Neuronal Transmission Quiz

Tiny sacs at nerve terminals called ________, release contents from the cell when calcium flows in.

vesicles

Products from the soma of a neuron are transported to the synaptic terminals by ________ axoplasmic transport.

anterograde

The following are the steps involved in transmission at a cholinergic synapse. 1. Chemically gated sodium channels on the postsynaptic membrane are activated. 2. Calcium ions enter the synaptic knob. 3. Acetylcholinesterase hydrolyzes acetylcholine. 4. An action potential depolarizes the synaptic knob at the presynaptic membrane. 5. The synaptic knob reabsorbs choline. 6. Acetylcholine is released from storage vesicles by exocytosis. 7. Acetylcholine binds to receptors on the postsynaptic membrane. 8. Calcium ions are removed from the cytoplasm of the synaptic knob. The correct sequence for these events is

4,2,6,7,1,8,3,5

The following are the main steps in the generation of an action potential. 1. Sodium channels are inactivated. 2. Voltage-gated potassium channels open and potassium moves out of the cell initiating depolarization. 3. Sodium channels regain their normal properties. 4. A graded depolarization brings an area of an excitable membrane to threshold. 5. A temporary hyperpolarization occurs. 6. Sodium channel activation occurs. 7. Sodium ions enter the cell and depolarization occurs. The proper sequence of these events is:

4,6,7,1,2,3,5,

Calcium ions.

A

The minimum graded depolarization needed to operate the voltage-gated sodium and potassium channels is indicated by the label

A

Which area of the graph shows when chemically-gated sodium channels are open? A)1 B)5 C)3 D) 2 E) 4

A) 1

What is occurring at the area labeled #4? A) Excessive potassium has diffused out causing hyperpolarization. B) Excessive depolarization of the axon has occurred. C) Chemically-gated potassium channels have opened. D) An inhibitory stimulus has occurred.

A) Excessive potassium has diffused out causing hyperpolarization.

________ channels open or close in response to physical distortion of the membrane surface. A) Mechanically-gated B) Voltage-gated

A) Mechanically-gated

Functionally which cellular location is the neuron's "decision-making site" as to whether or not an action potential will be initiated? A) axon hillock B) axonal membrane C) presynaptic membrane D) dendritic membrane

A) axon hillock

What is a change in the postsynaptic potential that brings membrane potential closer to threshold called? A) excitatory postsynaptic potential B) inhibitory presynaptic potential C) suprathreshold postsynaptic potential D) inhibitory postsynaptic potential

A) excitatory postsynaptic potential

A ________ is a subthreshold change in membrane potential within the cell body that decays as it travels away from its point of origin. A) graded potential B) hyperpolarization C) action potential D) polarization

A) graded potential

The neuron cannot respond to a second stimulus no matter how strong.

Absolute refractory period

The most common neurotransmitter is ________.

Acetylcholine

Also called a nerve impulse transmitted by axons.

Action potential

Postsynaptic membrane.

B

The membrane's permeability to sodium ions is at its maximum at label

B

What happens when a resting neuron's membrane depolarizes? A) There is a net diffusion of Na+ out of the cell. B) The neuron's membrane voltage becomes more positive. C) The equilibrium potential for K+ (EK) becomes more positive. D) The cell's inside is more negative than the outside.

B) The neuron's membrane voltage becomes more positive.

The sodium-potassium ion exchange pump A) transports potassium ions out of the cell during depolarization. B) moves sodium and potassium opposite to the direction of their electrochemical gradients. C) transports sodium ions into the cell during depolarization. D) must reestablish ion concentrations after each action potential.

B) moves sodium and potassium opposite to the direction of their electrochemical gradients.

The depolarization phase of the action potential is generated by a rapid ________. A) closure of potassium channels B) opening of sodium channels C) opening of potassium channels D) closure of sodium channels

B) opening of sodium channels

After the depolarization phase of an action potential the resting potential is restored by A) a decrease in the membrane's permeability to potassium and chloride ions. B) the opening of voltage-gated potassium channels and the closing of sodium channels. C) the opening of more voltage-gated sodium channels. D) a brief inhibition of the sodium-potassium pump.

B) the opening of voltage-gated potassium channels and the closing of sodium channels.

Where are neurotransmitter receptors located? A) the nodes of Ranvier B) the postsynaptic membrane C) the nuclear membrane D) synaptic vesicle membranes

B) the postsynaptic membrane

At what point in the graph are sodium channels closed (or closing) and potassium channels opened?

C

Synaptic vesicles.

C

The period in which voltage-gated potassium channels are open and hyperpolarization has yet to occur is at label

C

During which of the following states are the majority of voltage-gated sodium channels closed and incapable of opening? A) during depolarization B) during the after-hyperpolarization C) during the absolute refractory period D) during the relative refractory period

C) during the absolute refractory period

For a neuron with an initial membrane potential at -70 mV an increase in the movement of potassium ions out of that neuron's cytoplasm would result in the A) replacement of potassium ions with calcium ions. B) neuron switching on its sodium-potassium pump to restore the initial conditions. C) hyperpolarization of the neuron. D) replacement of potassium ions with sodium ions.

C) hyperpolarization of the neuron.

The same ________ can have different effects depending on the properties of the ________. A) propagation; neurotransmitter B) substrate; receptor C) neurotransmitter; receptor D) hormone; neurotransmitter

C) neurotransmitter; receptor

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. A) terminal : presynaptic B) parasynaptic : postsynaptic C) presynaptic : postsynaptic D) presynaptic : parasynaptic

C) presynaptic : postsynaptic

The membrane potential is closest to the equilibrium potential for potassium at label

D

IPSPs (inhibitory postsynaptic potentials) A) block the efflux of potassium ions. B) block the efflux of calcium ions. C) are graded depolarizations. D) are graded hyperpolarizations.

