Transcript nervous system

Central Nervous System “CNS”
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Brain and spinal cord- integrates,
processes, and coordinates sensory
information and motor commands
Peripheral Nervous Sys. “PNS”
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All neural tissue outside of the CNS
Cranial Nerves= Nerves connected to the
brain
Spinal Nerves= nerves connected to the
spinal cord
Afferent (sensory)- bring sensory info to
CNS from receptors
Efferent (motor)- carries motor commands
from the PNS to muscles and glands
PNS Divisions
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Somatic N.S.- controls skeletal muscle
contractions (both voluntary and
involuntary)
Autonomic N.S.- automatic regulation of
smooth muscle, cardiac muscle, and
glandular secretions
Neurons
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Cell body- contains nucleus, bundles of
neurofibrils that extend from cell body to
form dentrites, cytoplasm contains
perikaryon
– Organelles that synthesize
neurotransmitters
– Ribosomes, RER, stain darkly “nissl
bodies”, account for gray color of ares
containing gray matter
– CNS neurons can’t divide!Stem cells are
found in the nose and the hippocampus
Neuron Structure continued
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Dendrite- sensitive process that
receives info from other neurons
Axon- passes electrical impulses (action
potential) and ends with synaptic
terminals
Synapse- area where 2 nerves meet,
neurotransmitters are used for
communication
Neuroglia “glial cells” of CNS
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Supporting tissue for neurons
– Ependymal cells- specialized epithelial
tissue that lines the ventricles in the brain,
and they help to monitor Cerebrospinal
fluid
– Astrocytes- largest and most numerous,
maintain the blood brain barrier, provide a
structural framework for neurons, repair
damaged tissue, guiding neuron
development, control interstitial fluid
Glial cells of CNS cont.
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Oligodendrocytes- form myelin sheath
around axon allowing increase action
potential speed, regions w/ a lot of
myelinated neurons is called white
matter
Microglia- small cells that can migrate to
clear cellular debris, waste products,
etc.
Neuroglia of the PNS
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Neuron cell bodies are clustered
together in the PNS= ganglia
Satellite cells- surround neuron cell
bodies, regulate environment
Schwann cells- form a sheath around
every axon, can myelinate axons
Neural Physiology “how neurons
make electricity”
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Beginning in the brain/or at a sensory
receptor, a though or stimulus is applied
Na+ rushes into receptor=depolarization
– There must be enough Na+ to cause this to
happen and that is determined by the
strenght of the stimulus or the number of
receptors stimulated (a little K+ leaks out)
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This is an action potential, and
electricity is created
Neurophysiology
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The electricity at this point causes the next
section at the node Na+ gate to open, and
more Na+ rushes into the next section and
this causes electricity to jump from section to
section
– Propogation of nerve impulse
– While electricity moves onward, the section of
neuron behind it gets repolarized
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At the end of axon, the Ca+ gates open, this
causes a rush of Ca+ which makes the
vacuoles contain neurotransmitters to fuse w/
the synaptic knob and open
Neurophysiology
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The neurotransmitter enters the
synapse, which cause the Na+ gates to
open in the next neuron or effector
Repolarization- ATP powers Na+ and
K+ pump to reestablish resting potential
Nerves can’t be stimulated during
repolarization unless a huge stimulus
occurs, “you stick your wet finger into an
electrical outlet
Ready to fire again in .001 sec
Chemical Synapses
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Excitatory neurotransmitters- cause
depolarization and promote action
potential
Inhibitory Neurotransmitters- cause
hyperpolarization, and suppress action
potential
Acetylcholine (Ach)- neuromuscular
junction stimulates muscle contraction
Other Neurotransmitters
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Norepinephrine (NE)- widely distributed in the
brain, usually has an excitatory response
Dopamine- CNS neurotransmitter, has both
an excitatory and inhibitory effect
– Not enough leads to overstimulation of neurons
that control skeletal muscle leading to rigidity
“Parkinson’s Disease”
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Seratonin- CNS, inadequate amount effects
attention, emotions, and may be responsible
for depression