Chapter 12: Nervous Tissue Flashcards
(177 cards)
1
Q
communicates by means of chemical messengers (hormones) secreted into the blood
sends information
A
Endocrine system
2
Q
employs electrical and chemical means to send messages from cell to cell
processes information
A
nervous system
3
Q
- sense organs RECIEVES INFORMATION about changes in the body and the external environment and TRANSMIT CODED MESSAGES to the spinal cord and the brain
- brain &spinal cord PROCESS THIS INFORMATION relate it to past experiences and determine what response is appropriate to the circumstances
- brain & spinal cord ISSUE COMMANDS to muscles & gland cells to carry out such a response
A
Three basic steps to the nervous system
4
Q
tow major anatomical subdivisions of the nervous system
A
central and peripheral nervous system
5
Q
Brain and spinal cord enclosed in bony coverings & enclosed by cranium and vertebral column
A
Central nervous system (CNS)
6
Q
all the nervous system except the brain and spinal cord; composed of NERVES and GANGLIA
A
Peripheral nervous system (PNS)
7
Q
a bundle of nerve fibers (axons) wrapped in fibrous connective tissue
A
nerve
8
Q
a knot like swelling in a nerve where neuron cell bodies are concentrated
A
Ganglion
9
Q
brain & spinal cord
A
Central Nervous system
10
Q
sensory and motor division
A
peripheral nervous system
11
Q
visceral & somatic sensory division
A
sensory division
12
Q
sympathetic & parasympathetic division
A
Motor division-> visceral motor division
13
Q
carries sensory signals form various receptors to the CNS
informs the CNS of stimuli within or around the body
A
Sensory (afferent: accept or admit) division
14
Q
carries signal form receptors in the skin, muscles, bones, and joints (touch)
A
somatic sensory division
15
Q
visceral & somatic motor division
A
motor division
16
Q
Visceral sensory division
A
carries signals from the viscera of the thoracic and abdominal cavities
heart, lungs, stomach, and urinary bladder (internal organs)
17
Q
Motor (efferent: exit or effect) division
A
carries signals from the CNS to gland and muscle cells that carry out the body’s response
18
Q
effectors
A
cells and organs that respond to commands from the CNS
19
Q
Somatic motor division
A
carries signals to skeletal muscles (contraction)
output produces muscular contraction as well as somatic reflexes
20
Q
Somatic reflexes
A
involuntary muscle contractions
21
Q
visceral motor division (autonomic nervous system: self governed)
A
- not in control
- carries signals to glands, cardiac muscle, and smooth muscle
- involuntary and responses of this system and its receptors are visceral reflexes
- sympathetic & parasympathetic
22
Q
sympathetic division
A
fight or flight
23
Q
parasympathetic division
A
rest and digest
24
Q
tends to have calming effect slows heart rate and breathing stimulates digestive and urinary systems body says you are safe maintains homeostasis
A
Parasympathetic division (rest and digest)
25
tends to arouse body to action
accelerating heart beat and respiration, while inhibiting digestive and urinary systems
your body tells you that you are in danger
sympathetic division (fight or flight)
26
excitability (irritability)
conductivity
secretion
attributes of neurons
27
Excitability (irritability)
respond to environment changes called stimuli
28
Conductivity
Neurons respond to stimuli by producing electrical signals that are quickly conducted to other cells distant locations
Action Potential one after the other
29
Secretion
When electrical signal reaches end of the nerve fiber, a chemical neurotransmitter is secreted that crosses the gap and stimulates the next cell
30
inter neurons (association neurons)
Get job done
| are confined to the CNS
31
three classes of neurons
sensory
inter neurons
motor
32
neurons conduct signals from receptors to the CNS
specialized to detect stimuli
transmit info about them to the CNS
begin in almost every organ in the body and end in CNS
Sensory (afferent)
33
neurons conduct signals from the CNS to effectors such as muscles and glands
send signals out to muscles and gland cells
motor bc most of them lead to muscles
motor (efferent)
34
lie entirely within the CNS
receive signals from many neurons and carry out the integrative function ( process, store ,and retrieve info and "make decisions" that determine how the body will respond to stimuli)
90% of all neurons are interneurons
lie between and interconnect the incoming sensory pathways and the outgoing motor pathways of the CNS
Interneurons (association neurons)
35
the control center of the neurons
| also called neuroma, cell body, has a single, centrally located nucleus with large nucleolus
Soma
36
Vast number of branches coming from a few thick branches from the soma
Resemble bare branches of a tree in winter
Primary site for receiving signals from other neurons
