Transcript The Nervous System

The Nervous System
I. General organization of nervous system
A. CNS
1. brain
2. spinal cord
B. PNS
1. sensory
2. motor
a. Somatic
b. ANS
-sympathetic
-parasympathetic
II. Nervous Supporting Cells - neuroglia
A. Astrocytes
1.
2.
3.
Connect to
capillaries
Mopping up
chemical
environment of
brain as far as
potassium ions and
neurotransmitters
Help to create
blood brain barrier
B. Microglia
• 1. spider-like
phagocytes
• 2. debris, dead
brain cells, bacteria
C. Ependymal cells
• 1. lines cavities in CNS
• 2. beating of cilia moves
cerebrospinal fluid
• 3. fluid nourishes and cushions
CNS
• 4. creates CSF in the choroid
plexi of the brain’s ventricles
D. Oligodendrocytes
• 1. wrap axons of several nerve
cells with fatty layer
• 2. produces myelin sheath
• 3. speeds conduction
• 4. located with the CNS
E. Schwann cells
• 1. located outside of CNS
• 2. produce myelin sheath as
do the oligodendrocytes
• 3. takes several Schwann
cells to produce the myelin
sheath for one axon of one
nerve cell
F. Glia cells in general
• 1. resemble
neurons
• 2. not excitable
• 3. supportive
cells
• 4. capable of
repeated mitosis
• 5. gliomas-glial
tumors
III. Neurons
A. Structure
•
•
•
•
•
•
•
•
•
1.
2.
3.
4.
5.
6.
7.
8.
9.
cell body
nissl bodies-rer
dendrites
axon
axon hillock
axon collateral
axon terminals
neurotransmitters
synaptic cleft
B. Myelin sheath
•
•
•
•
1. functions
2. PNS-Schwann cell
3. Node of Ranvier
4. Can form a pathway for
regrowth of damaged
axon
• 5. multiple sclerosis
C. Neurons classified by function
•
•
•
•
•
•
•
1.
2.
3.
4.
5.
6.
7.
afferent
interneuron
efferent
ganglia
nuclei
gray matter
white matter
D. Neurons classified by structure
• 1. multipolarmost common
• 2. bipolarlocated in
some sensory
organs such as
the eye
• 3. unipolarsensory
neuron
IV. Neuron physiology
• A. Membrane traits
•
1. semipermeable
•
2. Na/K ion pump
•
3. Leak gates
•
4. gated channels
•
a. Ligand-gated
•
b. Voltage-gated
B. Resting membrane characteristics
• 1. semipermeable
• 2. negative charged
proteins
• 3. relatively
impermeable to Na and
Cl ions
• 4. bit more permeable
to K ions
• 5. due to action of Na/K
ion pump notice
separation of ions
• 6. potassium ions leak
out due to K ion leak
channels
C. Resting membrane potential
• 1. at rest, interior of
cell possesses slightly
negative charge
• 2. -70 mV
• 3. due to K ion
movement mainly
• 4. diffusion out
• 5. electrical attraction
in
• 6. slightly more
positive charge outside
• 7.http://www.youtube.
com/watch?v=YP_P6b
YvEjE
D. Changing the resting membrane potential
in a resting neuron
•
•
•
•
•
•
1. depolarization
2. hyperpolarization
3. changes in extracellular K ions (hypokalemia)
4. changes in extracellular Na ions
5. changes in extracellular Ca ions
a. Ca ions are attracted to negative proteins of Na gated
channels
• b. If Ca ion concentration falls-fewer Ca ions attached to Na
gated channels-causes channels to openproduces???hypocalcemia
•
c. If Ca ion levels rise-???
E. Graded potentials
• 1. strictly local event
• 2. caused by change in
local ion gates
• 3. change brought
about by several
possible stimulus
sources
• 4. chemical, voltage
changes, temperature,
mechanical stimulation
• 5. may be excitatory or
inhibitory
• 6. conducted but in a
decremental manner
F. Action potential
• 1. produced by graded
potentials
• 2. threshold potential
• 3. intiates series of
membrane gate changes
• 4. wave of depolarization
• 5. repolarization
• 6. hyperpolarization
• 7. return to normal
• 8. all-or-none
• 9.
https://highered.mcgrawhill.com/sites/007249585
5/student_view0/chapter
14/animation__the_nerve
_impulse.html
G. Refractory period
• 1. definition
• 2. absolute
• 3. relative
H. Frequency carries information
• 1. action potentials don’t vary in magnitude
• 2. threshold stimulus produces one action potential
• 3. submaximal stimuli produce increasing
frequency of action potentials until
• 4. maximal stimulus-lowest stimulus strength that
produces maximum frequency of action potentials
• 5. supramaximal stimulus
I. Propagation of action potentials
• 1. concentration difference of ions on either side of membrane
represents potential energy-kind of like of cocked gun
• 2. stacked dominoes waiting to fall over
• 3. one domino falling over initiates a wave of action potentials
spreading out like the ripples in a pond
• 4. each action potential is just as strong as the previous action
potential
• 5. strength does not diminish as nerve impulse moves down the
axon
• 6. http://highered.mcgrawhill.com/sites/9834092339/student_view0/chapter44/action_poten
tial_propagation_in_an_unmyelinated_axon.html
• 7. http://www.youtube.com/watch?v=DJe3_3XsBOg
V. Synapses
A. Anatomy
•
•
•
•
•
1. presynaptic membrane
2. synaptic cleft
3. postsynaptic membrane
4. synaptic vesicles
5. receptor sites for transmitter
substance
B. Physiology of synapse
• 1. action potential arrives
• 2. Calcium ion channels
open
• 3. synaptic vesicles fuse
with membrane
• 4. transmitter substance
released
• 5. diffusion of transmitter
substance
• 6. binding to receptors
• 7. creates a graded
potential
• 8. may bring postsynaptic
membrane to threshold
• 9. nerve gas-blocks
cholinesterase
• 10. IPSP or EPSP
C. You tube of synaptic events
• http://www.youtube.com/watch?v=LT3VKAr4r
oo
D. Types of Synapses
•
•
•
•
1. axo-dendritic
2. axo-somatic
3. axo-axonic
a. Presynaptic inhibition
of enkephalins and
endorphins in brain
sensory neurons blocking
Ca channels
• b. Presynaptic facilitation
due to serotonin releasecauses Ca channels to
open
E. Post synaptic fiber as a neural integrator
• 1. temporal summation
• 2. spatial summation
• 3. neural integrator