Nervous system Flashcards
1
Q
two main subdivisions of NS
A
central nervous system and the peripheral nervous system
2
Q
deals with normal functioning and disorders of the nervous system
A
Neurology
3
Q
consists of the brain and spinal cord
A
CNS
4
Q
Most signals that stimulate muscles to contract and glands to secrete originate in the
A
CNS
5
Q
include nerves and sensory receptors
A
Peripheral NS
6
Q
a bundle of hundreds to thousands of axons plus associated connective tissue and blood vessels that lies outside the brain and spinal cord
A
nerve
7
Q
no. of pairs of cranial nerves
A
12
8
Q
no. of pairs of spinal nerves
A
31
9
Q
refers to a structure of the nervous system that monitors changes in the external or internal environment.
A
sensory receptor
10
Q
The PNS is divided into
A
sensory and motor divisions
11
Q
conveys input into the CNS from sensory receptors in the body.
A
sensory or afferent division of the PNS
12
Q
This division provides the CNS with sensory information about the somatic senses and special senses
A
afferent division
13
Q
tactile, thermal, pain, and proprioceptive sensations
A
somatic senses
14
Q
smell, taste, vision, hearing, and equilibrium
A
special senses
15
Q
conveys output from the CNS to effectors (muscles and glands)
A
motor or efferent division of the PNS
16
Q
motor or efferent division of the PNS divisions
A
somatic nervous system and an autonomic nervous system
17
Q
conveys output from the CNS to skeletal muscles only. Because its motor responses can be consciously controlled, the action of this part of the PNS is voluntary.
A
somatic NS
18
Q
conveys output from the CNS to smooth muscle, cardiac muscle, and glands. Because its motor responses are not normally under conscious control, the action of this is involuntary
A
autonomic nervous system
19
Q
The ANS is comprised of two main branches
A
the sympathetic division and the parasympathetic division
20
Q
A third branch of the autonomic nervous system; an extensive network of over 100 million neurons confined to the wall of the digestive canal
A
enteric plexuses
21
Q
helps regulate the activity of the smooth muscle and glands of the digestive canal; can function independently, they communicates with and are regulated by the other branches of the ANS.
A
enteric plexuses
22
Q
three basic functions of NS
A
sensory (input), integrative (process), and motor (output)
23
Q
The nervous system processes sensory information by analyzing it and making decisions for appropriate responses—an activity known as
A
integration
24
Q
Nervous tissue comprises two types of cells
A
neurons and neuroglia
25
provide most of the unique functions of the nervous system, such as sensing, thinking, remembering, controlling muscle activity, and regulating glandular secretions
neurons
26
support, nourish, and protect neurons, and maintain the interstitial fluid that bathes them
neuroglia
27
the ability to respond to a stimulus and convert it into an action potential.
electrical excitability
28
is an electrical signal that propagates (travels) along the surface of the membrane of a neuron
nerve impulse (action potential)
29
Nerve impulses travel these great distances at speeds ranging from
0.5 to 130 meters per second (1 to 290 mi/hr)
30
Most neurons have three parts
(1) a cell body, (2) dendrites, and (3) an axon
31
contains a nucleus surrounded by cytoplasm that includes typical cellular organelles such as lysosomes, mitochondria, and a Golgi complex.
cell body
32
cell body is also known as
perikaryon or soma
33
Neuronal cell bodies also contain free ribosomes and prominent clusters of rough endoplasmic reticulum, termed
Nissl bodies
34
The cytoskeleton includes both
neurofibrils and microtubules
35
composed of bundles of intermediate filaments that provide the cell shape and support
neurofibrils
36
assist in moving materials between the cell
body and axon
microtubules
37
a pigment that occurs as clumps of yellowish-brown granules in the cytoplasm; a product of neuronal lysosomes that accumulates as the neuron ages, but does not seem to harm the neuron.
lipofuscin
38
These bumps are caused by many small projections of the plasma membrane, called ___; which are receptor sites that bind chemical messengers from other neurons
somatic spines
39
A collection of neuron cell bodies outside the CNS is called a
ganglion
40
is a general term for any neuronal process
(extension) that emerges from the cell body of a neuron
nerve fiber
41
neurons have two kinds of processes
multiple dendrites and a single axon
42
are the receiving or input portions of a neuron
Dendrites
43
Their cytoplasm contains Nissl bodies, mitochondria, and other organelles.
