Unit 4 Part 1 Flashcards
(190 cards)
1
Q
The master controlling and communication system of the body
A
Nervous System
2
Q
Controls and integrates all body activities within limits that maintain life
A
Nervous System
3
Q
Three basic functions of nervous system
A
- Sensory Function
- Integrative function
- Motor function
4
Q
▪ Monitors internal and external stimuli (changes)
▪ Afferent pathway to the brain
▪ Receptors
A
Sensory Function
5
Q
▪ Process and interprets information
▪ Decides appropriate response
A
Integrative Function
6
Q
▪ Efferent pathway to effector organs (muscles or glands), effects a response
A
Motor Function
7
Q
Basic divisions of the nervous system
A
Central Nervous System
Peripheral Nervous System
8
Q
Central Nervous System includes
A
brain and spinal cord
9
Q
Peripheral Nervous System includes
A
cranial nerves, spinal nerves, ganglia, enteric plexuses, sensory receptors
10
Q
Functional Classification of the PNS
A
Sensory (afferent) division
Motor (efferent) division
11
Q
- carrying toward a center (usually integrating center, the CNS)
-Nerve fibers that carry information to the central nervous system
-Somatic sensory
-Visceral sensory
A
Sensory (afferent) division
12
Q
Somatic sensory includes
A
(skin, skeletal muscle)
13
Q
Visceral sensory includes
A
(visceral organs)
14
Q
-Nerve fibers that carry impulses away from the central nervous system
-Activate (effect) muscles or glands to bring about a response.
A
Motor (efferent) division
15
Q
Motor (efferent) = 2 divisions
A
Somatic nervous system
Autonomic nervous system
16
Q
voluntary (skeletal muscles)
A
Somatic nervous system
17
Q
involuntary (smooth and cardiac muscles, glands)
A
Autonomic nervous system
18
Q
-basic structural units of the nervous system
-highly specialized cells
-conduct electrical signals from one part of the
body to another
-signals are transmitted along the plasma membrane in the form of nerve impulses or action potentials
A
Neuron
19
Q
Characteristics of Neurons
A
-They have extreme longevity.
-They do not divide
-They have an exceptionally high metabolic
rate
-Neurons cannot survive for more than a few
minutes without oxygen
20
Q
– metabolic center
A
Cell body
21
Q
info for protein synthesis
A
Nucleus
22
Q
Nissl bodies location
A
in ER
23
Q
maintain structure
A
Neurofilaments
24
Q
Cell processes
A
a) Dendrites
b) Axons
25
-Conducts impulses towards
the cell body (from other neurons or sensory receptors)
- short, highly branched & unmyelinated
- Surfaces specialized for contact with other neurons
-Most are extensions from the neuron cell body; others project from the peripheral ends of some axons
-Contains neurofibrils & Nissl bodies
Dendrites
26
-Conduct impulses away from cell body
-Long, thin cylindrical process of cell, branched or unbranched
-Arises at axon hillock
- Impulses arise from initial segment (trigger zone)
-Side branches (collaterals) end in fine processes called axon terminals
-Swollen tips called synaptic end bulbs contain vesicles filled with neurotransmitters
Axons
27
Neurons can be classified ___ or ____
structurally, functionally
28
Neurons are grouped ____ according to
the number of ___ that extend from the
cell body
structurally, processes
29
Structural Classification of Neurons
-Multipolar
-Bipolar
-Unipolar
30
-several dendrites & one axon
-most common cell type
multipolar
31
-one main dendrite & one axon
-found in retina, inner ear & olfactory
bipolar neurons
32
-one process only (develops from a bipolar)
-are always sensory
neurons
unipolar neurons
33
The ___ classification scheme groups neurons
according to the ___ in which the nerve impulse ___ relative to the CNS
functional; direction; travels
34
Functional Classification
▪ Sensory neurons
▪ Motor neurons
▪ Interneurons
35
-afferent neurons
-They transmit impulses toward the CNS from
sensory receptors in the PNS
-The single (unipolar) process is divided into the
central process and the peripherial process
Sensory Neurons
36
Sensory neurons have their cell bodies in __
outside of the ____
ganglia; cns
37
specialized to respond to changes in environment
Sensory receptors
38
Three ways to classify receptors:
