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KIN 3600

Lec 17

Importance of myelination? Function: speed up propaganda velocity by 25x - Lower energy expenditure
How is info coded? Pain coding? - Frequency of Action Potential - Frequency of nerve impulses
Axon - Longer & myelinated fibers - Branches in cells, nerve, gland, muscle - 1 branch = 1 muscle fiber
Synapse functional connections between neurons, between neurons & other cells – muscle & glands or between muscle cells
2 types of synaptic transmissions Electrical synapse Chemical Synapse
Electrical synapse -Minimal delay of impulse transmission (fast) -Bidirectional transmission of impulse -Stimulate 1 cell, all will stimulate together -Location: cerebellum
Chemical Synapse -Unidirectional transmission -Longer delay of transmission 0.5-4ms -Presynaptic terminal & presynaptic membrane
Sarcolemma muscle membrane
Synaptic clef -30-40nm -Membranes do not touch (gap)
Quanta # of neurotransmitter vesicles released per Action Potential
Neurotransmitters packed in vesicles Acetylcholine (Ach)
Release of Ach voltage regulated Ca++ gates high Ca++ concentration & activate enzyme
Simultaneous opening of Ach-regulated Na+ & K+ gates -Na+ out & K+ in -Membrane starts depolarizing (more Na+)
More AP more Ach released
^ frequency of AP ^ Quanta = ^ EEP
Characteristics of EPP - No overshoot - May go only up to 0mV - Graded --> No all-or-none response - Conducted decrementally along endplate - Very long duration - No refactory period
EPP may be summed - 1AP : 1EPP - 1 EPP : 1 ATP - On average EPP is approximately 70mV
How can we relax muscle? Acetylcholinesterase (key enzyme)
Acetylcholinesterase (key enzyme) Ach diffuses into the interstitial fluid -Breaking down to Choline & Acetate -Reabsorbed into presynaptic terminal -ATP will be used to combine choline & acetate
Nerve gas inactivates acetylcholinesterase –-> Spastic paralysis
Curare competitively binds to Ach receptors of post synaptic membrane – flaccid paralysis because it binds to neuro cell receptor blocked. Allowing no contraction. - Post-synaptic neuromuscular blockade
Botulinum Toxin prevents release of vesicles (Botox ) -Presynaptic blockade -Ach not released --> muscle cannot contract -Flaccid paralysis
Skeletal muscle Function - Force production for movement, locomotion - Force production for breathing - Force production for postural support - Pumping venous blood towards heart - Heat production during cold stress
4 principle characteristics of skeletal muscle -Excitability -Contractility -Extensibility -Elasticity
Excitability ability to respond to stimuli
Contractility ability to contract & produce a force
Extensibility ability to be stretched without rupture/tear
Elasticity ability to shorten/extend & return back to original shape (rubber band)
How muscle respond to stimuli contract
Muscle connective tissue Epimysium Perimysium Endomysium
Epimysium envelops individual muscles from outside providing structural integrity for whole muscle
Perimysium envelopes several hundred muscle fibers forming fascicles (200-300 fibers)
Endomysium envelopes each muscle fiber individually
Created by: rmart11