chapter 8

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).

-60 mV

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

-80 mV

A chemical synapse USUALLY includes ________. 1. axon terminal 2. presynaptic cell 3. synaptic cleft 4. postsynaptic cell 5. dendrite

1, 2, 3, 4

The following are steps involved in transmission at the cholinergic synapse: 1. Chemically regulated ion channels on the postsynaptic membrane are activated. 2. Calcium ions enter the axon terminal. 3. An action potential depolarizes the axon terminal at the presynaptic membrane. 4. Acetylcholine is released from storage vesicles by exocytosis. 5. Acetylcholine binds to receptors on the postsynaptic membrane. The correct sequence for these events is

3, 2, 4, 5, 1

Arrange the following events in the proper sequence: 1. Efferent neuron reaches threshold and fires an action potential. 2. Afferent neuron reaches threshold and fires an action potential. 3. Effector organ responds by performing output. 4. Integrating center reaches decision about response. 5. Sensory organ detects change in the environment.

5, 2, 4, 1, 3

Match the part of the neuron to its description. A. dendrites B. axon C. cell body receive(s) most of the incoming synapses

A. dendrites

When two or more graded potentials arrive at the trigger zone, which of the following could happen?

An excitatory and inhibitory signal can cancel each other out; two excitatory stimuli may be additive, and summation could occur; and two inhibitory stimuli may be additive, resulting in lower excitability.

Once the stimulus alters the receptor on the cell's membrane, what happens next?

Any of these actions could happen next.

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.

Which is/are the most common inhibitory neurotransmitter(s) of the CNS?

GABA and glycine

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 major determinant of the resting potential of all cells is

K+ gradient between the blood and interstitial fluid.

When voltage-gated Na+ channels of a resting neuron open,

Na+ enters the neuron and the neuron depolarizes.

The rising phase of the action potential is due to

Na+ flow into the cell only.

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

Nicotinic cholinergic

If a hyperpolarizing graded potential and a depolarizing graded potential of similar magnitudes arrive at the trigger zone at the same time, what is most likely to occur?

Nothing. They will cancel each other out.

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.

Myelin is formed by

Schwann cells and oligodendrocytes.

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

Stimulus 3

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.

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.

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?

a pseudounipolar neuron

A weak, subthreshold stimulus will result in _______.

a small depolarization at the receiving end of the neuron

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

absolute refractory period.

Match the type of signal to its description. A. graded potential B. action potential C. both originate(s) at the trigger zone

action potential

Match the type of signal to its description. A. graded potential B. action potential C. both require(s) a minimum stimulus to occur

action potential

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

afferent and sensory

The all-or-none principle states that

all stimuli great enough to bring the membrane to threshold will produce action potentials of identical magnitude.

A depolarizing synaptic potential is also known as _______.

an excitatory postsynaptic potential

Match the term with its description. A. ependymal cells B. astrocytes C. satellite cells D. schwann cells E. oligodendrocytes F. microglia highly branched cells that transfer nutrients between blood vessels and neurons

astrocytes

An excitatory postsynaptic potential occurs _______.

at the receiving end of the interneuron

Match the part of the neuron to its description. A. dendrites B. axon C. cell body location of voltage-gated ion channels

axon

Neurotransmitter is stored and released from

axon terminals and axon varicosities.

A damaged neuron has a better chance of survival and repair if the ________ is/are undamaged.

cell body

Match the part of the neuron to its description. A. dendrites B. axon C. cell body make(s) proteins necessary for repair of damaged neuron

cell body

Match the part of the neuron to its description. A. dendrites B. axon C. cell body supported by satellite cells

cell body

Match the glial cell to the nervous system division in which it is found. A. central nervous system B. peripheral nervous system ependymal cells

central nervous system

Match the glial cell to the nervous system division in which it is found. A. central nervous system B. peripheral nervous system microglia

central nervous system

At a(n) ________ synapse, a neurotransmitter is released to affect the postsynaptic cell.

chemical

Which type of synapse is most prevalent in the nervous system?

chemical

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.

An excitatory postsynaptic potential (EPSP)

depolarizes a neuron, increasing the likelihood of an action potential.

The absolute refractory period of an action potential

ensures one-way travel down an axon, allows a neuron to ignore a second signal sent that closely follows the first, and prevents summation of action potentials.

Match the term with its description. A. ependymal cells B. astrocytes C. satellite cells D. schwann cells E. oligodendrocytes F. microglia cells that are a source of neural stem cells

ependymal cells

Graded potentials that arrive at postsynaptic neurons are called ________ if they make that cell more likely to fire.

excitatory

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

The inactivation gate

is coupled to the movement of the activation gate, but is much slower.

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

leakage

A suprathreshold stimulus results in _______.

more action potentials

Spatial summation refers to

multiple graded potentials arriving at one location simultaneously.

Increasing the voltage resulted in which of the following?

no change to the action potential

The gaps between adjacent Schwann cells on an axon are called

nodes of Ranvier

A single action potential is described as _______.

not graded

Match the term with its description. A. ependymal cells B. astrocytes C. satellite cells D. schwann cells E. oligodendrocytes F. microglia cells in the CNS that form myelin

oligodendrocytes

Which glial cells form myelin in the central nervous system?

oligodendrocytes

The inhibitory neurotransmitters of the CNS, GABA and glycine, act by opening ________ channels.

only Cl-

Glial cells

only guide neurons during growth and repair. only help maintain homeostasis of the brain's extracellular fluid. provide structural and metabolic support and help maintain homeostasis of the brain's extracellular fluid. only provide structural and metabolic support. All of the answers are correct.

Interneurons are found

only in the CNS.

The point during an action potential when the inside of the cell has become more positive than the outside is known as the

overshoot.

Match the glial cell to the nervous system division in which it is found. A. central nervous system B. peripheral nervous system Schwann cells

peripheral nervous system

The afferent and efferent axons together form the

peripheral nervous system.

Which ion(s) is/are higher in concentration inside the cell compared to outside?

potassium

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

potassium ions leaving the cell

When sodium channels open during an action potential, the opening is caused by

presence of positive charge.

The sodium-potassium exchange pump

requires ATP to function

Match the term with its description. A. ependymal cells B. astrocytes C. satellite cells D. schwann cells E. oligodendrocytes F. microglia cells that form supportive capsules around cell bodies

satellite cells

Match the term with its description. A. ependymal cells B. astrocytes C. satellite cells D. schwann cells E. oligodendrocytes F. microglia cells that myelinate only one axon each; multiple cells per axon

schwann cells

To increase the amount of neurotransmitter released onto a postsynaptic cell, the presynaptic cell would have to

send action potentials with higher frequency.

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

sensory

The stimulus for graded potentials includes _______.

sensory stimuli and neurotransmitter

Calcium is important in the synapse because it

signals the exocytosis of the neurotransmitter.

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

sodium-potassium pump

Autonomic motor neurons are subdivided into the

sympathetic and parasympathetic divisions.

When a second EPSP arrives at a single synapse before the effects of the first have disappeared, what occurs?

temporal summation

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

the autonomic nervous system

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

The Nernst equation predicts

the membrane potential resulting from permeability to a single ion.

Which stimulus was at or above threshold?

the moderate and strong stimuli

What does the Goldman-Hodgkin-Katz equation take into account that the Nernst equation does NOT?

the permeabilities of the ions

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

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

threshold voltage

The resting membrane potential results from

uneven distribution of ions across the cell membrane and differences in membrane permeability to Na+ and K+.