Chapter 12 Nervous Tissue

The membrane potential - three important concepts

1. ECF and the ICF(cytosol) differ greatly in ionic composition (Concentration gradient of ions (Na+, K+) 2. Cells have selectively permeable membranes 3. Membrane permeability varies by ion

Neural tissue contains two kinds of cells

1. Neurons (main) 2. Neuroglia (glial cells - supporting)

Three Functional Classifications of Neurons are

1. Sensory neurons (afferent fibers) - information TO brain 2. Motor neurons (efferent fibers - axons) 3. Interneurons (association neurons)

Below are the events that occur during continuous propagation of action potential. Select the correct order in which the events occur. 1) Adjacent membrane segment depolarizes 2) Local current spreads to adjacent voltage gated channel 3) Threshold is met 4) Local current develops due to sodium moving in the cytosol

4,2,3,1

88) The equilibrium potential of potassium is A) -90mV. B) -65mV. C) -70mV. D) +30mV. E) +66mV.

A) -90mV.

102) Which area of the graph shows when voltage-gated sodium channels are open? A) 2 B) 4 C) 1 D) 5 E) 3

A) 2

___________ carry motor information to peripheral effectors. A) Efferent neurons B) Interneurons C) Unipolar neurons D) Multipolar neurons E) Afferent neurons

A) Efferent neurons

Which of the following types of nerve fiber possesses the fastest speed of impulse propagation? A) Type A B) Type E C) Type B D) Type D E) Type C

A) Type A

A deficiency in which neurotransmitter would cause Parkinson's-like symptoms? A) dopamine B) norepinephrine C) serotonin D) GABA E) endorphins

A) dopamine

The site of intercellular communication between a neuron and another cell is the A) synapse B) hillock C) collateral D) telodendria E) axolemma

A) synapse

When potassium channels open and the ions diffuse through the membrane, A) the inside of the membrane will become more negative B) the inside of the membrane will become more positive C) the membrane will depolarize to threshold D) the membrane will become depolarized E) there will be almost no effect on transmembrane potential

A) the inside of the membrane will become more negative

Sensory neurons of the PNS are A) unipolar B) anaxonic C) tripolar D) bipolar E) multipolar

A) unipolar

Which of the following does not influence the time necessary for a nerve impulse to be transmitted? A) whether or not the impulse begins in the CNS B) length of the axon C) presence of absence of myelin sheath D) diameter of the axon E) presence or absence of nodes

A) whether or not the impulse begins in the CNS

34) Identify the structure labeled "5."

Axon Terminals

101) Which area of the graph shows when chemically gated sodium channels are open? A) 3 B) 1 C) 2 D) 5 E) 4

B) 1

104) In which area of the graph do you see a sudden rush of sodium ions into the neuron? A) 1 B) 2 C) 3 D) 4

B) 2

Cholinergic synapses release the neurotransmitter A) GABA B) acetylcholine C) serotonin D) adrenalin E) norepinephrine

B) acetylcholine

Neurotransmitters ready for release are stored in the synaptic A) mitochondria B) vesicles C) telodendria D) neurosomes E) terminals

B) vesicles

103) Which area of the graph shows when potassium channels open? A) 1 B) 2 C) 3 D) 4

C) 3

106) Which point of the graph shows when potassium ion outflow exceeds sodium ion inflow? A) 1 B) 2 C) 3 D) 4

C) 3

Which area of the graph shows when potassium channels open? A) 1 B) 2 C) 3 D) 4

C) 3

30) The structures labeled "1" are dendrites. Their membranes contain numerous chemically-gated ion channels. A) The first statement is true but the second statement is false. B) The first statement is false but the second statement is true. C) Both statements are true. D) Both statements are false.

