biology final

The amino acid that operates at most inhibitory synapses in the brain is _____. endorphin nitric oxide acetylcholine gamma-aminobutyric acid (GABA)

gamma-aminobutyric acid (GABA)

Opening all of the sodium channels on an otherwise typical neuron, with all other ion channels closed (which is an admittedly artificial setting), should move its membrane potential to _____. 0 mV +62 mV -90 mV +30 mV

+62 mV

A neuron has a resting potential of about _____ millivolts. +50 +35 -55 -70 -80

-70

The following steps refer to various stages in transmission at a chemical synapse. 1. Neurotransmitter binds with receptors associated with the postsynaptic membrane. 2. Calcium ions rush into neuron's cytoplasm. 3. An action potential depolarizes the membrane of the presynaptic axon terminal. 4. The ligand-gated ion channels open. 5. The synaptic vesicles release neurotransmitter into the synaptic cleft. Which sequence of events is correct? 3 → 2 → 5 → 1 → 4 2 → 3 → 5 → 4 → 1 4 → 3 → 1 → 2 → 5 1 → 2 → 3 → 4 → 5

3 → 2 → 5 → 1 → 4

Refer to the following graph of an action potential to answer the question(s) below. The minimum graded depolarization needed to operate the voltage-gated sodium and potassium channels is indicated by the label _____. A B D E

A

Which term describes an electrical signal generated by neurons? Equilibrium potential. Membrane potential. Resting potential. Action potential.

Action potential.

Which of the following statements about action potentials is correct? Action potentials are propagated down the length of the axon. Action potentials for a given neuron vary in magnitude. Movement of ions during the action potential occurs mostly through the sodium pump. Action potentials for a given neuron vary in duration.

Action potentials are propagated down the length of the axon.

Which statement correctly describes what causes the second voltage-gated Na+ channel to open? As Na+ ions enter the cell through the first channel, they spread out from the channel. When these Na+ ions reach the second channel, it opens. As Na+ ions enter the cell through the first channel, Na+ ions outside the cell move toward the open Na+ channel. When the concentration of Na+ ions near the second channel becomes low enough, the second channel opens. After the first channel opens, the movement of Na+ ions (both inside and outside the cell) alters the Na+ ion distribution across the membrane near the second channel, causing it to open. After the first channel opens, the movement of many types of ions (both inside and outside the cell) alters the distribution of charges near the second channel, causing it to open.

After the first channel opens, the movement of many types of ions (both inside and outside the cell) alters the distribution of charges near the second channel, causing it to open.

Where in the neuron do action potentials begin? Axon hillock. Synapse. Dendrite. Cell body.

Axon hillock

Refer to the following graph of an action potential to answer the question(s) below. The membrane's permeability to sodium ions is at its maximum at label _____. A B C D

B

Refer to the following graph of an action potential to answer the question(s) below. The cell is not hyperpolarized; however, repolarization is in progress, as the sodium channels are closing or closed, and many potassium channels have opened at label _____. B C D E

C

Refer to the following graph of an action potential to answer the question(s) below. The membrane potential is closest to the equilibrium potential for potassium at label _____. A B C D

D

The myelin sheath plays an important role in neuron structure and function. However, when the myelin sheath is missing or not fully intact, there are consequences. There are many conditions that cause demyelination of neurons, some are autoimmune disorders, such as multiple sclerosis, and others are hereditary. The symptoms of these conditions vary, but often include speech impairment and difficulty coordinating movement. Which of the following correctly connects the symptoms of demyelination with the process of nerve impulse transmission? Demyelination slows nerve impulse transmission. Demyelination prevents the formation of an action potential in sensory neurons that transmit signals from the environment to the central nervous system. Demyelination targets the central nervous system. Demyelination prevents the uptake of neurotransmitters needed to propagate a message to the next neuron.

Demyelination slows nerve impulse transmission.

