MA&P Chapter 12

What is the magnitude (amplitude) of an action potential?

100 mV

What is the typical duration of a nerve action potential?

2 ms

The ________ division of the peripheral nervous system brings sensory information to the central nervous system.

afferent

The part of the peripheral nervous system that carries sensory information to the CNS is the

afferent division

The ________ principle states that the size and speed of the action potential are independent of the stimulus strength

all or none

The all-or-none principle states that

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

Neurons that are rare, small, and lack features that distinguish dendrites from axons are called

anaxonic

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

temporal

The simplest level of information processing takes place at the __________.

axon hillock

The site in the neuron where EPSPs and IPSPs are integrated is the

axon hillock

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

chemical

________ open or close in response to binding specific molecules.

chemically gated channels

Branches that may occur along an axon are called

collaterals

The ________ division of the nervous system carries motor commands to muscles and glands.

efferent

________ carry motor information to peripheral effectors.

efferent neurons

Binding of the neurotransmitter to its receptor causes the membrane to __________.

either depolarize or hyperpolarize

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

________ monitor the digestive, respiratory, cardiovascular, urinary, and reproductive systems.

internoceptors

A molecule that carries information across a synaptic cleft is a

neurotransmitter

Clusters of RER and free ribosomes in neurons are called

nissl bodies

The tiny gaps between adjacent Schwann cells are called

nodes of Ranvier

Adrenergic synapses release the neurotransmitter

norepinephrine

Which of these neurotransmitters is released at CNS adrenergic synapses?

norepinephrine

The myelin sheath that covers many CNS axons is formed by

oligodendrocytes

Hyperpolarization results from __________.

slow closing of voltage gated potassium channels

The velocity of the action potential is fastest in which of the following axons?

small myelinated axon

What ion is responsible for the depolarization of the neuron during an action potential?

sodium

When cholinergic receptors are stimulated,

sodium ions enter the postsynaptic neuron

The ________ nervous system controls the skeletal muscles.

somatic

Summation that results from the cumulative effect of multiple synapses at multiple places on the neuron is designated

spatial summation

What is the electrochemical gradient of an ion?

the sum of the electrical and chemical gradients for that ion

The minimum stimulus required to trigger an action potential is known as the

threshold stimulus

Which of the following types of nerve fiber possesses the fastest speed of impulse propagation?

type A

Sensory information from skeletal muscles travels over

type A fibers

Neurons in which dendritic and axonal processes are continuous and the soma lies off to one side are called

unipolar

Sensory neurons of the PNS are

unipolar

Neurotransmitters ready for release are stored in synaptic

vesicles

The generation of an action potential in a neuron requires the presence what type of membrane channels?

voltage gated channels

The depolarization phase of an action potential results from the opening of which channels?

voltage gated sodium channels

Deteriorating changes in the distal segment of an axon as a result of a break between it and the soma is called ________ degeneration.

wallerian

Regions of the CNS with an abundance of myelinated axons constitute the

white matter

Where do most action potentials originate?

initial segment

What is an example of a presynaptic cell?

neuron

The resting membrane potential of the cell is

-70 mV

The sodium-potassium exchange pump stabilizes resting potential of the neuron membrane at about __________.

-70 mV

In a typical neuron, what is the equilibrium potential for potassium?

-90 mV

The point at which there is no net movement of K+ into or out of the cell is

-90 mV

In a typical neuron, what is the equilibrium potential for sodium?

66 mV

The concentrations of which two ions are highest outside the cell?

Na+ and Cl−

What opens first in response to a threshold stimulus?

Voltage-gated Na+ channels

What type of channel in the postsynaptic membrane binds neurotransmitter?

a chemically gated channel

If the axolemma becomes more permeable to potassium ion,

a stronger stimulus will be required to cause an action potential.

The period during which an excitable membrane cannot respond to further stimulation is the ________ period.

absolute refractory

Cholinergic synapses release the neurotransmitter

acetylcholine.

The largest and most numerous of the glial cells in the central nervous system are the

astrocytes

The neuroglial cells that participate in maintaining the blood-brain barrier are the

astrocytes

When a person has a stroke, blood leaks into the brain tissue. Which type of neuroglia cells would repair the damage?

astrocytes

Where are action potentials regenerated as they propagate along a myelinated axon?

at the nodes

The ________ nervous system provides involuntary regulation of smooth muscle, cardiac muscle, and glandular activity.

autonomic

The plasma membrane of an axon is called the

axolemma

The axon is connected to the soma at the

axon hillock

What is the role of neurotransmitter at a chemical synapse?

binds to receptors on the postsynaptic cell membrane.