D) are graded hyperpolarizations.

Voltage-gated calcium channels in the axon terminal open in response to which of the following? A) neurotransmitter binding to receptor B) initiation of an action potential in the axon hillock C) summation of graded potentials at the axon hillock D) arrival of an action potential at the axon terminal

D) arrival of an action potential at the axon terminal

Presynaptic modulation occurs at what type of synapse? A) axo-somatic B) dendron-dendritic C) axo-dendritic D) axo-axonic

D) axo-axonic

The observation that the acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium channel and opens it is an example of a A) voltage-gated potassium channel. B) chemical that inhibits action potentials C) voltage-gated sodium channel. D) ligand-gated sodium channels

D) ligand-gated sodium channels

The repolarization phase of action potentials in neurons is due primarily to ________. A) sodium flow out of the cell B) potassium flow into the cell C) increased activity of the Na+/K+ pump D) potassium flow out of the cell

D) potassium flow out of the cell

A toxin that binds specifically to voltage-gated sodium channels in axons would be expected to A) increase the release of neurotransmitter molecules. B) prevent the hyperpolarization phase of the action potential. C) have most of its effects on the dendritic region of a neuron. D) prevent the depolarization phase of the action potential.

D) prevent the depolarization phase of the action potential.

Curare is a potent neurotoxin extracted from the Strychnos toxifera plant in Central and South America. Indigenous peoples of South America apply curare to arrows which they used to hunt and kill animals. Curare acts at synapses between motor neurons and skeletal muscle cells. When a motor neuron synapses with a skeletal muscle cell, the skeletal muscle cell may be stimulated or inhibited just like postsynaptic neurons are. Curare acts by binding temporarily to acetylcholine receptors on the postsynaptic cell and prevents acetylcholine from binding. What effect does curare likely have on the postsynaptic cell? A) hyperpolarizes the postsynaptic cell B) stimulates muscle contraction C) depolarizes the presynaptic cell D) prevents voltage-gated sodium channels from opening

D) prevents voltage-gated sodium channels from opening

The interior of the cell becomes less negative due to an influx of sodium ions.

Depolarization

The most common systemic disorder that causes peripheral neuropathy is ________.

Diabetes mellitus

Ion channel.

E

The neuronal membrane is at its resting potential at label

E

________ inhibit the release of pain neurotransmitters.

Endorphins

Which is the most important excitatory neurotransmitter in the brain?

Glutamine

Receptors that work through second messenger systems are called __________ receptors.

Metabotropic

________ is caused by an autoimmune attack on the myelin in the central nervous system.

Multiple sclerosis

________ is an autoimmune attack of the acetylcholine receptor at the neuromuscular junction.

Myasthenia gravis

A __________ is a compound that influences a postsynaptic cell's response to a neurotransmitter.

Neuromodulator

An exceptionally strong stimulus can trigger a response.

Relative refractory period

The specific period during which potassium ions diffuse out of the neuron due to a change in membrane permeability.

Repolarization

The synaptic delay required for responses to be generated within the postsynaptic neuron are primarily caused by:

The time required for calcium to induce exocytosis

The period from when an action potential begins until normal excitability returns is known as the ________ period.

absolute refractory

The time during which an excitable membrane cannot respond to further stimulation regardless of the stimulus strength is the __________.

absolute refractory period

Cholinergic synapses release the neurotransmitter

acetylcholine

The __________ principle states that the properties of the action potential are independent of the relative strength of the depolarizing stimulus.

all-or-none

At a(n) ________ synapse a neurotransmitter is released to stimulate the postsynaptic membrane.

chemical

The sensory loss and muscle weakness associated with multiple sclerosis are a consequence of ________.

demyelination

A shift of the resting transmembrane potential toward 0 mV is called ________.

depolarization

In a(n) ________ synapse current flows directly between cells.

electrical

The sum of the electrical and chemical forces acting on an ion is known as its ________.

electrochemical gradient

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

gap junctions

Potentials that are short-lived local changes in membrane potential that can be either depolarized or hyperpolarized are called ________ potentials.

graded

The opening of a calcium channel in the axon terminal results in the movement of calcium (into / out of) the cell.

into

The higher the frequency of action potentials generated the (more / less) neurotransmitter released at a synapse.

more

In myelinated nerve fibers where do action potentials occur?

nodes of Ranvier

Adrenergic neurons release the neurotransmitter _________________________.

norepinephrine

Guillain Barré syndrome is the autoimmune destruction of the ________ nervous system myelin and often occurs after a viral infection.

peripheral

At rest the plasma membrane is more permeable to (sodium / potassium).

potassium

The time during which an excitable membrane cannot respond to further stimulation is the _________________________.

refractory period

The period of time during which an excitable membrane can respond again but only if the stimulus is greater than the initial stimulus is the __________.

relative refractory period

During the rapid depolarization phase of an action potential the plasma membrane is more permeable to (sodium / potassium).

sodium

The buildup of depolarization when EPSPs arrive at several places on the neuron is called ________ summation.

spatial

The addition of several stimuli arriving from different locations on the same cell to produce an action potential is called __________.

spatial summation

The buildup of depolarization when EPSPs arrive in rapid succession is called ________ summation.

temporal

The addition of stimuli arriving in rapid succession to produce an action potential is called __________.

temporal summation

The minimum amount of stimulus required to depolarize an excitable membrane and generate an action potential is known as the _________________________.

threshold