Outline of the Nervous System

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NERVOUS SYSTEM OUTLINE

I.Nervous System = 2 Parts
A.Central Nervous System (CNS)
1.Brain
2.Spinal Cord
B.Peripheral Nervous System (PNS)
1.Nerves to parts of the body
2.Nerves from parts of the body
C.Functions
1.Sensory
a.receptors for stimuli (receive stimulus)
b.peripheral nerves (carry impulses to CNS)
c.activities monitored
1)light intensity (visual)
2)sound intensity (auditory)
3)temperature
4)oxygen concentration
5)internal fluid conditions
2.Motor
a.peripheral nerves (carry impulses from CNS)
b.effectors (muscles & glands)
3.Integration (CNS)
a.create sensations (awareness)
b.add to memory
c.help produce thoughts
d.make decisions (conscious & subconscious)
4.Importance = maintain homeostasis
II.Nerve Tissue
A.Neurons (structural & functional units of nervous system) B.Neuroglial Cells (accessory cells: support neurons)
1.Astrocytes (star shaped cell)
a.found between neurons and blood vessels
b.provide nutrition
c.support
d.form scar tissue after brain tissue injury (multiply)
2.Oligodendrocytes
a.smaller than astrocytes with fewer processes
b.found along neurons
c.form myelin sheath (brain and spinal cord neurons)
3.Microglia
a.very small cells with even fewer processes
b.found throughout CNS
c.phagaocytosis
d.increase in numbers during inflammation

4.Ependymal Cells
a.cube to columnar shaped cells
b.found lining ventricles & central canal of spinal cord
c.cover choroids plexuses in brain
III.Nerve Impulse Conduction
A.Resting Potential
1.positive charge outside
a.high sodium ion concentration
1) sodium pump
2.negative charge inside
a.phosphate & sulfate ions
b.negatively charged proteins
c.high potassium concentration
1)potassium pump
3.potential difference = -70 mV
B.Potential changes
1.–70 mV to 0 = depolarization
2.higher than –70 mV = hyperpolarizing
C.Action Potential occurs when Threshold Potential achieved 1.causes change in permeability
a.sodium channels open & sodium moves in
b.outside of membrane at site negatively charged
2.electric current flows to adjacent membrane
3.causes action potential in adjacent membrane
4.potassium channels open
a.repolarizes membrane behind next action potential
5.resting potential reset = refractory period
a.sodium & potassium pumps active
D.All or None Response
1.impulse either conducted or not after stimulus
2.impulse intensity the same regardless of stimulus intensity E.Unmyelinated Nerve Fibers
1.conduction occurs over entire surface
2.series of action potentials
F.Myelinated Nerve Fibers
1.action potentials occur at Nodes of Ranvier
a.saltatory conduction (faster)
G.Speed of impulse
1.faster for larger diameter axons
2.120 m/sec – thick myelinated motor nerve cell
3.0.5 m/sec – thin unmyelinated sensory nerve cell

IV.Synaptic Transmission
A.Neurotransmitters
1.acetylcholine
2.monoamines
a.epinephrine
b.norepinephrine
c.dopamine
d.serotonin
3.amino acids
a.glycine
b.glutamic acid
c.aspartic acid
d.gama amino butyric acid (GABA)
4.peptides
a.enkephalins
b.substance P
B.Release of neurotransmitters
1.action potential reaches synaptic knob
2.calcium channels open
3.calcium moves in
4.synaptic vesicles release neurotransmitter
5.neurotansmitter binds to receptor on next neuron
6.action potential occurs on next neuron
C.Fate of neurotransmitters
1.acetylcholine
a.decomposition by chlolinesterase
2.monoamines
a.decomposition by monoamine oxidase
3.other neurotransmitters
a.reabsorbed
1)into synaptic knob
2)into neuroglial cells
3)into nearby neurons
V.Neuropeptides
A.Synthesis
1.brain and spinal cord neurons
B.Functions
1.neurotransmitters
2.neuromodulators
a.block release of neurotransmitter
b.alter response to neurotransmitter

C.Examples
1.enkephalins (brain & spinal cord)
a.synthesized during painful...
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