- type of stimulus
- body location
- structural complexity
39
Classification by Stimulus Type
▪ Mechanoreceptors
▪ Thermoreceptors
▪ Photoreceptors
▪ Chemoreceptors
▪ Nociceptors
40
respond to touch, pressure, vibration, and stretch
Mechanoreceptors
41
sensitive to changes in temperature
Thermoreceptors
42
respond to light energy (example: retina)
Photoreceptors
43
respond to chemicals (examples: smell, taste, changes in blood chemistry)
Chemoreceptors
44
sensitive to pain-causing stimuli
(examples: extreme heat or cold, excessive pressure, inflammatory chemicals)
Nociceptors
45
Classification by Location
Exteroceptors
Interoceptors (visceroceptors)
Proprioceptors
46
-Respond to stimuli arising outside body
-Receptors in skin for touch, pressure, pain, and
temperature
-Most special sense organs
Exteroceptors
47
-Respond to stimuli arising in internal viscera and
blood vessels
-Sensitive to chemical changes, tissue stretch, and
temperature changes
-Sometimes cause discomfort but usually person is
unaware of their workings
Interoceptors (visceroceptors)
48
▪ Respond to stretch in skeletal muscles, tendons,
joints, ligaments, and connective tissue coverings of bones and muscles
▪ Inform brain of one's movements
Proprioceptors
49
Majority of sensory receptors belong to one of two
categories:
▪ Simple receptors of the general senses
▪ Receptors for special senses
50
▪ Modified dendritic endings of sensory neurons
▪ Are found throughout body and monitor most
types of general sensory information
Simple receptors of the general senses
51
▪ Vision, hearing, equilibrium, smell, and taste
▪ All are housed in complex sense organs
Receptors for special senses
52
▪ Neurons that carry impulses away from the CNS to effector organs (muscles and glands) are called motor or efferent neurons
▪ Upper motor neurons are in the brain
▪ Lower motor neurons are in PNS
▪ multipolar and their cell bodies are located in the CNS (except autonomic)
▪ form junctions with effector cells, signaling muscle to contract or glands to secrete
Motor Neurons
53
▪ lie between the motor and sensory neurons
▪ Form complex neural pathways
▪ Confined to CNS
▪ Make up 99.98% of the neurons of the body and are the principle neuron of the CNS
▪ Almost all are multipolar
▪ show great diversity in the size and branching patterns of their processes
Interneuron or Association Neurons
54
is the large neuron found in the primary motor cortex of the cerebrum
Pyramidal cell
55
interneuron from the cerebellum
Purkinje cell
56
-Supporting Cells
-Half of the volume of the CNS
-Smaller cells than neurons
-50X more numerous
-Not conduct impulses
-Cells can divide
Neuroglial Cells
57
▪ Star-shaped
▪ Most abundant
▪ Form blood-brain barrier
▪ Metabolize neurotransmitters (glutamate)
▪ Recapture and Recycle K+ ions
▪ Provide structural support
▪ Play a role in exchanges of ions between capillaries and neurons
▪ Involved with synapse formation in developing
neural tissue
▪ Produce molecules necessary for neural growth (brain-derived trophic factor BDTF)
▪ Propagate calcium signals that may be involved in memory
Astrocytes
58
Metabolize neurotransmitters
(glutamate)
59
Produce molecules necessary for neural growth
(brain-derived trophic factor BDTF)
60
Propagate ___ signals that may be involved in
memory
calcium
61
▪ Most common glial cell type
▪ Each forms myelin sheath around more than one axons in CNS
▪ Analogous to Schwann cells of PNS
Oligodendrocytes
62
▪ Smallest and least abundant cells found near
blood vessels
▪ Phagocytic role
▪ Derived from cells that also gave rise to macrophages & monocytes; migrate to the CNS during embryonic and fetal development
Microglia
63
clear away dead cells
Phagocytic role
64
▪ Form epithelial membrane lining cerebral cavities & central canal
▪ Produce cerebrospinal fluid (CSF)
▪ Cilia aid circulation of CSF
Ependymal cells
65
▪ These cells are similar in type and differ mainly in location
Neuroglia in the PNS
66
There are two supporting cells in the PNS
▪ Satellite cells
▪ Schwann cells
67
▪ Flat cells surrounding neuronal cell bodies in peripheral ganglia