C) Both statements are true. and relate to synaptic transmission

73) ________ open or close in response to binding specific molecules. A) Leak channels B) Activated channels C) Chemically gated channels D) Voltage-gated channels E) Voltage-gated and chemically gated channels

C) Chemically gated channels

99) What is occurring at the area labeled #4? A) An inhibitory stimulus has occurred. B) Chemically gated potassium channels have opened. C) Excessive potassium has diffused out causing hyperpolarization. D) Sodium ions have been pumped out of the neuron. E) Excessive depolarization of the axon has occurred.

C) Excessive potassium has diffused out causing hyperpolarization.

41) ________ monitor the digestive, respiratory, cardiovascular, urinary, and reproductive systems. A) Spinal nerves B) Unipolar neurons C) Internoceptors D) Exteroceptors E) Proprioceptors

C) Internoceptors (Interoceptors)

105) Which area of the graph shows when membrane potential approaches the potassium equilibrium potential? A) 1 B) 2 C) 3 D) 4

D) 4

107) When is the neuron in the relative refractory period? A) 1 B) 2 C) 3 D) 4

D) 4

39) ________ carry sensory information to the CNS. A) Motor neurons B) Efferent neurons C) Multipolar neurons D) Afferent neurons E) Interneurons

D) Afferent neurons

40) ________ provide information about the external environment. A) Spinal nerves B) Anaxonic neurons C) Internoceptors D) Exteroceptors E) Proprioceptors

D) Exteroceptors

74) ________ channels open or close in response to physical distortion of the membrane surface. A) Voltage-gated B) Chemically gated C) Active D) Mechanically gated E) Leak

D) Mechanically gated

100) What is occurring in the area between #2 and #3? A) An excitatory graded potential is occurring. B) Potassium ions are entering the axon and causing depolarization. C) Chemically gated sodium channels are open and sodium is diffusing into the axon. D) Sodium ions are entering the axon and causing depolarization. E) Repolarization of the axon due to sodium ions leaving the axon is occurring.

D) Sodium ions are entering the axon and causing depolarization.

98) Puffer fish poison blocks voltage-gated sodium channels like a cork. What effect would this neurotoxin have on the function of neurons? A) Neurons would depolarize more rapidly. B) Action potentials would lack a repolarization phase. C) The absolute refractory period would be shorter than normal. D) The axon would be unable to generate action potentials. E) None, because the chemically gated sodium channels would still function.

D) The axon would be unable to generate action potentials.

29) How does blocking retrograde axoplasmic transport in an axon affect the activity of a neuron? A) The neuron becomes unable to produce neurotransmitters. B) The neuron becomes unable to produce action potentials. C) The soma becomes unable to export products to the synaptic terminals. D) The soma becomes unable to respond to changes in the distal end of the axon. E) The neuron becomes unable to depolarize when stimulated.

D) The soma becomes unable to respond to changes in the distal end of the axon.

84) If acetylcholine (ACh) causes inhibition of a postsynaptic neuron, to what type of membrane channel did the ACh bind? A) mechanically-regulated channel B) voltage-regulated sodium channel C) voltage-regulated calcium channel D) chemically-regulated potassium channel E) chemically-regulated sodium channel

D) chemically-regulated potassium channel

What triggers the release of acetylcholine from a synaptic terminal? A) synaptic vesicles fuse to dendrites B) release of calcium ions from the synaptic vesicles C) graded potentials in the synaptic terminals D) diffusion of calcium ions into the synaptic terminal E) diffusion of sodium ions out of the synaptic terminal

D) diffusion of calcium ions into the synaptic terminal

Sensory information from skeletal muscles travels over ___________ fibers. A) type C B) type B C) type D D) type A E) type E

D) type A

89) The equilibrium potential of sodium is A) -90mV. B) -65mV. C) -70mV. D) +30mV. E) +66mV.

E) +66mV.

The effect that a neurotransmitter has on a postsynaptic membrane depends on A) the nature of the neurotransmitter B) the quantity of neurotransmitters released C) the frequency of neurotransmitter release D) the characteristics of the receptors E) All of the answer are correct

E) All of the answer are correct

12) The axoplasm of the axon contains which of the following? A) neurotubules B) mitocondria C) vesicles D) neurofibrils E) All of the answers are correct.

