Ch. 12 Homework

Assume all of the presynaptic synapses identified produce EPSPs. If two of these synapses fired simultaneously, which synaptic combination brings the initial segment closest to threshold based on spatial summation? Click on the appropriate synapses.

3,4

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

decrease

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

3. 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

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

1. 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

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

An inhibitory postsynaptic potential results from the opening of____________________.

potassium and/or chloride channels

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