ch 8 physiology

For cells that communicate by electrical synapses, the message travels between cells via

gap junctions

Which of the following statements about synapses is FALSE?

Neurotransmitters can move from one cell to another through gap junctions at an electrical synapse.

Which of the following statements about electrical synapses is FALSE?

Electrical synapses are usually for small-response, single neuron firing.

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

What type of synapse occurs between an axon terminal of one neuron and the axon from another neuron?

axoaxonic

What type of synapse occurs between an axon terminal of one neuron and the cell body of another neuron?

axosomatic

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 is necessary for the function of the axon and the axon terminal?

voltage-gated

Synaptic vesicles store

neurotransmitter

Most neurotransmitters are synthesized in what region of a neuron?

cytosol of the axon terminal

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

Which of the following is NOT a mechanism whereby neurotransmitters are rapidly removed from the synaptic cleft?

transport back up the axon to be immediately repackaged

Neurotransmitters can be reused through the process of \________, where neurotransmitters are transported back across the presynaptic membrane.

reuptake

The extent of neurotransmitter binding to receptors on the postsynaptic membrane is determined primarily by which of the following?

the concentration of neurotransmitter

The synaptic delay is caused by the time required for which step of neurotransmitter release?

calcium entry to trigger exocytosis

What type of receptor is responsible for the rapid opening of ion channels in response to the interaction between the ligand and receptor?

ionotropic

The action of any chemical messenger ultimately depends not on the nature of the messenger, but rather on the

signal transduction mechanism activated.

The rapid change in membrane potential that occurs when a ligand binds to an ionotropic receptor is caused by which of the following?

the presence of that protein functioning as both an ionotropic receptor and as the ion channel

Synaptic potentials are produced at what type of synapse?

pre-axon hillock synapses only

At metabotropic receptors, a(n)

neurotransmitter binding to a receptor stimulates a G-protein, which then activates a second messenger through one or more enzymatic actions.

Presynaptic modulation occurs at what type of synapse?

axoaxonic

Metabotropic receptor-induced gating of ion channels requires more time to occur because of which of the following?

Their gating is linked to a G protein

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

excitatory postsynaptic potential

The most common mechanism for producing a fast EPSP involves which of the following?

opening of channels that permit both sodium and potassium to flow through

What ion directly triggers neurotransmitter release from the presynaptic neuron?

calcium

An example of a slow excitatory postsynaptic potential that involves closure of potassium channels relies on cAMP produced by what enzyme?

adenylate cyclase

The duration of a slow, excitatory postsynaptic potential mediated by cAMP is driven by the extent of time that cAMP remains active before being degraded by what protein?

phosphodiesterase

Fast excitatory responses not only occur quickly, but they

end quickly.

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

In the absence of active chloride ion transport, opening of chloride channels in a cell that has hyperpolarized will result in which of the following?

net movement of chloride out of the cell

In the presence of active chloride ion transport within a neuron, the opening of chloride channels will result in which of the following?

net movement of chloride into the cell

If the resting membrane potential is equal to chloride's equilibrium potential, in which direction will chloride ions move if chloride channels open while the cell remains at resting membrane potential?

Ions will move equally in both directions.

In the absence of an active chloride transporter in the plasma membrane, chloride acts to \________ membrane potential by resisting any change in membrane potential.

stabilize

The opening of a chloride channel acts to \________ the development of an action potential at the axon hillock.

inhibit

Convergence in neurophysiology refers to which of the following?

the communication of several neurons to one postsynaptic cell

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

axon hillock

Divergence in neurophysiology refers to which of the following?

the presence of EPSPs and IPSPs on a neuron at the same time

For ionotropic receptors, their \________ response \________ the likelihood that two pulses from the same neuron will summate.

rapid : decreases

Which of the following would increase the likelihood of an action potential being generated in a postsynaptic cell?

presynaptic excitation at an excitatory synapse

Which of the following statements about inhibitory synapses is FALSE?

In presynaptic inhibition, the lower level potential generated interferes with the oncoming action potential.

How does temporal summation create an action potential?

Two or more postsynaptic potentials are generated in rapid succession at the same synapse before they can dissipate, thereby exceeding threshold.

As the amplitude of the excitatory postsynaptic potential increases above threshold, the time between each action potential will \________, thereby increasing the \________ of the action potentials.

decrease : frequency

Suprathreshold graded potentials within a neuron can generate \________ action potential(s) at the axon hillock, which allows for the \________ of the magnitude of the stimulus.

multiple : frequency coding

Axoaxonic synapses are responsible for \________ the extent of neurotransmitter released at the synapse.

modulating

Presynaptic modulation of neurotransmitter release involves modifying \________ at the axon terminal.

calcium influx

During presynaptic inhibition, the release of a neurotransmitter from the modulating neuron causes which of the following?

a decrease in calcium entry into the axon terminal of the neuron it is modulating

Which of the following BEST describes presynaptic facilitation?

The modulating neuron enhances neurotransmitter release to the postsynaptic cell.