▪ controlling the chemical environment of neurons
▪ Support neurons in the PNS ganglia; ACT AS
PROTECTIVE CUSHIONING
Satellite Cells
68
▪ produces part of the myelin sheath in the PNS
▪ protective role: aid in maintaining the integrity of normally functioning nerve fibers
▪ vital to peripheral nerve fiber regeneration – PNS only,
Schwann Cell
69
▪ Insulation of axon
▪ Increase speed of nerve impulse
▪ Makes impulse propagation more energy efficient
▪ White lipid protein substance
Myelination
70
▪ Prevents the leakage of electrical current from the axon
▪ Increases the speed of impulse conduction
Insulation of axon
71
All axons surrounded by a lipid & protein covering (myelin sheath) produced by
Schwann cells
72
cytoplasm & nucleus of Schwann cell
Neurilemma
73
gaps that occur at regular intervals about 1mm apart
nodes of ranvier
74
-found in portions of the autonomic nervous system as well as in some sensory fibers
-Thin, slowly conducting axons lack a myelin sheath
Unmyelinated fibers
75
▪ Neurilemma is found
▪ nodes of ranvier
▪ Only thick, rapidly conducting axons are sheathed in myelin
▪ nerve impulses do not travel along the myelin-covered regions of the axonal membrane, but instead jumps from the membrane of one Node of Ranvier to the next greatly increasing impulse conduction
Myelination: PNS
76
myelinated axons in PNS, nerve impulses do not travel along the myelin-covered regions of the axonal membrane, but instead____
jumps from the membrane of one Node of Ranvier
77
Myelinated axons transmit nerve impulses rapidly at what speed
150 meters/second
78
Unmyelinated axons transmit quite slowly at what speed
1 meter/second
79
▪ Oligodendrocytes myelinate axons
▪ Broad, flat cell processes wrap about ___ axons, but the cell bodies do not surround the axons
▪ No neurilemma is formed
▪ Little regrowth after injury is possible
Myelination: CNS
80
Little regrowth in CNS after injury is possible due to the
lack of a distinct tube or neurilemma
81
▪ Structure that contain a number of cell bodies in the
PNS
▪ Occurs in the PNS
▪ Form the plexuses
▪ Dorsal root ganglia, autonomic ganglia, cranial nerve ganglia
GANGLIA
82
▪ Structure that contain a number of cell bodies in the CNS
▪ Occur in the CNS
▪ Occur in the gray matter of the brain
▪ Caudate, putamen, dentate, emboliform, pallidum, substantia nigra, subthalamic nuclei
NUCLEI
83
Bundles of nerve fibers running through CNS
Tracts
84
Bundles of nerve fibers running through PNS
Nerves
85
Nerve Fibers
Tracts
Nerves
86
myelinated processes
White matter
87
nerve cell bodies, dendrites, axon terminals,
bundles of unmyelinated axons and neuroglia
Gray matter
88
Neurons are electrically excitable due to the
voltage difference across their membrane
89
Excitable cells communicate with 2 types of electric signals
Action potentials
Graded potentials
90
electric signal that can travel long distances
Action potentials
91
electric signal that are local membrane changes only
Graded potentials
92
In living cells, production of action potential or graded potential depends upon
upon the existence of resting membrane
potentials and existence of certain ions
93
Leakage (nongated)
channels are always
open
94
Gated channels can
open and close
95
gated channels can be:
a. Chemically (ligand)-gated
b. Mechanically-gated
c. Voltage-gated
96
-Leakage channels alternate between open
and closed
-K+ channels are more numerous than Na+ channels
Ion Channels in Neurons - Leakage
97
-Ligand-gated channels respond to chemical
stimuli (ligand binds to receptor)\
-Mechanically-gated channels respond to
mechanical vibration or pressure stimuli
-Voltage-gated channels respond to direct
changes in membrane potential
Ion Channels in Neurons - Gated
98
Nerve & Muscle cells are
“excitable”
99
Capable of self-generating electrical impulses
at their membranes
“excitable”
100
* Electrical potentials exist across the
membranes of essentially all cells of the
body
* Nerve & Muscle cells are “excitable” - -
Capable of self-generating electrical impulses
at their membranes
* Concentration difference of ions across a
selectively permeable membrane can
produce a membrane potential.
