Unit 4 The Nervous System and - MR. CRAMER … · Unit 4 The Nervous System and Nervous Tissue....
Transcript of Unit 4 The Nervous System and - MR. CRAMER … · Unit 4 The Nervous System and Nervous Tissue....
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ESSENTIALS
OF HUMAN
ANATOMY
& PHYSIOLOGY
Unit
4The Nervous System and
Nervous Tissue
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Nervous System Functions
�Sensory input- gathering information�Monitor stimuli inside and outside the body
�Integration�Process and interpret sensory input and decide
if action is needed
�Motor output�Response to integrated stimuli�Activates muscles or glands
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Nervous System Structural Classification
�Central nervous system (CNS)�Brain�Spinal cord
�Peripheral nervous system (PNS)�Nerves outside the brain and spinal cord
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Functional Classification of the PNS
�Sensory (afferent) division�Nerve fibers carry information to the CNS
�Motor (efferent) division� Nerve fibers carry impulses away from the
CNS
�Two subdivisions�Somatic nervous system = voluntary
�Autonomic nervous system = involuntary
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Organization of the Nervous System
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Nervous Tissue: Support Cells (Neuroglia)
�Astrocytes�Abundant, star-shaped cells�Brace neurons�Form barrier between capillaries and neurons�Control chemical environment of
the brain
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Nervous Tissue: Support Cells
�Microglia�Spider-like phagocytes�Dispose of debris
�Ependymal cells�Line cavities of the
brain and spinal cord�Circulate cerebrospinal
fluid
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Nervous Tissue: Support Cells
�Oligodendrocytes�Produce myelin sheath around nerve fibers in
the CNS
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Nervous Tissue: Support Cells
�Satellite cells�Protect neuron cell bodies
�Schwann cells�Form myelin sheath in the PNS
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Nervous Tissue: Neurons
�Neurons = nerve cells�Cells specialized to transmit messages�Major regions�Cell body- nucleus and metabolic center of the cell
�Processes- fibers that extend from the cell body
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Neuron Anatomy
�Cell body�Nissl substance- specialized rough ER�Neurofibrils- intermediate cytoskeleton that
maintains cell shape�Nucleus�Large nucleolus
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Neuron Anatomy
�Extensions outside the cell body�Dendrites- conduct impulses toward cell body�Axons- conduct impulses away from cell body
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Axons and Nerve Impulses
�Axons end in axonal terminals
�Axonal terminals:�Contain vesicles with neurotransmitters�Separated from next neuron by a gap�Synaptic cleft- gap between adjacent neurons
�Synapse- junction between nerves
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Nerve Fiber Coverings
�Myelin sheaths- jelly roll like
covering (schwann cells)
�Nodes of Ranvier- gaps in
myelin sheath along the
axon
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Neuron Cell Body Location
�Most are found in the CNS�Gray matter- cell bodies and unmylenated
fibers�Nuclei- clusters of cell bodies within the white
matter of the CNS
�Ganglia- collections of cell bodies outside
the CNS