LS 7C Practice Exam Questions

T/F: The changes in voltage seen during depolarization and hyperpolarization in the figure are caused by similar movements, in the same direction, of the same types of ions across the membranes.

False

T/F: The changes in voltage shown in the action potential figure are due to ligand-gated ion channels opening and closing along the axon.

False

T/F: The magnitude of the action potential is correlated with the strength of the stimulating input.

False

T/F: The trace in the action potential figure is following the voltage change as it moves down the axon.

False

T/F: A membrane that has no K+ channels will have a resting membrane potential that is higher than the one shown on the figure.

True

T/F: Action potential is an all or nothing response.

True

T/F: All voltage changes along the plasma membrane of an axon have the characteristic shape of an action potential shown above.

True

T/F: Different ion channels are responsible for generating the voltage change seen during depolarization and hyperpolarization in the figure.

True

T/F: Resting potential is generated mainly by the outward movement of K+ ions from inside the cell.

True

T/F: The voltage changes shown in the figure are measured just across the plasma membrane

True

T/F: When compared to the leg muscles of an Olympic sprinter, the muscles of an Olympic marathoner would likely show a greater proportion of oxidative slow-twitch fibers.

True

Sensory transduction requires: a. alteration of the conformation of a channel protein. b. All of these choices are correct. d. reaction of a receptor protein with a stimulus. e. a change in membrane potential.

b. All of these choices are correct

In the figure below, panel a shows a photoreceptor and its postsynaptic cell in the dark, and panel b shows both cells in the light. What causes the change observed in this figure? (neurotransmitters released in dark but not in light) a. Hyperpolarization of the rod cell in the light inhibits release of a neurotransmitter. b. Depolarization of the rod cell in the light inhibits release of neurotransmitter. c. This figure is incorrect; dark and light are reversed. d. Hyperpolarization of the rod cell in the dark causes release of a neurotransmitter.

a. Hyperpolarization of the rod cell in the light inhibits release of a neurotransmitter.

Sensory cells and sensory neurons allow multicellular animals to sense physical and chemical cues from their environment. What key properties of these cells enable them to perform this function? (Select all that apply.) a. Sensory cells and sensory neurons have protein receptors linked to intracellular or membrane-based signaling pathways that alter ion channel permeability. b. Sensory neurons have myelinated dendrites that serve as nerve endings. c. Sensory cells and sensory neurons have electrically excitable membranes that change in charge potential in response to binding an environmental signaling molecule. d. All sensory cells and sensory neurons fire action potentials when they bind a signaling molecule.

a. Sensory cells and sensory neurons have protein receptors linked to intracellular or membrane-based signaling pathways that alter ion channel permeability. c. Sensory cells and sensory neurons have electrically excitable membranes that change in charge potential in response to binding an environmental signaling molecule.

When iodine intake is too low, production of _____ by the anterior pituitary gland _____. a. TSH; increases b. triiodothyronine; decreases c. thyroxine; increases d. thyroxine; decreases d. TSH; decreases

a. TSH; increases

Macrophage cells undergo a process called phagocytosis in which material is brought into a cell in the form of membrane vesicles and then transported along microtubules toward the cell center. Assuming that the centrosome is near the cell center, you can predict that these vesicles are moving to the _____ end of microtubules using the motor protein _____. a. minus end; dynein b. minus end; kinesin c. plus end; kinesin d. plus end; dynein

a. minus end; dynein

Figure 9.15 shows how normal signaling works with a Ras protein acting downstream of a receptor kinase. You examine a cell line in which Ras is always activated even in the absence of a signaling molecule. This causes constant activation of the kinases in the MAP kinase pathway. Which of the following conditions would be MOST likely to turn off this abnormally active signaling pathway? a. the addition of a drug that prevents the final kinase from interacting with its target protein in the nucleus b. the addition of a drug that prevents the dimerization of the receptor kinase c. the addition of a drug that increases the binding affinity of Ras for MAP kinase enzymes in the cytoplasm d. the addition of a drug that prevents the phosphorylation of the receptor kinase

a. the addition of a drug that prevents the final kinase from interacting with its target protein in the nucleus

The transduction of sound waves to changes in membrane potential takes place: a. when stereocilia bend against the tectorial membrane, causing hair cell depolarization. b. as the vibrations received by the outer ear cause the eardrum to vibrate. c. in the oval window, which vibrates at the same frequency as the original sound. d. in the basilar membrane as it vibrates at different locations. e. within the tectorial membrane as it is stimulated by the hair cells.

a. when stereocilia bend against the tectorial membrane, causing hair cell depolarization.

