SECOND FUCKING UNIT QUIZ PHS 101

A patient develops a disorder affecting the myelin of axons within the central nervous system. Which glial cell is primarily responsible for forming this myelin?

A. Astrocyte
B. Microglia
C. Oligodendrocyte
D. Schwann cell

C. Oligodendrocyte

A patient suffers a peripheral nerve injury. The portion of the axon distal to the injury becomes swollen and the myelin develops bead-like structures. What process is occurring?

A. Saltatory conduction
B. Wallerian degeneration
C. Temporal summation
D. Anterograde transport

B. Wallerian degeneration

A toxin blocks kinesin activity in a neuron. Which process would be most directly impaired?

A. Transport from axon terminal to soma
B. Transport from soma to axon terminal
C. Neurotransmitter diffusion across the synapse
D. Continuous conduction

B. Transport from soma to axon terminal

Several different presynaptic neurons simultaneously provide subthreshold stimuli to a postsynaptic neuron. Their combined effect reaches threshold. What mechanism is responsible?

A. Temporal summation
B. Spatial summation
C. Absolute refractory period
D. Saltatory conduction

B. Spatial summation

A neuron has a resting membrane potential of −70 mV. A stimulus changes the membrane potential to −55 mV. What type of change has occurred?

A. Hyperpolarization
B. Depolarization
C. Repolarization
D. Refractoriness

B. Depolarization

A patient receives a local anesthetic before a minor surgical procedure. The drug decreases neuronal excitability by acting on sodium channels. Which effect is most consistent with the reviewer?

A. Increased sodium permeability
B. Decreased neuronal excitability
C. Increased action-potential amplitude
D. Increased neurotransmitter secretion

B. Decreased neuronal excitability

A patient has damage to the myelin surrounding peripheral nerve fibers. Which cells are primarily affected?

A. Astrocytes
B. Oligodendrocytes
C. Schwann cells
D. Microglia

C. Schwann cells

A patient has impaired saltatory conduction due to damage to specialized gaps along a myelinated axon. Which structures are damaged?

A. Nissl bodies
B. Nodes of Ranvier
C. Axon terminals
D. Dendrites

B. Nodes of Ranvier

A toxin blocks voltage-gated sodium channels in a neuron. Which phase of the action potential would be most directly affected?

A. Depolarization
B. Repolarization
C. Hyperpolarization
D. Resting potential

A. Depolarization

A neuron's resting membrane potential is −70 mV and its threshold is −55 mV. Approximately how much depolarization is required to reach threshold?

A. 5 mV
B. 10 mV
C. 15 mV
D. 25 mV

C. 15 mV

A patient develops a condition that decreases the diameter of a peripheral nerve fiber while its myelin remains intact. What would most likely happen to conduction velocity?

A. It increases
B. It decreases
C. It becomes independent of fiber diameter
D. It becomes completely absent

B. It decreases

A patient's laboratory results show significantly increased extracellular Ca²⁺ concentration. According to the reviewer, what effect would this have on neuronal excitability?

A. Increase excitability
B. Decrease excitability
C. Cause continuous action potentials
D. Have no effect on neuronal membranes

B. Decrease excitability

A patient with alkalosis develops increased neuronal excitability. Which statement best explains this finding?

A. Alkalosis decreases neuronal excitability
B. Alkalosis increases neuronal excitability
C. Alkalosis prevents sodium influx
D. Alkalosis causes Wallerian degeneration

B. Alkalosis increases neuronal excitability

A patient develops a disorder affecting cells lining the brain's ventricles, resulting in impaired CSF production and regulation. Which cells are involved?

A. Microglia
B. Astrocytes
C. Ependymal cells
D. Satellite cells

C. Ependymal cells

A sensory receptor in the skin detects a painful stimulus and sends an impulse toward the spinal cord. What functional type of neuron carries this signal?

A. Motor neuron
B. Interneuron
C. Sensory neuron
D. Efferent neuron

C. Sensory neuron

A researcher applies increasingly stronger stimuli to a nerve. The amplitude of each action potential remains the same, but the number of action potentials increases. How is stimulus intensity being encoded?

A. Increased action-potential amplitude
B. Increased impulse frequency
C. Increased myelin thickness
D. Increased axon diameter

B. Increased impulse frequency

A lesion damages the axon hillock of a neuron. Which function would be most directly affected?

A. Production of CSF
B. Generation of the initial action potential
C. Phagocytosis of damaged tissue
D. Formation of peripheral myelin

B. Generation of the initial action potential

A drug interferes with the absolute refractory period of a neuron. Which normal function of this period would be affected?

