Contractility

Question 1

Skeletal muscle

Answer 1

▪️striated muscle 
▪️voluntary 
▪️unbranched
▪️multi nuclei 
▪️bundles 
▪️contracts quickly and gets fatigued

Question 2

Smooth muscle

Answer 2

▪️non striated 
▪️involuntary
▪️spindle shaped 
▪️uni nucleated 
▪️arrayed in sheets 
▪️contracts slowly and don’t get fatigued

Question 3

Cardiac muscle

Answer 3

▪️involuntary
▪️short cylindrical branches cells 
▪️uni nucleated 
▪️network
▪️contract quickly and don’t get fatigued

Question 4

Excitation contraction coupling

Answer 4

▪️AP enters from neighbouring cell
▪️voltage gated Ca channels open and Ca enters cells
▪️Ca induces release of more Ca in sarcoplasmic reticulum (SR)
▪️sum of all Ca creates a Ca signal
▪️Ca ions binds to troponin to initiate contraction
▪️after contraction has occurred, Ca unbinds and muscle relaxes
▪️Ca is pumped back into SR for storage
▪️rest of Ca is exchanged with Na via 3Na/1Ca transporter
▪️Na gradient is maintained by 3Na/2K ATPase
-phospholamban regulates the Ca pump in cardiac muscles

Question 5

Muscle contraction

Answer 5

▪️Ca binds to troponin causing tropomyosin to change shape and move to expose actin myosin-binding site
▪️myosin head binds to actin- ATP converted to ADP and Pi
▪️myosin head pivots pulling actin filament towards centre- power stroke
▪️ATP causes cross bridge to detach
▪️myosin head can now form another cross bridge