Membrane Potentials
101
difference in potential ( voltage ) between
the inner side & outer side of the membrane
* Inside cell more negative and more K+
* Outside cell more positive and more Na+
102
– Must exist for action
potential to occur
– The value for Vm in
inactive muscle cells is
typically btwn –80 and
–90 millivolts.
– Cells that exhibit a Vm
are said to be
polarized.
– Vm can be changed by
influx or efflux of
charge.
Membrane Potentials
103
It ranges between -70 and -90 mV in different
excitable tissue cells
Resting Membrane Potential ( RMP)
104
MP in a stimulated cell that is producing a local, non-propagated potential;
-an electrical change which is measurable only in the immediate vicinity of the cell but not far
from it.
Graded Potential (Local Response )
105
Small deviations in
resting membrane
potential of
-70mV
(more negative
inside)
106
occurs in response to the
opening of a mechanically-gated or ligand-
gated ion channel
Graded Potentials
107
The amplitude of a graded potential
depends on the
stimulus strength
108
Graded potentials can be add together to
become larger
amplitude
109
MP in case of a
nerve/muscle that is generating a propagated
electrical potential after stimulation by effective
stimulus
Action potential ( AP)
110
– Large changes in cell membrane potential (charge)
– Inside of the cell becomes more positive relative
to the outside of the cell
– Function to transmit information over long
distances
– Electrical signal that travels along the nerve axon
and ends at the synaptic terminal
– All-or-none principle - Like camera flash system
– RESULTS IN: Releases neurotransmitter
(acetylcholine or ACh)
Action Potentials
111
level of depolarization
needed to trigger an action potential. Action
potential does not occur until
threshold potential has been reached.
Threshold potential
112
state membrane
suddenly becomes permeable to Na+ ions;
Allows tremendous numbers of (+) charged
Na+ ions to flow to the interior of the axon;
Potential rises rapidly in the (+) direction
Depolarization stage
113
Na channels begin to close; K
channels open more than they normally
do; Rapid diffusion of K+ ions to the exterior
re-establishes the normal negative resting
membrane potential
Repolarization
114
Membrane potential may
briefly become over negative; due to opened
voltage-gated K channels
Hyperpolarization
115
Ion channels open:
1. Na+ rushes ___
(__polarization)
2. K+ rushes ___
(__polarization)
in; de
out; re
116
Action potentials can only occur if the
membrane potential reaches
threshold
117
Period of time during which neuron can
not generate another action potential
Refractory Period of Action Potential
118
▪ even very strong stimulus will
not begin another AP
▪ From beginning of action potential
until near end of repolarization
▪ Na+ channels are open or
recovering
Absolute refractory period
119
▪ a suprathreshold stimulus will be
able to start an AP
▪ Occurs when the membrane is
hyperpolarised (-80mV), where the
K+ channels are open
▪ Relative refractory period
120
Resting membrane
potential is at
-70mV
121
Depolarization is the
change from
-70mV to
+30 mV
122
Repolarization is the
reversal from
+30 mV
back to -70 mV)
123
▪ nerve is -70mV
▪ skeletal & cardiac muscle is closer to -90mV
Resting membrane potential
124
Duration of nerve impulse is
1/2 to 2 msec
125
Duration muscle action potential
skeletal
cardiac & smooth
1-5 msec
10-300msec
126
Fastest nerve conduction velocity is ___ times faster than velocity over skeletal muscle fiber
18
127
Propagation of An Action Potential
▪ as Na+ flows into the cell
during depolarization, the
voltage of adjacent areas
is effected and their
voltage-gated Na+
channels open
▪ self-propagating along the
membrane
128
nerve
impulse
traveling action
potential
129
Nerve impulse conduction
in which the impulse jumps
(Salta) from node to node
Saltatory Conduction
130
The propagation speed of a nerve impulse is not related to__
stimulus strength.
