Muscle Contraction Flashcards
How long are skeletal muscle cells?
30cm
What are skeletal muscle cells made up of and why do they have lots of nuclei?
Lots of myoblasts joined together
Why are skeletal and cardiac muscle stripy?
Due to contractile proteins
Name the three types of muscle
Skeletal
Cardiac
Smooth
How many nuclei does cardiac and smooth muscle cells have?
One
Give examples of smooth muscle
Arteries
Gut
Bladder
Reproductive organs
Why isn’t smooth muscle stripy?
The contractile proteins aren’t arranged in a logical pattern
What is contraction?
The interaction between actin and myosin
What is contraction fuelled by?
ATP and Ca2+
Whats a group of bundles called in a muscle?
Fascicle
What’s the thick strand in muscles?
Myosin
What’s the thin strand in muscles?
Actin
What’s the I band in muscles comprised of?
Only actin
What’s the A band in muscles comprised of?
Only myosin
What’s the stuff between two z discs called?
Sarcomere
What is the sarcoplasmic reticulum?
Complex, convoluted store of calcium
What does troponin C bind to?
Calcium
What does troponin T bind to?
Tropomyosin
What can block a certain site on actin where myosin would interact?
2 disc formed of alpha actin in
What are the two important regions on the myosin head?
Binding domain
ATPase
What does the binding domain in a myosin head do?
Interacts with the active cycloactin
What does the ATPase in a myosin head do?
Hydrolysed the ATP->ADP
What is binding in between myosin and actin?
Myosin cross bridge bonds to an actin molecule
What is the power stroke in muscle contraction?
Cross bridge bends, pulling thin myofilament forwards
What is detachment in muscle contraction?
Cross bridge detaches at end of power stroke and returns to OG conformation
Write out the muscle contraction cycle
Binding, power stroke, detachment, binding (but in more detail)
What happens when ATP binds to myosin
Detachment of myosin from actin, cross bridge dissociates
What happens when ATP hydrolysis occurs in muscle contraction
Myosin head is cocked
What does calcium do in muscle contraction
Binds to troponin which binds to tropomyosin which pulls tropomyosin out the way allowing the myosin and actin to interact
What happens to [Ca2+] when nicotinic AchR is bound by an agonist?
Causes massive depolarisation down the T tubules
How does the depolarisation happen in the T tubules in skeletal muscle?
DMP proteins that physically interact with a calcium release channel in the sarcoplasmic reticulum (RYR)
What does DMP stand for?
Dihydropyridine
What does RYR stand for?
Ryanodine receptor
How does the depolarisation happen in the T tubules in cardiac muscle?
When the cell is stimulated, the DHP receptor changes conformation alters the RYR causing calcium to be released
What does CICR stand for?
Calcium induced calcium release
How does smooth muscle contract?
Wring out like a tea towel
How does calcium get released in smooth muscle?
Either receptor mediated diffusion or the production of a diffusible messenger called inocytrial disphosphate
What is inocytrial disphosphate made from?
A membrane lipid, broken down down through a number of enzyme steps which leads to a calcium release
Is there troponin in smooth muscle?
No
Does tropomyosin interact with the myosin binding sites in smooth muscle?
No
Go draw a table that has skeletal cardiac and smooth along the top and T tubules, arranged myofilaments, calcium sensor and contraction mechanism along the side and fill it out
Skeletal. Cardiac. Smooth
T tubules ✅. ✅. ❌
Arranged ✅. ✅. ❌
Myofilaments
Calcium troponin. Calmodulin
sensor
Contraction. Removal of MLCK
mechanism. Tropomyosin.
