chap 11

27) What channels open or close in response to physical distortion of the membrane surface, such as vibrations or pressure? A) voltage-gated B) chemically-gated C) mechanically-gated D) ligand-gated

C) mechanically-gated

15) The most common type of neuron in the human body is: A) unipolar. B) pseudounipolar. C) multipolar. D) bipolar.

C) multipolar.

66) After acetylcholinesterase (AChE) acts, the presynaptic neuron: A) reabsorbs acetylcholine. B) reabsorbs the acetate. C) reabsorbs the choline. D) reabsorbs synaptic vesicles.

C) reabsorbs the choline.

8) The autonomic nervous system does NOT carry signals to: A) smooth muscle. B) cardiac muscle. C) skeletal muscle. D) glands.

C) skeletal muscle.

4) Upon entering your house, you noticed the smell of cake baking in the oven. What division of the peripheral nervous system is responsible? A) visceral motor division B) somatic motor division C) somatic sensory division D) visceral sensory division

C) somatic sensory division

62) Summation that results from the cumulative effect of multiple synapses at multiple places on the neuron is designated: A) temporal summation. B) hyperpolarization. C) spatial summation. D) impulse transmission.

C) spatial summation.

29) If a resting axon increases its permeability to sodium ions: A) the membrane potential will repolarize. B) the membrane potential will hyperpolarize. C) the influx of sodium ions will increase and the membrane will depolarize. D) the outward movement of sodium ions will decrease.

C) the influx of sodium ions will increase and the membrane will depolarize.

23) Myelinated axons in the CNS are known as: A) internodes. B) gray matter. C) white matter. D) dark matter.

C) white matter.

19) Which neuroglial cell helps form the blood-brain barrier? A) astrocyte B) oligodendrocyte C) satellite cell D) ependymal cell

A) astrocyte

14) The conducting region of the neuron is the: A) axon. B) axon terminals (synaptic knobs). C) dendrites. D) cell body.

A) axon.

2) Which of the following are organs of the central nervous system? A) brain and spinal cord B) spinal cord and spinal nerves C) brain and cranial nerves D) brain, cranial nerves, spinal cord, and spinal nerves

A) brain and spinal cord

18) Bundles of axons known as tracts are part of the: A) central nervous system. B) peripheral nervous system. C) ganglion. D) myelin sheath.

A) central nervous system.

53) What type of synapse must have receptors to transmit signals? A) chemical synapse B) electrical synapse C) both chemical and electrical synapses D) neither chemical nor electrical synapses

A) chemical synapse

50) The presence of a synaptic cleft between cells is characteristic of: A) chemical synapse. B) electrical synapse. C) both chemical and electrical synapses. D) neither chemical nor electrical synapses.

A) chemical synapse.

10) Determine the direction in which an electrical signal is carried in a typical multipolar neuron. A) dendrites, cell body, axon B) axon, cell body, dendrites C) dendrites, axon, cell body D) cell body, axon, dendrites

A) dendrites, cell body, axon

34) What is more likely to promote an action potential? A) depolarization B) hyperpolarization C) repolarization D) absolute refractory period

A) depolarization

What is NOT a function of the nervous system? A) direct long-term functions such as growth B) integrate sensory information C) sense the internal and external environments D) control effectors

A) direct long-term functions such as growth

57) Which of the following is most likely to produce an action potential? A) excitatory postsynaptic potential (EPSP) B) opening of potassium ion channels C) inhibitory postsynaptic potential (IPSP) D) hyperpolarization

A) excitatory postsynaptic potential (EPSP)

52) What is NOT associated with a chemical synapse? A) gap junction B) presynaptic neuron C) synaptic cleft D) neurotransmitter

A) gap junction

28) What type of ion channels is always open? A) leak B) local C) active D) regulated

A) leak

47) Determine the fiber type in which propagation of an action potential will occur most quickly. A) myelinated type A fiber B) unmyelinated type B fiber C) myelinated type B fiber D) type C fiber

A) myelinated type A fiber

63) The same ________ can have different effects depending on the properties of the ________. A) neurotransmitter; receptor B) hormone; neurotransmitter C) receptor; neurotransmitter D) substrate; enzyme

A) neurotransmitter; receptor

46) During saltatory conduction, action potentials are generated: A) only at nodes of Ranvier of myelinated axons. B) along the entire length of the unmyelinated axon. C) regardless if threshold is reached. D) when the entire axolemma is depolarized.

A) only at nodes of Ranvier of myelinated axons.