E) All of the answers are correct.

75) Any stimulus that opens a ________ ion channel will produce a graded potential. A) voltage-gated B) chemically gated C) sodium D) mechanically gated E) All of the answers are correct.

E) All of the answers are correct.

81) Ions can move across the plasma membrane in which of the following ways? A) through voltage-gated channels as in the action potential B) through passive or leak channels C) by ATP-dependent ion pumps like the sodium-potassium exchange pump D) through chemically gated channels as in neuromuscular transmission E) All of the answers are correct.

E) All of the answers are correct.

66) Which of the following can cause demyelination? A) arsenic poisoning B) diphtheria C) multiple sclerosis D) mercury exposure E) Demyelination can be caused by arsenic, diphtheria, multiple sclerosis and mercury.

E) Demyelination can be caused by arsenic, diphtheria, multiple sclerosis and mercury.

95) How would a chemical that prevents the opening of voltage-regulated Na+ channels affect the function of a neuron? A) The neuron will only be able to hyperpolarize. B) The neuron will depolarize more rapidly. C) Action potentials will lack a repolarization phase. D) The neuron will automatically and repeatedly produce graded potentials. E) The neuron will only be capable of producing graded potentials.

E) The neuron will only be capable of producing graded potentials.

64) Which of the following is not a function of astrocytes? A) They create a three dimensional framework for the CNS. B) They maintain the blood-brain barrier. C) They guide neuron development. D) They rebuild injured neurons. E) They adjust the composition of the interstitial tissue.

E) They adjust the composition of the interstitial tissue.

If the axon terminal of a motor neuron suddenly became permeable to calcium ion, A) neurotransmitter release will be blocked B) the neuron will become unable to stimulate the muscle cell C) the neuron will fire an action potential D) the motor end plate will be hyperpolarized E) the motor end plate will be depolarized

E) the motor end plate will be depolarized

54) ________ line the brain ventricles and spinal canal.

Ependymal cells

44) The most common neuron of the nervous system is the

Interneuron

___________ neurons are the most common class in CNS.

Multipolar

51) ________ account for roughly half of the volume of the nervous system.

Neuroglia

16) Clusters of RER and free ribosomes in neurons are called

Nissl bodies

____________ neurons form the afferent division of the PNS.

Sensory

10) ________ nerves are nerves that connect to the spinal cord.

Spinal

33) Identify the structure labeled "4."

Telodendria

The period during which an excitable membrane cannot respond to further stimulation is the

absolute refractory period

6) The ________ division of the peripheral nervous system brings sensory information to the central nervous system.

afferent

22) Neurons that are rare, small, and lack features that distinguish dendrites from axons are called

anaxonic

52) The neuroglial cells that participate in maintaining the blood-brain barrier are the

astrocytes

8) The ________ nervous system provides involuntary regulation of smooth muscle, cardiac muscle, and glandular activity.

autonomic

42) The plasma membrane of an axon is called the

axolemma

Wallerian degeneration

axon distal to injury degenerates and Schwann cells form new path for new growth and wrap new axon in myelin

17) The axon is connected to the soma at the

axon hillock

24) Neurons that have one axon and one dendrite, with the soma in between, are called

bipolar

The sensory loss and muscle weakness associated with multiple sclerosis are a consequence of

demyelination

7) The ________ division of the nervous system carries motor commands to muscles and glands.

efferent

The sum of the electrical and chemical forces acting on an ion is known as its

electrochemical gradient

Neuron cells bodies in the PNS are clustered together in masses called

ganglia

55) Small, wandering cells that engulf cell debris and pathogens in the CNS are called

microglia

After a stroke what type of glial cell accumulates within the affected brain region?

microglia

25) Neurons that have several dendrites and a single axon are called

multipolar

The presence of _____________ dramatically increases the speed at which an action potential moves along the axon.

myelin

What is contained inside the structure labeled "5"?

