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Name _______________________ Per ____ Muscle Physiology Project
OBJECTIVES: Learn the biochemistry steps behind muscle cell contraction and
relaxation
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:

neuromuscular junction: motor neuron axon, synaptic knob, synaptic cleft,
muscle fiber (cell)

sarcolemma

transverse tubules (at least one)

sarcoplasmic reticulum

correct placement of ions (charged molecules): calcium (Ca2+), sodium (Na+),
potassium (K+)

correct movement of ions (during contraction and relaxation)

movement of ACh and AChE

all channels (either opened or closed at the correct times): calcium (Ca2+)
channel, sodium (Na+) channel, potassium (K+) channel

all mentioned pumps: calcium (Ca2+) pump, sodium (Na+)/potassium (K+) pump,
use of ATP to power pumps

sarcomere (zoomed-in view): troponin and tropomyosin covering binding sites,
myosin heads jacked-back, then forming cross-bridges with actin, sarcomere
initially relaxed, contracting, then returning to the relaxed state
*If doing PPT animations/transitions:
1. Ensure that each step of contraction and relaxation are shown
SEPERATELY AND NOT COMBINED.
2. Set animations to occur with every mouse click. DO NOT MAKE
ANIMATIONS AUTOMATIC. Exception: the movements that make-up
each step may proceed automatically.
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Tips:
 color-coordinate and shape-coordinate ions, channels and pumps

FOLLOW ALL STEPS, including “TO START THINGS OFF”

use ramps, not meter sticks support phones (less bounce)

bring iPhone 4/5 cable to connect to desktops; select “trust” on your phone

place all your picts in a folder on your network drive

not enough room on your drive? place your picts in a desktop folder & use
my 4Gb memory stick

I will run them through compression software and will return them to your
folder

ENSURE that all pictures are RIGHT-SIDE-UP prior to inserting them into
PPT

import pictures into PPT using “insert album” feature
Recommended par levels (minimum):

Ca2+
12 (4 for synaptic knob, 8 for sarcoplasmic reticulum)

Na+
6 (must be 3:2 ratio of Na+ : K+)

K+
4

Ca2+ channels
2

Ca2+ pumps
2

Na+ channels
1

K+ channels
1

Na+/K+ pumps
1

ACh
3

AChE
1

ATP
7

ADP + Pi combined 7




tropomyosin/troponin complexes 4
movable actin
2
myosin block
1
myosin heads
4
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To start things off (15 conditions that MUST be shown at beginning of project):
_____synaptic vesicles containing Acetylcholine (ACh) are in motor neuron
_____sodium (Na+) is concentrated in the synaptic cleft
_____all ligand-gated sodium (Na+) channels in sarcolemma are closed
_____potassium (K+) is concentrated within the muscle fiber
_____all slow leak potassium (K+) channels in the sarcolemma are open
_____Ca2+ has been sequestered (captured) within the sarcoplasmic reticulum in the
muscle fiber.
_____Ca2+ is highly concentrated outside the synaptic knob
_____all calcium (Ca2+) channels in the membrane of the synaptic knob are closed
_____all calcium (Ca2+) channels in the membrane of the sarcoplasmic reticulum are
closed
_____the interior of the motor neuron is negatively charged
_____the interior of the muscle fiber is negatively charged
_____the myosin heads are cocked back
_____ADP and Pi present on myosin heads
_____tropomyosin (large) and troponin (small) covers the actin binding sites
_____the muscle fiber is relaxed
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Contraction (18 steps):
_____within the neuron, an electrical impulse (positive charge) travels down axon to
synaptic knob
_____interior of synaptic knob becomes positively charged
____ voltage-gated Ca2+ channels in membrane of synaptic knob open
_____ Ca2+ diffuses into synaptic knob
_____ synaptic vesicles containing acetylcholine (ACh) fuse with neuron membrane in
synaptic knob
_____ACh released out 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)
_____ ligand-gated sodium (Na+) channels open in sarcolemma (and transverse
tubules)
_____Na+ diffuses into muscle fiber
_____interior of muscle fiber becomes positively charged
____ voltage-gated Ca2+ channels in sarcoplasmic reticulum membrane open
_____Ca2+ diffuses from sarcoplasmic reticulum throughout sarcoplasm
_____Ca2+ binds to troponin (the “lock”)
_____ there is a conformational change (change in shape) in tropomyosin (the bicycle
chain) which rolls out of the way, exposing actin binding sites
_____the myosin heads bind with the actin binding sites, forming cross-bridges
power stroke:
_____myosin heads flex and pull on actin, causing
_____sarcomeres to shorten and causing
_____the release of ADP and Pi from the myosin head
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Relaxation (21 steps):
_____ATP binds to the myosin heads
_____ ATP “jacks” back the myosin heads into their origin position (like a mouse trap)
_____ because we used the energy stored in ATP, ATP is hydrolyzed into ADP and Pi
_____sarcomeres slide apart, thereby relaxing the sarcomere
_____ electrical impulse (positive charge) in synaptic knob dissipates (goes away)
_____ interior of synaptic knob becomes negatively charged again
_____ voltage-gated Ca2+ channels in the membrane of the motor neuron close
_____ Ca2+ pumps in synaptic knob membrane pump Ca2+ out (using ATP)
_____ Show ATP use  ADP and Pi
_____ACh is broken-down into acetyl (A) and choline (Ch) by the enzyme
acetylcholinesterase (AChE) in the synaptic cleft.
_____Acetyl and Choline are both recycled back into the synaptic knob where they are
combined back into ACh and stored once again in synaptic vesicles
_____ ligand-gated Na+ channels in the sarcolemma close
_____ potassium (K+) leak channels in sarcolemma allow SLOW leak/diffusion of K+
from inside muscle fiber out to synaptic cleft
_____ interior of the muscle fiber becomes negatively charged once again
_____ voltage-gated Ca2+ channels in the sarcplasmic reticulum membrane close
_____Ca2+ pumps in the SR membrane actively pump Ca2+ (using ATP) from
sarcoplasm back into the SR
____ Show ATP use  ADP and Pi
_____ Ca2+ releases from troponin
_____tropomyosin slides back over to cover the actin binding sites
_____the Na+/K+ ATP pumps in the sarcolemma pumps 3 Na+ back out into the synaptic
cleft along with 2 K+ pumped into the muscle fiber using ATP
_____ Show ATP use  ADP and Pi
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