Skeletal Muscle Contraction SEM1

Question 1

How does skeletal and cardiac muscle appear + what are they described as

Answer 1

Appear striped and described as striated

Question 2

What are the components of the gross skeletal muscle (in order from external to internal)

Answer 2

1)tendon
2)muscle
3)connective tissue
4)nerve and blood vessels
5)connective tissue
6)fascicle
7)muscle fibre
8)nucleus

Question 3

What are myofibril

Answer 3

Units of muscle cells that contain arrays of thick and thin filaments

Question 4

Where are thin filaments located

Answer 4

Attached at either end to the Z-disc

Question 5

Where are thick filaments located

Answer 5

In the centre and overlap with thin filaments on both ends except in the central region- the H-zone

Question 6

What are thick filaments composed of

Answer 6

Myosin

Question 7

What are thin filaments composed of

Answer 7

Actin

Question 8

What is the sliding filament hypothesis of muslce contraction

Answer 8

Sarcomere length shortens but filaments stay same length

Question 9

What is the overall process of excitation-contraction (EC) coupling process in skeletal muscle

Answer 9

1)neuromuscular transmission
2)action potential propagation
3)calcium release
4)muscle contraction
5)relaxation

Question 10

What is the process of neuromuscular transmission in excitation-contraction (EC) coupling process in skeletal muscle

Answer 10

Acetylcholine (Ach) released from a motor neuron binds to receptors on muscle cells motor end plate triggering a muscle action potential

Question 11

What is the process of action potential propagation in excitation-contraction (EC) coupling process in skeletal muscle

Answer 11

Action potential spreads along muscle membrane and into the T-tubules where it activates dihydropyridine (DHP) receptors

Question 12

What is the process of calcium release in excitation-contraction (EC) coupling process in skeletal muscle

Answer 12

Activation of DHP receptors leads to opening of calcium channels on the sarcoplasmic reticulum causing a release of calcium ions into the muscle cytoplasm

Question 13

What is the process of muscle contraction in excitation-contraction (EC) coupling process in skeletal muscle

Answer 13

The surge in calcium triggers muscle contraction by facilitating the interaction of actin and myosin within the muscle fibres

Question 14

What is the process of relaxation in excitation-contraction (EC) coupling process in skeletal muscle

Answer 14

Calcium pumped back into the sarcoplasmic reticulum, lowering cytoplasmic calcium levels causing muscle relaxation

Question 15

What are L-type Ca2+ channels linked to

Answer 15

Ryanodine receptors on the sarcoplasmic reticulum

Question 16

What does depolarisation of the L-type channels cause

Answer 16

Causes ryanodine receptors to open and release Ca2+ into the cytoplasm

Question 17

What is troponin

Answer 17

A regulatory protein attached to thin filaments (actin)

Question 18

What does calcium bind to to allow myosin to bind to actin

Answer 18

Calcium binds to troponin

Question 19

What does the binding of calcium induce in troponin

Answer 19

Induces conformational change in troponin and shifts tropomyosin away from these sites and myosin head binds to actin

Question 20

What occurs following the attachment of the myosin head binding to actin

Answer 20

ADP and Pi are released which triggers the power stroke which pulls the actin filament toward the centre of the sarcomere causing muscle contraction

Question 21

How does the myosin head detach from actin

Answer 21

A new molecule of ATP binds to myosin head, causing it to detach from actin

Question 22

What does the hydrolysis of ATP and Pi provide energy for in relation to Ca2+ contraction

Answer 22

Hydrolysis of ATP into ADP and Pi provides energy for myosin head to return to its original angle

Question 23

What happens when the concentration of calcium decreases

Answer 23

Conc of Ca2+ decreases leads to Ca2+ detaching from troponin and prevents myosin from binding leads to muscle relaxation

Question 24

What is isometric contraction

Answer 24

Contraction at constant length