neurotransmitter molecules

31) The structure labeled "2" is a(n)

soma, cell body

The minimum stimulus required to trigger an action potential is known as the

threshold

62) Regions of the CNS with an abundance of myelinated axons constitute the ________ matter.

white

68) At the normal resting membrane potential of a typical neuron, its sodium-potassium exchange pump transports

3 intracellular sodium ions for 2 extracellular potassium ions

67) Which of the following is not true regarding the establishment of a neuron's resting membrane potential? A) Chemical and electrical forces both favor sodium ions entering the cell. B) Electrical forces do not push sodium ions into the cell. C) The chemical gradient for potassium ions tends to drive them out of the cell. D) Ion pumps in the plasma membrane eject sodium ions as fast as they cross the membrane. E) Resting membrane permeability to Na+ is very low.

B) Electrical forces do not push sodium ions into the cell.

87) A shift of the resting transmembrane potential toward 0 mV is called A) potential difference. B) depolarization. C) hyperpolarization. D) polarization. E) repolarization.

B) depolarization.

80) When potassium channels open and the ions diffuse through the membrane, A) the inside of the membrane will become more positive. B) the inside of the membrane will become more negative. C) there will be almost no effect on transmembrane potential. D) the membrane will become depolarized. E) the membrane will depolarize to threshold.

B) the inside of the membrane will become more negative.

86) The sum of the electrical and chemical forces acting on an ion is known as its A) permeability gradient. B) thermodynamic difference. C) electrochemical gradient. D) action potential. E) summation difference.

C) electrochemical gradient.

71) Voltage-gated channels are present A) at the motor end plate. B) on the surface of dendrites. C) in the membrane that covers axons. D) on the soma of neurons. E) along the perikaryon of neurons.

C) in the membrane that covers axons.

32) Which type of membrane channels are found at label "3"? A) voltage-gated Na+ channels B) voltage-gated K+ channels C) chemically-gated Na+ and K+ channels D) voltage-gated Ca2+ channels E) both voltage-gated Na+ channels and voltage-gated K+ channels

E) both voltage-gated Na+ channels and voltage-gated K+ channels

9) ________ carry motor information to peripheral effectors.

efferent division

4) The efferent division of the peripheral nervous system innervates ________ cells.

glandular smooth muscle skeletal muscle heart muscle

63) Regions of the CNS where neuron cell bodies dominate constitute the ________ matter.

gray

43) The basic functional unit of the nervous system is the

neuron

77) Which of the following is not involved in creating the resting membrane potential of a neuron? A) diffusion of potassium ions out of the cell B) diffusion of sodium ions into the cell C) membrane permeability for sodium ions greater than potassium ions D) membrane permeability for potassium ions greater than sodium ions E) The interior of the plasma membrane has an excess of negative charges.

C) membrane permeability for sodium ions greater than potassium ions

91) The all-or-none principle states that A) all stimuli will produce identical action potentials. B) all stimuli great enough to bring the membrane to threshold will produce identical action potentials. C) the greater the magnitude of the stimuli, the greater the magnitude of the action potential. D) only sensory stimuli can activate action potentials. E) only motor stimuli can activate action potentials.

B) all stimuli great enough to bring the membrane to threshold will produce identical action potentials.

65) All of the following cause demyelination except A) heavy-metal ion poisoning. B) diphtheria. C) multiple sclerosis. D) dopamine deficiency. E) All of these cause demyelination.

D) dopamine deficiency.

13) Which of the following is not a recognized structural classification for neurons? A) anaxonic B) bipolar C) multipolar D) pseudopolar E) unipolar

D) pseudopolar

2) The ________ nervous system controls the skeletal muscles.

Peripheral

46) Deteriorating changes in the distal segment of an axon as a result of a break between it and the soma is called ________ degeneration.