The synthesis of acetylcholine involves an enzyme called \________, which is present within the axonal cytosol and is responsible for converting \________ into acetylcholine + CoA.

choline acetyl transferase : choline + acetate

Neurons that synthesize and release acetylcholine are called \________ neurons.

cholinergic

Once released, acetylcholine is degraded by extracellular enzymes into what product(s)?

acetate + choline

What is transported back into the axon terminal of cholinergic neurons to be resynthesized into active neurotransmitter?

choline

What type of receptor is both ionotropic and cholinergic?

nicotinic

What type of receptor is both metabotropic and cholinergic?

muscarinic

Which of the following is a neurotransmitter that contains a six-carbon ring with two hydroxyl groups and an amine group?

norepinephrine

Which of the following couplings between neurotransmitter and neurotransmitter class is INCORRECT?

adenosine : amino acid

Histamine has receptors in the hypothalamus, RAS system, stomach, blood vessels, and bronchioles. What creates histamine's differing effects seen in each of these areas?

There are different message transduction systems.

Biogenic amines are synthesized in what region of a neuron?

cytosol of the axon terminal

The action of adrenergic receptors identifies them as \________ receptors.

metabotropic

Which of the following is a biogenic amine that is NOT classified as a catecholamine?

serotonin

What two enzymes catalyze the breakdown of catecholamines?

monoamine oxidase and catechol-O-methyltransferase

Epinephrine binds best to which of the following receptor types?

beta2 adrenergic receptors

Fast EPSPs are produced at which of the following types of receptor?

both nicotinic cholinergic and AMPA receptors

Histidine, tyrosine, and tryptophan all go on to become what class of neurotransmitters?

biogenic amines

\________ is an amino acid neurotransmitter at excitatory synapses whereas \________ is an amino acid neurotransmitter at inhibitory synapses.

Aspartate : glycine

Which of the following GABA receptor types is coupled to chloride channels?

GABAA only

Why are amino acid neurotransmitters NOT considered biogenic amines?

Biogenic amines still contain an amine group, but are no longer amino acids.

What is the most common inhibitory neurotransmitter in the central nervous system?

GABA

Neuropeptides are synthesized in what region of a neuron?

in the rough endoplasmic reticulum

Which of the following compounds is NOT a neuropeptide?

epinephrine

Which of the following is a hypothalamic neuropeptide that regulates the sleep-wake cycle?

orexin

Nitric oxide is a(n) \________ that functions as a neurotransmitter.

gas

Which of the following chemicals is NOT a known neurotransmitter?

carbon dioxide

What chemical targets CB1 receptors?

tetrahydrocannabinol

Which of the following neurotransmitters is a neuropeptide?

substance P

Which of the following neurotransmitters is an amino acid neurotransmitter released at excitatory synapses?

aspartate

Which of the following neurotransmitters is a catecholamine?

norepinephrine

Which of the following neurotransmitters is a biogenic amine, but not a catecholamine?

serotonin

Which of the following neurotransmitters is an amino acid neurotransmitter released at inhibitory synapses?

glycine

Which of the following neurotransmitters is the most common neurotransmitter in the peripheral nervous system?

acetylcholine

What happens to the resting membrane potential of -70 mV when sodium channels open?

depolarization

What happens to the resting membrane potential of -70 mV when sodium leak channels close?

hyperpolarization

What happens to the resting membrane potential of -70 mV when potassium channels open?

hyperpolarization

What happens to the resting membrane potential of -70 mV when potassium channels close?

depolarization

What happens to the resting membrane potential of -70 mV when channels for an anion with an equilibrium potential of -80 mV open?

hyperpolarization

What happens to the resting membrane potential of -70 mV when channels for a cation with an equilibrium potential of -80 mV open?

hyperpolarization

What happens to the resting membrane potential of -70 mV when channels for a cation with an equilibrium potential of -30 mV open?

depolarization

What happens to the resting membrane potential of -70 mV when channels, that permit both sodium and potassium to move through, open?

depolarization

Which enzyme catalyzes the synthesis of cAMP?

adenylate cyclase

Which enzyme catalyzes the synthesis of acetylcholine?

adenylate cyclase

What enzyme catalyzes breakdown of catecholamines in the synaptic cleft and in the mitochondria of the axon terminal of the presynaptic cell?

monoamine oxidase

What enzyme catalyzes breakdown of catecholamines in the synaptic cleft only?

catechol-O-methyltransferase

What enzyme catalyzes breakdown of acetylcholine?

acetylcholinesterase

All of the following receptor sub-types are metabotropic, EXCEPT

nicotinic cholinergic.

All of the following receptor sub-types are ionotropic, EXCEPT

muscarinic cholinergic.

What is occurring in Step 2 of Figure 8.1, and how is that process originated?

influx of calcium : depolarization causes voltage-gated calcium channels to open

dentify the structure on the postsynaptic membrane that bind with the neurotransmitter in Step 4 of Figure 8.1, and indicate its function.

a receptor that can stimulate a cellular response by gating its ion channel or stimulating a G protein to gate an ion channel

Identify the structure on the postsynaptic membrane that binds with the neurotransmitter in Step 6 of Figure 8.1, and indicate its function.

an enzyme used to remove neurotransmitter from the synaptic cleft