Physiology Mastering Ch. 8

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Which membrane potential opens a sufficient number of the voltage-gated Na+ channels to cause a significant change in the membrane potential (making it much less negative).

-60mv

What is the resting membrane potential of the neuron used in the experiment?

-80 mv

Which two properties determine the conduction velocity in a mammalian neuron?

Axon diameter and the leak resistance of the membrane

Which of the following describes a similarity between graded potentials and action potentials?

Both can involve voltage-gated sodium channels.

The part of the neuron that receives most of the incoming signals is the __________.

Dendrite

The multiple thin, branched structures on a neuron whose main function is to receive incoming signals are the

Dendrites

Anterograde and retrograde axonal transport are forms of ________ transport.

Fast

An axon that is more negative than the resting membrane potential is said to be _______.

Hyperpolarized

Where do most action potentials originate?

Initial segment

During an action potential, activation of voltage-gated sodium and potassium channels occurs at different rates. What is the effect of this difference on ion flow across an axon membrane?

Initially, Na+ flows into the cell followed by K+ flowing out of the cell.

If an increase in extracellular potassium hyperpolarizes a neuron, which of the following would be correct?

It would change the membrane potential to a more negative value.

What would happen to the membrane potential if a resting cell suddenly becomes more permeable to Na+?

It would depolarize

The channels that provide for the movement of potassium in the resting neuron are _______.

Leakage

Which type of receptor would bind acetylcholine and be found in skeletal muscle?

Nicotinic cholinergic

Which glial cells form myelin in the central nervous system?

Oligodendrocytes

What characterizes repolarization, the second phase of the action potential?

Once the membrane depolarizes to a peak value of +30 mV, it repolarizes to its negative resting value of -70 mV.

What effect did decreasing the extracellular sodium have on the resting membrane potential?

Only a small change occurred, because the resting neuron is not very permeable to sodium.

Interneurons are found

Only in the CNS

The afferent and efferent axons together form the

Peripheral nervous system

Most neurons have at least two processes extending from the soma, or cell body. Which type of neuron only has one process extending from the cell body?

Pseudounipolar neuron

Myelin is formed by

Schwann cells and oligodendrocytes.

Which of the following neurons or groups of neurons are NOT considered to be a part of the efferent pathway?

Sensory

Establishing the resting membrane potential requires energy through the use of the _______.

Sodium-potassium pump

In this experiment, which stimulus causes the membrane potential to reach the threshold value?

Stimulus 3

The sympathetic and parasympathetic nervous systems are divisions of which system?

The autonomic nervous system

What characterizes depolarization, the first phase of the action potential?

The membrane potential changes from a negative value to a positive value.

What event triggers the generation of an action potential?

The membrane potential must depolarize from the resting voltage of -70 mV to a threshold value of -55 mV.

What effect did increasing the extracellular potassium have on the resting membrane potential?

The resting membrane potential became less negative

Why are Na+, K+, and Cl- the only ions considered in the GK equation when calculating resting membrane potential (Vm)?

These are the ions to which cell membranes are permeable at rest.

The minimum voltage that is required to generate an action potential is called the _______.

Threshold voltage

What opens first in response to a threshold stimulus?

Voltage-gated Na+ channels

What is the first change to occur in response to a threshold stimulus?

Voltage-gated Na+ channels change shape, and their activation gates open.

A weak, subthreshold stimulus will result in _______.

a small depolarization at the receiving end of the neuron

Information coming into the central nervous system is transmitted along ________ neurons.

afferent and sensory

A depolarizing synaptic potential is also known as _______.

an excitatory postsynaptic potential

An excitatory postsynaptic potential occurs _______.

at the receiving end of the interneuron

Neurotransmitter is stored and released from

axon terminals and axon varicosities.

A suprathreshold stimulus results in _______.

more action potentials

Increasing the voltage resulted in which of the following?

no change to the action potential

A single action potential is described as _______.

not graded

Which of the following would NOT cause the membrane potential to change from -70 mV to +30 mV?

potassium ions leaving the cell

The stimulus for graded potentials includes _______.

sensory stimuli and neurotransmitter

Autonomic motor neurons are subdivided into the

sympathetic and parasympathetic divisions.

Increasing the strength of the stimulus applied to the sensory receptor increased _______.

the frequency of action potentials in the sensory neuron, the amount of neurotransmitter released at the axon terminal of the sensory neuron and the frequency of action potentials in the interneuron

Which stimulus was at or above threshold?

the moderate and strong stimuli

Whether or not a neuron produces an action potential at a given moment depends on ________.

the total potential change reaching threshold voltage at the trigger zone


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