Wallerian

3) The part of the peripheral nervous system that carries sensory information to the CNS is designated

afferent division

18) Branches that may occur along an axon are called

collaterals

37) On which structure do most neuron to neuron communications occur?

dendrite

70) Opening of sodium channels in the axon membrane causes

depolarization

76) If the permeability of a resting axon to sodium ion increases, A) the membrane potential will repolarize. B) the membrane potential will hyperpolarize. C) inward movement of sodium ion will increase. D) outward movement of sodium ion will decrease. E) inward movement of sodium will increase and the membrane will depolarize.

inward movement of sodium will increase and the membrane will depolarize.

61) The tiny gaps between adjacent Schwann cells are called

nodes (Nodes of Ranvier)

57) Glial cells that surround the neurons in ganglia are

satellite cells

20) The site of intercellular communication between a neuron and another cell is the

synapse

35) What is contained inside the structure labeled "5"?

synaptic vesicles

19) Axons terminate in a series of fine extensions known as

telodendria

23) Neurons in which dendritic and axonal processes are continuous and the soma lies off to one side are called

unipolar

26) Sensory neurons of the PNS are

unipolar

36) Which part(s) of the neuron can propagate an action potential?

3- axon

90) The following are the main steps in the generation of an action potential. Arrange them in sequence 1. Sodium channels are inactivated. 2. Voltage-gated potassium channels open and potassium moves out of the cell, initiating repolarization. 3. Sodium channels regain their normal properties. 4. A graded depolarization brings an area of an excitable membrane to threshold. 5. A temporary hyperpolarization occurs. 6. Sodium channel activation occurs. 7. Sodium ions enter the cell and depolarization occurs.

4,6,7,1,2,3,5

97) Which of the following is true about threshold for an action potential? A) It is more positive than the resting membrane potential. B) Voltage-gated potassium channels begin to close. C) Voltage-gated potassium channels begin to open. D) The membrane begins to hyperpolarize. E) Threshold for a typical neuron is approximately -30 mV.

A) It is more positive than the resting membrane potential.

38) ________ monitor the position of skeletal muscles and joints. A) Proprioceptors B) Internoceptors C) Photoreceptors D) Exteroceptors E) Pressoreceptors

A) Proprioceptors

92) Which of the following statements about the action potential is false? A) The rapid depolarization phase is caused by the entry of potassium ions. B) During the repolarization phase, sodium channels close and potassium channels open. C) During the depolarization phase, membrane potential becomes positive. D) During the hyperpolarization phase, the ion pumps re-establish the sodium and potassium concentrations across the cell membrane. E) Repolarization occurs as potassium ions leave the axon.

A) The rapid depolarization phase is caused by the entry of potassium ions.

49) The largest and most numerous of the glial cells in the central nervous system are the A) astrocytes. B) satellite cells. C) oligodendrocytes. D) microglia. E) ependymal cells.

A) astrocytes.

85) A movement of charges in response to a potential difference is called A) current. B) depolarization. C) hyperpolarization. D) action potential. E) electricity.

A) current.

96) A threshold stimulus is the A) depolarization necessary to cause an action potential. B) peak of an action potential. C) hyperpolarization of an axon. D) resting membrane potential. E) electrical current that crosses the synaptic cleft.

A) depolarization necessary to cause an action potential.

83) Voltage-gated sodium channels have both an activation gate and a(n) ________ gate. A) inactivation B) ion C) swinging D) repolarization E) threshold

A) inactivation

27) Which of the following activities or sensations is/are not monitored by interoceptors? A) sight B) pain C) activities of the digestive system D) cardiovascular activities E) urinary activities

A) sight

78) If the sodium-potassium pumps in the plasma membrane fail to function, all of the following occur except A) the intracellular concentration of potassium ions will increase. B) the neuron will slowly depolarize. C) the membrane will slowly lose its capacity to generate action potentials. D) the inside of the membrane will have a resting membrane potential that is more positive than normal. E) the intracellular concentration of sodium ions will increase.

A) the intracellular concentration of potassium ions will increase.

