) cyclic nucleotide formation.
- C) G protein inhibition.
- D) gene transcription.
- E) protein kinase activation.
Answer: D
Section: Signal Pathways
Learning Outcome: 6.2
Bloom’s Taxonomy: Comprehension
58) Both insulin and glucagon are peptide hormones that target liver cells. The response of the target cells to each of these two hormones is opposite. This information implies that
- A) the two hormones bind to different cell surface receptors.
- B) one hormone binds to a receptor on the cell membrane and the other to an intracellular receptor.
- C) each of the two hormones uses a different second messenger.
- D) both hormones interact with receptors at the cell nucleus.
- E) the two hormones bind to different receptors and use a different second messenger.
Answer: E
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.10
Bloom’s Taxonomy: Comprehension
59) Each of the following is an example of homeostasis except one. Identify the exception.
- A) Increased pressure in the aorta triggers mechanisms to lower blood pressure.
- B) A rise in blood calcium levels triggers the release of a hormone that lowers blood calcium levels.
- C) A rise in estrogen during the menstrual cycle increases the number of progesterone receptors in the uterus.
- D) Increased blood sugar stimulates the release of a hormone from the pancreas that stimulates the liver to store blood sugar.
- E) A decrease in body temperature triggers a neural response that initiates physiological changes to increase body temperature.
Answer: C
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.13
Bloom’s Taxonomy: Application
60) Homeostatic control that takes place at the tissue or cell by using paracrine or autocrine signals is called
- A) local control.
- B) reflex control.
- C) Cannon’s law.
- D) down-regulation.
Answer: A
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.10
Bloom’s Taxonomy: Comprehension
61) A physiological parameter which is regulated in an up-down fashion by signals that are always present but change in intensity is said to be under ________.
Answer: tonic control
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.10
Bloom’s Taxonomy: Comprehension
62) Insulin increases glucose transport across the cell membrane of an adipocyte, but not across the membrane of a liver cell. How can one hormone have two different effects?
Answer: The two types of cells differ either in the receptors on their cell membranes or in the signal transduction that occurs after binding of insulin.
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.10
Bloom’s Taxonomy: Application
63) Describe the four classes of membrane receptor molecules.
Answer: Ligand-gated receptors are ion channels, integrins are linked to the cytoskeleton, receptor-enzymes activate intracellular enzymes, G protein-coupled receptors involve activation of G proteins. See Figure 6.3.
Section: Signal Pathways
Learning Outcome: 6.4
Bloom’s Taxonomy: Comprehension
64) What general action is shared by about half of the medical drugs currently in use?
Answer: These drugs act on membrane receptor proteins.
Section: Signal Pathways
Learning Outcome: 6.2, 6.3
Bloom’s Taxonomy: Comprehension
65) Describe the signal molecule derivatives of arachidonic acid.
Answer: Leukotrienes are secreted by certain types of white blood cells and play a role in asthma and anaphylaxis. Prostanoids, including prostaglandins and thromboxanes, have a variety of target tissues and effects.
Section: Novel Signal Molecules
Learning Outcome: 6.7
Bloom’s Taxonomy: Comprehension
66) Describe or diagram the basic pattern of a biological signal transduction pathway.
Answer: See Figure 6.4 and the “Membrane Proteins Facilitate Signal Transduction” section in the chapter.
Section: Signal Pathways
Learning Outcome: 6.5
Bloom’s Taxonomy: Comprehension
67) What are NSAIDs, what is their function, and what are some drawbacks to their use?
Answer: Nonsteroidal anti-inflammatory drugs, such as aspirin and ibuprofen, prevent inflammation. They have side effects such as bleeding in the stomach.
Section: Novel Signal Molecules
Learning Outcome: 6.7
Bloom’s Taxonomy: Comprehension
68) Define tonic control and give a physiological example.
Answer: Tonic control regulates physiological parameters in an up-down fashion. An example is the neural regulation of blood vessel diameter (see Fig. 6.15).
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.10
Bloom’s Taxonomy: Comprehension
69) Design a flow chart or concept map to summarize the information in the text under the heading “Cell-to-Cell Communication.” This chart should make clear the four basic methods of cell-to-cell communication, and the relevance of and distinction between paracrine, autocrine, neurocrine, and cytokine chemicals.
Answer: This is discussed in the “Cell-to-Cell Communication” section in the chapter.
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Synthesis
70) Compare and contrast hormones, neurotransmitters, and neurohormones.
Answer: See Figure 6.1 and the “Long-Distance Communication May Be Electrical or Chemical” section in the chapter.
Section: Cell-to-Cell Communication
Learning Outcome: 6.1
Bloom’s Taxonomy: Synthesis
71) Briefly explain the effects of the hormone insulin on glucose transport. What is diabetes mellitus? How are types I and II different? Why do insulin injections help alleviate one type but not the other?