Refer to the following graph of an action potential to answer the question(s) below. The neuronal membrane is at its resting potential at label _____. A B D E

E

True or false? Action potentials travel in only one direction down an axon because potassium channels in the neuron are refractory and cannot be activated for a short time after they open and close. True False

False

Which of the following terms describes how a neuronal membrane's potential is altered in the presence of inhibitory signals? Hyperpolarization. Repolarization. Polarization. Depolarization.

Hyperpolarization.

Neurotransmitters affect postsynaptic cells by _____. I) initiating signal transduction pathways in the cells II) causing molecular changes in the cells III) affecting ion-channel proteins IV) altering the permeability of the cells I, II, III, and IV I and III III and IV II and IV

I, II, III, and IV

In a resting potential, an example of a cation that is more abundant as a solute in the cytosol of a neuron than it is in the interstitial fluid outside the neuron is _____. Cl- Ca++ Na+ K+

K+

Which of the following ions is most likely to cross the plasma membrane of a resting neuron? Cl- K+ Na+ Ca2+

K+

Resting neurons are most permeable to which of the following ions? Na+. Cl--. K+. O--.

K+.

Self-propagation and refractory periods (states) are typical of _____. graded hyperpolarizations threshold potentials excitatory postsynaptic potentials action potentials

action potentials

Which term describes the difference in electrical charge across a membrane? Electrical potential. Resting potential. Membrane potential. Electrical current.

Membrane potential.

Which structure is not part of a neuron? Myelin sheath. Cell body. Axons. Dendrite.

Myelin sheath.

What happens if twice as many inhibitory postsynaptic potentials (IPSPs) as excitatory postsynaptic potentials (EPSPs) arrive at a postsynaptic neuron in close proximity? A weaker action potential results. A stronger action potential results. No action potential results.

No action potential results.

Which channel is mainly responsible for the resting potential of a neuron? Potassium leak channel. Chloride leak channel. Voltage-gated sodium channel. Voltage-gated potassium channel.

Potassium leak channel.

What type of cell makes up the myelin sheath of a motor neuron? astrocytes microglial cells Ranvier cells ependymal cells Schwann cells

Schwann cells

How is an action potential propagated down an axon after voltage-gated sodium channels open in a region of the neuron's membrane? Sodium ions enter the neuron and diffuse to adjacent areas, resulting in the opening of voltage-gated sodium channels farther down the axon. Sodium ions enter the neuron and diffuse to adjacent areas, resulting in the opening of voltage-gated potassium channels farther down the axon. Potassium ions enter the neuron and diffuse to adjacent areas, resulting in the opening of voltage-gated sodium channels farther down the axon. Potassium ions enter the neuron and diffuse to adjacent areas, resulting in the opening of voltage-gated potassium channels farther down the axon.

Sodium ions enter the neuron and diffuse to adjacent areas, resulting in the opening of voltage-gated sodium channels farther down the axon.

Why are action potentials usually conducted in one direction? Voltage-gated channels for both Na+ and K+ open in only one direction. The axon hillock has a higher membrane potential than the terminals of the axon. The brief refractory period prevents reopening of voltage-gated Na+ channels. The nodes of Ranvier conduct potentials in one direction.

The brief refractory period prevents reopening of voltage-gated Na+ channels.

Which event triggers the creation of an action potential? Voltage-gated potassium channels open, and K+ ions diffuse out of the neuron. There is an undershoot of the resting potential. The membrane depolarizes above a certain threshold potential. The sodium—potassium pump shuttles ions across the membrane.

The membrane depolarizes above a certain threshold potential.

If you experimentally increase the concentration of K+ inside a cell while maintaining other ion concentrations as they were, what would happen to the cell's membrane potential? The membrane potential would remain the same. The membrane potential would become less negative. The membrane potential would become more negative.

The membrane potential would become less negative.

If you experimentally increase the concentration of Na+ outside a cell while maintaining other ion concentrations as they were, what would happen to the cell's membrane potential? The answer depends on the thermodynamic potential. The membrane potential would be unaffected. The membrane potential would increase. The membrane potential would decrease.

The membrane potential would increase.

