Download • - Hatboro

Name _______________________ Per ____
Muscle Physiology Project
OBJECTIVES:

Learn the biochemistry behind muscle cell contraction and relaxation

Relate the structures of a nerve cell and muscle cell to their functions
You may create a stand-alone poster, animated PPT (animations or stop-action),
stop-action photography, videotaped skit, illustrated book or any other medium
that will effectively complete the objectives in a visual manner. All steps must be
shown in order. You must show the following structures/events:

motor neuron

synaptic knob

muscle fiber (cell)

synaptic cleft

transverse tubules

sarcoplasmic reticulum

movement of ions (charged molecules)

movement of ACh and AChE

all mentioned channels

all mentioned pumps

myosin heads cocked-back

myosin heads forming cross-bridges with actin

sarcomere relaxed

sarcomere contracted
40 steps x 2 pts apiece = 80 + 10pts for creativity/neatness = 90 pts total
Step Score _____/40
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Step Score x 2
______
+ Creativity Score
______
= Total Score
______/90
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To start things off (9):
_____synaptic vesicles containing Acetylcholine (ACh) are in motor neuron
_____sodium (Na+) is concentrated in the synaptic cleft
_____potassium (K+) is concentrated within the muscle fiber
_____Ca2+ has been sequestered within the sarcoplasmic reticulum in the
muscle fiber.
_____Ca2+ is also highly concentrated outside the synaptic knob
_____The myosin heads are cocked back, with ADP and Pi present
_____Tropomyosin covers the actin binding sites
_____The interior of the muscle fiber is negatively charged
_____the muscle fiber is relaxed
Contraction (17):
_____within neuron, electrical impulse travels down axon to synaptic knob
_____voltage-gated Ca2+ channels in synaptic knob open in response to impulse
_____ Ca2+ diffuses into synaptic knob
_____ synaptic vesicles containing acetylcholine (ACh) fuse with neuron
membrane in synaptic knob
_____ACh released into synaptic cleft through exocytosis, diffuses across cleft
_____ACh binds with ligand-gated Na+ channels in motor end plate of muscle
fiber (and transverse tubules)
_____Sodium (Na+) channels open in sarcolemma (and transverse tubules)
_____Na+ diffuses into muscle fiber
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_____interior of muscle fiber becomes positively charged (due to Na+)
_____voltage-gated Ca2+ channels in sarcoplasmic reticulum open
_____Ca2+ diffuses from sarcoplasmic reticulum into sarcoplasm
_____Ca2+ binds to troponin (the “lock”), causing a conformational change
(change in shape)
_____Tropomyosin (the dead-bolt) fibers are pushed out of the way, exposing
actin binding sites
_____The myosin heads of the thick fibers bind with the actin, forming crossbridges
_____myosin heads flex (causing the release of ADP and Pi, from the myosin
head) and pull on actin, causing sarcomeres to shorten.
_____potassium (K+) channels open SLOWLY in sarcolemma (and transverse
tubules)
_____K+ diffuses out of muscle fiber (although more slowly than Na+ diffuses in)
Relaxation (14):
_____voltage-gated Ca2+ channels in the motor neuron close
_____Ca2+ pumps in the motor neuron cell membrane pump Ca2+ out of motor
neuron and out of synaptic knob using ATP
_____ACh is broken-down into acetyl (A) and choline (Ch) by the enzyme
acetylcholinesterase (AChE) in the synaptic cleft. Both are recycled back into the
neuron where acetyl and choline are combined back into ACh and stored once
again in synaptic vesicles (endocytosis)
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_____chemically-gated Na+ channels in the sarcolemma close
_____K+ channels in sarcolemma close
_____the Na+/K+ ATP pump in the sarcolemma pumps 3 sodium back out into
the synaptic cleft along with 2 potassium pumped into the muscle fiber using ATP
_____This makes the interior of the muscle fiber negatively charged once again
_____ voltage-gated Ca2+ channels in the SR close because the muscle fiber is
now negatively charged
_____Ca2+ pumps in the SR membrane actively (using ATP) pump Ca2+ back
into the SR
_____ Ca2+ releases from the actin binding sites
_____ATP binds to the myosin head, causing it to release from actin binding site
_____ ATP is hydrolyzed into ADP and Pi, causing a conformational (shape)
change in the myosin head and “cocking” it back to the origin position (like a
mouse trap)
_____tropomyosin slides back over to cover the actin binding sites
_____Sarcomeres slide apart, thereby allowing the muscle to relax
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