58) What would most likely lead to an IPSP? A) opening of potassium ion channels B) opening of calcium ion channels C) opening of sodium ion channels D) closure of chloride ion channels

A) opening of potassium ion channels

60) Which of the following would NOT terminate the effects of the neurotransmitter? A) presence of calcium ions in the presynaptic neuron B) reuptake of neurotransmitter into the presynaptic neuron C) degradation of the neurotransmitter by enzymes D) diffusion of the neurotransmitter into the extracellular fluid

A) presence of calcium ions in the presynaptic neuron

55) If the receptor site for a neurotransmitter were completely blocked: A) synaptic transmission would fail. B) a weaker action potential would result. C) neurotransmitter release would stop. D) the presynaptic neuron would release a different neurotransmitter.

A) synaptic transmission would fail.

26) Resting membrane potential is maintained by the Na+/K+ pump which brings: A) two potassium ions into the cytosol and three sodium ions into the extracellular fluid. B) three potassium ions into the cytosol and three sodium ions into the extracellular fluid. C) two potassium ions into the cytosol and two sodium ions into the extracellular fluid. D) three potassium ions into the cytosol and two sodium ions into the extracellular fluid.

A) two potassium ions into the cytosol and three sodium ions into the extracellular fluid.

48) Which type of fiber has the largest diameter? A) type A B) type B C) type C D) type D

A) type A

69) Where are neuronal pools located? A) within the CNS B) within ganglia C) within the PNS D) within nerves

A) within the CNS

110) Acetylcholine (ACh) may excite postsynaptic neurons in the CNS; however, it may inhibit some postsynaptic neurons in the PNS. Explain how acetylcholine can be both excitatory and inhibitory.

Acetylcholine can have an excitatory effect if it induces an EPSP when it binds a receptor. An inhibitory effect results if it produces an IPSP in the postsynaptic neuron. The type of receptor to which the neurotransmitter ACh binds determines the postsynaptic response.

16) Which of the following best describes a bipolar neuron? A) one axon and multiple, highly branched dendrites B) one axon and one dendrite C) one axon that splits into two processes D) multiple axons and one dendrite

B) one axon and one dendrite

38) During repolarization of a neuron: A) sodium ions move out of the cell. B) potassium ions move out of the cell. C) sodium ions move into the cell. D) potassium ions move into the cell.

B) potassium ions move out of the cell.

6) Which of the following is controlled by the somatic motor division? A) cardiac muscle B) skeletal muscle C) glands D) smooth muscle

B) skeletal muscle

68) Which neuropeptide neurotransmitter is released from fibers transmitting sensory information about pain and temperature? A) endorphin B) substance P C) neuropeptide Y D) opioids

B) substance P

61) When a second EPSP arrives at a single synapse before the effects of the first have disappeared, what results? A) spatial summation B) temporal summation C) hyperpolarization D) inhibition of the impulse

B) temporal summation

64) Neurotransmitters that bind ionotropic receptors control: A) the formation of a second messenger inside the postsynaptic neuron. B) the movement of ions into or out of the postsynaptic neuron. C) the activation of G-proteins inside the postsynaptic neuron. D) some metabolic process inside the postsynaptic neuron.

B) the movement of ions into or out of the postsynaptic neuron.

51) A neuron that receives neurotransmitters from another neuron is called: A) the presynaptic neuron. B) the postsynaptic neuron. C) an oligodendrocyte. D) a Schwann cell.

B) the postsynaptic neuron.

82) Electrical synapses are faster than chemical synapses due to the presence of gap junctions between cells.

true

81) Axons with a smaller diameter can conduct nerve impulses more quickly than axons with a larger diameter.

false

39) Voltage-gated sodium channels have both an activation gate and: A) an inactivation gate. B) a leak gate. C) a threshold gate. D) a swinging gate.

A) an inactivation gate.

65) Cholinergic synapses use the neurotransmitter: A) acetylcholine. B) serotonin. C) norepinephrine. D) epinephrine.

A) acetylcholine.

116) Does a local potential guarantee the creation of an action potential? Explain.

A local potential must be strong enough to depolarize the axon to a level known as threshold, usually -55 mV. Without threshold, an action potential cannot be achieved.

117) Explain how a polarized neuron differs from a hyperpolarized neuron.

A resting neuron is polarized and typically has a resting membrane potential of -70 mV. Resting membrane potential results from the unequal distribution of ions and their different abilities for crossing the membrane. If potassium channels are opened, and potassium ions follow their electrochemical gradient out of the cell, the cell will lose positive charges. The membrane potential becomes more negative than it is at rest, known as hyperpolarization. Hyperpolarization may also result from the opening of anion channels which would allow negatively charged ions to flow into the cell.

