Chapter 9: Nervous Tissue Connect Quiz

What is produced 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 up in the synaptic cleft.

If a drug 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.

2. 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.

Place the components of a peripheral nerve in sequence from outside to inside.

Epineurium, Nerve, Perineurium, fasicles, endoneurium, neurolemmocytes, axolemma

T/F: At resting membrane potential, voltage-gated potassium ion channels are open.

False

T/F: EPSPs and IPSPs have a long-term effect on a neuron.

False

T/F: One function of the nervous system is to always respond to sensory input.

False

T/F: The inside of the cell membrane becomes negative at the time of an action potential.

False

3. 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

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.

T/F: Axoplasmic flow is an example of slow axonal transport.

True

T/F: If extracellular concentrations of potassium are increased dramatically, a neuron may not be able to repolarize during an action potential.

True

Indicate the summative effect that brings the initial segment closest to threshold.

Two EPSPs in proximity to each other

If extracellular calcium was absent, which would likely be true?

Vesicles containing neurotransmitter would not merge with the plasma membrane.

What are excitatory neurotransmitter actions?

binds to a chemically gated sodium channel; sodium moves down concentration gradient into the neuron; the inside of the neuron becomes more positive

At the synaptic knob, voltage-gated ______________ channels open, thereby stimulating 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 -70 mV indicates that the ________________.

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

Demyelinating diseases cause a(n) ______________ in the conduction velocity of action potentials.

decrease

On a graph of an action potential, the small depolarizations that lead to threshold are from

excitatory postsynaptic potentials (EPSPs).

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

extracellular fluid.

Action potentials occur ____________________________.

in the unmyelinated regions of an axon

Neuronal pools are composed of

interneurons

When voltage-gated sodium channels are open, sodium flows _____________ the neuron making the inside of the cell more _______________.

into; positive

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 than potassium ions diffuse out of it.

The most common type of neuron contains many dendrites and a single axon. Structurally, this is classified as a(n) ______________ neuron.

multipolar

What is the structural classification of neurons?

multipolar, bipolar, unipolar

Assume in a laboratory you were able to isolate a neuron and remove the Acetylcholine receptors from the postsynaptic membrane. The substance _________________ would no longer cause facilitation of this neuron.

nicotine

The absolute refractory period assures that action potential propagation is

only in one direction.

Myelin sheaths mainly consist of which part of the glial cells that form them?

plasma membranes

When sodium enters the neuron via chemically gated sodium channels, the membrane will depolarize. Therefore, the membrane potential will become more

positive

An inhibitory postsynaptic potential results from the opening of____________________.

potassium and/or chloride channels

What are inhibitory neurotransmitter actions?

potassium moves down the concentration gradient out of the neuron; binds to a chemically gated potassium channel; binds to a chemically gated chloride channel; chloride moves down its concentration gradient into the neuron

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. This is an example of ________________ summation.

reducing; temporal

The following information best describes the _____________ phase of an action potential • A membrane potential reading of +10 mV • Inactivated voltage-gated sodium channels • Open voltage-gated potassium channels

repolarization

What is the functional classification of neurons?

sensory, motor, interneuron

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

If all the sodium leakage channels were removed from the cell membrane of a neuron,

the membrane potential would be about -90 millivolts.