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Muscle Lab

Physiology 2010

Motor unit a motor neuron plus all the muscle fibers it innervates
Cell body aka soma, receiver, located in the brain and spinal cord
Dendrites extension from cell body, receiver
Axon hillock area on axon where signal priority is highest
Axon extension from cell body where action potential is conducted
Schwann cells myelin sheath in PNS, keeps AP from leaking out and increases speed of AP
Nodes of Ranvier spaces between myelin sheaths
Salivatory conduction AP jumps from node to node (400x faster)
Resting membrane potential (-70mV) cell is more negative inside than outside
Threshold (-55mV) need to reach the threshold in order to fire an AP
Depolarization (-70mV to +40mV) voltage gated Na+ channels opens and Na+ flows in
Repolarization (+40mV to -70mV) voltage gated Na+ channels close, voltage gated K+ channels slowly open amd K+ flows out
Hyperpolarization (+40mV to -90mV) voltage gated K+ channels slowly close but K+ still leaks out
Which voltage gated channels open and close fastest? Na+ is faster than K+
Absolute refractory period channels lock so AP doesn't travel backwards
Properties of muscle tissue excitability, contractibility, extensibility, and elasticity
Excitability ability to receive and respond to stimulus
Contractability ability to shorten forcbly when adequately stimulated
Extensibility ability to be stretched or extended
Elasticity ability of muscle fibers to resume to its resting length
3 types of muscles skeletal, smooth, and cardiac
Skeletal muscle striated, voluntary and multinucleated
Smooth muscle smooth, involuntary and uninucleated
Cardiac muscle striated, involuntary and uninucleated
Epimysium dense irregular CT that suurounds the entire muscle
Perimysium CT that surrounds each fascicle
Endomysium CT that surrounds each muscle fiber
4 functions of skeletal muscle produce voluntary movement, maintain posture, stabilize joints, and generate heat
Transverse Tubules (T-tubes) in between sacroplasmic reticulum
Sacroplasmic Reticulum stores Ca+ and is made of myofilaments actin and myosin
Myosin thick filament
Actin thin filament, has binding sites for myosin but is blocked by tropomyosin
Tropomyosin covers myosin binding sites
Troponin binds with Ca+ to remove tropomyosin so myosin can attach to actin
Cross bridges are created when myosin attaches to actin, need ATP to detach
Power stroke the myosin heads pull actin and actin promotes ATP --> ADP + Pi
ATP Hydrolysis cocks myosin heads to start another cycle
A band contains myosin and actin
I band contains actin and z discs
Latency period time from stimulation to beginning of contraction
Contraction period length of time to get a maximum response
Relaxation period dissociation of myosin from actin, myofilaments sliding back in to original positions and Ca+ is pumped back into the SR
Temporal (time) summation increase frequency, increases magnitude
Tetanus long sustained contraction
Spatial summation (recruitment) increase voltage, strengths current to increase magnitude, and recruits more motor units
Isometric contraction length of muscle does not change (example: holding a bag)
Concentric isotonic contraction muscle is getting shorter (example: lifting a book)
Eccentric isotonic contraction muscle is getting longer (example: lowering a book)
Created by: tmg1116