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Peripheral Nervous System: Structure, Function, and Components, Quizzes of Physiology

Definitions and descriptions of the peripheral nervous system (pns), its two divisions - spinal and cranial nerves, and the functions of each. Additionally, it discusses the motor division, somatic and autonomic nervous systems, neuroglia, and specific glial cells such as astrocytes and microglial cells. The document also touches upon ependymal cells, oligodendrocytes, and satellite cells.

Typology: Quizzes

2017/2018

Uploaded on 03/25/2018

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TERM 1
What are the three organizations of the
nervous system?
DEFINITION 1
Central Nervous System (CNS)Peripheral Nervous System
(PNS)Autonomic Nervous System (ANS)
TERM 2
What are the two division of the central
nervous system (CNS)?
DEFINITION 2
BrainSpinal Cord
TERM 3
What is the function of the central nervous
system (CNS)?
DEFINITION 3
The functions of the CNS are:
Interpreting Sensory Input (Afferent Input)
Directing the Motor Response (Efferent Output)
*The afferent and efferent input leads to homeostasis.
TERM 4
Describe the peripheral nervous system (PNS)
and the function of the PNS
DEFINITION 4
The peripheral nervous system (PNS) is the part of the
nervous system located outside of the CNS; consisting mainly
of nerves (any nerves located outside of the spinal cord and
brain are referred to as the PNS). The function of the PNS is
to act as communication lines (how human beings sense the
world).
TERM 5
What are the two divisions (nerves) of the
peripheral nervous system (PNS)? Describe
the function of each division
DEFINITION 5
The two divisions of nerves in the PNS are:
Spinal Nerves: send information to and from the spinal
cord
Cranial Nerves: send information to and from the brain
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What are the three organizations of the

nervous system?

Central Nervous System (CNS)Peripheral Nervous System

(PNS)Autonomic Nervous System (ANS)

TERM 2

What are the two division of the central

nervous system (CNS)?

DEFINITION 2

BrainSpinal Cord

TERM 3

What is the function of the central nervous

system (CNS)?

DEFINITION 3

The functions of the CNS are:

Interpreting Sensory Input (Afferent Input)

Directing the Motor Response (Efferent Output)

*The afferent and efferent input leads to homeostasis.

TERM 4

Describe the peripheral nervous system (PNS)

and the function of the PNS

DEFINITION 4

The peripheral nervous system (PNS) is the part of the

nervous system located outside of the CNS; consisting mainly

of nerves (any nerves located outside of the spinal cord and

brain are referred to as the PNS). The function of the PNS is

to act as communication lines (how human beings sense the

world).

TERM 5

What are the two divisions (nerves) of the

peripheral nervous system (PNS)? Describe

the function of each division

DEFINITION 5

The two divisions of nerves in the PNS are:

Spinal Nerves: send information to and from the spinal

cord

Cranial Nerves: send information to and from the brain

How many cranial nerves are located within

the peripheral nervous system?

TERM 7

Describe the motor (efferent) division of the

peripheral nervous system (PNS)

DEFINITION 7

The motor (efferent) division (carrying away) of the PNS

contains nerves that are sent to effector organs (activating

muscles to contract or glands to secrete); a way to effect or

work all of the different motor responses (effect or bring

about a motor response).

TERM 8

Describe the somatic nervous system of the

peripheral nervous system (PNS)

DEFINITION 8

The somatic nervous system is composed of somatic motor nerve

fibers that conduct impulses from the CNS to skeletal muscles

(often referred to as the voluntary nervous system; conscious

control of muscles). The motor (efferent) division of the PNS is also

considered the somatic nervous system. The somatic nervous

system is made up of motor nerves, that are always attached to

muscle and innervate muscles that are voluntary.

TERM 9

Describe the autonomic nervous system

(ANS)

DEFINITION 9

The autonomic nervous system (ANS) consists of visceral

motor nerve fibers that regulate the activity of smooth

muscles, cardiac muscles and glands (innervate organs). The

ANS is an involuntary system (no control).

TERM 10

What are the two sub-divisions of the

autonomic nervous system (ANS)? What are

the functions of each sub-division?

