MSK Flashcards
Skeletal muscle
attaches to bone and skin
*YES striations
Cardiac Muscle
walls of the heart
*YES striations
Smooth muscle
walls of hollow organs; eye muscles, airways and large arteries, stomach
*NO striations
Structure & Organizations of Muscle layer
muscle
fascicle
muscle fiber / cell
Connective Tissue wrappings
Muscle (epimysium)
Fascicle (perimysium)
Muscle Fiber (endomysium)
Sarcolema
plasma membrane
myoglobin
oxygen storage
glycosome
glycogen / glucose storage
Sarcoplasmic Rediculum
fluid filled membrane channels that are wrapped around the myofibrils
T tubules
ingavinations of the sarcolemma, forms a closed tunnel system throughout the uscle that contains Extracellular fluid
triad
junction of T tubule with the SR on each side
I band
where there are two thin filaments
*straddles 2 sacromeres
Z line
arrays of thin filaments are attached to one end
H zones
portion of the A band that does not have thin filaments
A band
where there is some overlap of thin and thick filaments
Actin
thin filament
Myocin
Thick filament
elastin
coiled = contracted
relaxed = stretched
Tyopomyocin and troponin
proteins that regulate contraction, they are bound to actin
tropomyosin
regulatory protein
prevents binding of myosin
troponin
helps initiate muscle contraction
binds to calcium and tells them to move
Titin
elastic filaments are made up of a protein called titin
titin function
hold thick filaments in place
help muscle recoil after stretch
protect the muscle from excessive stretch
Nebulin
support protein that anchors actin
myomesin
anchors myosin (thick) filaments
Desmin
links myofibrils and connects them to cell membrane
C proteins
located in thick filament of sarcomere
mutations: encode cardiac versions of myBP-C which are associated with cardiomyopathies
motor end plate
sarcolemma at the site of NMJ
end plate potential
the binding of ACh to nicotinic receptors causes a graded potential called an end plate potential
Neuromuscular Junction Events
- Ap arrives at axon terminal
- Voltage gated calcium channels open, calcium enters motor neuron
- Calcium entry causes release of ACh neurotransmitter into synaptic cleft
- ACh diffuses across to ACh receptors (NA chemical gates) on sarcolemma
- ACh binding to receptors, opens gates, allowing Na+ to enter resulting in end plate potential
- Acetylcholine sterase degrades ACh
Achtylcholinesterase pathology…
tetanus… (cannot uncontract)
Botulinum toxin (unable to contract)
Where is the calcium causing the muscle contraction coming from
Sarcoplasmic reticulum
General actions of an Action Potential
action potential
depolarization
Ryr (ryanodine receptor causes lease from SR)
activation receptor
calcium leaves Sarcoplasmic reticulum
Cross Bridge Cycling
- energized myosin attaches to an actin myofilament… this forms a new cross bridge
- ADP and P are released and myosin head pivots and bends… changing to its bent low-energy state. as a result it pulss the actin filament toward the M line…
3.After ATP attaches the link between myosin and actin weakens… and the myosin head?
- ATP is hydrolyzed to ADP and P the myosin head returns to its prestorke high-energy “cocked” position
Low intracellular Calcium
Tennis arm muscle
Overworked
Extensor Carpi radialis
Most frequently injured rotator cuff muscle
supraspinatus muscle
schwann cells
principle glial cells of peripheral nervous system
Satellite cells
