bio exam 3

Ligand-gated ion channels are found within the postsynaptic neuron's cell membrane. Why are ligand-gated ion channels critical to how synapses communicate information? Select all that apply. (1)Ligand-gated ion channels are found within a neuron's dendrites but not its axon. (2)Ligand-gated ion channels enable specific neurotransmitters released by presynaptic neurons to exert either excitatory or inhibitory effects on the postsynaptic cell. (3)Ligand-gated ion channels allow the postsynaptic cell to control, through intracellular signaling, which neurotransmitters the postsynaptic cell responds. (4)Ligand-gated ion channels open more rapidly than voltage-gated ion channels.

1 + 2

T or F: Each time an excitatory neuron binds to its ligand-gated channel, an action potential will occur.

False

T or F: The changes in voltage shown in an action potential graph are due to ligand-gated ion channels opening and closing along the axon.

False

Which channel is responsible for helping to maintain the resting membrane potential?

K+ leak channels

What structure is found in the synapse?

Neurotransmitter

Imagine you genetically engineered a neuron to produce voltage-gated Na+ and K+ channels that opened at the same time in response to a change in voltage. How would that change the action potential?

No action potential would be generated

There is a mutation in an inhibitory ligand-gated channel so that it does not bind its ligand (the inhibitor). How would resting membrane potential be affected?

Resting membrane potential will not be affected by a mutation in the inhibitory ligand-gated channel.

An important function of myelin is to....

SPEED UP nerve signal transmission along the axon

What happens when a ligand binds to a ligand-gated Na+ channel?

Sodium ions flow passively from high concentration to low concentration

Where would you expect to find ligand-gated ion channels in the plasma membranes of these cells?

dendrites

Threshold potential refers to the membrane potential required to.....

initiate an action potential and open voltage-gated sodium ion channels.

An inhibitory postsynaptic potential (IPSP) occurs when...

ligand-gated chloride ion channels open.

If Na+ channels were not present in the membrane of a neuron, then resting membrane potential would _____________ compared to normal resting potential.

more negative

Under conditions of resting membrane potential, the inside of the cell is _____ charged with respect to the outside, but when an action potential is generated, the inside becomes _____ with respect to the outside of the cell.

negatively; positive

The permeability of a nerve cell membrane depends upon the....

number of open channels

What are the nodes of Ranvier?

open spaces separating regions of myelination along an axon

During synaptic transmission: (1)neurotransmitter-filled vesicles fuse with the postsynaptic membrane. (2)neurotransmitters are absorbed by the postsynaptic membrane. (3)receptors that bind neurotransmitters trigger a change in postsynaptic membrane potential. (4)voltage-gated calcium channels open in the postsynaptic membrane.

receptors that bind neurotransmitters trigger a change in postsynaptic membrane potential.

The movement of potassium ions out of a resting neuron is a consequence of....

the high concentration of potassium ions inside the cell and the presence of potassium ion channels in the membrane.

If voltage-gated sodium channels are blocked and excitatory neurotransmitters bind to their ligand-gated channels, then the membrane ______ be able to depolarize

will

T or F: Resting potential is generated mainly by the outward movement of K+ ions from inside the cell

True

T or F: The trace (blue) line in the figure is following the voltage change as it moves down the axon

false

T or F: Neurons can synapse with many different types of cells including muscle cells, secretory cells, and other neurons.

True

What class of membrane-transport protein is associated with triggering an action potential?

a voltage-gated ion channel

The phrase saltatory propagation refers to the....

ability of an action potential to "jump" from one node of Ranvier to the next.

Why does an action potential travel in one direction down an axon?

because voltage-gated sodium ion channels cannot immediately reopen

The release of neurotransmitter from the axon terminal is controlled by voltage-gated...

calcium ion channels

Predict what would happen to a neuron's resting membrane potential if the number of sodium ion channels increased.

The membrane potential would become more positive.