Skeletal Muscle

Question 1

Describe the structure of skeletal muscle

Answer 1

Whole muscle made up from bundle of muscle fibres
-each bundle of muscle fibres made up from loads of single muscle fibres
-single muscle fibre consists of many myofibrils that are made from sarcomeres

Question 2

What else co-exists with the single muscle fibres

Answer 2

Capillaries, that supply blood and nerves

Question 3

What are some unique features of single muscle fibres?

Answer 3

-they are striated
-theyre multinucleate (multiple nuclei as the cell essentially merge together)

Question 4

During contraction what happens in a sarcomere?

Answer 4

-H-zone gets smaller
-I band gets smaller
-A band does not change

Question 5

Describe the sliding filament model:

Answer 5

-at a neuromuscular junction (effector), ACh binds to the ligand gated Na+ ion channels, allowing sodium into the sarcomere through the sarcolemma
-the Na+ cause Ca2+ ions to leave the sarcoplasmic reticulum and move into the sarcoplasm
-Ca2+ ions bind to troponin, that causes tropomyosin to move and expose the actin binding site
-myosin heads bind to actin
-ADP in myosin head dissociates, causes a change in shape and therefore a powerstroke
-ATP associates with myosin head, which causes another change in shape so it releases from the actin
-ATP hydrolysed into ADP to be reused

Question 6

Muscle fibre types and uses (only need around 4 things)

Answer 6

Fast-twitch:
-short contraction relaxation cycle
-few capillaries
-ATP mostly from anaerobic respiration
-little mitochondria
-more Ca2+ ions in SR
-large amount of phosphocreatine and glycogen
-faster rate of ATP hydrolysis
-tire quickly

Slow twitch muscles are opposite to F.T

Question 7

what forms when myosin heads bind to the actin binding sites?

Answer 7

actinomyosin bridges are formed