DEFINITION 10

The two sub-divisions of the autonomic nervous system are:

Sympathetic: stimulates

Parasympathetic: inhibits

*The sub-divisions can reverse roles for specific organs.

Describe an ependymal cell. What are the two

functions of an ependymal cell?

An ependymal cell is a squamous, columnar cell will cilia (hairs)

that line the brain and spinal cord cavities. The two functions of an

ependymal cell are:

Barrier: ependymal cells act as a barrier between cerebral

spinal fluid (CSF) and the tissues of the central nervous system

(CNS); ependymal cell are one of the constructs of the blood-

brain barrier (nothing enters the spinal cord or brain)

Circulation: ependymal cells help control the circulation of

cerebral spinal fluid (CSF) with cilia (the CSF acts as

cushioning)

TERM 17

Describe an oligodendrocyte. What is the

function of an oligodendrocyte?

DEFINITION 17

An oligodendrocyte is round, with very few processes and is

located between two neurons. The function of an

oligodendrocyte is to wrap around a neuron of the CNS,

essentially forming the myelin sheath. The myelin sheath is

an insulated covering for the neuron (akin to an electrical

wiring covering).

TERM 18

What are the two types of neuroglia found

within the peripheral nervous system (PNS)?

How do the two types differ from one

another?

DEFINITION 18

Satellite CellsSchwann Cells*The two types of neuroglia

found within the PNS only differ in terms of location.

TERM 19

Describe the satellite cells of the peripheral

nervous system (PNS)

DEFINITION 19

The satellite cells surround the neuronal cell bodies located in the

peripheral nervous system (PNS); clusters of neuronal cell bodies

in the PNS are referred to as ganglia. The satellite cells of the PNS

have many of the same functions as the astrocytes from the CNS.

The satellite cells regulate and stabilize the environment around

ganglion cell bodies.*The satellite cells and Schwann Cells of the

PNS only differ in terms of location.

TERM 20

Describe the Schwann Cells of the peripheral

nervous system (PNS)

DEFINITION 20

The Schwann Cells of the PNS surround all nerve fibers located in

the PNS and form the myelin sheath for thicker nerve fibers.

Functionally, Schwann Cells are similar to Oligodendrocytes

(Oligodendrocytes form the covering for thicker nerve fibers of the

CNS). The Schwann Cells are vital to regeneration of damaged

peripheral nerve fibers (a Schwann Cell assists in the repair of

peripheral nerves).

What is an important distinct characteristic of

the peripheral nervous system (PNS), that is

absent in the central nervous system (CNS)?

An important characteristic of the PNS, that is absent in the

CNS is the ability the PNS contains to repair itself (a nerve

located within the CNS can't repair itself); destroying a nerve

in the brain or spinal cord (CNS) will render the nerve

inoperable and unrepairable.

TERM 22

Describe neurons (nerve cells)

DEFINITION 22

A neuron contains a cell body, a nucleus contained within the cell body, dendrites

that originate from the cell body and a main axon (runs away from the cell body).

The direction of a stimulus runs from a cell body, originating at the axon hillock

and initiating further travel (many points of contact to bring

information=network).Nerve cells live an entire lifetime with the proper nutrition

and are amitotic (inability to divide; once a nerve cell dies, the neuron is lost

forever).The olfactory and hippocampus (a very primitive par of the brain

participating in the storage of memories) are the only two neurons that contain

stem cells (preserving of the neurons; production of new neurons due to stem

cells, if damage has occurred)A neuron is typically very large and the structure

varies.A neuron has an exceptionally high metabolic rate and requires

continuous/abundant supplies of oxygen/glucose.

TERM 23

What are the only two neurons that contain

stem cells (ability to produce new neurons, if

damage occurs)

DEFINITION 23

Olfactory NeuronsHippocampal Neurons

TERM 24

Describe the cell body (soma) or perikaryon of

a neuron.

DEFINITION 24

The cell body of a neuron is the bio-synthetic center of a

neuron; consisting of a spherical nucleus surrounded by

cytoplasm. The cell body ranges in diameter from 5-

micrometers long. The cell body contains all of the usual

organelles (except centrioles) needed to synthesize proteins.

