How Synapse Works

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Mastering Chap 11: Synapse

The small space between the sending neuron and the receiving neuron is the

synaptic cleft

A molecule that carries information across a synaptic cleft is a

neurotransmitter

When calcium ions enter the synaptic terminal,

they cause vesicles containing neurotransmitter molecules to fuse to the plasma membrane of the sending neuron.

When neurotransmitter molecules bind to receptors in the plasma membrane of the receiving neuron,

ion channels in the plasma membrane of the receiving neuron open.

If a signal from a sending neuron makes the receiving neuron more negative inside,

the receiving neuron is less likely to generate an action potential.

Prior to being released by the neuron in response to an action potential, the neurotransmitters are stored in the__________.

synaptic vesicles

The chemical synapse is bounded by the ________ neuron, from which neurotransmitters are released across the synaptic cleft, to the ________ neuron, where the receptors for that neurotransmitter are located.

presynaptic : postsynaptic

The neurotransmitter that is released from the presynaptic neuron must diffuse across the ________ to reach the postsynaptic neuron.

synaptic cleft

What type of ion channels are necessary for the function of the axon and the axon terminal?

voltage-gated

Synaptic vesicles store ________.

neurotransmitter

Neurotransmitter release occurs by what mechanism?

exocytosis

Voltage-gated calcium channels in the axon terminal open in response to which of the following?

arrival of an action potential at the axon terminal

The influx of calcium into the axon terminal of a chemical synapse is responsible for which of the following?

fusion of vesicles to the membrane and of exocytosis neurotransmitter

The opening of ion channels that is stimulated by the binding of a neurotransmitter to its receptor on a neighboring neuron, and the subsequent movement of ions across that membrane, describes the development of which of the following?

postsynaptic potential

What is a change in the postsynaptic potential that brings membrane potential closer to threshold called?

excitatory postsynaptic potential

What ion directly triggers neurotransmitter release from the presynaptic neuron?

calcium

The binding of a neurotransmitter to its receptor at an inhibitory synapse can lead to the ________ of ________ channels.

opening : chloride

The binding of a neurotransmitter to its receptor at an inhibitory synapse can lead to the ________ of ________ channels.

opening : potassium

True/False: When voltage-dependent calcium channels open, calcium moves out of the cell.

false

True/False: Excitatory postsynaptic potentials can occur as either fast or slow responses.

true

True/False: An action potential is triggered if the membrane potential at the axon hillock is depolarized to threshold.

true

True/False: Closing of potassium channels causes a hyperpolarization.

false

True/False: If the equilibrium potential of a cation is -40 mV, then opening of channels for this cation will result in excitation of the neuron.

true

The final integration of postsynaptic potentials that determines whether an action potential is generated occurs within what region of a neuron?

axon hillock

True/False: IPSPs can only summate with IPSPs, and EPSPs can only summate with EPSPs.

false

True/False: Two or more graded potentials originating from a different synapse on the same neuron at approximately the same time will cause spatial summation.

true

True/False: Most communication between neurons in the central nervous system is one-to-one, that is, one presynaptic neuron communicates to just one postsynaptic neuron.

false

In a synapse, neurotransmitters are stored in vesicles located in the __________.

presynaptic neuron

An action potential releases neurotransmitter from a neuron by opening which of the following channels?

voltage-gated Ca2+ channels

Binding of a neurotransmitter to its receptors opens __________ channels on the __________ membrane.

chemically gated; postsynaptic

Binding of the neurotransmitter to its receptor causes the membrane to __________.

either hyperpolarize or depolarize

The mechanism by which the neurotransmitter is returned to a presynaptic neuron's axon terminal is specific for each neurotransmitter. Which of the following neurotransmitters is broken down by an enzyme before being returned?

acetylcholine

Which type of synapse is most prevalent in the nervous system?

chemical

Inhibitory neurotransmitters of the CNS act by opening __________ channels.

Cl- or K+

Once the stimulus alters the receptor on the cell's membrane, what happens next?
a. the membrane permeability is altered
b. ion channels open, allowing ions to enter or exit
c. a second messenger is activated on the inside of the cell.
d. any of the above could happen next

d. any of the above could happen next

An excitatory postsynaptic potential (EPSP)

depolarizes a neuron, increasing the likelihood of an action potential.

Inhibitory postsynaptic potentials (IPSPs )

result in local hyperpolarizations

If a hyperpolarizing graded potential and a depolarizing graded potential of similar magnitudes arrive at the trigger zone at the same time, what happens?

nothing. They will cancel each other out

Temporal summation refers to

additional graded potential(s) arriving before previous ones have ceased.

When a second EPSP arrives at a single synapse before the effects of the first have disappeared, what occurs?

temporal summation

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