Answer: Insulin promotes glucose transport into most types of cells. Diabetes mellitus results when insulin regulation of blood glucose concentrations is impaired. In type I, the pancreas fails to produce insulin, whereas in type II insulin levels are normal to high, but target cells fail to respond properly. Insulin injections can successfully treat type I, but not type II, because the endogenous insulin production in type II is sufficient, but the response is abnormal.
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.13
Bloom’s Taxonomy: Synthesis
72) Compare and contrast neural and endocrine control.
Answer: See Table 6.2 in the chapter.
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.12
Bloom’s Taxonomy: Synthesis
73) Compare and contrast neural, neuroendocrine, and endocrine reflex pathways.
Answer: See Table 6.3 in the chapter.
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.12
Bloom’s Taxonomy: Synthesis
74) Nobel Prizes were awarded to the discoverers of G proteins, the G protein-coupled adenylyl cyclase-cAMP system, and nitric oxide. Summarize each of these, and explain the importance of these discoveries to our understanding of signal pathways.
Answer: G proteins are coupled to hundreds of different receptors on cells. These are receptors that bind ligands such as hormones, neurotransmitters, and molecules important in sensory systems. Activated G proteins open ion channels or alter enzyme activity. The G protein-coupled adenylyl cyclase-cAMP system was the first signal transduction pathway discovered, and therefore paved the way for our understanding of signal transduction. cAMP is the second messenger in many signaling systems. Nitric oxide functions as a neurotransmitter, neuromodulator, and paracrine important in cardiovascular regulation.
Section: Novel Signal Molecules
Learning Outcome: 6.5
Bloom’s Taxonomy: Synthesis
75) Food items are occasionally shown to offer protective effects to those who eat them. Garlic, for example, may improve heart health. The pungency of garlic is due to sulfur-containing compounds. Explain how these compounds are good candidates for garlic’s heart benefits.
Answer: When sulfur compounds are metabolized, hydrogen sulfide may be produced. This gas has recently been shown to be a signal molecule that relaxes blood vessels.
Section: Novel Signal Molecules
Learning Outcome: 6.7
Bloom’s Taxonomy: Synthesis
76) “Too much of a good thing can hurt you.” “It’s all good.” We’ve all heard phrases like this, and know that they contain some truth. For example, both life essentials water and sunshine can harm us. Not enough cholesterol in the body is worse than too much. What otherwise poisonous gas has recently been shown to be a signal molecule? What does it do in the body?
Answer: Carbon monoxide is one of the gaseous signal molecules. It activates guanylyl cyclase and cGMP in smooth muscle and neural tissue.
Section: Novel Signal Molecules
Learning Outcome: 6.7
Bloom’s Taxonomy: Synthesis
77) Receptors in cell signaling are not to be confused with receptors that activate a reflex arc. Explain the difference, using specific examples.
Answer: Receptor molecules are proteins on or in cells that bind to ligands. This binding triggers a response within a cell, to the signaling chemical. For example, this is how a hormone exerts its effect on a target cell. Receptors in a reflex arc are not protein molecules but rather are entire cells, parts of cells, or multicellular structures. These receptors cause a signal to be sent to an integrating center, which may or may not then initiate a response usually involving many cells. For example, a blood pressure receptor detects a decrease in pressure, and sends a neural signal to cardiovascular integrating centers to trigger a vascular response to increase pressure.
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.11
Bloom’s Taxonomy: Synthesis
78) You are part of a research team designing a robot for competition. Your robot needs to be able to respond to painful stimuli like stepping on broken glass. What type of human control system will you model your robot after? Explain your reasons for choosing it.
Answer: One should choose the nervous system and a simple neural reflex because of its ability to rapidly respond and remove the robot from potential harm. The response will be specific for the region in harm and the robot will get a sense of the intensity of pain via a change in the frequency of signaling.
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.12
Bloom’s Taxonomy: Synthesis
79) The fight-or-flight reaction prepares an animal to respond to a threatening situation, by either fighting or running away. One aspect of this response is changes in blood flow such that the skeletal muscles and heart receive higher blood flow (vessels dilate) while digestive organs receive less (vessels constrict). Which signal molecule(s) is/are involved in this response, and how do they produce these changes in blood vessels? Explain how this example illustrates one or more of the following concepts: multiple ligands for one receptor, multiple receptors for one ligand, agonists and antagonists.
Answer: The signal molecules are norepinephrine and epinephrine. Both of these chemicals bind to the same adrenergic receptors (multiple ligands) and have the same effect on their receptors, so they are agonists. When alpha-adrenergic receptors are activated in digestive organs, blood vessels constrict. When beta-adrenergic receptors are activated in skeletal and cardiac muscles, blood vessels dilate (multiple receptors).