What happens if a neuron is stimulated enough midway in an axon to trigger an action potential? The nerve impulse could not be transmitted because it must be initiated at the dendrite end of a neuron. Since neuron transmission is one-way, the nerve impulse would only be transmitted to the end of the axon and then through neurotransmitters to the next neuron. The nerve impulse would go both directions from the stimulus point, but only the axon end could transfer the message trough neurotransmitters to another neuron. The nerve impulse would go both directions and the dendrite end would be stimulated to send a second message through this neuron.

The nerve impulse would go both directions from the stimulus point, but only the axon end could transfer the message trough

What would probably happen if a long neuron had one continuous myelin sheath down the length of the axon with no nodes of Ranvier? The action potential would be propagated nearly instantaneously to the synapse. The signal would fade because it is not renewed by the opening of more sodium channels. There could be no action potential generated at the axon hillock.

The signal would fade because it is not renewed by the opening of more sodium channels.

What behavior is observed if the voltage across a neuronal membrane is set to -20 mV? The potassium channel opens, and K+ ions flow in. The sodium channel opens, and Na+ ions flow out. The voltage-gated sodium and potassium channels both remain closed. The sodium channel opens, and Na+ ions flow in.

The sodium channel opens, and Na+ ions flow in. Sodium ions flow into the cell when the membrane potential is between -20 mV and 30 mV

Which channel maintains the concentration gradients of ions across a neuronal membrane? The sodium-potassium pump moving Na+ ions in and K+ ions out. The sodium-potassium pump moving Na+ ions out and K+ ions in. The potassium leak channel allowing K+ ions out. The sodium leak channel allowing Na+ ions out.

The sodium-potassium pump moving Na+ ions out and K+ ions in.

Which of the following statements about action potentials in a given neuron is false? They occur after the threshold potential is reached. They are identical in magnitude. They are identical in duration. They are propagated down the length of the dendrite.

They are propagated down the length of the dendrite.

A neurophysiologist is investigating nerve reflexes in two different animals: a crab and a fish. Action potentials are found to pass more rapidly along the fish's neurons. What is the most likely explanation? Unlike the crab, the fish's axons are wrapped in myelin, and the fish's axons are smaller in diameter; small axons transmit action potentials faster than large axons do. The fish's axons are smaller in diameter; small axons transmit action potentials faster than large axons do. Unlike the crab, the fish's axons are wrapped in myelin. There are more ion channels in the axons of the crab compared with fish axons.

Unlike the crab, the fish's axons are wrapped in myelin.

Which of the following is a direct result of depolarizing the presynaptic membrane of an axon terminal? Voltage-gated calcium channels in the membrane open. Ligand-gated channels open, allowing neurotransmitters to enter the synaptic cleft. The postsynaptic cell produces an action potential. Synaptic vesicles fuse with the membrane.

Voltage-gated calcium channels in the membrane open.

At the neuromuscular junction, the arrival of acetylcholine on the muscle most immediately causes _____. a graded hyperpolarization the release of second messengers, such as cAMP a graded depolarization an inhibitory postsynaptic potential a single action potential

a graded depolarization

Acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium channel and opens it. This is an example of _____. a voltage-gated potassium channel a chemical that inhibits action potentials a second-messenger-gated sodium channel a ligand-gated sodium channel

a ligand-gated sodium channel

C.elegans is a model organism and was the first eukaryotic organism to have its genome sequenced. The free-living nematode is often used in laboratories investigating reproduction, particularly egg-laying. There are 16 muscles, 2 types of neurons, and multiple receptors involved in the process of laying eggs in C.elegans, and there are mutations in all of those structures for the study of the process. One particular mutation that prevents the laying of eggs by the worm is rescued by the neurotransmitter, serotonin. That rescue suggests that this mutation is most likely in which of the following? a receptor for serotonin on cells needed for egg-laying one of the muscles needed for egg-laying a pre-synaptic neuron involved in egg-laying a post-synaptic neuron involved in egg-laying

a post-synaptic neuron involved in egg-laying

Excitatory postsynaptic potentials (EPSPs) produced nearly simultaneously by different synapses on the same postsynaptic neuron can also add together, creating _____. a tetanus a spatial summation a temporal summation the refractory state