The more dendrites the neuron has, the more info it can receive & incorporate into decision making
Provide precise pathway for the reception & processing of neural info
Pick of information
Dendrites
37
Transmit information
Originates from a mound on one side of the soma called axon hillock
Cylindrical,relatively u branches for most of its length , axon collaterals
Branch extensively on distal end
Specialized for rapid conduction of nerve signals to points remote to the soma
Axon (nerve fiber)
38
Originates from a mound on one side of the soma
Axon hillock
39
Branches of axon
Axon collaterals
40
Only one axon per neuron
Schwann cells and myelin sheath enclose axon
Distal end, axon has terminal arborization
Synaptic knob
Contains synaptic vesicles full of neurotransmitter
Axon (nerve fiber) continue
41
Extensive complex of fine branches
| Terminal where one cell connects to another
Terminal arborization
42
Little swelling that forms a junction (synapse) with the next cell
Synaptic knob
43
Space in between Schwann cells
Nose of Ranvier
44
One axon and multiple dendrites
Most common
Most neurons in the brain and spinal cord
Multipolar neurons
45
One axon and one dendrite
| Olfactory cells, retina, inner ear
Bipolar neuron
46
Single process leading away from the soma
| Sensory from skin and organs to spinal cord ( motor neurons)
Unipolar neuron
47
Many dendrites but no axon
| Help in visual processes
Anaxonic neuron
48
Two way passage of proteins, organelles, and other material along an axon
Anterograde transport
Retrograde transport
Many proteins made in soma must be transported to axon and axon terminal
Micro tubules guide materials along axon
Axon transport
49
Movement down the axon away from soma
Anterograde transport
50
Movement up the axon toward the soma
| Return
Retrograde transport
51
Guide materials along axon
| Motor proteins carry materials "on their backs" while they "crawl" along micro tubules (tracks )
Micro tubules
52
No stop in between
Fast anterograde transport (up to 400 mm/day)
Fast retrograde transport
Fast axonal transport
53
Organelles, enzymes, synaptic vesicles, and small molecules
Fast anterograde transport
54
For recycled materials
Fast retrograde transport
55
Stops in between
Always anterograde
Moves enzymes, cytoskeletal components, and new axon plasm down the axon during repair and regeneration of damaged axons
Slow axonal transport or axoplasmic flow
56
1 trillion neurons
Neuralgia Outnumber the neurons by as much as 50:1
Neuralgia or glial cells
Supportive cells
57
Support and protect the neurons
Bind neurons together and form framework for nervous tissue
If mature neuron is not in synaptic contact with another neuron it is covered by glial cells
Prevent neurons from touching each other
Gives precision to conduction pathways
Schwann cells are
Neuralgia or glial cells
58
Four types of neuroglia that occur only in CNS
Oligodendrocytes
59
Form myelin sheaths in CNS
Oligodendrocytes
60
Secretes and circulates (produces) cerebrospinal fluid
Ependymal cells
61
Small wandering macrophages formed from white blood cells called monocytes
Wander in search of cellular debris to phagocytize
Consume things they need to get rid of
Micro glia
62
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Most abundant glial cell in CNS
Gray matter ; multitask cell
Form a supportive framework
Have blood brain barrier
Covert blood glucose to lactate and supply lactate to the neurons for nourishment
Nerve growth factors
Communicate electrically with neurons
Regulate chemical composition using neurotransmitters
Astrophysics
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Astrocytes
63
Have extensions (peri vascular feet) that contact blood capillaries that stimulate them to form a tight seal
Blood brain barrier
64
When neuron is damaged astrocytes form harden scar tissue and fill space formerly occupied by the neuron
Astrocytosis or sclerosis
65
Two types of neuroglia that occur only in PNS
Schwann cells
| Satellite cells
66
Create myelin for PNS
| Regenerate damaged fibers
Schwann cells
67
Provide electrical insulation around the soma (insulate soma)
Regulate the chemical environment
Satellite cells
68
Masses of rapidly dividing cells
Rumors
69
Mitosis out of control
Meninges
Metastasis from non neuronal rumors in other organs
Often glial cells that motors ally active throughout life
Outside easier to treat
Brain tumor arise from
70
Grow rapidly and are highly malignant
Blood brain barrier decreases effectiveness of chemotherapy
Treatment consists of radiation or surgery
Harder to treat inside
Gliomas
71
An insulating layer around a nerve fiber
Formed by oligodendrocytes in CNS and Schwann cells in PNS
Mostly fat 80% fat
Nonpolar
Myelin sheath
72
Production of the myelin sheath
Begins at week 14 of fetal development
