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Human Physiology An Integrated Approach 7th Edition By Silverthorn -Test Bank

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Human Physiology An Integrated Approach 7th Edition By Silverthorn -Test Bank

Human Physiology: An Integrated Approach, 7e (Silverthorn)
Chapter 6 Communication, Integration, and Homeostasis

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:

A. threshold
B. effector
C. integrating center
D. setpoint
E. 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:
1. transfer signal molecules to adjacent cells through gap junctions
2. use contact-dependent signals, which rely on interactions between cell surface molecules on different cells
3. use locally acting chemicals, called paracrines, autocrines, or neuromodulators
4. 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

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