a spatial summation

The botulinum toxin, which causes botulism, reduces the synaptic release of _____. acetylcholine endorphin gamma-aminobutyric acid (GABA) nitric oxide

acetylcholine

The heart rate decreases in response to the arrival of _____. gamma-aminobutyric acid (GABA) endorphin nitric oxide acetylcholine

acetylcholine

An example of ligand-gated ion channels is _____. acetylcholine receptors at the neuromuscular junction cAMP-dependent protein kinases the spreading of action potentials in the heart action potentials on the axon

acetylcholine receptors at the neuromuscular junction

Which of these causes the release of neurotransmitter molecules? the receipt of a signal from the postsynaptic neuron the opening of voltage-regulated calcium channels and the diffusion of calcium ions out of the neuron an action potential reaching the end of the cell body an action potential reaching the end of the axon an action potential reaching the end of the dendrite

an action potential reaching the end of the axon

A nerve impulse moves away from a neuron's cell body along _____. dendrites Nissl bodies synapses axon glia

axon

An action potential moves along a(n) _____. myelin sheath axon dendrite synapse cell body

axon

Why do Na+ ions enter the cell when voltage-gated Na+ channels are opened in neurons? because the Na+ concentration is much higher outside the cell than it is inside, and the Na+ ions are actively transported by the sodium-potassium pump into the cell because the Na+ ions are actively transported by the sodium-potassium pump into the cell because the Na+ concentration is much higher outside the cell than it is inside, and the Na+ ions are attracted to the negatively charged interior because the Na+ concentration is much lower outside the cell than it is inside

because the Na+ concentration is much higher outside the cell than it is inside, and the Na+ ions are attracted to the negatively charged interior

Acetylcholine receptors on skeletal muscles are described as being "ionotropic" receptors because _____. acetylcholine is an excitatory stimulus to the muscle binding of acetylcholine to the receptor protein converts the protein to an open ion channel these receptors have a corequisite binding of magnesium ions in order to function binding of acetylcholine to its receptor triggers release of a second messenger, e.g., cAMP, inside the muscle the receptors ionize as a result of binding acetylcholine, and this directly alters membrane potentials

binding of acetylcholine to the receptor protein converts the protein to an open ion channel

The simultaneous arrival of graded depolarization and a graded hyperpolarization of equal but opposite magnitude at a particular location on the dendritic membrane is likely to _____. cause the apoptosis of the neuron cancel each other out, making it appear as if there was no change in membrane potential cause hyperpolarization, because graded hyperpolarizations are more important to neuron function cause depolarization, because graded depolarizations are more important to neuron function allow only the entry of sodium ions into the neuron, and prevent potassium ions from exiting the neuron

cancel each other out, making it appear as if there was no change in membrane potential

A neuron's nucleus is located in its _____. cell body axon myelin sheath dendrite synaptic terminals

cell body

True or false? The potential energy of a membrane potential comes solely from the difference in electrical charge across the membrane. True False

false

Motor neurons release the neurotransmitter acetylcholine (ACh) and acetylcholinesterase degrades ACh in the synapse. If a neurophysiologist applies onchidal (a naturally occurring acetylcholinesterase inhibitor produced by the mollusc Onchidella binneyi) to a synapse, what would you expect to happen? paralysis of muscle tissue convulsions due to constant muscle stimulation decrease in the frequency of action potentials no effect

convulsions due to constant muscle stimulation

The activity of acetylcholine in a synapse is terminated by its_____. diffusion across the presynaptic membrane diffusion across the postsynaptic membrane degradation on the postsynaptic membrane active transport across the postsynaptic membrane

degradation on the postsynaptic membrane

A nerve impulse moves toward a neuron's cell body along _____. dendrites synaptic terminals oligodendrocytes axons nodes of Ranvier

dendrites

The "information receiving" section of a neuron is its _____. dendrites axon terminal Schwann cells glia

dendrites

Of these choices, neuronal communication between the brain and the muscles of the leg is best conceptualized as _____. the transcription of genes electrical and chemical signaling the transcription and translation of genes electrical signaling chemical signaling

