Quiz - CH 08 Neurophysiology

All of the following are true except:

 

a) Under normal conditions, all action potentials in a given neuron are identical.

 

b) The amplitude (size) of an action potential depends on the amplitude (size) of the graded potential(s) that triggered it.

 

c) Increasing the concentration of K⁺ in the extracellular fluid will normally depolarize a neuron.

 

d) Between nodes of Ranvier, the action potential begins to weaken and so must be regenerated at the next node of Ranvier.

b) The amplitude (size) of an action potential depends on the amplitude (size) of the graded potential(s) that triggered it.

If a neuron is depolarized, it has a membrane potential,

A) more negative than 0 mV.

B) more negative than resting membrane potential.

C) more positive than resting membrane potential.

D) more positive than 0 mV.

C) more positive than resting membrane potential.

Neurotransmitters are removed from the synaptic cleft by all of the following mechanisms except:

a) They move into dendrites through the pores of receptor channels and are destroyed.

 b) They are destroyed by enzymes attached to the cell membranes of dendrites.

 

c) They are transported back into the axon terminal and re-used or degraded.

 

d) They diffuse out of the synaptic cleft.

a) They move into dendrites through the pores of receptor channels and are destroyed.

Graded potentials may do all of the following except:

A) hyperpolarize the membrane of a neuron.

B) combine with other graded potentials (that may have been introduced at other dendrites, for example).

C) be conducted over long distances as a result of positive feedback.

D) depolarize the membrane of a neuron to the threshold voltage.

be conducted over long distances as a result of positive feedback.

Which type of ion channel would most likely cause an inhibitory graded potential (a.k.a. an IPSP) in the dendrites of a neuron?

A)A voltage-gated Na⁺ channel

B) A ligand-gated Na⁺ channel

C) A voltage-gated K⁺ channel

D) ligand-gated K⁺ channel

ligand-gated K⁺ channe

An action potential is only conducted along an axon in one direction (i.e. never back in the direction from which it came) because:

A) saltatory conduction allows an action potential to “jump” from one node of Ranvier to the next.

B) voltage-gated ion channels exhibit positive feedback.

C) the myelin sheath insulates the axon.

D) inactivation of voltage-gated Na+ channels prevents backward conduction.

inactivation of voltage-gated Na+ channels prevents backward conduction.

During the absolute refractory period of an action potential,

A) voltage gated sodium channels are inactivated.

B) voltage gated potassium channels are inactivated.

C) voltage gated potassium channels are closed but not inactivated.

D) voltage gated sodium channels are closed but not inactivated.

voltage gated sodium channels are inactivated.

When the dendrites of an afferent sensory neuron are exposed to a strong stimulus (e.g. you accidentally touch a hot frying pan), the sensory neuron will release more neurotransmitter because the strong stimulus produces a graded potential with a _______ that triggers _________.

A) large amplitude; an action potential with a large amplitude

B) small amplitude; a large number (i.e. a high rate) of action potentials

C) small amplitude; an action potential with a large amplitude

D) large amplitude; a large number (i.e. a high rate) of action potentials

large amplitude; a large number (i.e. a high rate) of action potentials

Conduction of an action potential is faster in myelinated axons than in unmyelinated axons because myelinated axons

a) prevent positively charged ions from leaking out of the axon.

 

b) have a larger diameter than unmyelinated axons.

 

c) exhibit positive feedback.

 

d) have voltage-gated Na+ channels everywhere along their entire length.

a) prevent positively charged ions from leaking out of the axon.

Neuron A and neuron B both form synapses onto neuron C.  Neuron A releases a neurotransmitter onto the cell body of neuron C that causes a large IPSP near the axon hillock.  At the same time, neuron B releases a neurotransmitter onto a dendrite of neuron C that causes a small EPSP.  What is the likely result? 

( draw a diagram of the neurons described above)

a) After a brief delay, neurons A and B will both be depolarized and fire action potentials.

 

b) Neuron C will remain near resting potential and fire an action potential.

 

c) Neuron C will be very depolarized and fire an action potential.

 

d) Neuron C will be hyperpolarized or remain near resting potential and no action potential will be fired.

d) Neuron C will be hyperpolarized or remain near resting potential and no action potential will be fired.