A. Formation of myelin
B. Production of neurotransmitters
C. Separation of successive action potentials and one-way transmission
D. Maintenance of the blood-brain barrier

C. Separation of successive action potentials and one-way transmission

A patient has a peripheral nerve injury. The proximal portion of the damaged axon begins growing toward the separated portion at approximately 1–4 mm/day. Which statement is most accurate?

A. Peripheral axons can regenerate
B. CNS axons regenerate more effectively than PNS axons
C. The distal axon remains completely functional
D. Regeneration occurs through ependymal cells

A. Peripheral axons can regenerate

A neurologic disorder damages glial cells that normally encapsulate ganglion cells in the peripheral nervous system. Which cells are affected?

A. Satellite cells
B. Oligodendrocytes
C. Ependymal cells
D. Microglia

A. Satellite cells

Distribution of sodium channels in a neuron are greatest at the

a.) nodes of Ranvier

b.) myelin sheath surface

c.) axon hillock

d.) terminal endings

a.) nodes of Ranvier

Which of the following contain channels formed by hemichannels called connexons and are the morphological correlate of electrical synapses?

a.) gap junctions

b.) synaptic cleft

c.) presynaptic membrane

d.) synaptic vesicle

a.) gap junctions

Which of the following is a local hypopolarization of the postsynaptic membrane that can bring the neuron to threshold potential?

a.) Excitatory Post Synaptic Potential

b.) Inhibitory Post Synaptic Potential

c.) Suppression Potential

d.) Miniature End Plate Potential

a.) Excitatory Post Synaptic Potential

Which of the following can occur when the same synapse is activated multiple times in rapid succession because axons can fire action potentials at rates well over 100 Hz?

a.) Temporal summation

b.) Spatial summation

c.) Paired-Pulse facilitation

d.) Post-tetanic inhibition

a.) Temporal summation

Which functional zone of a neuron is mainly involve in AP generation?

a. Zone II

b. Zone I

c. Zone III

d. Zone IV

a. Zone II

Which of the following statements distinguishes excitatory chemical synapses in the brain?

a.) Temporal summation and spatial summation onto the postsynaptic cell increase the likelihood that a postsynaptic action potential will be evoked

b.) Excitation is produced by ligand-gated channels

c.) Ligand-gated channels increase permeability to both Na+ and K+

d.) Postsynaptic action potentials are triggered when a sufficient number of voltages-gated Na+ channels are opened by an EPP or by summating EPSPs

a.) Temporal summation and spatial summation onto the postsynaptic cell increase the likelihood that a postsynaptic action potential will be evoked

Which of the following control pain and pleasure by blocking the neurotransmitter Substance P which transmits pain impulses to the brain?

a.) Endorphin

b.) Glutamate

c.) Glycine

d.) Neuropeptide Y

a.) Endorphin

Membrane conductance at resting state is greater with

a) potassium

b) sodium

c) calcium

d) chloride

a) potassium

Which of the following statements is TRUE of relative refractory period?

a) The cell is able to fire a second action potential but a stronger than normal stimulus intensity is required

b) A cell is unable to fire a second action potential no matter how strongly it is stimulated

c) The cell is refractory because a large fraction of its Na+ channels are voltage activated and cannot be reopened until the membrane is repolarized

d) In this state the critical number of Na+ channels required to produce an action potential cannot be recruited

10. The minimum intensity of a stimulus capable of immediate

a) The cell is able to fire a second action potential but a stronger than normal stimulus intensity is required

The minimum intensity of a stimulus capable of immediate generation action potential is _________.

a) threshold stimulus intensity

b) maximal stimulus intensity

c) sub-threshold stimulus intensity

d) supra-maximal stimulus intensity

a) threshold stimulus intensity

The following statements are TRUE regarding saltatory conduction, EXCEPT

a) Does not depend on of the nerve membrane

b) It occurs only in myelinated fibers.

c) Has a slower velocity in cold than in warm conditions

d) Is faster than non-saltatory conduction in nerve fibers with

diameters around 10micrometer.

a) Does not depend on of the nerve membrane

The following are directly proportional to conduction velocity of an impulse, EXCEPT.

a) Negativity of RMP

b) Nerve diameter

c) Sodium conductance

d) Myelination

a) Negativity of RMP

Unmyelinated axons differ from myelinated axons in that they are

a) refractory for a longer period after excitation

b) sheathed in Schwann cells.