Section: Modulation of Signal Pathways
Learning Outcome: 6.8
Bloom’s Taxonomy: Synthesis
80) Blood glucose levels are kept fairly steady in healthy people through the action of the hormones insulin and glucagon. Insulin decreases blood glucose by promoting glucose uptake by cells, whereas glucagon increases blood glucose by promoting release of glucose from cells. Describe these hormone actions as simple reflex pathways, identifying the stimulus, integrating center, efferent pathway, and response.
Answer: Stimulus: increased blood glucose. Integrating center: endocrine cell (in pancreas). Efferent pathway: insulin secretion. Response: increased cellular uptake of glucose. Feedback: negative. Stimulus: decreased blood glucose. Integrating center: endocrine cell (in pancreas). Efferent pathway: glucagon secretion. Response: release of glucose from cells. Feedback: negative.
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.13
Bloom’s Taxonomy: Synthesis
81) Brain cells are able to absorb glucose independent of insulin. What must be missing from brain cells compared to most other cell types? One of the risks of diabetes mellitus is diabetic coma, which results when insufficient glucose is available to the brain. Would you expect diabetic coma to be triggered when insulin is low or high? Explain. (Hint: Think about regulation of the number of glucose transporters in brain cells and how the hyperglycemia present prior to insulin treatment may affect transporters.)
Answer: Brain cells lack the insulin receptors that stimulate glucose uptake, because an insulin-independent mechanism for glucose uptake is present. Brain cells will down-regulate their glucose transporters during periods of hyperglycemia. When insulin levels increase during treatment of type I diabetes, promoting lower concentrations of glucose in the blood, this can trigger diabetic coma because the brain cells have too few glucose transporters for the new, lower levels of blood glucose.
Section: Homeostatic Reflex Pathways
Learning Outcome: 6.13
Bloom’s Taxonomy: Synthesis
82) Asthma is a respiratory disorder characterized by construction of airways and mucus production which makes it very difficult to breathe. The constriction of airways, mucus production, and altered gene expression in the cells lining the airways of asthmatics is due to increased release of neurotransmitter acetylcholine. Explain how a single molecule can have such a large and diverse effect in a single cell.
Answer: See Figures 6.5, 6.6 and 6.8; signal amplification.
Section: Signal Pathways
Learning Outcome: 6.5
Bloom’s Taxonomy: Synthesis
Human Physiology: An Integrated Approach, 7e, (Silverthorn)
Chapter 7 Introduction to the Endocrine System
1) Which of the following is NOT a method of hormone action?
- A) control of enzymatic reaction rates
- B) control of ion or molecule transport across cell membranes
- C) control of electrical signaling pathways
- D) control of gene expression and protein synthesis
- E) All are methods of hormone action.
Answer: E
Section: Hormones
Learning Outcome: 7.2
Bloom’s Taxonomy: Knowledge
2) When a catecholamine or peptide hormone binds to receptors on the surface of a cell,
- A) the cell membrane becomes less permeable.
- B) a second messenger appears in the cytoplasm.
- C) the cell becomes inactive.
- D) the hormone is transported to the nucleus where it alters the activity of DNA.
- E) None of the answers are correct.
Answer: B
Section: Hormones
Learning Outcome: 7.2
Bloom’s Taxonomy: Knowledge
3) The link between a first messenger and a second messenger in a cell that responds to peptide hormones is usually
- A) cAMP.
- B) cGMP.
- C) adenylyl cyclase.
- D) a G protein.
- E) calcium.
Answer: D
Section: The Classification of Hormones
Learning Outcome: 7.5
Bloom’s Taxonomy: Knowledge
4) When adenylyl cyclase is activated,
- A) calcium ions are released from intracellular stores.
- B) cAMP is formed.
- C) cAMP is broken down.
- D) protein kinases are metabolized.
- E) steroids are produced.
Answer: B
Section: The Classification of Hormones
Learning Outcome: 7.5
Bloom’s Taxonomy: Knowledge
5) Typically, when steroid hormones bind to their receptors,
- A) adenylyl cyclase is activated.
- B) cyclic nucleotides are formed.
- C) G proteins are inhibited.
- D) gene transcription may increase or decrease.
- E) protein kinases are activated.
Answer: D
Section: The Classification of Hormones
Learning Outcome: 7.5
Bloom’s Taxonomy: Knowledge
6) Steroid hormones are synthesized in the ________ of the cell.
- A) rough endoplasmic reticulum
- B) smooth endoplasmic reticulum
- C) Golgi apparatus
- D) mitochondria
- E) nucleus
Answer: B
Section: The Classification of Hormones
Learning Outcome: 7.5
Bloom’s Taxonomy: Knowledge
7) Each of the following statements concerning peptide hormones is true except one. Identify the exception.
- A) Peptide hormones are first synthesized as prohormones.
- B) Prohormones can be activated before their release via post-translational modification.
- C) Peptide hormones remain in circulation for relatively short periods of time.
- D) Peptide hormones in the bloodstream are always bound to carrier proteins.
- E) Peptide hormones interact with receptors on the surface of their target cells.
