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Anatomy & Physiology, Muscular System, Motor Unit, Principle of…
Anatomy & Physiology
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History
Hippocrates
Hippocratic Oath, urged physicians to seek natural causes for disease instead of supernatural
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Claudius Galen
Physician to Roman gladiators, dissected only animals, published his findings but people read them to dogmatically for 1500 years
Moses ben Maimon
Jewish rabbi and physician, wrote 10 medical books
Ibn Sina
Read and questioned Aristotle and Galen, wrote and influenced western medicine
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Robert Hooke
Designed compound microscope, observed cells
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Muscular System
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Characteristics
Excitability
responsiveness to chemical signals, stretch, electrical changes across plasma membrane
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Motor Unit
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For fine control, like hand or eyes, we use
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For strength, like large muscles, we need
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Nervous System
Neurons
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3 Functional Classes:
Sensory (afferent)
detect stimuli (light, heat, pressure, chemicals,) and transmit info to CNS
Interneurons
Lie entirely within CNS, connecting motor and sensory pathways (90% of all neurons)
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Structure of a Neuron
Soma
cell body, large nucleolus w/nucleus
Cytoplasm has organelles, inclusions - nutrients or pigments (glycogen, lipid droplets, melanin), Cytoskeleton
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Axon
Nerve Fiber, rapid conduction, starts at the axon hillock
Has its own: Axoplasma, Axolemma, it has Axon collaterals (branches), terminals (swellings for contact points), myelin sheath
Synapse
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Presynaptic can synapse with dendrite (axodendritic), neurosoma (axosomatic), or axon (axoaxonic) of postsynaptic neuron
Spinal Motor Neuron has 8,000 axon terminals on its dendrites, and 2,000 on its neurosoma
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electrical synapses exist between some neurons, neuroglia, cardiac and single-unit smooth muscle
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Cessation of Signal
Presynaptic Cell stops releasing neurotransmitter, nt in synapse is cleared by either:
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Diffusion (Neurotransmitter or its breakdown products simple diffuse away from synapse into nearby ECF
two-way passage of proteins, organelles, etc. along axon from and to soma is called:
Axonal Transport
away from soma:
Anterograde Transport
Organelles, enzymes, synaptic vesicles, small molecules
towards soma:
Retrograde Transport
Recycled materials, pathogens
Slow Axonal Transport
Always Anterograde, "stop+go" movement causes slowness, enzymes, cytoskeletal compounds, new axoplasm, time for damaged axons to regenerate due to transport speed
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Nerve Regeneration
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Steps:
Axon distal to injury degenerates, Macrophages clean up tissue debris
Neurosoma swells, ER breaks up, and nucleus moves off center
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Neural Circuits
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Reverberating Circuits
Neurons stimulate e/o in linear sequence but one or more of later cells restimulate the first cells to continue process (Diaphragm + Intercostal Muscles)
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Serial Processing
Neurons and neural pools relay information along pathway in relatively simple linear fashion - only process one flow of info at a time
Parallel Processing
Information is transmitted along diverging circuits through different pathways that act on it simultaneously
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