________ neurons are short, with a cell body between dendrite and axon, and occur in special sense organs

bipolar

Raising the potassium ion concentration in the extracellular fluid surrounding a nerve cell will have what effect?

both hyperpolarize it and decrease the magnitude of the potassium equilibrium potential

During depolarization, which gradient(s) move(s) Na+ into the cell?

both the electrical and chemical gradients

Which ion triggers synaptic vesicles to discharge neurotransmitter into the synaptic cleft?

calcium

The afferent division of the PNS __________.

carries sensory information

The ________ nervous system is composed of the brain and spinal cord.

central

Most neurons lack ________ and so are permanently blocked from undergoing cell division.

centrioles

Leak channels allow the movement of potassium and sodium ions by what type of membrane transport?

channel mediated diffusion

Functions of astrocytes include all of the following except

conducting action potentials

Integral membrane proteins that connect electrical synapses are called

connexons

What type of conduction takes place in unmyelinated axons?

continuous conduction

A movement of charges in response to a potential difference is called

current

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

Opening of sodium channels in the axon membrane causes

depolarization

A threshold stimulus is the

depolarization necessary to cause an action potential

What triggers the release of acetylcholine from a synaptic terminal?

diffusion of calcium ions into the synaptic terminal

Which of the following is a recognized class of opioid neuromodulators?

endomorphins, dynorphins, enkephalins and endorphins

Which of these substances is considered a neuromodulator?

endorphins

________ line the brain ventricles and spinal canal.

ependymal cells

What mechanism releases neurotransmitter from presynaptic neurons?

exocytosis

________ provide information about the external environment.

exteroceptors

What type of membrane transport causes the depolarization phase of the action potential in neurons?

facilitated diffusion

Compared to nerve action potentials, muscle action potentials do NOT have __________.

faster propagation

Damage to ependymal cells would most likely affect the

formation of cerebrospinal fluid

The efferent division of the peripheral nervous system innervates ________ cells.

glandular, heart muscle, skeletal muscle and smooth muscle

Regions of the CNS where neuron cell bodies dominate constitute the

gray matter

Voltage-gated channels are present

in the membrane that covers axons

Voltage-gated sodium channels have both an activation gate and a(n) ________ gate.

inactivation

What is the function of the myelin sheath?

increases the speed of action potential conduction from the initial segment to the axon terminals

Which of the following is true about threshold for an action potential?

it is more positive than the resting potential

If a nerve cell receives many IPSPs in different locations at the same time, __________.

it will show spatial summation

Ion channels that are always open are called

leak channels

________ open or close in response to physical distortion of the membrane surface.

mechanically gated channels

Which of the following is not a function of the neuroglia?

memory

Small, wandering cells that engulf cell debris and pathogens in the CNS are called

microglia

The sodium-potassium ion exchange pump

moves sodium and potassium to the direction opposite of their gradients

Neurons that have several dendrites and a single axon are called

multipolar

The most abundant class of neuron in the central nervous system is

multipolar

In which type of axon will velocity of action potential conduction be the fastest?

myelinated axons with the largest diameter

Saltatory propagation occurs in _________ axons, in which action potentials _________.

myelinated; move from one node of Ranvier to another

________ account for roughly half of the volume of the nervous system.

neuroglia

Compounds that alter the rate of neurotransmitter release by the presynaptic neuron or change the postsynaptic cell's response to neurotransmitters are called

neuromodulators

The basic functional unit of the nervous system is the

neuron

The repolarization phase of an action potential results from __________.

opening of voltage gated potassium channels

Which type of ion channel is always open?

passive channel

The cytoplasm that surrounds the nucleus of a neuron is called the

perikaryon

The nervous tissue outside of the central nervous system composes the ________ nervous system.

peripheral

A neuron that receives neurotransmitter from another neuron is called

postsynaptic neuron

What ion causes repolarization of the neuron during an action potential?

potassium

During repolarization of a neuron

potassium ions move out of the cell

The most abundant intracellular cation is __________ while the most abundant extracellular anion is __________.

potassium; chloride

The separation of positive and negative charges across the membrane creates a ________ difference, or voltage.

potential

GABA produces what?

presynaptic inhibition

In a synapse, neurotransmitters are stored in vesicles located in the __________.

presynaptic neuron

________ monitor the position of skeletal muscles and joints.

proprioceptors

The period during which an excitable membrane can respond again, but only if the stimulus is greater than the threshold stimulus, is the ________ period.

relative refractory

A change in the conditions in the synaptic terminal can influence the soma as a result of ________ transport.

retrograde

Rapid impulse conduction from "node" to "node" is called

saltatory propagation

Glial cells that surround the neurons in ganglia are

satellite cells

Which of the following is a type of glial cell found in the peripheral nervous system?

satellite cells

________ neurons form the afferent division of the PNS.

sensory

Opioids relieve pain by blocking the release of

substance P

The __________ nervous system controls glandular secretion.

sympathetic and parasympathetic

The site of intercellular communication between a neuron and another cell is the

synapse

Axons terminate in a series of fine extensions known as

telodendria