Midterm Part 3 Functional Neuro-muscular Units Flashcards
Functional Neuro-muscular Units (90 cards)
Order of the organization of functional skeletal muscle:
Muscle -> Fascicle -> Muscle Fibers -> Myofibrils -> Thick and Thin Filaments (sarcomere)
skeletal muscle surrounded by _____ and contains _______
epimysium, muscle fascicles
muscle fascicles surrounded by ______ and contains ______
perimysium, muscle finbers
muscle fiber surrounded by ______ and contains _______
endomysium, myofibrils
sarcomere contains ______
thick and thin filaments
Neuromuscular Junction.
where is it?
what are its components?
site where axon and muscle fiber communicate.
Five basic components:
- motor neuron - motor end plate - synaptic cleft - synaptic vesicles - neurotransmitters
Muscle Contraction
motor nerve impulses cause release of ACh from synaptic vesicles which bind to receptors on motor end plate and generate muscle contraction
Muscle Relaxation
acetylcholinesterase breaks down ACh, motor neuron impulses stop, Ca moves back into sarcoplasmic reticulum, myosin and actin binding prevented
motor unit
a single motor neuron and all the muscle fibers it controls
true or false?
when a motor unit fires all the muscle fibers contract together
true
true or false?
one muscle fiber may be innervated by several motor neurons
true
small amount of muscle fibers makes for fine or strength control?
fine: extraocular muscles (20 fibers)
Twitch
a single brief stimulus to a muscle that produces a quick cycle of contraction and relaxation lasting less than 1/10 sec. aka a single muscle contraction. 3 phases: latent, contraction, relaxation
Is a single twitch contraction strong enough to do any useful work?
no. normal activities require more tension - sustained muscle contraction of the whole muscle!
Treppe
relaxation is complete before next stimulus occurs. ea contraction a little stronger than previous. 10-20 stimuli/sec.
Wave summation
temporal summation.
if a second stimulus is applied before relaxation is complete, the second contraction is greater. rapid sequence of stimuli cause twitches to fuse together – more strength of contraction.
20-40 stimuli/sec
Tetanus
w higher frequency of stimulation, muscle relaxation between contractions is reduced.
incomplete or complete tetanus?
sustained maximal contraction at peak tension
complete
incomplete or complete tetanus?
produces peak tension during rapidly alternating cycles of contraction and partial relaxation
incomplete
ea stimulus produces an identical twitch response. true or false?
true
twitch, treppe, summation or tetanus?
ea subsequent contraction is stronger than previous until after a few stimuli, all contractions are equal.
treppe
twitch, treppe, summation or tetanus?
ea stimulus arrives before the previous twitch is over.
wave summation. as the frequency of stimulus increase, frequency of contraction increases.
twitch, treppe, summation or tetanus?
20-40 stimuli/sec
wave summation or incomplete tetanus
twitch, treppe, summation or tetanus?
muscle fibers partially relax between contraction
incomplete tetanus