dendrites
44
propagates nerve impulses toward another neuron, a muscle fiber, or a gland cell
axon
45
An axon is a long, thin, cylindrical projection that often joins to the cell body at a cone shaped elevation called the
axon hillock
46
The part of the axon closest to the axon hillock is the
initial segment
47
In most neurons, nerve impulses arise at the junction of the axon hillock and the initial segment, an area called the _____from which they travel along the axon to their destination.
trigger zone
48
contains mitochondria, microtubules, and neurofibrils.
axon
49
it does not have RER
axon
50
The cytoplasm of an axon, called axoplasm, is surrounded by a plasma membrane known as the
axolemma
51
axon side branches
axon collaterals
52
The axon and its collaterals end by dividing into many fine processes called
axon terminals or axon telodendria
53
The site of communication between two neurons or between a neuron and an effector cell is called a
synapse
54
The tips of some axon terminals exhibit a string of swollen bumps called
Varicosities
55
is a molecule released from a synaptic vesicle
that excites or inhibits another neuron, muscle fiber, or gland cell.
neurotransmitter
56
two types of transport systems carry materials from the cell body to the axon terminals and back
slow and fast axonal transport
57
The slower system, which moves materials about 1–5 mm per day; t conveys axoplasm in one direction only
slow axonal transport
58
supplies new axoplasm to developing or regenerating axons and replenishes axoplasm in growing and mature axons.
slow axonal transport
59
which is capable of moving materials a distance of 200–400 mm per day, uses proteins that function as “motors” to move materials along the surfaces of microtubules of the neuron’s cytoskeleton
fast axonal transport
60
moves materials in both directions—away from and toward the cell body
fast axonal transport
61
moves organelles and synaptic vesicles from the cell body to the axon terminals
anterograde
62
moves membrane vesicles and other cellular materials from the axon terminals to the cell body to be degraded or recycled.
retrograde
63
substances include trophic chemicals such as nerve growth factor and harmful agents such as tetanus toxin and the viruses that cause rabies, herpes simplex, and polio travels in what direction
fast retrograde transport
64
usually have several dendrites and one axon
Multipolar neurons
65
Most neurons in the brain and spinal cord are of this type, as well as all motor neurons
Multipolar neurons
66
have one main dendrite and one axon
Bipolar neurons
67
found in the retina of the eye, the inner ear, and the olfactory area of the brain
Bipolar neurons
68
have dendrites and one axon that are fused together to form a continuous process that emerges from the cell body
Pseudounipolar or unipolar neurons
69
The trigger zone for nerve impulses in a unipolar neuron is at the
junction of the dendrites and axon
69
The dendrites of most pseudounipolar neurons function as
sensory receptors
70
neurons are named for the histologist who
first described them
Purkinje cells
71
named based on their shape
pyramidal cells, found in the cerebral cortex of the brain
72
Functional Classification of neurons
sensory, motor and interneurons
73
Motor neurons structure
multipolar
74
integrate (process) incoming sensory information from sensory neurons and then elicit a motor response by activating the appropriate motor neurons.
interneurons
75
do not generate or propagate nerve impulses, and they can multiply and divide in the mature nervous system.
neuroglia
76
Brain tumors derived from glia, called
gliomas
77
four types of neuroglia found in the CNS
astrocytes, oligodendrocytes, microglia, and ependymal cells
78
two types of neuroglia found in the PNS
Schwann cells and satellite cells
79
Neuroglia of the CNS can be classified on the basis of
size, cytoplasmic processes, and intracellular organization
80
These star-shaped cells have many processes and are the largest and most numerous of the neuroglia
astrocytes
81
astrocytes that have many short branching processes and are found in gray matter
Protoplasmic astrocytes
82
astrocytes have many long unbranched processes and are located mainly in white matter
Fibrous astrocytes
83
The processes of astrocytes make contact with
blood capillaries, neurons, and the pia mater
84
functional neurons of the PNS
sensory and motor neurons
85
restricts the movement of substances between the blood and interstitial fluid of the CNS.
blood–brain barrier
86
The functions of astrocytes include
1. Astrocytes contain microfilaments that give them considerable strength, which enables them to support neurons
2. Processes of astrocytes wrapped around blood capillaries isolate neurons of the CNS from various potentially harmful substances in blood by secreting chemicals that maintain the unique selective permeability characteristics of the endothelial cells of the capillaries
87
In the embryo, they secrete chemicals that appear to regulate the growth, migration, and interconnection among neurons in the brain
astrocytes
88
help to maintain the appropriate chemical environment for the generation of nerve impulses.