131
the___, myelinated fibers conduct impulses __ due to size & saltatory conduction
larger; faster
132
myelinated somatic sensory & motor to skeletal muscle
largest
A fibers
133
a fibers speed
(5-20 microns & 130 m/sec)
134
myelinated visceral sensory & autonomic preganglionic
medium
B fibers
135
B fibers speed
(2-3 microns & 15 m/sec)
136
▪ unmyelinated sensory & autonomic motor
smallest
C fibers
137
C fibers speed
.5-1.5 microns & 2 m/sec
138
Action potentials can travel along axons at speeds of
of 0.1-100m/s.
138
Action potentials can travel along axons at speeds of
of 0.1-100m/s.
139
The speed is affected by 3 factors:
Temperature
Axon diameter
Myelin sheath
140
increases the speed
of propagation dramatically,
saltatory propagation
141
Application : Local Anesthetics
▪ Prevent opening of voltage-gated Na+ channels
▪ Nerve impulses cannot pass the anesthetized region
▪ Novocaine and lidocaine
142
(1)May be blocked in its transmission from one neuron
to the next
(2)May be changed from a single impulse into
repetitive impulses
(3)May be integrated with impulses from other
neurons to cause highly intricate patterns of
impulses in successive neurons.
Fate of Action Potentials
143
*A connection between a neuron and a second cell
*In the CNS, this other cell is also a neuron.
*In the PNS, the other cell may be either a neuron or an effector cell e.g. gland or muscle
Synapse
144
from axon to dendrite
axodendritic
145
from axon to cell body
axosomatic
146
from axon to axon
axoaxonic
147
from dendrite to dendrite
dendrodenritic
148
from dendrite to cell body
dendrosomatic
149
2 Types of synapses
electrical
chemical
150
▪ ionic current spreads to next cell through gap
junctions
▪ faster, two-way transmission & capable of
synchronizing groups of neurons
electrical
151
one-way information transfer from a presynaptic
neuron to a postsynaptic neuron
chemical
152
both electrical and chemical,
e.g. neurons in lateral vestibular nucleus
CONJOINT SYNAPSE
153
1. Have direct open fluid channels that conduct electricity from one cell to the next without interruption
2. Have gap junctions which allow the movement of ions
3. Very few in the CNS (brain and glial cells) but are the
predominant type in the periphery of the body (i.e.
skeletal, cardiac and smooth muscle contraction)
4. The bidirectional transmission of electrical synapses
permits them to help coordinate the activities of large
groups of interconnected neurons.
