Chapter 12

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.

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.

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

1. _______________ 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

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.

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

Two EPSPs in proximity to each other

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 fire under the same circumstances in the absence of the facilitator

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

decrease

Action potentials occur

in the unmyelinated regions of an axon

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

Graded potentials are produced within the _______________________ segment of a neuron.

receptive

The following information best describes the _____________ phase of an action potential.

repolarization

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