A key difference between hormonal regulation of the reproductive systems of males and females is that: a. LH is released continuously in males and FSH is released cyclically in females. b. LH and FSH are released cyclically in females but nearly continuously in males. c. LH is released in males and FSH is released in females. d. LH and FSH are released only in males. e. LH and FSH are released only in females.

b. LH and FSH are released cyclically in females but nearly continuously in males.

Some people have low levels of calcium circulating in the blood, a condition known as hypocalcemia. While for many this disorder has little to no effect, for some it can be life-threatening. How could low levels of calcium harm an individual? a. Low levels of calcium would cause sustained depolarization of the presynaptic cell. b. Low levels of calcium would result in fewer signals sent between the pre- and postsynaptic cell. c. Low levels of calcium would not have any effect on synaptic transmission.

b. Low levels of calcium would result in fewer signals sent between the pre- and postsynaptic cell.

Imagine you genetically engineered a neuron to produce voltage-gated Na+ and K+ channels that opened at the same time in response to a change in voltage. How would that change the recording shown in the action potential figure? a. The period of hyperpolarization would be longer. b. No action potential would be generated. c. The peak would occur over a longer period of time. d. The peak voltage would be higher. e. Threshold values would increase.

b. No action potential would be generated

Aging can sometimes lead to an increase in the stiffness at the base of the basilar membrane. What effect would this have on a person's hearing? a. The person would only be able to hear loud sounds. b. The person would lose the ability to hear high-pitched sounds. c. The person would not be able to distinguish the amplitude of a sound. d. The person would lose the ability to hear low-pitched sounds.

b. The person would lose the ability to hear high-pitched sounds.

Vascular endothelial growth factor (abbreviated VEGF and pronounced "Veg-F") is a peptide signaling molecule related to platelet-derived growth factor. VEGF is important in the formation of the circulatory system because its signaling pathway causes the formation of blood vessels in developing embryos during normal development. Tumors also produce and secrete VEGF, causing the formation of new blood vessels that supply these tumors. Given what you know about the different kinds of cell signaling and VEGF, which one of the following statements is TRUE? a. VEGF is an endocrine-signaling molecule because it is released from platelets into the bloodstream and is carried throughout the body, causing widespread activation of platelet-derived growth factor receptors on cells in a variety of tissues. b. VEGF is a paracrine signaling molecule because it binds to receptors on cells at the site where new blood vessels are needed. c. VEGF is an endocrine-signaling molecule because it circulates through the bloodstream inside of platelets.

b. VEGF is a paracrine signaling molecule because it binds to receptors on cells at the site where new blood vessels are needed.

If a skeletal muscle is no longer able to make enough ATP, then: a. the muscle will be unable to shorten. b. actin and myosin in the sarcomeres will remain bound. c. actin and myosin in the sarcomeres are in the unbound state. d. there will be low levels of acetylcholine at the motor endplate.

b. actin and myosin in the sarcomeres will remain bound.

Kisspeptin is a protein in humans that has an important role in initiating secretion of the releasing factor gonadotropin-releasing hormone (GnRH). Endocrinologists are finding that the protein kisspeptin and its receptor are central to sexual maturation at puberty. Neurons that release kisspeptin carry estrogen receptors. If this is a negative feedback system, high levels of estrogen would be expected to: a. neither increase nor decrease kisspeptin synthesis because steroid hormones do not affect protein synthesis. b. decrease kisspeptin synthesis. c. increase kisspeptin synthesis.

b. decrease kisspeptin synthesis.