c) not capable of regeneration after section.

d) found only in the autonomic nervous system.

a) refractory for a longer period after excitation

The resting transmembrane potential (Vm ) of a nerve axon is essential for signal generation. Instantaneous elimination of which of the following would MOST RAPIDLY bring Vm close to 0 mV?

a) High membrane permeability to K+

b) Active transport of K+ out of the cell

c) Active transport of Na+ in of the cell

d) High membrane permeability to Na+

a) High membrane permeability to K+

Which ion influx is involved in neurotransmitter release in the pre-synaptic membrane?

a) Calcium

b) Sodium

c) Potassium

d) Chloride

a) Calcium

The nicotinic receptor at the motor end plate for acetylcholine is an example of an ion channel that is

a) ligand-gated channel

b) voltage-gated channel

c) leaky channel

d) none of the above

a) ligand-gated channel

Which of the following statements is TRUE of local potential?

a) The amplitude of the response is proportional to the stimulus intensity

b) It propagates down the entire length of the nerve fiber.

c) It maintains its size and shape as it is regenerated along

the axon

d) It is a much larger response in which the polarity of the

membrane potential actually overshoots

a) The amplitude of the response is proportional to the stimulus intensity

Neuron C responds to stimulation of neuron A with a propagated action potential only when neuron B (which terminates only on neuron C) is also simultaneously stimulated. Which of the following inferences is justified?

a) Neuron B releases an excitatory neurotransmitter

b) Neuron C releases glycine.

c) The synapse between A and C is axono-somatic.

d) The neurotransmitter released by neuron A opens K+

channels in neuron C.

a) Neuron B releases an excitatory neurotransmitter

Membrane depolarization in post synaptic terminal is due to

a) sodium influx

b) potassium influx

c) chloride influx

d) sodium efflux

a) sodium influx

Which of the following is NOT TRUE when volley of impulses travelling in a pre-synaptic neuron?

a) The generation of at least one action potential in the post-

synaptic neuron.

b) An increase in the permeability of the pre-synaptic nerve terminals to calcium.

c) Vesicles in the nerve endings to fuse with the cell membrane and release their contents.

d) Neurotransmitter to travel down the nerve axon.

a) The generation of at least one action potential in the post-

synaptic neuron

Which of the following is the usual site where action potentials

are generated because of its high concentration of necessary channels?

a) Axon hillock

b) Cell body

c) Dendrite

d) Axon

a) Axon hillock

Which of the following will NOT happen when a nerve cell membrane is depolarized by 5 mV?

a) An action potential is generated

b) Its permeability to sodium increases.

c) Sodium ions move into the cell to cause further depolarization.

d) Chloride ions move inwards down their electrochemical gradient.

a) An action potential is generated

Which nerve fiber is highly susceptible to conduction block by anesthesia?

a) Type C

b) Type D

c) Type A

d) Type B

a) Type C

Which of the ff is coupled to a G protein that initiates second messenger cascades that can ultimately affect ion channels? a)

a) Metabotropic receptors

b) Ionotropic receptors

c) Directly ligand gated receptors

d) Somatotropic receptors

a) Metabotropic receptors

Which of the following factors would decrease conduction

velocity of nerve fibers?

a) Decrease in fiber diameter

b) Myelination

c) Increase in temperature

d) Increase in surface area

a) Decrease in fiber diameter

Which of the following toxins inhibits the release of acetylcholine from alpha-motor neurons?

a) Botulinum toxin

b) Choleratoxin

c) Saxitoxin

d) Tetanus toxin

a) Botulinum toxin

Which of the following cells in the CNS is primarily involved in

the re-uptake of excitatory neurotransmitters released by neurons?

a) Astroglial cell

b) Microglial cell

c) Oligodendroglial cell

d) Ependymal cell

a) Astroglial cell

Transport of vesicles from the soma to the synaptic terminal requires all of the following, EXCEPT.

a) Dynein

b) Calcium

c) Metabolic energy

d) Kinesin

a) Dynein

Which of the following refers to the process by which a neuron

generates an action potential as a result of its inputs?

a) Synaptic integration

b) Synaptic current

c) Synaptic modulation

d) Synaptic depression

a) Synaptic integration

Which of the following is/are TRUE of an excitatory post synaptic potential (EPSP)?

a) Increase in sodium influx

b) Increase in potassium efflux

c) Increase in chloride influx

d) All of the choices are TRUE

a) Increase in sodium influx