Answer: D
Section: The Classification of Hormones
Learning Outcome: 7.5
Bloom’s Taxonomy: Comprehension
8) Each of the following hormones is an amino acid derivative EXCEPT one. Identify the exception.
- A) epinephrine
- B) norepinephrine
- C) thyroid hormone
- D) thyroid-stimulating hormone
- E) melatonin
Answer: D
Section: The Classification of Hormones
Learning Outcome: 7.6
Bloom’s Taxonomy: Knowledge
9) The majority of hormones in the body are
- A) peptide hormones.
- B) steroid hormones.
- C) amino acid-derived hormones.
- D) neurohormones.
- E) All of the hormones are present in equal amounts in the body.
Answer: A
Section: The Classification of Hormones
Learning Outcome: 7.5
Bloom’s Taxonomy: Comprehension
10) The most complex endocrine responses involve the
- A) thyroid gland.
- B) pancreas.
- C) adrenal glands.
- D) hypothalamus.
- E) thymus.
Answer: D
Section: Control of Hormone Release
Learning Outcome: 7.7
Bloom’s Taxonomy: Comprehension
11) The posterior pituitary gland secretes
- A) FSH.
- B) TSH.
- C) ACTH.
- D) ADH (Vasopressin).
- E) MSH.
Answer: D
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Knowledge
12) The pituitary hormone that controls the release of glucocorticoids from the adrenal cortex is
- A) TSH.
- B) ACTH.
- C) FSH.
- D) LH.
- E) STH.
Answer: B
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Knowledge
13) The pituitary hormone that controls hormone synthesis and release from the thyroid gland is
- A) TSH.
- B) ACTH.
- C) FSH.
- D) LH.
- E) STH.
Answer: A
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Knowledge
14) The pituitary hormone that stimulates milk production by the mammary glands is
- A) TSH.
- B) ACTH.
- C) growth hormone.
- D) FSH.
- E) prolactin.
Answer: E
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Knowledge
15) The pituitary hormone that stimulates cell growth and metabolism in many tissues is
- A) ACTH.
- B) MSH.
- C) prolactin.
- D) insulin.
- E) somatotropin.
Answer: E
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Knowledge
Match each term with the appropriate description.
- peptide hormone
- steroid hormone
- amino acid-derived hormone
- anterior pituitary
- hypothalamus
- posterior pituitary
16) lipophobic molecule that interacts with receptors on cell surface
Answer: A
Section: The Classification of Hormones
Learning Outcome: 7.4
Bloom’s Taxonomy: Comprehension
17) site of vasopressin synthesis
Answer: E
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Knowledge
18) true endocrine gland of epithelial origin
Answer: D
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Comprehension
19) cannot be stored in secretory vesicles
Answer: B
Section: The Classification of Hormones
Learning Outcome: 7.5
Bloom’s Taxonomy: Comprehension
20) derivatives of tyrosine
Answer: C
Section: The Classification of Hormones
Learning Outcome: 7.6
Bloom’s Taxonomy: Comprehension
21) storage and release site for oxytocin
Answer: F
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Comprehension
Match each hormone with its primary source.
- prolactin
- insulin
- aldosterone
- melatonin
- calcitonin
- epinephrine
22) adrenal medulla
Answer: F
Section: Control of Hormone Release
Learning Outcome: 7.7
Bloom’s Taxonomy: Comprehension
23) pancreas
Answer: B
Section: Control of Hormone Release
Learning Outcome: 7.7
Bloom’s Taxonomy: Comprehension
24) thyroid
Answer: E
Section: Control of Hormone Release
Learning Outcome: 7.9
Bloom’s Taxonomy: Comprehension
25) anterior pituitary
Answer: A
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Comprehension
26) adrenal cortex
Answer: C
Section: Control of Hormone Release
Learning Outcome: 7.9
Bloom’s Taxonomy: Comprehension
27) pineal
Answer: D
Section: The Classification of Hormones
Learning Outcome: 7.6
Bloom’s Taxonomy: Comprehension
28) The study of hormones is known as the field of ________.
Answer: endocrinology
Section: Hormones
Learning Outcome: 7.1
Bloom’s Taxonomy: Comprehension
29) The ________ of a hormone is an indicator of how long a hormone is active in the body.
Answer: half-life
Section: The Classification of Hormones
Learning Outcome: 7.4
Bloom’s Taxonomy: Comprehension
30) A circulatory route that has two sets of capillaries is known as a ________.
Answer: portal system
Section: Control of Hormone Release
Learning Outcome: 7.7
Bloom’s Taxonomy: Comprehension
31) The posterior pituitary gland is also known as the ________.
Answer: neurohypophysis
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Comprehension
32) The anterior pituitary gland is also known as the ________.
Answer: adenophyophysis
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Comprehension
33) The sex hormones that regulate the male and female reproductive organs are collectively called ________.
Answer: gonadotropins
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Comprehension
34) ________ is a decrease in the number of receptors of target cells in order to dampen the effects of excess hormone.