Which of the following is an example of the effector's role in maintaining homeostasis? a. increased body temperature during a workout b. increased sweating on a hot summer day c. vasodilation on a cold winter day d. decrease in body temperature on a cold day

b. increased sweating on a hot summer day

Which of the following is an example of a negative feedback altering homeostatic control? a. a person shivering as temperatures rise on a hot summer day b. the concentration of salt in urine increases after eating a large bag of salty chips c. a person's heart rate drops as she runs d. the production of oxytocin (a hormone) increases as oxytocin levels rise in the body

b. the concentration of salt in urine increases after eating a large bag of salty chips

Some researchers have suggested that obesity is due to a change in "set point" in the brain that is related to the number of calories a person needs, therefore people eat more than they need and gain weight. Permanently raising the set point would involve a permanent change in which of the following? a. the effector b. the sensor c. the stimulus d. the response

b. the sensor

When a person has a few drinks containing alcohol, they often feel the need to urinate. This response suggests interplay between alcohol and antidiuretic hormone (ADH). Which of the following could explain how alcohol and ADH interact? (note: ADH causes a decrease in urine production) a. Alcohol increases the release of ADH. b. Alcohol inhibits the binding of ADH to receptors in the brain, so individuals "feel" the need to urinate. c. Alcohol decreases the release of ADH. d. Alcohol facilitates the binding of ADH to receptors in the brain, so individuals "feel" the need to urinate.

c. Alcohol decreases the release of ADH.

Many birth-control pills release a constant amount of synthetic estradiols and progesterone for 21 days, followed by 7 days when no hormones are ingested. Which of the following statements MOST accurately describes the effects of birth-control pills? a. Birth-control pills inhibit the development of the uterine lining so implantation of a fertilized oocyte cannot occur. b. The 7 days with no hormones does not allow a thick enough uterine lining to form so a fertilized oocyte cannot implant. c. Birth-control pills maintain constant levels of estrogens and/or progesterone so there is no surge in LH and ovulation does not occur. d. Birth-control pills maintain constant levels of estrogens and/or progesterones and mask the release of the oocyte from the follicle.

c. Birth-control pills maintain constant levels of estrogens and/or progesterone so there is no surge in LH and ovulation does not occur.

Phosphatases are a family of enzymes that remove phosphate groups from specific proteins; these phosphate groups had been added to the proteins by protein kinases. Vanadate is an inhibitor of phosphatases in eukaryotic cells. What effect would vanadate have on the response of cells to signals received by receptor kinases? a. The response of the cell would be shorter than it normally would. b. The signal would still bind the receptor, so there would be no effect. c. The response of the cell would last longer than it normally would.

c. The response of the cell would last longer than it normally would.

In many cells, the adhesion to the extracellular matrix through integrins causes the activation of kinases in the cytoplasm. This suggests that: a. extracellular matrix proteins are receptors and integrins are ligands. b. integrins are kinases. c. integrins promote the activation of signal-transduction pathways.

c. integrins promote the activation of signal-transduction pathways.

If a mutation occurred in the cadherin gene so that the cytoplasmic domain no longer attached to the cytoskeleton, which of the following would occur? a. Cadherins in desmosomes would no longer be anchored to microfilaments. b. Cadherins in adherens junctions would no longer be anchored to microtubules. c. Cadherins in hemidesmosomes would no longer be anchored to intermediate filaments. d. Cadherins in desmosomes would no longer be anchored to intermediate filaments.

d. Cadherins in desmosomes would no longer be anchored to intermediate filaments.

Imagine that you are talking with one of your friends about your biology course. He states that the somatic nervous system is subdivided into sympathetic and parasympathetic components, and is responsible for involuntary responses. Is this statement correct? a. Yes, this statement is correct. The somatic nervous system has both sympathetic and parasympathetic components and controls involuntary responses. b. No, although the somatic nervous system does have both sympathetic and parasympathetic subdivisions, it is responsible for voluntary responses. c. No, although the somatic nervous system controls involuntary responses, it is the autonomic nervous system that is subdivided into parasympathetic and sympathetic components. d. No, the somatic nervous system is responsible for voluntary responses, and is not subdivided into sympathetic and parasympathetic components.

d. No, the somatic nervous system is responsible for voluntary responses, and is not subdivided into sympathetic and parasympathetic components.