108) What type of postsynaptic potential would be more likely to promote an action potential - an IPSP or EPSP? Explain.

A small, local depolarization called an EPSP moves the membrane potential closer to threshold. If threshold is reached, an action potential is triggered. A small, local hyperpolarization known as an IPSP moves the membrane potential farther from threshold. Threshold is critical for achievement of an action potential. Thus, an EPSP is more likely to promote an action potential while an IPSP is less likely to promote an action potential.

33) Using the information provided in this graph, which statement best summarizes the activity in this neuron? A) The cell gains positive charges, making the inside less negative. B) Positive charges are lost from the cell, making the inside more negative. C) The cells gains negative charges, making the inside more negative. D) The cell gains chloride ions, making the cell hyperpolarize.

A) The cell gains positive charges, making the inside less negative.

118) The nerve agent, sarin, was developed during World War II to block the effects of acetylcholinesterase. Explain the effects of this nerve agent on the synapse.

Acetylcholinesterase (AChE) is an enzyme that terminates the effects of acetylcholine once it has been released into the synaptic cleft. AChE degrades acetylcholine into acetic acid and choline. The choline is taken back up by the presynaptic neuron to be used in the synthesis of new acetylcholine molecules. Without sufficient AChE, acetylcholine will continue to exert its effects on the postsynaptic cell. Since acetylcholine is largely excitatory, postsynaptic cells will continue to be stimulated.

Discuss the role of calcium ions in the transmission of an action potential at the synapse.

An action potential reaching the axon terminal triggers voltage-gated calcium ion channels to open. The presence of calcium ions in the axon terminal causes synaptic vesicles to release neurotransmitters into the synaptic cleft. Neurotransmitters bind to receptors on the postsynaptic neuron. Ion channels respond and a local potential is created.

111) Kelly takes an antihistamine for allergies. Explain why sleepiness is a side effect of this medicine.

Antihistamines are drugs that block histamine receptors outside the nervous system to alleviate allergy symptoms. However, most drugs also block histamine receptors within the CNS as well. Since histamine plays a role in arousal, blocking its action often leads to the side effect of drowsiness.

41) Which number on the graph represents when voltage-gated sodium channels are open?

B) 2.

40) Place these steps of the action potential in the correct order. 1. Sodium ions channels return to the resting state and repolarization continues. 2. Voltage-gated sodium ion channels activate, sodium ions enter, and the axon section depolarizes. 3. As potassium ion channels return to resting state, the axolemma may hyperpolarize before returning to the resting membrane potential. 4. A local potential depolarizes the axolemma of the trigger zone to threshold. 5. Sodium ion channels inactivate, and voltage-gated potassium ion channels activate, so sodium ions stop entering and potassium ions leave, beginning repolarization. A) 4, 2, 3, 5, 1 B) 4, 2, 5, 1, 3 C) 4, 2, 1, 3, 5 D) 2, 4, 5, 1, 3

B) 4, 2, 5, 1, 3

56) Which of the following must happen first in the order events at a chemical synapse? A) Ion channels respond to the neurotransmitter and lead to a local potential, or possibly an action potential. B) Calcium ion channels in the axon terminal open. C) Calcium ions cause synaptic vesicles to release neurotransmitters into the synaptic cleft. D) Neurotransmitter binds to receptors on the postsynaptic neuron.

B) Calcium ion channels in the axon terminal open.

22) Which of the following is an effect of myelination? A) Myelination increases the rate at which phagocytosis occurs in the brain. B) Myelination increases the speed of conduction of action potentials. C) Myelination increases the rate of mitosis in damaged neurons. D) Myelination increases the volume of cerebrospinal fluid in circulation.

B) Myelination increases the speed of conduction of action potentials.

20) Because of their ability to rapidly divide during brain injury, which type of neuroglial cell would be more likely to form a brain tumor? A) oligodendrite B) astrocyte C) ependymal cell D) Schwann cell

B) astrocyte

54) What ion triggers synaptic vesicles to release neurotransmitters into the synaptic cleft? A) sodium B) calcium C) magnesium D) chlorine

B) calcium

12) What is the most metabolically active part of a neuron? A) axon hillock B) cell body C) dendrites D) axon

B) cell body

3) The two anatomical divisions of the nervous system are the: A) sensory division and motor division. B) central nervous system and peripheral nervous system. C) somatic sensory division and visceral sensory system. D) visceral motor division and somatic motor division.