Answer: Down-regulation
Section: Endocrine Pathologies
Learning Outcome: 7.12
Bloom’s Taxonomy: Comprehension
35) The ________ gland sits along the superior border of the kidney.
Answer: adrenal
Section: The Classification of Hormones
Learning Outcome: 7.1
Bloom’s Taxonomy: Comprehension
36) The outer layer of the adrenal gland is called the ________.
Answer: adrenal cortex
Section: The Classification of Hormones
Learning Outcome: 7.1
Bloom’s Taxonomy: Comprehension
37) The inner portion of the adrenal gland is called the ________.
Answer: adrenal medulla
Section: The Classification of Hormones
Learning Outcome: 7.1
Bloom’s Taxonomy: Comprehension
38) The adrenal cortex produces a steroid hormone called ________ that controls Na+ and K+ homeostasis and another steroid hormone called ________ that controls blood glucose levels.
Answer: aldosterone, cortisol
Section: The Classification of Hormones
Learning Outcome: 7.1
Bloom’s Taxonomy: Comprehension
39) The term for two hormones that have additive effects is ________.
Answer: synergists
Section: Hormone Interactions
Learning Outcome: 7.11
Bloom’s Taxonomy: Comprehension
40) The term that describes the need for one hormone to be present for a second hormone to produce a full effect is called ________.
Answer: permissive
Section: Hormone Interactions
Learning Outcome: 7.11
Bloom’s Taxonomy: Comprehension
41) Two hormones that have opposing effects are called ________.
Answer: antagonists
Section: Hormone Interactions
Learning Outcome: 7.11
Bloom’s Taxonomy: Comprehension
42) When an organ or gland shrinks due to lack of use, that condition is referred to as ________.
Answer: atrophy
Section: Endocrine Pathologies
Learning Outcome: 7.12
Bloom’s Taxonomy: Comprehension
43) The term for any hormone that controls the secretion of another hormone is a ________.
Answer: trophic hormone
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Comprehension
44) The hormones of the anterior pituitary are controlled by trophic hormones from the ________.
Answer: hypothalamus
Section: Control of Hormone Release
Learning Outcome: 7.7
Bloom’s Taxonomy: Comprehension
45) The trophic hormones reach the pituitary through the ________.
Answer: hypothalamic-hypophyseal portal system
Section: Control of Hormone Release
Learning Outcome: 7.7
Bloom’s Taxonomy: Comprehension
46) ________ pathologies arise in the last endocrine gland in a reflex.
Answer: Primary
Section: Endocrine Pathologies
Learning Outcome: 7.8
Bloom’s Taxonomy: Knowledge
47) A ________ is a problem with one of the tissues producing trophic hormones.
Answer: secondary pathology
Section: Endocrine Pathologies
Learning Outcome: 7.13
Bloom’s Taxonomy: Knowledge
48) Chemical signals released into the blood by neurons are called ________.
Answer: neurohormones
Section: Hormones
Learning Outcome: 7.1
Bloom’s Taxonomy: Knowledge
49) When stimulated by a particular hormone, there is a marked increase in the activity of G proteins in the membrane. The hormone is probably
- A) a steroid.
- B) a peptide.
- C) testosterone.
- D) estrogen.
- E) aldosterone.
Answer: A
Section: The Classification of Hormones
Learning Outcome: 7.5
Bloom’s Taxonomy: Comprehension
50) After a hormone has exerted its effects, it typically
- A) continues to act until an opposing hormone is secreted.
- B) spontaneously degrades.
- C) is inactivated or removed from the blood.
- D) is absorbed by its target cell.
- E) is absorbed by the gland that secreted it.
Answer: C
Section: Hormones
Learning Outcome: 7.2
Bloom’s Taxonomy: Comprehension
51) Hormones are not typically considered to be cytokines because hormones are ________ like cytokines.
- A) synthesized in advance and stored, not
- B) not peptides
- C) not effective in small amounts
- D) secreted into the blood, not
- E) secreted by cells, not
Answer: A
Section: Hormones
Learning Outcome: 7.1
Bloom’s Taxonomy: Comprehension
52) In a simple endocrine reflex, the endocrine cell is the
- A) sensor only.
- B) integrating center only.
- C) target.
- D) sensor and integrating center.
- E) integrating center and target.
Answer: D
Section: Control of Hormone Release
Learning Outcome: 7.7
Bloom’s Taxonomy: Comprehension
53) Synergism occurs when
- A) one hormone triggers the secretion of a second hormone.
- B) one hormone inhibits the release of a second hormone.
- C) hormones working together produce a larger effect than predicted.
- D) hormones working together produce a smaller effect than predicted.
- E) a hormone can exert its full effects only in the presence of another hormone.
Answer: C
Section: Hormone Interactions
Learning Outcome: 7.11
Bloom’s Taxonomy: Comprehension
54) Hormones acting through signal transduction pathways elicit a ________ response compared to hormones that produce genomic effects.