50) Functions of astrocytes include all of the following except A) maintaining the blood-brain barrier. B) conducting action potentials. C) guiding neuron development. D) responding to neural tissue damage. E) forming a three-dimensional framework for the CNS.

B) conducting action potentials.

47) Which of the following is not a function of the neuroglia? A) support B) memory C) secretion of cerebrospinal fluid D) maintenance of blood-brain barrier E) phagocytosis

B) memory

94) During repolarization of a neuron A) sodium ions move out of the cell. B) potassium ions move out of the cell. C) potassium ions move into the cell. D) both sodium and potassium ions move into the cell. E) sodium ions move into the cell.

B) potassium ions move out of the cell.

21) The rabies virus travels to the CNS via A) anterograde axoplasmic transport. B) retrograde axoplasmic transport. C) blood vessels. D) subcutaneous connective tissue. E) cerebrospinal fluid.

B) retrograde axoplasmic transport.

48) Which of the following is a type of glial cell found in the peripheral nervous system? A) astrocytes B) satellite cells C) oligodendrocytes D) microglia E) ependymal cells

B) satellite cells

93) How would the absolute refractory period be affected if voltage-regulated sodium channels failed to inactivate? A) It would last indefinitely. B) It would be much briefer. C) It would be basically unaffected.

C) It would be basically unaffected. (the membrane cannot respond to further stimuli)

60) In the peripheral nervous system, Schwann cells participate in the repair of damaged nerves by A) producing new axons. B) regenerating cell bodies for the neurons. C) forming a cellular cord that directs axonal regrowth. D) clearing away cellular debris. E) producing more satellite cells that fuse to form new axons.

C) forming a cellular cord that directs axonal regrowth.

69) Ion channels that are always open are called ________ channels. A) active B) gated C) leak D) regulated E) local

C) leak

79) 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 be either a depolarization or a hyperpolarization. D) are often all-or-none. E) cause repolarization.

C) may be either a depolarization or a hyperpolarization.

14) The most abundant class of neuron in the central nervous system is A) anaxonic. B) bipolar. C) multipolar. D) pseudopolar. E) unipolar.

C) multipolar.

58) Damage to ependymal cells would most likely affect the

CSF - cerebrospinal fluid

1) The ________ nervous system is composed of the brain and spinal cord.

Central

11) ________ nerves are nerves that connect to the brain.

Cranial

72) The sodium-potassium ion exchange pump A) must reestablish ion concentrations after each action potential. B) transports sodium ions into the cell during depolarization. C) transports potassium ions out of the cell during repolarization. D) moves sodium and potassium opposite to the direction of their electrochemical gradients. E) depends on a hydrogen gradient for energy.

D) moves sodium and potassium opposite to the direction of their electrochemical gradients.

82) Raising the potassium ion concentration in the extracellular fluid surrounding a nerve cell will have what effect? A) depolarize it B) hyperpolarize it C) increase the magnitude of the potassium equilibrium potential D) decrease the magnitude of the potassium equilibrium potential E) both hyperpolarize it and decrease the magnitude of the potassium equilibrium potential

E) both hyperpolarize it and decrease the magnitude of the potassium equilibrium potential

59) When pressure is applied to neural tissue, all of the following effects are possible except A) a decrease in blood flow. B) a decrease in available oxygen. C) a change in neuron excitability. D) glial cells degenerate. E) neurons are triggered to divide.

E) neurons are triggered to divide.

15) The cytoplasm that surrounds the nucleus of a neuron is called the A) protoplasm. B) nucleoplasm. C) sarcoplasm. D) neuroplasm. E) perikaryon.

E) perikaryon.

5) The nervous tissue outside of the central nervous system composes the ________ nervous system.

Peripheral

56) The neurilemma of axons in the peripheral nervous system is formed by

Schwann cells

45) Most neurons lack ________ and so are permanently blocked from undergoing cell division.

centrioles

28) ________ are the most numerous type of neuron in the CNS.

multipolar

53) The myelin sheath that covers many CNS axons is formed by

oligodendrocytes