Anatomy Chapter 12

The equilibrium potential of sodium is

+66mV.

The equilibrium potential of potassium is

-90mV.

On which structure do most neuron to neuron communications occur?

A

__________ carry sensory information to the CNS.

Afferent neurons

Neurofilament

C

Which of the following can cause demyelination?

Demyelination can be caused by arsenic, diphtheria, multiple sclerosis and mercury.

________ carry motor information to peripheral effectors.

Efferent neurons

Which part(s) of the neuron can propagate an action potential?

L

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 designated

afferent.

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.

What type of membrane channels are found at label "L"?

both voltage-gated Na+ channels and voltage-gated K+ channels

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

central

The sum of the electrical and chemical forces acting on an ion is known as its

electrochemical gradient.

The most common neuron of the nervous system is the

interneuron

Ion channels that are always open are called ________ channels.

leak

Graded potentials

may be either a depolarization or a hyperpolarization.

Which of the following is not involved in creating the resting membrane potential of a neuron?

membrane permeability for sodium ions greater than potassium ions

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

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

skeletal muscle, smooth muscle, heart muscle, glandular

The ________ nervous system controls the skeletal muscles.

somatic

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

synapse.

Identify the structure labeled "N"

synaptic terminals

Axons terminate in a series of fine extensions known as

telodendria

Identify the structure labeled "M"

telodendria

When potassium channels open and the ions diffuse through the membrane,

the inside of the membrane will become more negative.

If the sodium-potassium pumps in the plasma membrane fail to function, all of the following occur except

the intracellular concentration of potassium ions will increase.

Ions can move across the plasma membrane in which of the following ways?

through voltage-gated channels as in the action potential, through passive or leak channels, by ATP-dependent ion pumps like the sodium-potassium exchange pump, through chemically gated channels as in neuromuscular transmission

Sensory neurons of the PNS are

unipolar

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

unipolar.

Any stimulus that opens a ________ ion channel will produce a graded potential.

voltage-gated, chemically gated, sodium, mechanically gated

Regions of the CNS with an abundance of myelinated axons constitute the ________ matter.

white

The following are the main steps in the generation of an action potential. 1. Sodium channels are inactivated. 2. Voltage-gated potassium channels open and potassium moves out of the cell, initiating repolarization. 3. Sodium channels regain their normal properties. 4. A graded depolarization brings an area of an excitable membrane to threshold. 5. A temporary hyperpolarization. 6. Sodium channel activation occurs. 7. Sodium ions enter the cell and depolarization.

4, 6, 7, 1, 2, 3, 5

_______ open or close in response to binding specific molecules.

Chemically gated channels

________ nerves are nerves that connect to the brain.

Cranial

Dendrites

Dendrites membranes contain numerous chemically gated ion channels.

Which of the following is not true regarding the establishment of a neuron's resting membrane potential?

Electrical forces do not push sodium ions into the cell.

_________ line the brain ventricles and spinal canal.

Ependymal cells

What is happening at the low point?

Excessive potassium has diffused out causing hyperpolarization.

__________ provide information about the external environment.

Exteroceptors

___________ are the most numerous type of neuron in the CNS.

Interneurons

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

Internoceptors

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

It is more positive than the resting membrane potential.

Which of the following is not a function of astrocytes?

They rebuild injured neurons.

Branches that may occur along an axon are called

collaterals

Damage to ependymal cells would most likely affect the

formation of cerebrospinal fluid.

The basic functional unit of the nervous system is the

neuron.

When pressure is applied to neural tissue, all of the following effects are possible except

neurons are triggered to divide

The rabies virus travels to the CNS via

retrograde axoplasmic transport

Glial cells that surround the neurons in ganglia are

satellite cells.

At the normal resting membrane potential of a typical neuron, its sodium-potassium exchange pump transports

3 intracellular sodium ions for 2 extracellular potassium ions.

How would the absolute refractory period be affected if voltage-regulated sodium channels failed to inactivate?

It would last indefinitely.

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

Mechanically gated

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

Neuroglia

Clusters of RER and free ribosomes in neurons are called

Nissl bodies

___________ monitor the position of skeletal muscles and joints.

Proprioceptors

The neurilemma of axons in the peripheral nervous system is formed by

Schwann cells

What is happening between the middle and high point?

Sodium ions are entering the axon and causing depolarization.

________ nerves are nerves that connect to the spinal cord.

Spinal

Puffer fish poison blocks voltage-gated sodium channels like a cork. What effect would this neurotoxin have on the function of neurons?

The axon would be unable to generate action potentials.

How would a chemical that prevents the opening of voltage-regulated Na+ channels affect the function of a neuron?

The neuron will only be capable of producing graded potentials.

Which of the following statements about the action potential is false?

The rapid depolarization phase is caused by the entry of potassium ions.

How does blocking retrograde axoplasmic transport in an axon affect the activity of a neuron?

The soma becomes unable to respond to changes in the distal end of the axon.

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

Wallerian

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.

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

Neurons that have one axon and one dendrite, with the soma in between, are called

bipolar.

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

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

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

centrioles

If acetylcholine (ACh) causes inhibition of a postsynaptic neuron, to what type of membrane channel did the ACh bind?

chemically-regulated potassium channel

Functions of astrocytes include all of the following, except

conducting action potentials.

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

current.

A threshold stimulus is the

depolarization necessary to cause an action potential.

A shift of the resting transmembrance potential toward 0 mV is called

depolarization.

Opening of sodium channels in the axon membrane causes

depolarization.

All of the following cause demyelination except

dopamine deficiency.

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

efferent

In the peripheral nervous system, Schwann cells participate in the repair of damaged nerves by

forming a cellular cord that directs axonal regrowth.

Regions of the CNS where neuron cell bodies dominate constitute the ________ matter.

gray

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

If the permeability of a resting axon to a sodium ion increases,

inward movement of sodium will increase and the membrane will depolarize.

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 opposite to the direction of their electrochemical gradients.

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

multipolar

Neurons that have several dendrites and a single axon are called

multipolar.

What is contained inside a synaptic terminal?

neurotransmitter molecules

The axoplasm of the axon contains which of the following?

neurotubules, mitochondria, vesicles, neurofibrils

The tiny gaps between adjacent Schwann cells are called

nodes of Ranvier.

The myelin sheath that covers many CNS axons is formed by

oligodendrocytes.

During depolarization of a neuron

potassium ions move out of the cell.

Which of the following is not a recognized structural classification for neurons?

pseudopolar

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

satellite cells

Which of the following activities or sensations is/are not monitored by interoceptors?

sight