- A) faster
- B) slower
- C) equal
Answer: A
Section: The Classification of Hormones
Learning Outcome: 7.5
Bloom’s Taxonomy: Comprehension
55) A cell’s or tissue’s response to a hormone primarily depends on ________ and ________.
Answer: cell receptors, signal transduction pathways
Section: Hormones
Learning Outcome: 7.2
Bloom’s Taxonomy: Comprehension
56) The signal molecule produced by one animal that may affect the behavior of another animal of the same species is the ________.
Answer: pheromone or ectohormone
Section: Hormones
Learning Outcome: 7.1
Bloom’s Taxonomy: Knowledge
57) A signal molecule that is secreted into the external environment, instead of into the blood, is called a(n) ________.
Answer: ectohormone or pheromone
Section: Hormones
Learning Outcome: 7.1
Bloom’s Taxonomy: Knowledge
58) Describe the classic steps for identifying an endocrine gland. Are these steps practical for identifying the sources of all the hormones we know of today? Explain.
Answer:
- Remove the suspected gland, and observe the animal.
- Restore the gland or administer a gland extract, and observe the animal.
- Add a gland or gland extract to a normal animal, and observe the animal for excessive response.
- Purify gland extracts and isolate the substance. There are many hormones that are secreted from cells that are not part of a discrete gland and therefore not removable without causing problems beyond loss of the hormone.
Section: Hormones
Learning Outcome: 7.1
Bloom’s Taxonomy: Comprehension
59) List and explain two ways hormones affect their targets.
Answer: Second messenger systems activated by peptide hormones modify existing proteins or activate gene transcription to synthesize new proteins. Steroid hormones activate gene transcription to synthesize new proteins, and like peptide hormones, some steroids have nongenomic responses.
Section: The Classification of Hormones
Learning Outcome: 7.5
Bloom’s Taxonomy: Comprehension
60) List the three types of hormone interactions and provide an example of each.
Answer: Synergism, permissiveness, and antagonism. An example of synergism is epinephrine’s ability to potentiate the effects of glucagon in elevating blood glucose levels. Reproductive hormones along with adequate thyroid hormone have a permissive effect on the reproductive system because both are required for normal development. Glucagon and insulin are antagonistic hormones because they have opposing physiological actions on blood glucose levels.
Section: Hormone Interactions
Learning Outcome: 7.11
Bloom’s Taxonomy: Comprehension
61) Explain the differences among the terms paracrine, autocrine, hormone, and cytokine.
Answer: Discussed in Chapters 6 and 7. Hormones are chemical messengers that are traditionally defined as being secreted by specialized cells into the blood and transported via the circulatory system to distant cells and tissues. Paracrine and autocrine chemical messengers diffuse only very short distances through interstitial fluid. Cytokines may act both at local and long-distance targets.
Section: Hormones
Learning Outcome: 7.1
Bloom’s Taxonomy: Comprehension
62) What are two benefits of having a portal system that connects the hypothalamus with the anterior pituitary gland? Are there any other endocrine axes connected by a portal system?
Answer: One benefit of a portal system is that it ensures that the controlling hormones will be delivered directly to the target cells. Secondly, since the hormones go directly to their target cells without first passing through the general circulation they are not diluted. The hypothalamus can control the cells of the pituitary with much smaller amounts of releasing and inhibiting hormones than would be necessary if the hormones had to first go through the circulatory pathway before reaching the pituitary. This is the only endocrine portal system.
Section: Control of Hormone Release
Learning Outcome: 7.7
Bloom’s Taxonomy: Comprehension
63) A given hormone generally has the same effect on different target tissues. Is this statement TRUE or FALSE? Defend your answer.
Answer: False. A target tissue’s response is dependent upon the exact receptor involved, as well as a variety of other factors. For example, insulin causes skeletal muscle to increase its rate of transport of glucose into the cell, but in the liver insulin affects the activity of enzymes not directly related to glucose transport.
Section: Hormones
Learning Outcome: 7.2
Bloom’s Taxonomy: Comprehension
64) What normally stops hormone action, and why is this important?
Answer: Hormones are degraded by enzymes and eliminated in the urine. This disposal of hormones is essential to the ability to regulate their action and prevent them from being too effective. For example, if insulin were not closely regulated, too much glucose could be removed from the blood, depriving brain cells of their only fuel source and causing brain damage, coma, and/or death.
Section: Hormones
Learning Outcome: 7.2
Bloom’s Taxonomy: Comprehension
65) How does the embryological origin of the two distinct parts of the pituitary gland relate to the control of secretion and the types of hormones produced?