Dietary fat is important to CNS development
Myelination
73
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Is segmented
Nodes of Ranvier
Internodes
Initial segment
Trigger zone
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Myelin sheath
74
Gap between segments
Nodes of Ranvier
75
Myelin covered segments from one gap to the next
Internodes
76
Short section of nerve fiber between the axon hillock and the first glial cell
Initial segment
77
The axon hillock and the initial segment
Trigger zone
78
Degenerative disorders of the Mullen sheath
Multiple sclerosis
| Tay each disease
79
A hereditary disorder
| Abnormal accumulation of glycolipids called GM2 in the myelin sheath
Tay Sachs disease
80
1 Schwann cell many axon
Unmyelinated
81
Many Schwann cells 1 axon
Myelinated
82
Larger fibers have more surface area and conduct signals more rapidly and myelinated
Fastest conduction speed
83
The faster the conduction speed the faster
We are burning energy
84
_____ signals supply the stomach and dilate pupil where speed is less of an issue
Slow
85
___signals supply skeletal muscles and transport sensory
Fast
86
Regeneration of damaged peripheral nerve fiber can occur if:
It's soma is intact
| At least some neurilemma remains
87
What can not regenerate neurons
CNS
88
Cellular mechanisms for producing electrical potentials and currents
basis for neural communication and muscle contraction
Electrophysiology
89
a difference in the concentration in the concentration of charged particles between one point and another
electrical current
90
a flow of charged particles form one point to another
in the body currents are movements of ions, such as NA or K through gated channels in the plasma membrane
gated channels are opened or closed by various stimuli
enables cell to turn electrical currents on and off
Electrical current
91
Neurons & muscle cells
| living cells are
Polarized
92
charge difference across the plasma membrane
about -70 mV
negative value means there are more neg charged particles on the inside of the membrane than on the outside
Resting membrane potential
93
disturbances in membrane potential when a neuron is stimulated
anything disturbing the RMP
neurons response begins at the dendrite, spreads through the soma
neurons stimulated by chemicals, light, heat , or mechanical disturbances
opens the Na gates and allows Na to rush into the cell
Na inflow neutralizes some of the internal neg charge
Voltage measured across the membrane drifts toward zero
Deploarization
Local potentials
94
Na diffuses for short distance on the inside of the plasma membrane producing a current that travels toward the cells trigger zone; this short- range change in voltage is called what
Local potential
95
case in which membrane voltage shifts to a less negative value
depolarization
96
graded, decremental , reversible, and either excitatory or inhibitory
differences of local potentials from action potentials
97
vary in magnitude with stimulus strength
stronger stimuli open more Na gates
strength
Graded
98
get weaker the farther they spread from the point of stimulation
voltage shift causes by Na inflow diminishes rapidly with distance
decremental
99
when stimulation ceases K diffusion out of cell returns the cell to its normal resting potential
reversible
100
some neurotransmitters ( glycine) make the membrane potential more neg- hyperpolarize it- so it becomes less sensitive and less likely to produce an action potential
either excitatory or inhibitory
101
positive comes into the cell
excitatory
102
negative comes into the cell
inhibitory
103
action potential and for a few milliseconds after it is difficult or impossible to stimulate that region of a neuron to fire again
the period of resistance to stimulation
Absolute and relative
Refractory period
104
No stimulus of any strength will trigger AP
Absolute refractory period
105
only especially strong stimulus will trigger new AP
Relative refractory period
106
for communication to occur the nerve signal must travel to what
the end of the axon
107
has voltage regulated ion gates along its entire length
diffusion of Na ( incased in Schwann cells )
Action potential from the trigger zone causes Na to enter the axon and diffuse into adjacent regions beneath the membrane
the depolarization excites voltage regulated gates immediately distal to the action potential
Na and K gates open and close producing a new action potential
by repetition the membrane distal to that is excited
chain reaction continues to the end of the axon
Unmyelinated fiber
108
cant go both ways in the nerve fiber bc
refractory period
109
Voltage- gated channels needed for AP's
Faster Na diffusion occurs between nodes
salutatory conduction
Myelinated
110
nerve signal seems to jump from node to node
salutatory conduction
111