astrocytes
89
serve as a conduit for the passage of nutrients and other substances between blood capillaries and neurons
astrocytes
90
play a role in learning and memory by influencing the formation of neural synapses
astrocytes
91
are responsible for forming and maintaining the myelin sheath around CNS axons
Oligodendrocytes
92
is a multilayered lipid and protein covering around some axons that insulates them and increases the speed of nerve impulse conduction
myelin sheath
93
These neuroglia are small cells with slender processes that give off numerous spinelike projections
microglia
94
function as phagocytes; they remove cellular debris formed during normal development of the nervous system and phagocytize microbes and damaged nervous tissue
Microglial cells or Microgliocytes
95
are cuboidal to columnar cells arranged in a single layer that possess microvilli and cilia.
ependymal cells
96
line the ventricles of the brain and central canal of the spinal cord (spaces filled with cerebrospinal fluid, which protects and nourishes the brain and spinal cord)
ependymal Cells
97
produce, possibly monitor, and assist in the circulation of cerebrospinal fluid. They also form the blood–cerebrospinal fluid barrier
ependymal cells
98
they form the myelin sheath around axons of PNS
Schwann cell
99
A single oligodendrocyte myelinates several axons, but each of these glial cells myelinates a single axon
Schwann cell or neurolemmocyte
100
participate in axon regeneration, which is more easily accomplished in the PNS than in the CNS.
Schwann cell
101
These flat cells surround the cell bodies of neurons of PNS ganglia; provide structural support; regulate the exchanges of materials between neuronal cell bodies and interstitial fluid
satellite cells
102
The outer nucleated cytoplasmic layer of the Schwann cell, which encloses the myelin sheath, is the
neurolemma (sheath of Schwann)
103
aids regeneration by forming a regeneration tube that guides and stimulates regrowth of the axon in PNS
neurolemma
104
Gaps in the myelin sheath
myelin sheath gaps (nodes of Ranvier)
105
puts forth about 15 broad, flat processes that spiral around CNS axons, forming a myelin sheath
oligodendrocyte
106
No neurolemma; few nodes of Ranvier; display little regrowth after injury
Axons in the CNS wrapped with oligodendrocytes
107
Neuronal cell bodies are often grouped together
in clusters
108
The axons of neurons are usually grouped together in
bundles
109
widespread regions of nervous tissue are grouped together as either
gray matter or white matter
110
refers to a cluster of neuronal cell bodies located in the PNS; closely associated with cranial and spinal nerves
ganglion
111
a cluster of neuronal cell bodies located in the CNS
nucleus
112
is a bundle of axons that is located in the PNS.
axons
113
is a bundle of axons that is located in the CNS; interconnect neurons in the spinal cord and brain
Tracts
114
is composed primarily of myelinated axons.
white matter
115
contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia
gray matter
116
It appears grayish, rather than white, because of the
Nissl bodies
117
in the brain, a thin shell of ______ covers the surface of the largest portions of the brain, the cerebrum and cerebellum
gray matter
118
They communicate with one another using two types of electrical signals:
graded and action potentials
119
perception, the conscious awareness of a sensation, is primarily a function of the
cerebral cortex
120
a type of motor neuron that synapses with a lower motor neuron farther down in the CNS in order to contract a skeletal muscle
upper motor neuron
121
a type of motor neuron that directly supplies skeletal muscle fibers
lower motor neuron
122
The production of graded potentials and action potentials depends on two basic features of the plasma membrane of excitable cells:
the existence of a resting membrane potential
and the presence of specific types of ion channels.
123
an electrical potential difference (voltage) across the membrane. In excitable cells, this voltage is termed the
resting membrane potential
124
a concentration (chemical) difference plus an electrical difference
electrochemical gradient
125
The electrical signals produced by neurons and muscle fibers rely on four types of ion channels:
leak channels
ligand-gated channels
mechanically gated channels
voltage-gated channels:
126
channels are found in nearly all cells, including the dendrites, cell bodies, and axons of all types of neurons
leak channels
127
opens and closes in response to the binding of a ligand (chemical) stimulus.
ligand-gated channel
128
The neurotransmitter acetylcholine opens cation channels that allow Na+ and Ca2+ to diffuse __ and K+ to diffuse___
inward; outward
129
opens or closes in response to mechanical stimulation in the form of vibration (such
as sound waves), touch, pressure, or tissue stretching
mechanically gated channel
130
gated channels are those found in auditory receptors in the ears, in receptors that monitor stretching of internal organs, and in touch receptors and pressure receptors in the skin.
mechanically gated channel
131
channels are located in the dendrites of some sensory neurons, such as pain receptors, and in dendrites and cell bodies of interneurons and motor neurons
ligand-gated channel
132
opens in response to a change in membrane potential (voltage); participate in the generation and conduction of nerve impulses in the axons of all types of neurons.
voltage-gated channel
133
potential exists because of a small buildup of negative ions in the cytosol along the inside of the membrane, and an equal buildup of positive ions in the extracellular fluid (ECF) along the outside surface of the membrane
resting membrane potential
134
contains equal numbers of positive and negative charges and is electrically neutral.
