A&p Lecture Test 4

Front 1

The nervous system has two major anatomical subdivisions:

Back 1

central nervous system (CNS)
peripheral nervous system (PNS)

Front 2

consists of the brain and spinal cord

Back 2

central nervous system (CNS)

Front 3

consists of all the nervous system except the brain and spinal cord. It is composed of nerves and ganglia

Back 3

peripheral nervous system (PNS)

Front 4

fibers always conduct signals away from the CNS

Back 4

Motor (efferent)

Front 5

fibers always conduct signals toward the CNS

Back 5

Sensory (afferent)

Front 6

fibers innervate skeletal muscle, the skin, bones, and joints.

Back 6

Somatic

Front 7

fibers innervate cardiac muscle, smooth muscle, and glands.

Back 7

Visceral

Front 8

There are three general classes of neurons;

Back 8

Sensory (afferent) neurons, Interneurons (association neurons), and motor (efferent) neurons

Front 9

About 90% of our neurons are

Back 9

interneurons

Front 10

The control center of the neuron is the

Back 10

soma

Front 11

also called the neurosoma, cell body, or perikaryon

Back 11

soma

Front 12

There are six kinds of neuroglia (glial cells)

Back 12

Four types occur only in the CNS, and two occur only in the PNS.

Front 13

Oligodendrocytes produce the myelin in the CNS, and Schwann cells produce the myelin in the PNS

Back 13

two occur only in the PNS

Front 14

Since the myelin consists of the plasma membranes of these glial cells, its composition is like that of plasma membranes in general

Back 14

It is 80% lipid and 20% protein

Front 15

They resemble a cuboidal epithelium, line the internal cavities of the brain and spinal cord, and are responsible for the production of cerebrospinal fluid (CSF)

Back 15

Ependymal cells are found only in the CNS

Front 16

They are the most abundant glial cells in the CNS

Back 16

Astrocytes
are also found only in the CNS and are responsible for formation of the blood-brain barrier

Front 17

are the macrophages of the CNS

Back 17

Microglia

Front 18

have one axon and multiple dendrites

Back 18

Multipolar neurons

Front 19

have one axon and one dendrite

Back 19

Bipolar neurons

Front 20

have only a single process leading away from the soma

Back 20

Unipolar neurons

Front 21

Conduction speed of nerve fibers depends on two factors:

Back 21

the diameter of the fiber and the presence or absence of myelin

Front 22

Large diameter fibers conduct signals

Back 22

more rapidly than small diameter fibers

Front 23

Myelinated fibers conduct signals

Back 23

more rapidly than unmyelinated fibers

Front 24

the fastest signal-conducting fibers in our nervous system are large

Back 24

myelinated fibers

Front 25

The myelin covering a nerve fiber is

Back 25

segmented

Front 26

The myelinated segments are called

Back 26

internodes

Front 27

the unmyelinated gaps in between the myelinated segments are called

Back 27

nodes of Ranvier

Front 28

In order for a peripheral nerve fiber to regenerate it must have an

Back 28

intact soma and at least some neurilemma intact

Front 29

Damaged nerve fibers in the CNS cannot

Back 29

regenerate

Front 30

Potassium ions have the greatest influence on the resting membrane potential (RMP)

Back 30

because the plasma membrane is more permeable to potassium than any other ion

Front 31

the opening of sodium gates causes sodium ions to come into the cell, which leads to depolarization of the plasma membrane

Back 31

During an action potential

Front 32

Chloride ions, being negatively charged, cause the membrane potential to become more negative when they enter the cell. When a cell is at its RMP, any decrease in voltage that causes the voltage to become more negative than the RMP is called

Back 32

hyperpolarization

Front 33

At threshold

Back 33

both sodium and potassium gates are opening

Front 34

___________ of an action potential no stimulus of any strength will trigger a new action potential

Back 34

During the absolute refractory period

Front 35

____________ it is possible to trigger a new action potential, but only with an unusually strong stimulus

Back 35

During the relative refractory period

Front 36

____________ each action potential at the current node has the same strength as the one at the previous node

Back 36

saltatory conduction

Front 37

Synapses that employ acetylcholine as the neurotransmitter are called

Back 37

cholinergic synapses

Front 38

Amino acid neurotransmitters include,

Back 38

glycine, glutamate, aspartate, and gamma-aminobutyric acid (GABA)

Front 39

There are four major classes of neurotransmitters

Back 39

Acetylcholine is in a class by itself

Front 40

GABA is considered an inhibitory neurotransmitter

Back 40

because the binding of GABA to its receptor opens chloride(Cl-) gates that hyperpolarize the membrane

Front 41

The monoamines include

Back 41

norepinephrine, epinephrine, dopamine, and others

Front 42

The monoamines act through second-messenger systems such as

Back 42

cyclic AMP.

Front 43

The neuropeptides are

Back 43

chains of 2 to 40 amino acids. Some examples are beta-endorphin and substance P

Front 44

Even though all action potentials are the same, the brain can differentiate a variety of stimuli by source and intensity. The mechanism by which the nervous system converts these action potentials into meaningful information is called

Back 44

neural coding

Front 45

Synapses are not fixed for life; in response to experience, they can be added, taken away, or modified to make transmission easier or harder. This ability of synapses to change is called

Back 45

synaptic plasticity

Front 46

________ is the ability to hold something in mind for just a few seconds

Back 46

Immediate memory

Front 47

________ lasts from a few seconds to a few hours

Back 47

Short-term memory

Front 48

lasts up to a lifetime

Back 48

Long-term memory

Front 49

The meninges of the spinal cord from superficial to deep

Back 49

dura mater (dural sheath), arachnoid mater, and pia mater

Front 50

The spinal cord is divided into

Back 50

cervical, thoracic, lumbar, and sacral regions

Front 51

The space between the dura mater and vertebral bones is called the

Back 51

epidural space

Front 52

_______ is introduced into this space to block pain signals during pregnancy

Back 52

Epidural anesthesia

Front 53

The space between the arachnoid mater and pia mater is the

Back 53

subarachnoid space

Front 54

The subarachnoid space is filled with

Back 54

cerebrospinal fluid (CSF)

Front 55

The spinal cord has a central core of gray matter surrounded by

Back 55

white matter.