electrical and chemical signaling

The membrane potential in which there is no net movement of the ion across the membrane is called the _____. equilibrium potential threshold potential action potential graded potential

equilibrium potential

Neurotransmitters are released from axon terminals via _____. exocytosis active transport osmosis diffusion

exocytosis

Which of the following characteristics determines when the refractory period ends? how low the membrane potential drops below resting potential during the undershoot phase how long it takes for the membrane potential to return to resting potential after the undershoot phase how long it takes for the voltage-gated K+ channels to close during the undershoot phase how long it takes for the voltage-gated Na+ channels to close at the end of an action potential how long it takes for the voltage-gated Na+ channels to reactivate at the end of an action potential

how long it takes for the voltage-gated Na+ channels to reactivate at the end of an action potential

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 _____. depolarization of the neuron replacement of potassium ions with calcium ions hyperpolarization of the neuron replacement of potassium ions with sodium ions

hyperpolarization of the neuron

Neurotransmitters categorized as inhibitory are expected to _____. open sodium channels close potassium channels hyperpolarize the membrane act independently of their receptor proteins

hyperpolarize the membrane

Tetrodotoxin blocks voltage-gated sodium channels and ouabain blocks sodium-potassium pumps. If you added both tetrodotoxin and ouabain to a solution containing neural tissue, what responses would you expect? immediate loss of action potential with gradual loss of resting potential immediate loss of resting potential slow decrease of resting potential and action potential amplitudes No effect; the substances counteract each other.

immediate loss of action potential with gradual loss of resting potential

A simple nervous system _____. must include chemical senses, mechanoreception, and vision includes sensory information, an integrating center, and effectors includes a minimum of twelve effector neurons has information flow in only one direction: away from an integrating center

includes sensory information, an integrating center, and effectors

How could you increase the magnitude of inhibitory postsynaptic potentials (IPSPs) generated at a synapse? increase K+ permeability increase sodium-potassium pump activity increase the influx of calcium All of the listed responses are correct.

increase K+ permeability

A graded hyperpolarization of a membrane can be induced by _____. increasing its membrane's permeability to K+ increasing its membrane's permeability to Ca++ decreasing its membrane's permeability to Cl- increasing its membrane's permeability to Na+

increasing its membrane's permeability to K+

Most of the neurons in the human brain are _____. sensory neurons peripheral neurons motor neurons interneurons

interneurons

The Nernst equation specifies the equilibrium potential for a particular ion. This equilibrium potential is a function of _____. osmotic gradient ion concentration gradient hydrostatic pressure temperature (thermal) gradient

ion concentration gradient

The motor (somatic nervous) system can alter the activities of its targets, the skeletal muscle fibers, because _____. its signals bind to receptor proteins on the muscles it is electrically coupled by gap junctions to the muscles it is connected to the internal neural network of the muscles its signals reach the muscles via the blood

its signals bind to receptor proteins on the muscles

Ionotropic receptors found at synapses are operated via _____. ligand-gated ion channels inhibitory, but not excitatory, synapses excitatory, but not inhibitory, synapses electrical synapses

ligand-gated ion channels

The "threshold" potential of a membrane is the _____. minimum hyperpolarization needed to prevent the occurrence of action potentials peak amount of depolarization seen in an action potential minimum depolarization needed to operate the voltage-gated sodium and potassium channels lowest frequency of action potentials a neuron can produce

minimum depolarization needed to operate the voltage-gated sodium and potassium channels

