Muscle Physiology

Question 1

Skeletal muscle

Answer 1

Is under voluntary control it enables us to move and breath

Question 2

Cardiac. Muscle

Answer 2

Found only In heart

Question 3

Smooth muscle

Answer 3

Is surrounding hollow organs eg blood vessels stomach and gut

Question 4

What properties to all muscles share

Answer 4

Contraction. Is initiated by rise in intercellular ca2+ contration

Question 5

What properties are different in all muscles

Answer 5

Skeletal and muscle are satiated muscle have similar contractile proteins
Contractile proteins in smooth muscle are organised in much more haphazard way
In striated muscle ca2+ binds. Trope in complex to initiate contraction
In smooth muscle ca2+ binds to caldodulin to initiate contraction

Question 6

What happens to bands in contraction

Answer 6

The A band remains the Same width but distance between Z bands ie sacromere length decreases

Question 7

What happens when ca2+ binds

Answer 7

Causes conformational change such that tropomyosin. Moves and uncovers myosin binding sites to enable cross bridges

Question 8

What is the cross bridge cycle in skeletal and cardiac muscle

Answer 8

Atp binds to myosin heads
Atp is hydrolysed
Cross bridges form new position on actin
P is released and conformational change results in power stroke
Atp is released

Question 9

Excitation contraction coupling in skeletal muscle

Answer 9

1) AP in motor neurone cause release of ACH
2) endplate potential initiates action potential in skeletal muscle
3) ap causes release of ca2+ from sarcoplasm reticulum
4) raised intercellular ca2+ iniates contraction

Question 10

how to end the contraction

Answer 10

Voltage gates ca2+ channels close the ca2+ release channels on the sarcoplasm reticulum also close. SERCA takes ca2+ from cytoplasm reticulum and the na/ca exchanger removes ca2+ back to extracellular fluid
In skeletal and cardiac muscle ca2+ unbinds from troponin complex which occludes the myosin binding sites again
In smooth muscle calodulin no longer stimulates myosin light chain kinase

Question 11

What is the strucure of smooth muscle

Answer 11

There are no striations in smooth muscle and the contractile machinery is less organised then cardiac or skeletal muscle

Question 12

Excitation contraction coupling in smooth muscle can occur through at least two mechanisms

Answer 12

Slow depolarisation of the menrbane potential activates voltage gated ca2+ chAnnels ca2+ entry through ca2+ to i its contraction
Receptor activated release of ca2+ from sarcoplasm in reticulum will also imitate contraction