Exam 4: Principles of Neural and Hormonal Communication

A stimulus that is too weak to depolarize the membrane to threshold produces an action potential that is weaker than normal.

During the resting membrane potential, the inside of a neuron has a net ____________________ charge.

Neuromodulators

The longest part of a typical neuron is the ____________________.

The falling phase of the action potential is due to

Increased permeability of the postsynaptic cell to Cl⁻ lessens the likelihood that the postsynaptic cell will undergo an action potential.

Indicate whether an excitatory or inhibitory synapse is being described. a.excitatory synapse b.inhibitory synapse -Increased PCl₋ of the subsynaptic membrane

Indicate which characteristic applies to classical neurotransmitters and neuropeptides. a.neurotransmitters b.neuropeptides c.both neurotransmitters and neuropeptides d.neither neurotransmitters nor neuropeptides -Usually open specific ion channels

For graded potentials, the magnitude of triggering is coded for in frequency rather than amplitude of depolarizations.

Choose the match for each substance listed. a.covering on the axon b.second messenger c.branching process from a cell body d.impulse-conducting region e.junction between neurons f.neurotransmitter -Axon

Action potentials are initiated at the axon hillock region because it has the lowest threshold voltage.

The passive current flow of a graded potential fades quickly.

Only neurons and muscle cells establish resting membrane potentials.

An action potential in a presynaptic neuron induces opening of voltage-gated ____________________ channels in the synaptic knob, which triggers exocytosis of synaptic vesicles.

Indicate the direction that the force in question tends to move the involved ion under the stated conditions by writing the appropriate letter in the blank, using the following answer code: a.tends to move the involved ion out of the cell b.tends to move the involved ion into the cell -Electrical gradient for K⁺ at the peak of an action potential

During the absolute refractory period, the voltage-gated Na⁺ channels are not capable of opening again in response to another triggering event.

A neuron starts to depolarize when _________________ ions move into the cell.

CaM is more closely associated with lipophilic hormones than with hydrophilic hormones.

The conduction velocity of a nerve impulse is slower in myelinated fibers than in unmyelinated fibers because myelin acts as an insulator that slows down the flow of current.

Saltatory conduction