Chapter 11 Flashcards
Nervous System (132 cards)
1
Q
Nervous system is responsible for
A
- Controls our perception and experience of the world
- Directs voluntary movement
- Consciousness, personality, learning, and memory
- Works with other systems to maintain homeostasis, including regulating respiratory rate, blood pressure, body temperature, the sleep/wake cycle, and blood p H
2
Q
Nervous system is divided into
A
- CNS
- PNS
3
Q
CNS stands for
A
central nervous system
4
Q
PNS stands for
A
Peripheral Nervous System
5
Q
CNS consists of
A
- brain
- spinal cord
6
Q
pns consists of
A
- cranial nerves
- spinal nerves and their branches
7
Q
how many cells in brain
A
100 billion
8
Q
what are cells in the brain called
A
neuron/nerve cell
9
Q
how many nerve cells in spinal cord
A
100 million
10
Q
spinal cord merges where
A
with the brain at the foramen magnum and passes through the vertebral foramen of the first cervical vertebra; continues to the first or second lumbar vertebra
11
Q
how many pairs of cranial nerves
A
12
12
Q
where do cranial nerves originate
A
the brain
13
Q
how many pairs of spinal nerves
A
31
14
Q
where do spinal nerves originate
A
the spine
15
Q
Sensory Division is in the
A
pns
16
Q
motor division is in the
A
pns
17
Q
sensory division aka
A
afferent division
18
Q
motor division aka
A
efferent division
19
Q
what division does the sensory input functions
A
sensory - pns
20
Q
what division does the integrative functions
A
cns
21
Q
what division does the motor output functions
A
motor division - pns
22
Q
what are the sensory input functions
A
Involve gathering information about the internal and external environments of the body
23
Q
what are the integrative functions
A
Analyze and interpret the detected sensory stimuli and determine an appropriate response
24
Q
what are the motor output functions
A
Actions performed in response to integrations
25
sensory stimuli is detected by
sensory receptors
26
somatic sensory division is in the pns or cns
pns
27
somatic sensory division is voluntary or involuntary
voluntary
28
what is somatic sensory division
Neurons carry signals from skeletal muscles, bones, joints, and skin; includes sensory neurons from the organs for vision, hearing, taste, smell, and balance
29
visceral sensory division is part of pns or cns
pns
30
visceral sensory division is voluntary or involuntary
involuntary
31
what is the visceral sensory division
Neurons carry signals from viscera (organs) such as the heart, lungs, stomach, intestines, kidneys, and urinary bladder
32
cns disregards how much information
99%
33
somatic motor division is part of
pns motor division
34
visceral motor division is part of
pns motor division
35
somatic motor division is voluntary or involuntary
voluntary
36
visceral motor division is voluntary or involuntary
involuntary
37
what is the somatic motor division
Neurons transmit signals to skeletal muscles
38
what does the visceral motor division do
Neurons carry signals to thoracic and abdominal viscera; regulates secretion from some glands, controls smooth muscle and cardiac muscle in the heart
39
what is the pns motor division
Neurons carry out motor functions such as muscle contractions and secretion from glands; organs that carry out the effects are Effectors
40
about how much of nervous tissue volume is cells vs ecm
80% - 20%
41
what are neuroglial cells
Smaller and more prevalent cells which generally do not transmit signals but serve a variety of supportive functions (support, nutrient supply, immune response, insulation, etc.)