The cytosol or extracellular fluid
135
A cell that exhibits a membrane potential is said to be
polarized
136
The resting membrane potential of a cell can be measured in the following way:
The tip of a recording microelectrode is inserted inside the cell, and a reference electrode is placed outside the cell in the extracellular fluid.
137
The resting membrane potential arises from three major factors
(1) unequal distribution of ions in the ECF and cytosol
(2) inability of most anions to leave the cell,
and
(3) the electrogenic nature of the Na+–K+ ATPases.
138
The CNS contains billions of neurons organized into complicated networks; functional groups of neurons that process specific types of information
neural circuits
139
Degeneration of the distal portion of the axon and myelin sheath is called
Wallerian degeneration
140
major factor that contributes to the resting membrane potential is the unequal distribution of various ions in extracellular fluid and cytosol
Unequal distribution of ions in the ECF and cytosol
141
Because the plasma membrane typically has more K+ leak channels than Na+ leak channels, the number of potassium ions that diffuse down their concentration gradient out of the cell into the ECF is greater than the number of sodium ions that diffuse down their concentration gradient from the ECF into the cell.
Unequal distribution of ions in the ECF and cytosol
142
As more and more positive potassium ions exit, the inside of the membrane becomes
increasingly negative
143
They cannot follow the K+ out of the cell
because they are attached to nondiffusible molecules such as ATP and large proteins
Inability of most anions to leave the cell.
144
Membrane permeability to Na+ is very low because there are only a few sodium leak channels. The small inward Na+ leak and outward K+ leak are offset by the Na+–K+ ATPases (sodium–potassium pumps). Recall that the Na+–K+ ATPases expel three Na+ for each two K+ imported
Electrogenic nature of the Na+–K+ ATPases
145
Since these pumps remove more positive
charges from the cell than they bring into the cell, they ____ which means they contribute to the negativity of the resting membrane potential. Their total contribution, however, is very small: only −3 mV of the total −70 mV resting membrane potential in a typical neuron
electrogenic,
146
a small deviation from the resting membrane potential that makes the membrane either more polarized (inside more negative) or less polarized (inside less negative).
graded potential
147
occurs when a stimulus causes mechanically gated or ligand-gated channels to open or close in an excitable cell’s plasma membrane
148
Hence, graded potentials occur mainly in
dendrites and cell body of a neuron.
149
This mode of travel by which graded potentials
die out as they spread along the membrane is known as
decremental conduction
150
process by which graded potentials add together
summation
151
when a graded potential occurs in the dendrites or cell body of a neuron in response to a neurotransmitter
postsynaptic potential
152
is a sequence of rapidly occurring events that decrease and reverse the membrane potential and then eventually restore it to the resting state.
Action potential
153
once a nerve impulse is generated the amplitude of a nerve impulse is always the
same and does not depend on stimulus intensity
154
In other words, a nerve impulse either occurs completely or it does not occur at all. This characteristic of a nerve impulse is known as the
all or none principle
155
The slower opening of voltage-gated K+ channels and the closing of previously open voltage-gated Na+ channels produce the
repolarizing phase of the nerve impulse.
156
allows inactivated Na+ channels to revert to the resting state
Repolarization
157
is the period of time during which a second nerve impulse can be initiated, but only by a larger-than-normal stimulus
relative refractory period
158
mode of conduction is called
propagation
159
Factors That Affect the Speed of Propagation
amount of myelination, axon diameter,
and temperature
160
largest diameter axon; The axons of sensory neurons that propagate impulses associated with touch, pressure, position of joints, and some thermal and pain sensations
A fibers
161
conduct sensory nerve impulses from the viscera to the brain and spinal cord. They also constitute all of the axons of the autonomic motor neurons that extend from the brain and spinal cord to the ANS relay stations called autonomic ganglia.
B fibers
162
Autonomic motor fibers that extend from autonomic ganglia to stimulate the heart, smooth muscle, and glands are
C fibers
163
is a type of neurotransmitter receptor that contains a neurotransmitter binding site and an ion channel.
ionotropic receptor
164
