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KIN 3600
Lec 17
| Term | Definition |
|---|---|
| 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
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