TERM 25

What organelle is absent in a neuron? Why is

the organelle absent from the neuron?

DEFINITION 25

CentriolesA centriole is absent from a neuron because the

organelle is necessary for division; nerve cells don't divide. A

centriole is the only organelle absent in neurons.

Describe dendrites. What is the function of a

dendrite?

A dendrite is a short arm that forms off of the cell body;

dendrites contain the same organelles found within the cell

body. The function of dendrites is to receive input, to covey

impulses to the body of the neuron (bringing information into

the cell body).*Dendrites are very short and are always

unmyelinated.

TERM 32

Do dendrites receive information via graded

potentials or action potentials?

DEFINITION 32

A dendrite receives information via a graded potential (dendrites

don't require an action potential, due to size); the information only

travels a short distance from the peripheral to the soma (graded

potentials are for local change in membrane potentials).A nearby

neuron will send information to a dendrite, the dendrite then

carries the information a short distance to the cell body.*An action

potential is much stronger than a graded potential.

TERM 33

Where does an axon originate

from?

DEFINITION 33

Cell Body (Soma)The axon is the major arm (part) of the

neuron, extending from the cell body.An axon is typically

very short, but can vary in length (a few centimeters to 3 or 4

feet). A shorter neuron contains a smaller axon hillock, while

a longer neuron contains a larger axon hillock.*Axons can be

myelinated or unmyelinated.

TERM 34

Where is a nerve impulse generated in a

neuron (the site of the originating nerve

impulse)?

DEFINITION 34

Axon Hillock

TERM 35

What is an axon collateral?

DEFINITION 35

The branching of an axon along the length at right angles

forms axon collaterals.

What is a terminus?

A terminus is located at the end of an axon; termini (more than

one terminus) can branch into numerous termini (as many as

10,000) (an axon branches profusely at the terminus or end,

referred to as terminal branches). The various termini can connect

to another neuron, a muscle or a nerve; at the end of every

terminus is a synaptic cleft, with a pre- and post-synaptic cleft.

TERM 37

What is an axon terminal?

DEFINITION 37

An axon terminal are knoblike distal endings of terminal branches (located at the

end of any branch) (also known as synaptic knobs). The axon terminal helps form

the myoneural junction. Many neurotransmitters are located within the axon

terminals (an action potential reaching the axon terminals, results in the release

of neurotransmitters into the synaptic cleft).The function of an axon terminal is

to perform as the secretory component of the axon (secreting

neurotransmitters), for the purpose of the conduction of a nerve impulse.The

released neurotransmitters will then innervate or activate whatever is located at

the end of the terminal bud (a gland, a muscle, an organ or a different nerve).The

axon terminal contains synaptic vesicles; the vesicles merge and undergo

exocytosis in response to calcium; the axon terminal then ejects the

neurotransmitters into the synaptic cleft.The neurotransmitters of the axon

terminal cross the synaptic cleft and bind to receptors on the post-synaptic cleft

(a fluid-filled space typically 35-50 nanometers wide; very small)

TERM 38

What functions as the secretory component of

the axon (secreting neurotransmitters and

conducting a nerve impulse) (the ending site

of a nerve impulse)?

DEFINITION 38

Axon Terminals

TERM 39

What two organelles do axons lack?

DEFINITION 39

Nissl BodiesGolgi Apparatus*The organelles of the axon are

the same as the dendrite, with two exceptions.*The reason

for lacking the two organelles is the lack of protein synthesis

(no repair).*The axon is dependent on the soma for repair;

repairing of the damage depends on the proximity of the

damage to the soma.

TERM 40

What are axons responsible for (in terms of

movement)?

DEFINITION 40

Axons are responsible for the movement of an impulse.

What are the two branches of a unipolar

neuron? Describe the two branches.

The two branches of a unipolar neuron are:

Proximal: conduct action potentials from the dendrite

Distal: typically associated with sensory information;

located within the PNS

TERM 47

What is an important characteristic of an

action potential?

DEFINITION 47

An action potential is self-propagating (the stimulus and

action potential are continuous, until the information is

carried where it needs to go; the process happens quickly);

once a stimulus is created, all of the nerves will self-

propagate the impulse until the particular impulse reaches

an effect

TERM 48

What is sufficient stimulus, in regards to

threshold? What is sub-threshold?

