Skeletal, Cardiac and Smooth muscle

Question 1

What is skeletal muscle?

Answer 1

under voluntary control- it enables us to move or breath

Question 2

What is cardiac muscle?

Answer 2

is only found in the heart

Question 3

What is smooth muscle?

Answer 3

is found surrounding hollow organs- blood vessels stomach and gut

Question 4

What does Ca2+ bind to in striated muscle?

Answer 4

troponin complex

Question 5

What does Ca2+bind to in smooth muscle?

Answer 5

calmodulin (a protein called troponin C)

Question 6

In sarcomere what remains the same width, and what decreases?

Answer 6

a band

distance between z bands decreases

Question 7

Cross bridge cycle in skeletal and cardiac muscle

Answer 7

• ATP binds to myosin head
• ATP is hydrolysed. Myosin head returns to resting position
• Cross bridge forms at new position on actin
• P is released and conformational change results in power-stroke
• ADP is released

Question 8

Excitation contraction coupling in skeletal muscle

Answer 8

• AP in the motor neurone causes release of ACh
• the end plate potential initiates an AP in the skeletal muscle
• This AP causes release of Ca2+ from the sarcoplasmic reticulum
• The raised intracellular Ca2+ initiates contraction

Question 9

Tetanus in muscles

Answer 9

strong contraction

Question 10

Excitation contraction coupling in cardiac muscle

Answer 10

• AP is initiated within the sinoatrial node of the heart
• it travels through the cardiac muscle
• Ca2+ enters each heart cell during the AP
• Ca2+ causes release of more Ca2+ from the sarcoplasmic reticulum
• The raised intracellular Ca2+ initiates contraction

Question 11

From what value to what value does the intracellular Ca2+ rise to to trigger contraction?

Answer 11

100nM to 900nM

Question 12

What 2 mechanisms does excitation coupling occur in smooth muscle?

Answer 12

1) Ca2+ entry through Ca2+ channels raises internal Ca2+ to initiate contraction
2) Receptor activated release of Ca2+ from the sarcoplasmic reticulum initiates contraction

Question 13

How do you end a contraction?

Answer 13

• As voltage gated Ca2+ channels close the calcium ion release channels also close
• SERCA (a Ca2+ pump) takes Ca2+ from the cytoplasm back into the sarcoplasmic reticulum and Na/Ca exchanger removes Ca2+ back into the extracellular fluid
• In skeletal and cardiac muscle Ca2+ unbinds from the troponin complex which occludes the myosin binding sites again
• in smooth muscle calmodulin no longer stimulates myosin light chain kinase