B) central nervous system and peripheral nervous system.

21) Ependymal cells: A) help form the blood-brain barrier. B) circulate cerebrospinal fluid. C) form myelin in the brain and spinal cord. D) serve as wandering phagocytes during brain injury.

B) circulate cerebrospinal fluid.

11) Branches that may occur along an axon are called: A) hillocks. B) collaterals. C) telodendria. D) dendrites.

B) collaterals.

67) Which of the following is the most important excitatory neurotransmitter in the CNS? A) dopamine B) glutamate C) glycine D) GABA

B) glutamate

36) What membrane potential must generally be met in order to achieve threshold? A) -85 mV B) -70 mV C) -55 mV D) -30 mV

C) -55 mV

71) What best describes a converging circuit? A) One neuron communicates with multiple parts of the brain. B) One axon of an input neuron branches to make contact with multiple postsynaptic neurons. C) Axon terminals from multiple input neurons join onto a single postsynaptic neuron. D) An increasing number of neurons are excited down the pathway of the circuit.

C) Axon terminals from multiple input neurons join onto a single postsynaptic neuron.

45) When is the generation of an action potential impossible, no matter the strength of the stimulus? A) depolarization B) threshold C) absolute refractory period D) relative refractory period

C) absolute refractory period

13) What specific part of the neuron communicates with a target cell and serves as the secretory region of the cell? A) myelin sheath B) dendrites C) axon terminals (synaptic knobs) D) cell body

C) axon terminals (synaptic knobs)

49) The majority of synapses in the nervous system are: A) electrical. B) voltage. C) chemical. D) mechanical.

C) chemical.

30) The influx of positive charges makes the membrane potential more positive and is known as: A) polarization. B) repolarization. C) depolarization. D) hyperpolarization.

C) depolarization.

31) A series of measurements with a voltmeter show a neuron's membrane potential becoming more negative, from -70 mV to -85 mV. This neuron is experiencing a: A) depolarization phase. B) repolarization phase. C) hyperpolarization phase. D) polarization phase.

C) hyperpolarization phase

17) What type of neuron is found within the CNS to perform the job of information processing? A) bipolar neurons B) motor (efferent) neurons C) interneurons (association neurons) D) sensory (afferent) neurons

C) interneurons (association neurons)

25) Which of the following is the primary factor in the maintenance of a negative charge during resting membrane potential? A) ligand-gated channels B) voltage-gated channels C) leak channels D) sodium-potassium pump

C) leak channels

32) Graded potentials: A) produce an effect that increases with distance from the point of stimulation. B) produce an effect that spreads actively across the membrane surface. C) may cause either a depolarization or a hyperpolarization. D) cause repolarization.

C) may cause either a depolarization or a hyperpolarization.

106) Discuss the two main factors to influence conduction speed of an action potential.

Conduction speed is influenced by two main factors: 1) diameter of the axon, and 2) presence or absence of a myelin sheath. Larger axons have lower resistance to the conduction of an action potential, and current flows through them more easily. Saltatory conduction occurs in the presence of a myelin sheath while continuous conduction occurs in the absence of a myelin sheath. Since myelin is an excellent insulator of electrical charge, the flow of current is far more efficient in a myelinated axon. Therefore, saltatory conduction is significantly faster than continuous conduction.

119) Describe the type of neural circuit that controls skeletal muscle movement.

Converging circuits are important for controlling skeletal muscle movement. The interneurons in the spinal cord receive input from neurons in different regions of the brain, which then converge to synapse on the motor efferent neurons that stimulate motor neuron contraction.

43) Determine the membrane potential (mV) during the relative refractory period. A) -85 mV B) -55 mV C) +15 mV D) +30 mV

D) +30 mV

42) Which area on the graph shows when the neuron is in the refractory period?

D) 4

35) Which statement best describes the all-or-none principle? A) Local, or graded, potentials will always become action potentials. B) All voltage-gated sodium channels will open or none will open. C) All neurons conduct an action potential together, or none do. D) An action potential happens completely, or it doesn't happen at all.

D) An action potential happens completely, or it doesn't happen at all.

37) Which of the following is correct about threshold? A) Voltage-gated potassium channels inactivate. B) Voltage-gated potassium channels begin to close. C) The membrane begins to hyperpolarize. D) Threshold is more positive than the resting potential.

D) Threshold is more positive than the resting potential.