42
how do neurons send and receive signals
What is it called when it happens
action potentials
43
neurons are short lived or long lived
long lived
44
T/F neurons are amitotic
true
45
neurons are composed of
- central cell body
- dendrites
- one axon
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cell body of neuron aka
soma
47
what is a soma
most metabolically active part of the neuron; maintains a large cytoplasmic volume and manufactures proteins
48
what organelles are in the soma
- free ribosomes
- rough er
- golgi apparatus
- one or more nucleoli
- mitochondria in large numbers
49
neuronal cytoskeleton is composed of
many intermediate filaments bundled into neurofibrils that extend into the dendrites and axon and microtubules that support the cell and allow transport of chemicals
50
what are neurofibrils
protein filaments that are found in in the cytoplasm of nerve cells, and are responsible for maintaining the cell's structure
51
what are the functions of neurofibrils
- structural suppoprt
- axonal transport
- conduction of nerve impulses
52
what are dendrites
Typically short, highly forked processes resembling branches of a tree limb
- Receive input from other neurons and transmit it in the form of electrical impulses toward the cell body
- Possess most of the same organelles as the cell body
- Dendrites can grow and are “pruned” as a person matures and the demands on the nervous system change
53
what are the parts of the axon
- axon hillock
- axon collaterals
- telodendria
- axon terminals (synaptic knobs)
- axolemma
- axoplasm
- axonal transport (flow)
54
what is the axon
Processes that can generate and conduct action potentials
55
what is the axon hillock
Area of the cell body where the axon arises
56
what is axon collaterals
Branches of the axon
57
what are telodendria
Fine branches of axon and its collaterals
58
what are axon terminals
Ends of telodendria that communicate with target cells; Neurons typically have 1,000 or more
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axon terminals aka
synaptic knobs
60
synaptic knobs aka
axon terminals
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what is the axolemma
Plasma membrane of the axon
62
what is axoplasm
Cytoplasm of the axon;
63
what is axonal transport
Substances travel through the axoplasm toward or away from the cell body
64
what are the functional regions of neurons
- receptive region
- conducting region
- secretory region
65
what is the receptive region
Dendrites and cell body receive
66
what is the conducting region
Axon continues the signal
67
what is the secretory region
What does it do
Secrete chemicals for target cells
68
what are the different structural classifications of neurons
- multipolar
- bipolar
- pseudounipolar
69
what are multipolar neurons
Over 99% of neurons; single axon with multiple highly branched dendrites; wide variety of shapes and sizes
70
what are bipolar neurons
One axon and one dendrite; most are sensory; found in the retina of the eye and olfactory epithelium
71
what are pseudounipolar neurons
Single axon with one half that brings sensory stimuli to the cell body (peripheral process or axon) and the other half that carries stimuli to the spinal cord (central process or axon); found in your sensory receptors (detect touch, pressure, and pain)
72
what are the functional classifications of neurons
- sensory (afferent)
- interneurons (associate)
- motor (efferent)
73
what are sensory neurons
What do they do
Carry signals toward the C N S and facilitate motor coordination
74
what shape are sensory neurons
pseudounipolar or bipolar
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what are interneurons
Relay messages within the C N S; vast majority of neurons
76
what shape are interneurons
multipolar
77
what are motor neurons
What do they do
Carry signals away from the C N S to muscles and glands;
78
what shape are motor neurons
multipolar
79
what are neuroglia
- Hold neurons together
- Maintain the environment around neurons
- Protect neurons and assist in their functions
- Can undergo mitosis and will fill in gaps when neurons die
80
how many types of neuroglia
6
81
how many types of neuroglia in the cns
4
82
how many types of neuroglia in the pns
2
83
what are the types of neuroglia in the cns
- astrocytes
- oligodendrocytes
- microglia
- ependymal
84
astrocytes are what shape
star
85
what neuroglia are most abundant in the cns
astrocytes
86
functions of astrocytes
- anchoring neurons and blood vessels in place
- regulate extracellular environment of the brain
- assisting in the formation of the blood brain barrier
- repairing damaged brain tissue
87
elaborate: astrocytes -Regulate the extracellular environment of the brain
Remove excess extracellular potassium ions and neurotransmitters
88
elaborate: astrocytes - Anchoring neurons and blood vessels in place
Facilitate transport of nutrients and gases from the blood vessels to neurons
89
elaborate: astrocytes -Assisting in the formation of the blood brain barrier
separates blood from the extracellular fluid, ensuring selective transport of substances between the fluids
90
elaborate: astrocytes -Repairing damaged brain tissue
Divide rapidly, but may impede regrowth of neurons, leading to more damage
91
what are oligodendrocytes
- neuroglia in the CNS
- have radiating processes w flattened ends that wrap around part of the axons of certain neurons
- form concentric layers of plasma membrane collectively called Myelin
92
repeating segments of myelin form ...
