Contraction of the muscle Fiber Flashcards
The 3 structures that are directly controlling the muscle contraction
Muscle
Nerve
Synapse
Theory stating that muscle contraction is based on shortening of sarcomeres throughout the skeletal muscle. Because sarcomeres are end to end, all the way down the length of the skeletal muscle cell, the muscle cell shortens too.
Huxley’s Sliding Filament Theory
Huxley’s Sliding Filament Theory predicts that thick and thin filaments must overlap and slide past one another. Greater overlap = shorter or longer muscle?
Shorter Muscle
Contractile element that is made of myosin that has hinged tail and 2 heads which are capable of flexing
Thick Filament
What two binding sites are on the heads of myosin?
ATP and Actin binding sites
Name the 3 components of thin filament
Actin
Tropomyosin
Troponin Complex
There is a binding site on the actin molecules for
myosin
Two additional things that are necessary for contraction to occur
Calcium Ions
ATP
When a muscle is relaxed, is there maximal or minimal filament overlap?
Is there action potential from the nerve?
Minimal
No.
“Activated” myosin heads are holding…
ADP and inorganic phosphate after hydrolization from ATP
Is the ATP kinetic or potential energy?
Potential
Is there Ca in the cytoplasm surrounding microfibrils?
No
Where does the Calcium come from?
Terminal cisternae of the sarcolplasmic reticulum
What causes the calclium to enter the cytoplasm and surround the myofibrils?
Action potential along the nerve
What does Ca bind with in the myofibril?
Troponin
What happens to the troponin once Ca binds with it?
It changes shape
What is troponin attached to?
Tropomyosin
What forms when the myosin (charged) binds to actin (thick and thin filament of myosin head binds to actin)
Cross Bridge Attachment
Flexion of myosin head an tail that pulls thin filament along after cross bridge attachment
Power Stroke
What happens when the power stroke goes on the entire sarcomere?
Sarcomere Shortening
What occurs next, a process that requires ATP binding to the myosin head?
Cross Bridge Detachment
Where does ATP come from?
Cytoplasm
What cleaves the ATP into ADP and inorganic phosphate?
Myosin ATPase
What does cleaving of ATP into ADP by myosin ATPase achieve?
Storage of the potential energy in the myosin head for next cross bridge
What if there is no more contraction/action potential to occur?
Returns to relaxed state
What happens to Ca and ATP if there is no more contraction to occur
Calcium goes to terminal cysternae
ATP be bound to myosin head
Which step of sarcomere shortening actually uses ATP?
Power stroke
Structure that tells the muscle what to do and when to do it
Motor nerve
Axon of nerve comes from spinal chord and expands into three
terminal boutons
Terminal bouton contains these, which are contained within it
Synaptic Vesicles
Neurotransmitter which functions as ligand within terminal bouton
Acetylcholine
Channels in terminal bouton in addition to typical Na and ATPase channels (maintenance proteins)
Ca channels
Muscle side of neuromuscular junction that contains sarcolemma is called
Motor End Plate
What formation occurs on the motor end plate to increase surface area?
Junctional Folds
Within junctional folds are receptors for acetylcholine
Ach Receptors
The space between the nerve and muscle that has glycoproteins to hold structures in place
Synaptic Cleft
Action potential causes what to change in the plasma membrane of the terminal bouton
Voltage Change
The voltage change causes opening of which voltage gated channels to allow its movement from outside bouton to inside the bouton?
Calcium Voltage Gated Channels
What does the calcium cause when its released in the terminal bouton?
Vesicle migration
When vesicles reach end of terminal boutons, what occurs?
Exocytosis of acetocholyne
Acetylcholine crosses the synapse and binds with what on the motor end plate?
Receptors
What does acetycholine migration across the membrane cause?
Graded potential (Na+ flows in)
What follows the graded potential?
Action potential along membrane of skeletal muscle
How is acetylcholine removed to stop action potentials from recurring?
Acetylcholinesterase
Means when you excite the cell a contraction will follow
Excitation-Contraction Coupling
What structure of muscle cell is exciteable and brings the action potential to the muscle fibers?
T-tubules
What is released after excitation of t-tubules?
Calclium voltage gated channels in terminal cysternae open and Ca diffuses