Answer: The posterior pituitary is an extension of the brain, specifically of the hypothalamus. This part of the pituitary secretes hormones that are synthesized in the hypothalamus, in response to signals from the hypothalamus. The hormones secreted are neurohormones. The anterior pituitary is an outgrowth from the roof of the mouth that fuses to the posterior pituitary during fetal development. This part of the pituitary is true glandular epithelium, and the secretion of its hormones is regulated by releasing and inhibiting hormones secreted by the hypothalamus. In either case, then, the types of hormones and the regulation of their secretion is predictable based on the type of tissue involved.
Section: Control of Hormone Release
Learning Outcome: 7.8
Bloom’s Taxonomy: Comprehension
66) Explain the concept of evolutionary conservation of hormone activity, and how recognition of that phenomenon has influenced hormone therapies.
Answer: Hormone structure and function in some cases have changed little from primitive vertebrates through mammals. Evidence for this includes the similar response in humans to injected hormones from nonhuman sources. An example of the importance of this relationship is provided by the hormone insulin, which, from extracts of cow, pig, or sheep pancreas, successfully treated diabetes mellitus in humans. Prior to that, diagnosis of diabetes mellitus was followed shortly by death.
Section: Hormone Evolution
Learning Outcome: 7.14
Bloom’s Taxonomy: Comprehension
67) One hypothalamic hormone triggers a pituitary hormone to cause release of an adrenal hormone. Fill in the names of the hormones below. If a tumor in the adrenal cortex resulted in hypercortisolism, how would this affect the relative levels of hormone produced from each source? What type of reflex pathway is involved?
Hormone Source Tumor effects
________ Hypothalamus increase decrease
________ Anterior pituitary increase decrease
________ Adrenal cortex increase decrease
Answer: Corticotropin-releasing hormone, decrease
Adrenocorticotrophic hormone, decrease
Cortisol, increase
This type of relationship is called long-loop negative feedback.
Section: Endocrine Pathologies
Learning Outcome: 7.13
Bloom’s Taxonomy: Application
68) Dexamethasone is a drug used to suppress the secretion of ACTH from the anterior pituitary gland. Two patients with hypersecretion of cortisol are given dexamethasone. Anika’s cortisol secretion level falls to normal after the medication, but Bonnie’s cortisol secretion remains elevated. Which patient has primary hypercortisolism, also known as Cushing’s syndrome? Explain your reasoning.
Answer: Dexamethasone suppresses the pituitary’s activity, the secretion of ACTH, which then allowed Anika’s level to decline. Since Bonnie’s level did not decline, this shows that the hypersecretion is NOT due to ACTH, thus it must be coming from the adrenal gland. This is the definition of a primary hypersecretion—an elevated amount from the last gland in the reflex pathway.
Section: Endocrine Pathologies
Learning Outcome: 7.13
Bloom’s Taxonomy: Analysis
69) The following statement contains three parts that are either TRUE or FALSE. You must address ALL THREE parts of the statement explaining either why it is TRUE or why it is FALSE.
Neurohormones from the anterior pituitary are called trophic because their release is stimulated by a releasing hormone from the hypothalamus.
Answer:
- The anterior pituitary is an endocrine gland; it does not release neurohormones because its cells are not neurons.
- The word trophic is used incorrectly; the term refers to a hormone that causes another gland to release hormone.
- Anterior pituitary hormones are in fact triggered by releasing hormones from the hypothalamus.
Section: Control of Hormone Release
Learning Outcome: 7.7
Bloom’s Taxonomy: Analysis
70) Carl is suffering from hypothyroidism. What is hypothyroidism? How could his physician determine whether the malfunction is in the hypothalamus and pituitary or at the level of the gland itself?
Answer: Hypothyroidism results when the thyroid gland produces lower than normal amounts of thyroid hormones. The physician could order blood tests to determine the levels of T3, T4, and TSH in the blood. If the condition is due to disease of the thyroid gland, you would expect to see elevated levels of TSH because of a lack of feedback inhibition by thyroid hormones. If, on the other hand, the problem is due to problems at the level of the hypothalamus or pituitary, you would expect to see decreased levels of TSH.
Section: Endocrine Pathologies
Learning Outcome: 7.13
Bloom’s Taxonomy: Analysis
71) Candace is a normal-looking 15-year-old girl but has never had a menstrual period, though she has other signs of puberty such as breasts and pubic and axillary hair. During a pelvic exam her physician determines that she has no uterus. Blood tests reveal that she has elevated amounts of testosterone in her blood, similar to that expected in young adult males. Name two typical sources of testosterone. Given the lack of a uterus, what is the likely source of testosterone in this case? What may be wrong with her? (Hint: Consider general principles of hormone secretion and action.) Why is there no uterus? What genetic test may confirm this suspicion?
Answer: Testosterone is produced by adrenal glands and testes. The presence of elevated testosterone combined with absence of a uterus suggests that she has testes rather than ovaries. The lack of masculinization indicates that her tissues do not respond to the testosterone that is present. There is no uterus because she is genetically male. This can be confirmed by examining her chromosomes. Such individuals have “androgen insensitivity syndrome.”
