Which of the following is expected in a neuron that is receiving input through tens of thousands of synapses?

highly branched dendrites

A nerve is a collection of ________

axons

Which of the following best explains the observation that a resting neuron membrane, while highly permeable to potassium ions, is not at the equilibrium potential for potassium?

The membrane is also slightly permeable to sodium ion

The activity of the sodium-potassium pump results in the movement of which ions across the plasma membrane

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

A researcher uses the chemical inhibitor cyanide to reduce ATP production in a neuron. What would be one effect of preventing ATP production?

The "resting" distribution of potassium and sodium ions would be altered

Which of these ions is more abundant in the interior of a resting neuron than in the fluid surrounding the neuron?

K+

What do we call a membrane potential in which there is no net movement of an ion across a membrane?

an equilibrium potential

Which of the following describes the ion channels of a resting neuron?

The channels are open or closed depending on their type, and are specific as to which ion can traverse them

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 membrane potential would become less negative

The concentrations of sodium and potassium ions are very different inside and outside a neuron. What contributes to these differences

sodium-potassium pumps

The Nernst equation specifies the equilibrium potential for a particular ion. This equilibrium potential is a function of ________

the ion concentration gradient

If you treat a neuron with a drug that increases membrane permeability to Na+, how would you expect the equilibrium potential for Na+ to change?

remaine unchanged

For a neuron with an initial membrane potential at -70 mV, what would be the result of an increase in the movement of potassium ions out of that neuron's cytoplasm?

hyperpolarization of the neuron

Which of the following will induce a graded hyperpolarization of a membrane under normal resting conditions?

increasing its permeability to K+

Conduction and refractory periods are typical of __

action potentials

Action potentials move along axons ________

more rapidly in myelinated than in unmyelinated axons

After the depolarization phase of an action potential, the resting potential is restored by ________.

voltage-gated potassium channels opening and sodium channels inactivating

Which of the following describes the cause of the undershoot phase of hyperpolarization?

the sustained opening of voltage-gated potassium channels

Which of the following would produce the fastest possible conduction velocity of action potentials?

thick, myelinated axons

Which of the following would most likely occur if you experimentally depolarize the middle of an axon to threshold using an electronic probe?

two action potentials will be initiated and will proceed in opposite directions

Why are action potentials conducted usually in one direction along an axon

The brief refractory period prevents reopening of voltage-gated sodium channels

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 become more negative

Which of the following statements about action potentials is correct?

Action potentials propagate towards the synaptic terminal of an axon

Which answer explains why Na+ ions enter the cell when voltage-gated Na+ channels are opened in neurons

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

A neurophysiologist is investigating 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 a likely explanation?

the fish's axons are myelinated. The crab's axons are not myelinated

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 shift of resting potentia

In multiple sclerosis, the myelin sheaths around the axons of the brain and spinal cord are damaged and demyelination results. How does multiple sclerosis manifest at the level of the action potential

Action potentials move more slowly along the axon.

If a pebble is tossed into a pond, it generates small ripples that decrease in size as the ripples move away from the point where the pebble struck the water. The decreasing size of the ripples as they move away from the initial splash is most like the way that signals spread ______

in a graded potential

At a neuromuscular junction, what process releases acetylcholine into the synaptic cleft?

exocytosis

Acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium/potassium channel and opens it. This is an example of ________

a ligand gated channel

An inhibitory postsynaptic potential (IPSP) will occur if a membrane is made more permeable to

potassium ions

The following are events in the transmission of a signal 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

Which of the following is an example of a ligand-gated channel?

acetylcholine receptors at a neuromuscular junction

Neurotransmitters categorized as inhibitory are expected to ____

hyperpolarize the membrane

Excitatory postsynaptic potentials (EPSPs) occurring at multiple synapses on the same postsynaptic neuron can add together through __

spatial summation

Which of the following explains why one-way synaptic transmission occurs?

Receptors for neurotransmitters are mostly found on the postsynaptic membrane.

Which of the following is a characteristic of an electrical synapse?

gap junctions

The botulinum toxin, which causes botulism, inhibits __

presynaptic release of acetylcholine

Which of the following will decrease the heart rate of a vertebrate?

acetylcholine

What chemical affects neuronal function but is not stored in presynaptic vesicles

nitric oxide

What would most likely happen if twice as many inhibitory postsynaptic potentials (IPSPs) as excitatory postsynaptic potentials (EPSPs) arrive in close proximity at a postsynaptic neuron?

no action potential

Which of the following is the most likely effect of applying the naturally occurring acetylcholinesterase inhibitor onchidal (produced by the mollusc Onchidella binneyi) to a neuromuscular junction?

the muscle cell would receive constant stimulation

Where are neurotransmitters released in a synapse?

the presynaptic membrane

A common feature of action potentials is that they ________

are triggered by a depolarization that reaches threshold

Why are action potentials usually conducted in one direction?

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

Suppose a particular neurotransmitter causes an IPSP in postsynaptic cell X and an EPSP in postsynaptic cell Y. A likely explanation is that ______

cells X and Y express different receptor molecules for this particular neurotransmitter

Which of the following is the most direct result of depolarizing the presynaptic membrane of an axon terminal?

Voltage-gated calcium channels in the membrane open