Chapter 12- Nervous System Physiology Homework

when voltage-gated sodium channels are open, sodium flows _____ the neuron making the inside of the cell more _____.

into; positive

anterograde goes from

the cell body to the synaptic knobs

as a result of the neuron's inner cell membrane becoming more positively charged

the sodium channels open and sodium ions pour into the intracellular fluid

if demyelination occurs, why don't action potentials occur at regions of the axon that were previously myelinated?

these regions lack the appropriate concentration of voltage-gated sodium channels

what happens when depolarization of a cell membrane reaches threshold?

a new action potential is produced

if acetylcholinesterase became mutated and nonfunctional, what would be the immediate result?

acetylcholine would build ip in the synaptic cleft.

if a drug that was developed that interfered with the proper functioning of the microtubules found within the axons of neurons, how would you expect this to impact axonal transport processes?

both anterograde and retrograde transport processes would cease

an EPSP will cause

both sodium and potassium gates to open, allowing sodium to diffuse into the cell and potassium to diffuse out of the cell

what type of voltage-gated ion channels open at the synaptic knob, resulting in the stimulation of the synaptic vesicles to release their neurotransmitters by exocytosis?

calcium

substances that cause facilitation of a neuron _____.

cause the neuron to fire that may not under the same circumstances in the absence of the facilitator

a resting membrane potential of -70mV indicates that the

charges lining the inside of the plasma membrane are negative compared to the charges lining the outside

the enzyme choline acetyltransferase catalyzes the reaction between acetyl-CoA and choline resulting in the formation of the neurotransmitter acetylcholine. this enzyme is produced within the cell body of neurons, but the synthesis of acetylcholine occurs within the axon terminals. which statement best describes the axonal transport mechanism associated with this process?

choline acetyltransferase is transported in the anterograde direction

do demyelinating diseases cause a decrease or increase in the conduction velocity of action potentials?

decrease

activation gates in the cell membrane for voltage-gated sodium ion channels open into the

extracellular fluid

graded potentials result from the opening of _____.

ligand-gated channels

the cell membrane immediately adjacent to an action potential depolarizes because of

local currents

depolarization is initiated by a stimulus that makes the membrane potential

more positive

depolarization of a cell membrane occurs because

more sodium ions diffuse into the cell that potassium ions diffuse out of it

what substance would cause the facilitation of a neuron that is isolated and remove the acetyl choline receptors from the postsynaptic membrane?

nicotine

the absolute refractory period assures that action potential propagation is

only in one direction

an inhibitory postsynaptic potential results from the opening of...

potassium and/or chloride channels

graded potentials are produced within the _____ segment of a neuron

receptive

_____ the time between signals sent from the same presynaptic terminal increases the strength of the graded potential. what type of summation is this an example of?

reducing;temporal

the following information best describes what phase of an action potential? - a membrane potential reading +10mV - inactivated voltage-gated sodium channels - open voltage-gated potassium channels

repolarization

suppose that a new virus is discovered that specifically infects motor neurons. assume that this virus enters neurons in conjunction with choline molecules. once inside the cell, the virus enters the nucleus and replicates. which direction describes the axonal transport route taken by this virus?

retrograde transport

normally, sodium and potassium leakage channels differ because...

sodium ions diffuse through leakage channels into the cell, but potassium ions diffuse through leakage channels out of the cell

an inhibitory postsynaptic potential will make...

the membrane potential of a neurons inner cell membrane more negative

an excitatory postsynaptic potential will make

the membrane potential of a neurons inner cell membrane more positive

upon arriving at the node of a myelinated neuron, the excitatory postsynaptic potential causes

the neuron's inner cell membrane to become more positively charged

retrograde goes from

the synaptic knobs to the cell body

what is the summative effect the brings the initial segment closest to threshold

two EPSPs in proximity to each other

do action potentials occurs in the myelinated, unmyelinated or both regions of an axon?

unmyelinated regions