Section: Endocrine Pathologies
Learning Outcome: 7.13
Bloom’s Taxonomy: Analysis
72) Your roommate Sally has just found out her mother has high cholesterol. Knowing that health problems often run in families, Sally has decided to eliminate cholesterol from her diet. Her goal is to have no cholesterol in her body. She has asked you for advice on achieving this goal. Is her goal realistic? Explain. What information should you give her to help her establish a more realistic goal? Assuming she could banish cholesterol from her body, what would be the endocrine consequences?
Answer: Her goal is not realistic. If Sally avoids eating animal products, she can easily eliminate cholesterol from her diet. She cannot, however, eliminate cholesterol from her blood because it is produced by her own liver. Furthermore, such a goal is incompatible with life, as cholesterol is a structural component of cell membranes. Cholesterol is also the precursor to the steroid hormones, which are essential for normal health.
Section: The Classification of Hormones
Learning Outcome: 7.4
Bloom’s Taxonomy: Analysis
73) Thyroid hormone secretion decreases with age. Treatment with thyroid-releasing hormone is less effective in younger patients, while treatment with thyroid hormone is more effective in younger patients.
What name is given to the condition of decreased thyroid hormone secretion? What related hormones are likely to decrease as well? Propose an explanation for the loss of responsiveness to the releasing hormone. Propose an explanation for the increased responsiveness to treatment with thyroid hormone (consider both how hormones affect target cells and how hormone action is halted).
Answer: The condition is hypothyroidism. Thyroid-stimulating hormone and thyroid-releasing hormone likely also decrease. Decreased responsiveness to injected releasing hormone may indicate a loss of hormone receptors in the anterior pituitary. Increased responsiveness to injected thyroid hormone may indicate up-regulation of hormone receptors in the target tissues, or it may indicate decreased metabolism of the circulating hormone.
Section: Endocrine Pathologies
Learning Outcome: 7.13
Bloom’s Taxonomy: Analysis
74) There are two forms of diabetes: diabetes mellitus (lack of insulin regulation of cellular uptake of glucose) and diabetes insipidus (lack of regulation of water loss in the urine by the hormone antidiuretic hormone or ADH). In each case, there are two similar explanations for the resulting pathology. What are they? (Hint: Consider general principles of hormone action.)
Answer: Diabetes mellitus can result from lack of insulin secretion or from lack of response of insulin receptors. Diabetes insipidus can result from lack of ADH secretion or lack of responsiveness of ADH receptors.
Section: Endocrine Pathologies
Learning Outcome: 7.13
Bloom’s Taxonomy: Analysis
75) Assume the following: The total area of cell membrane in a single fat cell is 104 mm2, there is one insulin receptor per 1 mm2 of membrane, and 1 mm2 of cell membrane contains 106 phospholipid molecules.
- How many insulin receptors are in a fat cell?
- How many phospholipids molecules are in a fat cell?
- How many phospholipid molecules are there for each insulin receptor?
- What general principle of hormone action does your answer support?
Answer:
- 1 receptor/1 mm2× 104mm2/cell = 104 receptors per cell.
- 104mm2/cell × 106phospholipids/mm2 = 1010 phospholipid molecules per cell.
- (1010phospholipids/cell) / (104receptors/cell) = 106 phospholipid molecules per insulin receptor.
- Hormones exert their effects at very low concentrations (therefore it is not surprising that the hormone receptors, through which the hormones act, are also in low concentration).
Section: Hormones
Bloom’s Taxonomy: Analysis
76) Suzie wants to protect virgin forests from destruction. She climbs a tree to prevent loggers from cutting the oldest tree in the forest. Suzie did not eat for twelve hours until a friend, Jammie, took over the vigilance. Match the correct levels of blood glucose concentration, blood insulin concentration and relative membrane insulin receptor concentration for a skeletal muscle cell 20 hours into Jammie’s fast and one hour after Suzie had eaten a peanut butter and banana sandwich and a bowl of sweet potato soup.
Plasma Glucose: 90 mg/dl; 125 mg/dl
Plasma Insulin: 10iuU/ml (70 pmol/L); 40iuU/ml (280 pmol/L)
Relative membrane insulin receptor concentration: increasing (high); decreasing (low)
| Fasting (Jammie) | Satiety (Suzie) |
| Plasma Glucose
| | |
| Plasma Insulin
| | |
| Relative Membrane
Insulin Receptor Levels | | |
Answer:
| Fasting (Jammie) | Satiety (Suzie) |
| Plasma Glucose | 90 mg/dl | 125 mg/dl |
| Plasma Insulin | 10iuU/ml (70 pmol/L); | 40iuU/ml (280 pmol/L) |
| Relative Membrane
Insulin Receptor Levels | increasing (high) | decreasing (low) |
Section: Control of Hormone Release
Learning Outcome: 7.5
Bloom’s Taxonomy: Analysis