5. Promotes synchronous firing of a group of interconnected
neurons - For example, in Mental attention, Emotions and
Memory, Arousal from sleep
Electrical Synapse
154
1. Almost all of the synapses in the CNS
2. First neuron secretes a neurotransmitter
3. Neurotransmitter binds to receptors on the second neuron
(excites, inhibits, or modifies its sensitivity)
4. Always transmit signals in one direction (from the pre-synaptic neuron (releases neurotransmitter) to the post-
synaptic neuron - Called the principle of one way conduction
Chemical Synapse
155
Factors Affecting Synaptic Transmission
1. pH of the interstitial fluid
2. Hypoxia – depresses neurons
3. Drugs, toxins and diseases
156
neuronal excitability; causes cerebral epileptic seizures (Increased excitability cerebral neurons) e. g. overbreating in person with
epilepsy
Alkalosis
157
–decreased neuronal activity; pH around 7.0 usually causes a coma
(e.g.severe diabetic or uremic acidosis)
Acidosis
158
depresses neurons
Hypoxia
159
caffeine found in coffee, tea,
strychnine, theophylline, theobromine increases neuronal
excitability by decreasing the threshold for excitation of neurons
Drugs, toxins and diseases
160
▪ More than 50 chemical substances have been proven
▪ Two groups: small molecule (rapidly acting) and neuropeptides (slowly acting)
Neurotransmitters
161
▪ Synthesized in the cytosol of the presynaptic
terminal
▪ Absorbed by means of active transport intro
transmitter vehicles
▪ Continuous recycling of vesicles
Small-Molecule Transmitters
162
▪ Typical small-molecule
transmitter
▪ released by many PNS neurons & some CNS
▪ Excitatory in the central nervous system
▪ Excitatory on NMJ but inhibitory at others – mixed action depending on receptor
▪ inactivated by acetylcholinesterase
Acetylcholine (ACh)
163
- modified
amino acids (tyrosine)
Biogenic Amines
164
regulates mood,
dreaming, awakening
from deep sleep
norepinephrine
165
regulating skeletal muscle tone
dopamine
166
control of mood, temperature regulation, & induction of sleep
serotonin
167
removed from synapse &
recycled or destroyed by
enzymes (monoamine
oxidase or catechol-0-
methyltransferase)
Biogenic Amines
168
secreted at the
synapses of spinal cord,
inhibitory
Glycine
169
released by nearly
all excitatory neurons in the
brain – sensory pathways
entering the CNS and spinal
cortex
Glutamate
170
inhibitory
neurotransmitter for 1/3 of all
brain synapses and spinal
cord
GABA Gamma Amino Butyric
Acid
171
Gamma Amino Butyric
Acid
Valium
172
▪ excitatory in both CNS & PNS
▪ released with other neurotransmitters (ACh & NE)
ATP and other purines (ADP, AMP & adenosine)
173
▪ formed from amino acid arginine by an enzyme
▪ formed on demand and acts immediately
▪ diffuses out of cell that produced it to affect
neighboring cells
▪ may play a role in memory & learning
▪ first recognized as vasodilator that helps lower blood pressure (cerebral and peripheral)
Gases (nitric oxide or NO)
174
▪ 3-40 amino acids linked by peptide bonds
▪ Slow acting→more prolonged actions
▪ Synthesized as integral parts of large-protein
molecules by ribosomes in the cell body
▪ Substance P
▪ Pain relief
Neuropeptides
175
enhances our
perception of pain
Substance P
176
pain-relieving effect by blocking the release of
substance P
enkephalins
177
___ may produce loss of pain sensation
because of release of ____ substances
such as ___ or ___
acupuncture, opioids-like, endorphins, dynorphins
178
Action potential travels from
axon
179
Action potential reaches
end bulb and voltage-gated Ca+ 2
channels open
180
Ca+2 flows___ the
concentration gradient
inward down
181
causes triggers
rapid fusion of synaptic
vesicles triggering release of
neurotransmitter
Inward diffusion
182
crosses synaptic cleft & binding to
ligand-gated receptors in the
post-synaptic membrane
Neurotransmitter
183
Quantity of transmitter
released is directly related to
the amount of Ca that enters
184
The effect of a
neurotransmitter can be either
excitatory or inhibitory
185
a depolarizing postsynaptic
potential is called
an EPSP
186
an inhibitory postsynaptic
potential is called
an IPSP
187
Diffusion out of synaptic
cleft into surrounding fluid
move down
concentration gradient
188
Enzymatic degradation
acetylcholinesterase
189
Uptake by neurons or glia
cells – active transport back
into pre-synaptic terminal
(norepinephrine)
neurotransmitter
transporters
