Muscle physiology Flashcards
Muscle is a group of what
Fascicles
What is the plasma membrane of muscle called?
Sarcolemma
What is the cytoplasm of the muscle
Sarcoplasm
myofibrils contain what?
Contractile machinery
Smooth ER in muscle is what
Sarcoplasmic reticulum, contains many mitochondira- high energy
what gives muscle striated appearance
myofibrils
What is myofibrils made of
It is bundle of overlapping thick and thin filaments made up from proteins actin and myosin
what is a sarcomere
Z line to Z line
What are the three proteins in thin filaments
Actin, Tropomyosin, and Troponin
What does actin have
Binding sites for myosin
What type of protein is Actin
Contractile
What does each g Actin have
Binding site for myosin
What is tropomyosin
Regulatory protein, overlaps binding sites on actin for myosin
What is Troponin
Regulatory protein
Troponins three proteins do what?
Attach to actin, attach to tropomysoin and binds calcium reversibly
What does calcium binding to troponin regulate?
Skeletal muscle contraction
The tails of thick filaments face what?
M-lines
Myosin head has how many binding sites
2, one for actin, one for ATP
What is TItin
Support protein, achors thick filaments between M-line and Z-line, provides structural support and elacticity
What happens within a sarcomere to ( A band , I band, H zone and sarcomere) during contraction
A band stays same length
I band shortens
H zone shortens
Sarcomere shortens
What is the crossbridge cycle
Cyclical formation of links between actin and myosin resulting in the sliding of thin filaments toward the M line of a sarcomere
During high energy form during cross cycle, what is bound to myosin and what is affinity for action
ADP and Pi bound to myosin, high affinity for actin
What does Crossbridge cycle rely on
ATP hydrolysis
Analogous to what
Rowing boat through water, our paddle is crossbridge
Link of thick filament to thin
Oar contact with water
Power stoke
Myosin head moves propelling thin filament toward center of muscle ( oar propelling boat)
Thick and thin filaments
Oar breaks contact with water
What is excitation contraction coupling. What does it depend on?
Sequence of events whereby an action potential in the sarcolemma causes contraction
Depends on neural input from motor neuron
What does excitation contraction coupling require
Calcium release from the sarcoplasmic reticulum
What occurs if no calcium in contraction?
Troponin holds tropomysoin over myosin binding sites on actin. No crossbrdiges form, muscle is relaxed
When calcium is present what is role in excitation contraction coupling
Calcium Present - binds to troponin, causing movement of troponin, causing movement of tropomyosin, exposing binding sites for myosin on actin
Crossbridges form, cycle occurs
List the steps of excitation contraction coupling
- Action potential in sarcolemma.
- Action potential down T tubles.
- DHP receptors of T tubules open Ca2+ channels .
- Calcium increases in cytosol
- Calcium binds to troponin shifting tropomyosin
- Cross bidge cycling occurs
What must occur to terminate the contraction?
Calcium must leave troponin, allowing tropomyosin to cover myosin binding sites on actin
ATP is used by muscle how?
Crossbridge cycle, splitting of ATP by myosin ATPase(power stroke)
Binding of fresh ATP to myosin to cause dissociation
Sources of ATP in muscle
Phosphorylation of ADP by creatine phosphate
Oxidative phosphorylation of ADP in mitochondria
Anaerobic Glycolysis
How to maintain adequate oxygen to muscle
Increase ventilation
Increase heart rate and contraction
Dilate vessels to muscle
Glucose is substrate for oxidative phosphorylatio for how long then what is after rthat
30 min, then fatty acids dominant