59) A local hyperpolarization that changes a postsynaptic neuron's membrane from resting potential to -85 mV is: A) a temporal stimulus. B) an excitatory postsynaptic potential (EPSP). C) a saltatory stimulus. D) an inhibitory postsynaptic potential (IPSP).

D) an inhibitory postsynaptic potential (IPSP).

5) Which nervous system division is responsible for the integration of sensory information? A) visceral motor division B) peripheral nervous system C) somatic motor division D) central nervous system

D) central nervous system

9) Which of the following is NOT a function of neurons? A) carrying sensory information B) integration C) transmitting motor information D) forming the myelin sheath

D) forming the myelin sheath

70) Neuronal pools are collections of: A) bipolar neurons. B) motor neurons. C) efferent neurons. D) interneurons.

D) interneurons.

44) Voltage-gated sodium channels are activated: A) after voltage-gated potassium channels are activated. B) during repolarization. C) during hyperpolarization. D) only if the cell is depolarized to threshold.

D) only if the cell is depolarized to threshold.

7) Sarah sensed a mosquito land on her arm and swatted it away with her hand. Which specific PNS division was responsible for the movement of Sarah's hand? A) visceral sensory division B) somatic sensory division C) autonomic nervous system D) somatic motor division

D) somatic motor division

24) Within the PNS, a neuron will regenerate only if: A) the surrounding neuroglia regenerate first. B) the neuron was myelinated. C) scar tissue is removed by phagocytosis. D) the cell body remains intact.

D) the cell body remains intact.

105) Why is a neuron unable to produce an additional action potential during the absolute refractory period?

During the absolute refractory period, sodium ion channels may not be activated until they return to their resting states with their activation gates closed and their inactivation gates open. It is during this period that an additional action potential cannot be produced, no matter how strong the stimulus

72) The sensory, or afferent, division of the peripheral nervous system carries information from the brain and spinal cord to effector organs.

False

76) The conduction of an action potential is faster in unmyelinated axons than in myelinated axons.

False

80) Saltatory conduction is slow due to the presence of insulating myelin around an axon.

False

112) Receptors on a postsynaptic CNS neuron bind glutamate. Describe how the postsynaptic neuron responds.

Glutamate is the most common excitatory neurotransmitter in the CNS. Upon binding glutamate, the postsynaptic neuron opens channels that can pass both sodium and calcium ions. The postsynaptic neuron will experience an EPSP.

98) Since Jerry's accident, he has had no sensations in his injured leg. Based on the functional classifications of neurons, explain the type of neuron that has been damaged. Why has he not regained lost nerve function?

Jerry has damaged a sensory, or afferent, neuron. Sensory neurons carry information toward the central nervous system. Sensory neurons receive information from sensory receptors and transmit this information to their cell bodies in the PNS, then down their axons to the brain or spinal cord. Jerry has not regained sensation in this injured leg because most neurons are amitotic, meaning that neurons have lost the ability to undergo mitosis and repair themselves. These neurons did not regenerate causing permanent loss of sensation.

102) Explain how leak channels and gated channels differ.

Leak channels are always open while gated channels are closed at rest. Gated channels only open in response to certain stimuli. Leak channels allow ions to follow their gradient into or out of the cell. Gated channels may be ligand-gated, voltage-gated, or mechanically gated. Ligand-gated channels open in response to a chemical binding to the channel while voltage-gated channels open or close in response to changes in voltage across the membrane. Mechanically gated channels open in response to mechanical stimulation such as stretch, pressure, or vibrations.

100) Discuss the type of glial cell that becomes activated within a brain region affected by stroke.

Microglia are activated by injury within the brain, such as stroke, and become wandering phagocytes that clean up the environment in the brain. When activated, microglia ingest dead neurons and other cellular debris.

115) Multiple sclerosis (MS) is a disease in which the myelin sheaths are destroyed in the brain and spinal cord. With what process does this interfere and what would be the consequences?

Myelin sheaths allow the action potential to propagate more quickly along the length of an axon during saltatory conduction. Demyelination results in slower propagation and even permanent cessation of nerve impulse transmission.

101) Relate the speed of conduction of an action potential to myelination.

Myelination makes an excellent insulator of electrical current for neurons with myelin sheaths. The insulating effect increases the speed of conduction of action potentials. In fact, myelinated neurons conduct action potentials about 15-150 times faster than unmyelinated axons.

113) Explain the purpose of a neuronal pool.

Neuronal pools are networks of interneurons in the CNS that perform a common function. The connections between pools allow for complex mental activity such as planned movement, cognition, and personality.