A nerve signal can go no further when it reaches the end of the axon ; triggers the releases of a neurotransmitter, stimulates a new wave of electrical activity in the net cell across
Synapses
112
First neuron in the signal path is the
| releases neurotransmitters
Presynaptic neuron
113
Second neuron is the
| responds to neurotransmitters
Postsynaptic neuron
114
presynaptic neuron and postsynaptic neuron
Synapse between two neurons
115
lots of vesicles blind into cell membrane & release the
neurotransmitters
116
__ may synapse with dendrite, soma, or axon of postsynaptic neuron to form axondendritic, axonaxonic, or axosomatic synapses
10,000 synaptic to as many as 1000,000
Presynaptic neuron
117
synthesized by the presynaptic neuron
released in response to stimulation (synaptic cleft)
Bind to specific receptors on the postsynaptic cell
alter the physiology of that cell (excite, inhibit)
Neurotransmitters
118
Some excitatory(speed up)
some inhibitory (slow down)
some the effect depends on what kind of receptor the postsynaptic cell has (same; excite& inhibit)
some open ligand regulated ion gates (neither ; just another molecule)
some act through second- messenger systems
basic ways neurotransmitters are diverse in their action
119
Acetylcholine (1 type of molecule )
Amino acids ( act as neurotransmitters)
Monoamines ( used to be amino neurotransmitter)
Neuropeptides
4 classes of neurotransmitters
120
A given __ does not have the same effect everywhere in the body
Multiple receptor types exist for a particular __
-14 receptor types for serotonin
Receptor governs the effect the __ has on the target cell
neurotransmitter
121
hormones, neuropeptides, and other messengers that modify synaptic transmission (release of neurotransmitters)
may stimulate a neuron to install more receptors in the postsynaptic membrane adjusting its sensitivity to the neurotransmitter
May alter the rate of neurotransmitters synthesis, release, reuptake, or breakdown
Neuromodulators
122
Then why do we have synapses?
to process information, store it, and make decisions
123
the ability of your neurons to process information, store and recall it, and make decisions
Neural integration
124
is based on the postsynaptic potentials produced by neurotransmitters
Neural integration
125
Resting membrane potential
-70 mV
126
threshold
-55 mV
127
Neural integration
excitatory postsynaptic potential
inhibitory postsynaptic potential
Postsynaptic potentials
128
An voltage change in the direction of threshold that males a neuron more likely to fire
- usually results from Na flowing into the cell canceling some of the negative charge on the inside of the membrane
anything we have it ready adjust RMP by the synaptic knobs
Excitatory Postsynaptic potential (EPSP)
129
Any voltage change away from threshold that makes a neuron less likely to fire
neurotransmitter hyperpolarizes the postsynaptic cell and makes it more negative than the RMP making it less likely to fire
Produces by neurotransmitters that open ligand regulated chloride gates
- causing inflow of Cl making the cytosol more negative
Inhibitory Postsynaptic potential (IPSP)
130
all the paths to our memories or anything have to be
Exhibitory & promoting
131
the process of adding up postsynaptic potentials and responding to their net effect
-occurs in the trigger zone
summation
132
the balance between EPSP's and IPSP's enable the nervous system to
make decisions
133
occurs when a single synapse generates EPSP's so quickly that each is generated before the previous one fades (wave after wave)
Temporal summation
134
occurs when EPSP's from several different synapses add up to threshold at an axon hillock (lets go team)
Spatial summation
135
the way in which the nervous system converts information to a meaningful pattern of action potentials
Neural coding
136
___ depends upon which neurons fire
easiest way(pressure receptor, etc)
labeled line code
Qualitative information
137
each nerve fiber to the brain leads from a receptor that specifically recognizes a particular stimulus type
light for optic nerves
sound from cochlear nerves
(neurons have them labeled that's how we know where info is coming from)
labeled line code
138
information about the intensity of stimulus is encoded in two ways
one depends on the fact that different neurons have different thresholds of excitation
-stronger stimuli causes a more rapid firing rate
-excitement of sensitive, low threshold fibers gives way to excitement of less sensitive, high threshold fibers as intensity of stimuli increases (depends on which neurons are firing depending on how strong or weak the stimuli is)
other way depends on the fact that the more strongly a neuron is stimulated, the more frequently it fires
- CNS can judge stimulus strength from the firing frequency of afferent neurons (frequency 7 which one fires depends on which neuron is stimulated)
