types of muscle contraction

Question 1

what are the 4 types muscle contraction

Answer 1

sliding filament mechanisms
- actin moving relative to myosin shortening muscle

cross-bridge cycle
- how myosin attaches to actin = movement

neuromuscular junction
- connection between NS and skeletal muscle

excitation-contraction coupling
- taking AP for NS and turn it into muscle contraction

Question 2

what is the sliding filament mechanism?

like explain it at relaxed, contracted and maximal muscle contraction

Answer 2

relaxed muscle:
actin myofilaments attached to z disks and m line holds. some overlap in myosin and actin

contracted muscle:
myosin is in the middle of the sarcomere but the heads pull the actin closer to the m-line

maximal muscle contraction:
actin overlaps the sarcomere = no h zone or i band. the syosin heads reach the z disks.

Question 3

what shortens during muscle contraction?

Answer 3

i band
h zone

Question 4

what band never changes in size?

Answer 4

a band

Question 5

what is the cross bridge cycle (contraction cycle)

Answer 5

1. during contraction of a muscle calcium binds to troponin, –> causing exposure of active sites on actin myofilaments
2. myosin heads bind to actin forming a cross bridges and phosphate is released from the myosin head
3. myosin cross bridges rotate towards the center of sarcomere
   - power stroke - ADP detaches
4. as myosin heads bind ATP, the cross-bridges detach from actin
5. myosin heads hydrolyze ATP and become reoriented and energized

Question 6

what are skeletal muscle electrical properties?

Answer 6

resting membrane potential:
- high [potassium] inside the cell
- low [sodium] outside of the cell
- depolarization causes muscle action potential

Question 7

neuromuscular junction (NMJ)

Answer 7

1. nerve impulse is comes from the spinal cord and moves along axon
2. reaches synaptic bulb, it hits those voltage gated calcium channels
3. voltage gated calcium channel opens and the calcium rushes into the cell
4. calcium stimulates synaptic vesicles and move to synaptic cleft where acetylcoline is released
5. acetylcholine diffuses across synaptic cleft and binds onto ligand-gates ion channels on the sarcolemma or the motor end plate of muscle

Question 8

what happens during excitation-contraction couping?

Answer 8

1. MAP propagated along sarcolemma and into T-tubules
2. calcium channel in the SR open and calcium is released into the sarcoplasm
3. calcium binds to troponin –> moves tropomyosin off myosin binding site
4. heads of myosin bind onto active site and form a cross bridge