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Sensory Division
picks up sensory information and delivers it to the CNS (Central Nervous System)
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Motor Division
Carries information to muscles and glands
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Somatic
division of the Motor Divsion: carries information to skeletal muscles
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Autonomic
Division of motor division: carries information to smooth muscle, cardiac muscle, and glands
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Functions of the nervous system
- 1.) receiving stimuli: sensory function
- 2.) deciding about stimuli: integrative function
- 3.) reacting to stimuli: motor function
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Sensory funtion
- -sensory receptors gather information
- - information is carries to the CNS
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Integrative Function
- Sensory information used to create: sensation, memory, thought, decision
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Motor Function
- -Decisions are acted upon
- - Impulses are carried to effectors
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White matter
- -contains myelinated axons
- - considered fiber tracts
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Gray Matter
- -contains unmyelinated structures
- -cell bodies, dendrites
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Major Groups of Neurons
- - bipoloar neurons
- - unipolar neurons
- - multipolar neurons
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Bipolar Neurons
- - contains two processes
- - eyes, ears, nose
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Unipolar Neurons
- - Contains one process
- - ganglia of PNS
- - Sensory
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Multipolar Neurons
- - 99% of neurons
- - contains many processes
- - most neurons of CNS
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Sensory Neurons
- - afferent
- - carry impulses to CNS
- - Most are unipolar
- - Some are bipolar
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Interneurons
- - Link neurons
- - (association neurons or internuncial neurons)
- - multipolar
- - located in CNS
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Motor Neurons
- -multipolar
- - carry impulses away from CNS
- - carry impulses to effectors
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Schwann Cell
- - produce myelin found on peripheral myelinated neurons
- - speed up neurotransmitters
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Satellite Cells
- support clusters of neuron cell bodies (ganglia)
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Microglia
- type of neuroglial cell
- - CNS
- - phagocytic cell
- - keeps CNS clean
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Astrocytes
- type of neuroglial cell
- - CNS
- - scar tissue
- - mop up excess ions
- - induce synapse formation
- - connect neurons to blood vessels
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Oligodendrocytes
- type of neuroglial cell
- - CNS
- - unmyelinating cell
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Ependyma or ependymal
- type of neuroglial cell
- - CNS
- - ciliated
- - line central canal of spinal cord
- - line ventricles of brain
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Resting Potential
- -polarized membrane
- - inside of cell is negative relative to the outside of the cell
- - 70 mV difference from inside to outside of cell
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Hyperpolarized
- if membrane potential become more negative
- - wont conduct an impulse
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Depolarized
if membrane potential become less negative
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Action potential
reaching threshold potential results in a nerve impulse starting this
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absolute refractory period
time when threshold stimulus does NOT start another action potential
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relative refractory period
time when stronger threshold stimulus can start another action potential
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synaptic transmission
where released neurotransmitters cross the synaptic cleft and react with specific molecules called receptors in the postsynaptic neuron membrane
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Excitatory Postsynaptic Potential (EPSP)
- depolarizes membrane of postsynaptic neurons
- -action potential of postsynaptic neuron becomes more likely
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Inhibitory Postsynaptic Potential (IPSP)
- Hyperpolarizes membrane of postsynaptic neuron
- - action potential of postsynaptic neuron become less likely
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summation
- EPSP's and IPSP's are added together in a process called this
- - more EPSP's lead to greater probability of an action potential
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Neuropeptides
- neurons in the brain or spinal cord synthesize these
- - act as neurotransmitters
- - examples: enkephalins, beta endorphin, substance P
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convergence
- neurons receive input from several neurons
- -incoming impulses represent information from different types of sensory receptors
- - allows nervous system to collect, process, and respond to information
- - makes it possible for a neuron to sum impulses from different sources
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divergence
- one neuron sends impulses to several neurons
- - can amplify an impulse
- - impulse from a single neuron in CNS may be amplified to activate enough motor units needed for muscle contraction
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