99) Discuss the neuroglial cells that form the myelin sheaths in the CNS and the PNS and some of their differences.

Oligodendrocytes wrap the axons of certain neurons in the CNS. The wrapped processes, collectively called myelin, form repeating processes that create a myelin sheath. Schwann cells form the myelin sheath around PNS axons. Although both oligodendrocytes and Schwann cells wrap axons in successively tighter bands, they do so in opposite directions from one another: Schwann cells wrap outward away from the axon while oligodendrocytes wrap inward toward the axon. Other differences between oligodendrocytes and Schwann cells include the presence or absence of a neurolemma, the number of axons myelinated by a single glial cell, and the timing of myelination. Schwann cells have a neurolemma, whereas oligodendrocytes do not. A single Schwann cell can only myelinate one axon, whereas one oligodendrocyte can help myelinate many axons. Schwann cells start myelinating axons earlier in fetal development than oligodendrocytes.

104) The porcupinefish produces a toxin that binds voltage-gated sodium channels. Determine the effect of the toxin on nerve function.

The axon of the neuron would be unable to generate action potentials. The activation of voltage-gated sodium channels is critical for the influx of sodium ions into the cell along their electrochemical gradient. Depolarization is dependent upon the influx of sodium ions (to about +30 mV).

114) While driving home, Henry watched as a large truck drifted into his lane from oncoming traffic. Henry's central nervous system integrated this information to determine the position of his own vehicle, and then he made a decision to swerve his vehicle closer to the side of the road to avoid a head-on collision. From this scenario, determine the sensory information and his motor functions.

The collection of information about one's internal and external environment qualifies as the sensory information. In this example, Henry noticed the truck heading into his lane from oncoming traffic using visual input. Upon integrating the information, Henry made a decision to initiate motor output to his skeletal muscles to swerve his vehicle closer to the side of the road.

109) A postsynaptic neuron is bombarded by synaptic inputs from several hundred presynaptic neurons. However, this neuron does not appear to transmit an impulse. Propose an explanation of why this could occur.

The input from each presynaptic neuron may be either excitatory or inhibitory. The postsynaptic neuron integrates this information into a single effect known as neural integration. In this situation, the IPSPs outnumber the EPSPs, and the neuron is inhibited from generating an action potential. The numerous IPSPs hyperpolarize the postsynaptic neuron.

103) Discuss the two main factors involved in the generation of a neuron's resting membrane potential.

The main factor is the ease at which potassium ions cross the membrane and cause a net loss of positive ions from the cytosol. The cytosol constantly loses more positive charges than it gains, leading to the negative value of the resting membrane potential. The second factor, the Na+/K+ pump, maintains a sodium gradient and a potassium gradient by moving two potassium ions into the cytosol as it moves three sodium ions into the extracellular fluid.

96) Summarize the differences between the somatic motor division and the autonomic nervous system.

The somatic motor division consists of neurons that transmit signals to skeletal muscles. Skeletal muscle tissue is under voluntary control, so this division is sometimes called the voluntary motor division. By contrast, the autonomic nervous system consists of neurons that carry signals primarily to the thoracic and abdominal viscera. The ANS regulates secretions from certain glands and contractions of both smooth and cardiac muscle tissue. The ANS is sometimes called the involuntary motor division since it controls functions that are generally under involuntary control.

73) The autonomic nervous system carries signals to cardiac muscle, smooth muscle, and glands.

True

74) Neurons are responsible for sending and receiving signals referred to as action potentials while neuroglial cells serve a variety of supportive functions.

True

75) Bipolar neurons have one axon and one dendrite.

True

77) Regeneration of neural tissue in the PNS is possible only if the neuron's cell body remains intact

True

78) During depolarization, the membrane potential becomes more positive.

True

79) During the absolute refractory period, production of an action potential is not possible.

True

83) Calcium ion entry into the axon terminal is necessary for the release of neurotransmitter into the synaptic cleft.

True

84) Neurotransmitters can be either excitatory or inhibitory depending upon the receptor present on the postsynaptic neuron.

True

85) Converting neural circuits are opposite to diverging neural circuits.

True

97) Rabies is caused by a virus that attacks the central nervous system. The virus is normally introduced by an animal bite that breaks the surface of the skin. Since the virus is not motile, how does it travel to the central nervous system?

When the animal bite punctures the skin, some nerve receptors are physically damaged. The virus gains entrance to the neuron through these damaged axons. Retrograde axonal transport moves the virus toward the cell body and toward the central nervous system, where it can reproduce and spread.