Action potentials move along axons _____. more rapidly in myelinated than in non-myelinated axons by activating the sodium-potassium "pump" at each point along the axonal membrane by reversing the concentration gradients for sodium and potassium ions more slowly in axons of large than in small diameter

more rapidly in myelinated than in non-myelinated axons

Axons insulated by a(n) _____ are able to conduct impulses faster than those not so insulated. node of Ranvier synaptic terminal myelin sheath layer of asbestos astrocytes

myelin sheath

A chemical that affects neuronal function but is not stored in presynaptic vesicles is _____. nitric oxide epinephrine acetylcholine gamma-aminobutyric acid (GABA)

nitric oxide

An impulse relayed along a myelinated axon "jumps" from _____ to _____. oligodendrocyte ... Schwann cell node of Ranvier ... Schwann cell node of Ranvier ... node of Ranvier Schwann cell ... Schwann cell Schwann cell ... node of Ranvier

node of Ranvier ... node of Ranvier

Which of the following will increase the speed of an action potential moving down an axon? I) Action potentials move faster in larger diameter axons. II) Action potentials move faster in axons lacking potassium ion channels. III) Action potentials move faster in myelinated axons. only I and II only I and III only II and III I, II, and III

only I and III

In multiple sclerosis the myelin sheaths around the axons of the brain and spinal cord are damaged and demyelination results. How does this disease manifest at the level of the action potential? I) Action potentials move in the opposite direction on the axon. II) Action potentials move more slowly along the axon. III) No action potentials are transmitted. only I only II only III only II and III

only II

Two fundamental concepts about the ion channels of a "resting" neuron are that the channels _____. are always open, but the concentration gradients of ions frequently change open and close depending on stimuli, and are specific as to which ion can traverse them open in response to stimuli, and then close simultaneously, in unison are always closed, but ions move closer to the channels during excitation

open and close depending on stimuli, and are specific as to which ion can traverse them

The transmission first triggers the _____. action of the sodium-potassium pump opening of voltage-gated sodium channels and the diffusion of sodium ions into the neuron opening of voltage-gated sodium channels and the diffusion of sodium ions out of the neuron opening of voltage-gated potassium channels and the diffusion of potassium ions out of the neuron opening of voltage-gated potassium channels and the diffusion of potassium ions into the neuron

opening of voltage-gated sodium channels and the diffusion of sodium ions into the neuron

Receptors for neurotransmitters are of primary functional importance in assuring one-way synaptic transmission because they are mostly found on the _____. presynaptic membrane postsynaptic membrane axonal membrane axon hillock

postsynaptic membrane

An inhibitory postsynaptic potential (IPSP) occurs in a membrane made more permeable to _____. sodium ions potassium ions ATP all neurotransmitter molecules

potassium ions

Choose the set that includes the most charged compounds that are more abundant inside neurons, in the cytosol, than outside the neurons, in the extracellular fluid. potassium ions and proteins sodium and potassium ions sodium and chloride ions chloride ions and proteins proteins and sodium ions

potassium ions and proteins (Proteins are abundant in all cells of the body and are mostly anions, thus contributing significantly to the membrane potential; and potassium ions are actively pumped into the cytosol of all cells in the body.)

A toxin that binds specifically to voltage-gated sodium channels in axons would be expected to _____. prevent graded potentials prevent the hyperpolarization phase of the action potential increase the release of neurotransmitter molecules prevent the depolarization phase of the action potential

prevent the depolarization phase of the action potential

A nerve poison that blocks acetylcholine receptors on dendrites would _____. inhibit the regeneration of acetylcholine for use by the presynaptic terminals inactivate acetylcholinesterase, allowing acetylcholine to persist in the synapse reduce the binding of acetylcholine to its receptors on the postsynpatic membrane cause continued stimulation of the postsynaptic membrane cause an immediate and enduring depolarization

reduce the binding of acetylcholine to its receptors on the postsynpatic membrane

Although the membrane of a "resting" neuron is highly permeable to potassium ions, its membrane potential does not exactly match the equilibrium potential for potassium because the neuronal membrane is also _____. fully permeable to calcium ions slightly permeable to sodium ions highly permeable to chloride ions impermeable to sodium ions

slightly permeable to sodium ions

A stimulus has opened the voltage-gated sodium channels in an area of a neuron's plasma membrane. As a result, _____ rushes into the neuron and diffuses to adjacent areas; this in turn results in the _____ in the adjacent areas. potassium ... opening of voltage-gated potassium channels sodium ... opening of voltage-gated potassium channels sodium ... opening of voltage-gated sodium channels sodium ... closing of voltage-gated sodium channels potassium ... opening of voltage-gated sodium channels