Suppose there is a mutation in a laminin-binding integrin gene that causes a loss of function in the cytoplasmic domains of the integrin. Which of the following would you expect to observe as a result of this mutation? a. The integrin would function normally because the cytoplasmic domain is not responsible for binding to laminin. b. Tissues would be weakened because the integrin could no longer associate with microfilaments in adherens junctions. c. Cell adhesion to laminin would decrease, but laminin-meditated gene expression would remain the same. d. The integrin would be unable to signal the cytoplasm when it had bound to laminin.

d. The integrin would be unable to signal the cytoplasm when it had bound to laminin.

All of the following would lead to an increase in the force generated by a muscle contraction EXCEPT: a. increasing the frequency of muscle stimulation by the motor nerve. b. increasing the number of muscle fibers activated. c. increasing the number of motor units activated. d. increasing the rate at which calcium is pumped back into the sarcoplasmic reticulum. e. maximizing the number of cross-bridges formed during a contraction.

d. increasing the rate at which calcium is pumped back into the sarcoplasmic reticulum.

An interneuron may receive multiple stimuli from the same sensory neuron over a very short period of time. The firing rate of the receiving neuron is proportional to the number of signals received from the sensory neuron over time. Of which of the following is this an example? a. hyperpolarization b. spatial summation c. action potential d. temporal summation

d. temporal summation

Dilated pupils, inhibited digestive activity, increased respiratory rate, and release of glucose from the liver are all signs of activity of: a. the somatic nervous system. b. the parasympathetic division of the autonomic system. c. both divisions of the autonomic nervous system. d. the sympathetic division of the autonomic system.

d. the sympathetic division of the autonomic system.

What effect does the nervous system have on the heart rate? a. Stimulation by sympathetic nerves sets the resting heart rate of the pacemaker cells in the SA node. b. Stimulation by either the sympathetic or parasympathetic nerves causes pacemaker cells in the SA node to depolarize more slowly. c. Stimulation by sympathetic nerves causes the pacemaker cells of the AV node to depolarize more rapidly than the pacemaker cells of the SA node. d. The nervous system does not directly affect the heart rate. e. Stimulation by parasympathetic nerves causes the heart rate to slow down.

e. Stimulation by parasympathetic nerves causes the heart rate to slow down.

Imagine you created a toxin such that when a neuron fired an action potential, the toxin would bind immediately to the sodium-potassium pump at the top of the action potential, but the sodium and potassium channels would still function. What process(es) would be affected? a. maintaining resting potential b. the depolarization phase of an action potential c. returning to resting potential after the hyperpolarization phase of an action potential d. the hyperpolarization phase of an action potential e. maintaining resting potential and returning to resting potential after the hyperpolarization phase of an action potential

e. maintaining resting potential and returning to resting potential after the hyperpolarization phase of an action potential

Which of the following would result in tetanus? a. allowing a muscle fiber to relax for several seconds between twitches b. stimulating a muscle fiber to contract when it has partially relaxed c. stimulating a muscle fiber to contract immediately after it has relaxed d. All of these choices are correct. e. stimulating the muscle fiber so frequently that it cannot relax at all

e. stimulating the muscle fiber so frequently that it cannot relax at all

You measure levels of Ca2+ in various locations within a motor neuron and a skeletal muscle fiber when the motor neuron is NOT depolarized, and the muscle fiber is at rest. Where do you expect to find high levels of Ca2+? a. diffusing into the motor neuron through specialized channels in the plasma membrane b. bound to troponin c. within the T-tubules d. binding to the receptors at the motor endplate of the muscle cell e. within the sarcoplasmic reticulum of the muscle fiber

e. within the sarcoplasmic reticulum of the muscle fiber