myelin sheath
93
what neuroglia make up myelin
oligodendrocytes
94
what does myelin sheath do
increases the speed of nerve impulse conduction
95
what are microglia
- tiny branching cells that are activated by brain injury
- become wandering phagocytes that ingest disease-causing organisms, dead neurons, and cell debris , and stimulate inflammation
96
what neuroglia in the CNS are tiny, branching cells activated by brain injury
microglia
97
what neuroglia have radiating process with flattened ends that wrap around part of the axons of certain neurons
oligodendrocytes
98
what are ependymal cells
- neuroglia in the CNS
- ciliated cells with many functions
- one main function is circulating cerebrospinal fluid
- some form the fluid others monitor its composition
99
what neuroglia are in the PNS
- neurolemmocytes (schwann cells)
- satellite cells
100
what are neurolemmocytes
- neuroglia in the PNS
- encase axons of neurons in the PNS
- cover some of those axons in a myelin sheath
- play a role in the repair of damaged axons
101
what are satellite cells
- neuroglia in the PNS
- enclose and support the cell bodies and link with other parts of the neuron, other satellite cells, and neighboring neurolemmocytes
- regulate the extracellular environment around the cell body
102
myelin sheath is formed by which neuroglial cells
- neurolemmocytes (schwann cells)
- oligodendrocytes
wrap themselves around the axons of some neurons, repeating layers of the plasma membrane
103
what does myeling sheath do
- coats the cells and prevents the movement of ions, which makes it an excellent insulator - like rubber tubing around a copper wire
104
myelin sheath is composed of
- glial cells
- lipids
- proteins
105
myelinated axons conduct action potetial by about ________ times faster than unmyelinated axons
15-150 times faster
106
what is myelination
the prcess of sheath formation
107
what are internodes
segments of an axon that are covered by myelin
108
what are the spaces between interodes called
myelin sheath gaps
or
nodes of ranvier
109
In the PNS, how does the neurolemmocyte wrap itself around the axon
wraps itself outward, away from the axon in successively tighter bands, up to 100 layers thick
110
what is a neurolemma
the outermost layer of the myelin sheath on a myelinated axon
111
when does myelination begin in the PNS
during the early fetal period
112
in the PNS, how many axons does a neurolemmocyte wrap
just one
113
In the CNS, how does an oligodendrocyte wrap intself around an axon
arms wrap inward, toward the axon
114
in the CNS, how many axons does an oligodendrocyte wrap
may send out multiple processes to envelop parts of several axons
115
when does myelination begin in the CNS
- begins much later than in the PNS, especially in the brain
- newborns have very little myelin in the brain
116
short axons are almost always myelinated or unmyelinated
unmyelinated
117
what is white matter
mylinated areas in the CNS
118
what is gray matter
unmyelinated areas in the CNS
119
What is regeneration
replacement of damaged tissue
120
What is regeneration like in the CNS
- dendrites and axons almost never regenerate
- oligodendrocytes inhibit neuronal growth
- growth factors are absent
- astrocytes create scar tissue
121
What is regeneration like in the PNS
- neural tissue is capable of regeneration if the cell body remains intact and the conditions are ideal
- repair occurs through certain steps
122
is there regeneration in nervous tissue in humans
its limited
123
what are the steps of regeneration in the PNS
1. The axon and myelin sheath distal to the injury degenerate
- Phagocytes digest the debris
2. Growth processes form from the proximal end of the axon
3. Neurolemmocytes and the basal lamina form a regeneration tube
4. A single growth process grows into the regeneration tube
- neurolemmocytes secrete growth factors
5. The axon is reconnected with target cells
124
what is conduction speed
The rate at which propagation occurs; determines how rapidly signaling can occur within the nervous system;
125
what is conduction speed influenced by
- diameter of the axon
- presence or absence of a myelin sheath
126
what is saltatory conduction
- conduction in myelinated cells
- The myelin sheath gaps are the only segments that must be depolarized to threshold
- Gaps with voltage-gated sodium ion channels are depolarized to threshold and the action potential current flows through the internode to the next gap
- Another action potential is generated and the cycle repeats by “jumping” from one gap to the next
127
what is continuous conduction
- conduction in unmyelinated cells
- Each section of the axolemma must be depolarized to threshold for the action potentials to move down the length of the axon
128
what are the types of conduction and their relative speeds
- continuous conduction (slower)
- saltatory conduction (faster)
129
what kind of conduction occurs with unmyelinated cells
continuous conduction
130
what kind of conduction occurs with myelinated cells
saltatory conduction
131
how does diameter of the axon affect conduction speed
larger axons have lower resistance to conduction, allowing current to flow through them more easily
132
how does myelin insulate an axon and increase its speed of a propagation
- Myelin “insulates” an axon to enable saltatory conduction
- Consider the basic principles of electricity
- Electric current will flow down a bare copper wire to illuminate the light bulb (left), but if you touch the wire with a metal probe, the current might flow down the probe (right) causing a short circuit
- If the wire is encased in a non-conducting material, the current is unable to move away from the copper wire
- Unmyelinated axons are similar to uninsulated wires; the axolemma is leaky and current flows to the E C F so the current has to be continuously regenerated
- The signal in a myelinated axon propagates without having to be regenerated