sodium ... opening of voltage-gated sodium channels

The operation of the sodium-potassium "pump" moves _____. sodium ions into the cell and potassium ions out of the cell sodium ions out of the cell and potassium ions into the cell sodium and potassium ions out of the cell sodium and potassium ions into the cell

sodium ions out of the cell and potassium ions into the cell

The concentrations of ions are very different inside and outside a nerve cell due to _____. osmosis diffusion sodium-potassium pumps symports and antiports

sodium-potassium pumps

In a neuron, during the depolarization phase that may trigger an action potential _____. most voltage-gated sodium channels are open most voltage-gated sodium and potassium channels are open most voltage-gated sodium channels become inactivated some voltage-gated sodium channels are open most voltage-gated potassium channels are open

some voltage-gated sodium channels are open

The "undershoot" phase of after-hyperpolarization is due to _____. slow opening of voltage-gated sodium channels slow restorative actions of the sodium-potassium ATPase sustained opening of voltage-gated potassium channels rapid opening of voltage-gated calcium channels

sustained opening of voltage-gated potassium channels

The point of connection between two communicating neurons is called the _____. dendrite synapse axon hillock cell body

synapse

The space between an axon of one neuron and the dendrite of another neuron is called a(n) _____. synaptic cleft node of Ranvier internodes synapse synaptic terminal

synaptic cleft

What part of a neuron relays signals from one neuron to another neuron or to an effector? dendrite axon hillock synaptic terminal axon node of Ranvier

synaptic terminal

Neurons store neurotransmitter molecules in vesicles located within _____. the cell body myelin the synaptic cleft dendrites synaptic terminals

synaptic terminals

When two excitatory postsynaptic potentials (EPSPs) occur at a single synapse so rapidly in succession that the postsynaptic neuron's membrane potential has not returned to the resting potential before the second EPSP arrives, the EPSPs add together producing _____. the refractory state tetanus temporal summation spatial summation

temporal summation

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

the opening of voltage-gated potassium channels and the closing of sodium channels

In a simple synapse, neurotransmitter chemicals are received by _____. the presynaptic membrane axon hillocks cell bodies the postsynaptic membrane

the postsynaptic membrane

In a simple synapse, neurotransmitter chemicals are released by _____. cell bodies the presynaptic membrane axon hillocks ducts on the smooth endoplasmic reticulum

the presynaptic membrane

At rest, which of these plays a role in establishing the charge differential across a neuron's plasma membrane? the sodium-potassium pump moving sodium ions into the neuron and potassium ions out of the neuron the diffusion of sodium ions out of the neuron the diffusion of potassium ions into the neuron the sodium-potassium pump moving sodium ions out of the neuron and potassium ions into the neuron the diffusion of sodium ions into the neuron

the sodium-potassium pump moving sodium ions out of the neuron and potassium ions into the neuron

Ions move in the direction opposite to that favored by the chemical concentration gradient when _____.

they are pumped by proteins that require ATP hydrolysis and when the electrical charge gradient repulses or attracts them

Select the choice that describes neurons with the fastest conduction velocity for action potentials. thick, nonmyelinated neurons thin, myelinated neurons thin, nonmyelinated neurons thick, myelinated neurons All of these choices conduct action potentials at the same velocity.

thick, myelinated neurons

The fastest possible conduction velocity of action potentials is observed in _____. thin, myelinated neurons thin, non-myelinated neurons thick, non-myelinated neurons thick, myelinated neurons

thick, myelinated neurons

Action potentials are normally carried in only one direction: from the axon hillock toward the axon terminals. If you experimentally depolarize the middle of the axon to threshold, using an electronic probe, then _____. two action potentials will be initiated, one going toward the axon terminal and one going back toward the hillock an action potential will be initiated and proceed only in the normal direction toward the axon terminal an action potential will be initiated and proceed only back toward the axon hillock no action potential will be initiated

two action potentials will be initiated, one going toward the axon terminal and one going back toward the hillock