DEFINITION 48

A sufficient stimulus has to occur for threshold (threshold has to be

surpassed for an action potential to occur) to be met (the point at which

depolarization will occur; when threshold is achieved, an action potential

will occur); the neuron has to be moved from resting membrane potential

(the resting membrane potential for a cell is -70mV). A sufficient stimulus

will move the neuron from resting membrane potential.A sufficient

stimulus depends on sodium influx (sodium entering the cell), sodium

influx causes depolarization.A sub-threshold is insufficient sodium influx

(no depolarization=the nerve is not stimulated).

TERM 49

What are absolute and relative refractory

periods?

DEFINITION 49

An absolute refractory period refers to when a patch of neuron membrane is

generating an action potential and voltage gated sodium channels are open; the

neuron can't respond to another stimulus, no matter how strong the stimulus is or

how often the stimulus occurs. A relative refractory period follows the absolute

refractory period (repolarization is occurring). The axon's threshold for action

potential generation is substantially elevated; so a stimulus that would normally

generate an action potential is no longer sufficient. An exceptionally strong

stimulus will be required to generate another action potential; stronger stimuli

trigger more frequent action potential's by intruding into the relative refractory

period.

TERM 50

Neurons are (in terms of coupling)...

DEFINITION 50

Electrically Coupled*The firing of one nerve causes a large amount

of different nerves to fire, which all terminate in different areas (a

single, unifying thought is impossible due to electrical coupling of

neurons)*The electrical coupling of neurons is very important in

the CNS (more cells are electrically coupled in the CNS, than in

any other area of the body=hippocampus; the production of

cascading emotions).*The electrical coupling of neurons is

important for stereotyped movement; movements need to be fluid

and rhythmic in nature.

When does the electrical coupling of neurons

begin to occur in the human body?

Embryonic Development

TERM 52

What are the eight events that occur at a

chemical synapse?

DEFINITION 52

A depolarization occurs at the axon terminal and immediately...

A calcium channel opens and a calcium influx (coming in to the cell) occurs

(calcium enters the neuron)...

The synaptic vesicles move to fuse with the axonal membrane then...

The exocytosis of neurotransmitters occur and neurotransmitters float into the

synaptic cleft (a fluid-filled space)

The diffusion/migration of receptors (via neurotransmitters) to the post-

synaptic membrane occurs...

The binding of neurotransmitters to receptors causes channels to open,

resulting in excitation or inhibition (depending on the neurotransmitter; possibly

causing depolarization or hyperpolarization)...

The enzymes in the synaptic cleft then degrade the neurotransmitters because

a constant stimulus from the neurotransmitters is unwanted (the enzyme that

accomplishes degradation of the neurotransmitters in the synaptic cleft, is

cholinesterase)...

As soon as cholinesterase is released into the synaptic cleft, the re-uptake of

neurotransmitters back into the pre-synaptic neuron occurs; the neuron is then

ready for another synaptic potential (the cycle continues and happens quickly) TERM 53

What is the difference between temporal and

spatial summation of an excitatory post-

synaptic potential (EPSP)?

DEFINITION 53

A temporal summation of an EPSP is when one or more pre-

synaptic neurons fires (starting the summation); creating another

EPSP before the first one dissipates (keeping the nerve excited,

directly before threshold)*The efficiency of nerve conduction is

tremendously enhanced through excitatory post-synaptic

potentials (EPSP's)A spatial summation is when the post-synaptic

neuron is stimulated by a large amount of pre-synaptic neurons, in

order to enhance depolarization (facilitate depolarization)

TERM 54

How do excitatory neurotransmitters

function? How do inhibitory neurotransmitters

function?

DEFINITION 54

An excitatory neurotransmitter functions through positive

feedback mechanisms, for control.An inhibitory

neurotransmitter functions through negative feedback

mechanisms, for control.

TERM 55

Which two systems (CNS, PNS or ANS) are

neurotransmitters typically deployed within?

DEFINITION 55

Central Nervous System (CNS)Peripheral Nervous System

(PNS)