Quantitative Information
139
neurons function in large groups, each of which consists of million of interneurons concerned with a particular body function
-control rhythm of breathing
-moving limbs rhythmically when walking
(large amount of neurons working together to bring stimulus)
Neural pools
140
A neural pool
Going into the brain
one branches into many
diverging
141
A neural pool
going out of the brain
many become one
converging
142
A neural pool
breathing (lungs)
a line that keeps going back to the beginning (like running suicides)
reverberating
143
A neural pool
last a long time (light echo)
many go down a line some go to the left and come back and a few more go to the right and come back
Parallel after- discharge
144
Excited skeletal muscle, inhibits cardiac muscle, and excitatory or inhibitory effects on smooth muscle and glands depending on location
Acetylcholine(ACh)
145
Glutamate, aspartate, glycine, and GABA are all
Amino acids
146
Norepinephrine, epinephrin, and dopamine are all
Monoamines (biogenic Amines)
| Catecholamines
147
Serotonin, histamine are
Other mono amines
148
Substance P, enkephalins, B-endorphin, and cholecystokinin are all
Neuron erodes
149
Accounts for about 75% of all excitatory synaptic transmission in the brain, involved in learning and memory
Glutamate (glutamic acid)
150
Effects similar to being involved in learning and memory
Aspartate
151
Most common inhibitory neurotransmitter in spinal cord
Glycine
152
The most common inhibitory neurotransmitter in the brain
GABA (y- aminobutyric acid)
153
Involved in dreaming, waking, and mood; excites cardiac muscle, can excite or inhibit smooth muscle and glands depending on location
Nonreinephrine
154
Effects similar to involved in dreams, waking and mood; excites cardiac muscle, can excite or inhibit smooth muscle and glands depending on location
Epinephrine
155
Involved in elevation of mood and control of skeletal muscle
Dopamine
156
Involved in sleepiness, alertness,thermoregulation,and mood
Serotonin
157
Also potent vasodilator released by mast cells of connective tissue and basophils of the blood
Histamine
158
Mediates pain transmission
substance P
159
Acts as analgesics (pain reliever) by inhibiting substance P, inhibit motility, secretion increased sharply in women in labor
Enkephalins
160
Also secretes as a hormone by the pituitary, suppressed pain, reduces perception of fatigue and may produce "runners high" in athletes
B-endorphins
161
Suppresses appetite
cholecystokinin
162
physical basis of memory is a pathway through the brain called
memory trace or engram
163
the ability of synapses to change
synaptic plasticity
164
the process of making transmission easier
synaptic potentiation
165
kinds of memory
| correlate with different modes of synaptic potentiation (depending on)
immediate, short, long term
166
the ability to hold something in your thoughts for just a few seconds (for here and now; understanding time moving)
Immediate memory
167
lasts from a few seconds to several hours
quickly forgotten if distracted
calling a phone number we just looked up
short term memory (STM)
168
facilitation causes memory to last longer
tetanic stimulation and posttetanic potentiation
169
rapid arrival of repetitive signals at a synapse
| Causes Ca accumulation and postsynaptic cell more likely to fire
Tetanic stimulation
170
to jog a memory
effects the Ca levels being high
Ca level in synaptic knob stays elevated
little stimulation needed to recover memory
Posttetiation potentiation
171
Types of long term memory
Declarative and procedural
172
retention of events that you can put into words
| build new synapses &maintain them
Declarative
173
retention of motor skills
| washing dishes , tying shoes ,etc
procedural
174
physical remodeling of synapses
new branching of axons or dendrites
175
changes in receptors and other features increase transmission across "experienced" synapses
effect is longer -lasting
repetition will help w this
Molecule changes- long term potentiation
176
memory loss for recent events moody combative lose ability to talk walk and eat
show deficiencies of acetylcholine (ACh) and nerve growth factor (NGF)
Neurofibrillary tangles and senile plaques (protein plaques)
B- amyloid protein (we find surface of neurons) from breakdown product of plasma
Alzheimer Disease
177
Progressive loss of motor function beginning in 50's or 60's no recovery
Degeneration of dopamine releasing neurons
Pilling rolling motion facial rigidity slurred speech (shaking slow motor movement)
treatment- drugs and physical therapy(dopamine precursor (Ldopa) crosses brain barrier
MAO inhibitor (work on enzymes that break it into dopamine; neutralize enzymes to make sure doesn't break up neurotransmitter (dopamine))
Surgical technique to relieve tremors (battery pack by clavicle)
Parkinson Disease