Front 56

The gray matter contains

Back 56

the somas, dendrites, and proximal parts of axons of neurons

Front 57

The white matter contains bundles of myelinated fibers called

Back 57

tracts running up and down the spinal cord

Front 58

Ascending tracts carry sensory signals

Back 58

up the spinal cord

Front 59

Descending tracts carry motor signals down

Back 59

the brainstem and spinal cord

Front 60

When the origin and destination of a tract are on opposite sides of the body we say they are

Back 60

contralateral to each other

Front 61

In most nerves, the nerve fibers are gathered in bundles called

Back 61

fascicles, with each fascicle wrapped in a sheath called the perineurium

Front 62

The connective tissue sheath surrounding the entire nerve is the

Back 62

epineurium

Front 63

The ventral (anterior) rami of the spinal nerves form five weblike nerve plexuses:

Back 63

cervical, brachial, lumbar, sacral, and coccygeal

Front 64

The most important nerve of the cervical plexus is the

Back 64

phrenic nerve, which plays an essential role in breathing

Front 65

The tibial and common fibular nerves travel together through a

Back 65

connective tissue sheath, and are collectively referred to as the sciatic nerve

Front 66

The gray matter contains

Back 66

the somas, dendrites, and proximal parts of axons of neurons

Front 67

The white matter contains bundles of myelinated fibers called

Back 67

tracts running up and down the spinal cord

Front 68

Ascending tracts carry sensory signals

Back 68

up the spinal cord

Front 69

Descending tracts carry motor signals down

Back 69

the brainstem and spinal cord

Front 70

When the origin and destination of a tract are on opposite sides of the body we say they are

Back 70

contralateral to each other

Front 71

In most nerves, the nerve fibers are gathered in bundles called

Back 71

fascicles, with each fascicle wrapped in a sheath called the perineurium

Front 72

The connective tissue sheath surrounding the entire nerve is the

Back 72

epineurium

Front 73

The ventral (anterior) rami of the spinal nerves form five weblike nerve plexuses:

Back 73

cervical, brachial, lumbar, sacral, and coccygeal

Front 74

The most important nerve of the cervical plexus is the

Back 74

phrenic nerve, which plays an essential role in breathing

Front 75

The tibial and common fibular nerves travel together through a

Back 75

connective tissue sheath, and are collectively referred to as the sciatic nerve

Front 76

The gray matter contains

Back 76

the somas, dendrites, and proximal parts of axons of neurons

Front 77

The white matter contains bundles of myelinated fibers called

Back 77

tracts running up and down the spinal cord

Front 78

Ascending tracts carry sensory signals

Back 78

up the spinal cord

Front 79

Descending tracts carry motor signals down

Back 79

the brainstem and spinal cord

Front 80

When the origin and destination of a tract are on opposite sides of the body we say they are

Back 80

contralateral to each other

Front 81

In most nerves, the nerve fibers are gathered in bundles called

Back 81

fascicles, with each fascicle wrapped in a sheath called the perineurium

Front 82

The connective tissue sheath surrounding the entire nerve is the

Back 82

epineurium

Front 83

The ventral (anterior) rami of the spinal nerves form five weblike nerve plexuses:

Back 83

cervical, brachial, lumbar, sacral, and coccygeal

Front 84

The most important nerve of the cervical plexus is the

Back 84

phrenic nerve, which plays an essential role in breathing

Front 85

The tibial and common fibular nerves travel together through a

Back 85

connective tissue sheath, and are collectively referred to as the sciatic nerve

Front 86

is a diagram of the cutaneous regions innervated by each spinal nerve. Because dermatomes overlap at their edges by as much as 50%, it is necessary to sever or anesthetize three successive spinal nerves to produce a total loss of sensation from one dermatome.

Back 86

A dermatome map

Front 87

Four important properties of a reflex:

Back 87

1. Reflexes require stimulation and do not occur spontaneously; they are responses to sensory input.
2. Reflexes are very predictable. They occur in essentially the same way every time.
3. Reflexes are involuntary.
4. Reflexes are quick and generally involve few if any interneurons.

Front 88

__________ has three principal classes of nerve fibers. A primary (group Ia) fiber, a secondary (group II) fiber, and a gamma motor neuron.

Back 88

A muscle spindle

Front 89

Muscle spindles are

Back 89

proprioceptors that respond to stretch

Front 90

Proprioceptors are sense organs which are

Back 90

specialized to monitor the position and movement of body parts

Front 91

A somatic reflex employs a reflex arc, in which signals travel along the following pathway:

Back 91

somatic receptor >>> afferent nerve fiber >>> integrating center >>> efferent nerve fiber >>> skeletal muscle

Front 92

The quickest reflex arcs involve only two neurons, thus forming

Back 92

monosynaptic reflex arcs

Front 93

The muscle fibers within a muscle spindle are called intrafusal fibers,

Back 93

while those that make up the rest of the muscle and do its work are called extrafusal fibers.

Front 94

When a muscle is stretched, it “fights back”. It contracts and feels stiffer than an unstretched muscle. This response is called the

Back 94

stretch (myotatic) reflex

Front 95

The tendon reflex is a response to excessive tension on the tendon.

Back 95

It inhibits alpha motor neurons to the muscle so the muscle does not contract as strongly.