1.12 Muscle Contraction Flashcards Preview

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Flashcards in 1.12 Muscle Contraction Deck (11)
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1
Q

How do action potentials pass along the muscle membrane?

A

Action potentials pass along the muscle membrane, in special invaginations of the sarcolemma called T tubules, which go deep into the muscle. They reach the sarcoplasmic reticulum and release Ca ions.

2
Q

Explain the calcium release in the sarcolemma…

A

Depolarisation along t-tubules activates the voltage sensitive calcium channels.
Mechanical coupling with SR causes SR calcium channels to open.
Calcium leaves SR and Ca also enters cell through calcium membrane channels.

3
Q

What are the types of calcium channels?

A

2 types of calcium channels;
• Calcium channel on t-tubule
○ L type channel
○ Also known as DHP receptor (dihydropyradines)
• Sarcoplasmic reticulum calcium channel
○ Ryanodine receptor - Inhibited by alkaloids ryanodine and caffeine

4
Q

What is this electrochemical coupling called?

A

There is an electromechanical coupling between the two - Calcium Induced Calcium Release.

5
Q

What is actin made up of?

A

Two actin strands fold into a double helix. Can be globilar or filamental

6
Q

What shape is tropomyosin?

A

Also helical

7
Q

What are the three types of troponin?

A

Troponin T - tropomyosin
Troponin I - actin
Troponin C - calcium

8
Q

What is myosin made up of?

A

Heavy chain - rod, hinge and hear

2 light chains - alkaline stabilising head - regulatory regulates ATPase

9
Q

Describe the structure of the sarcomere

A
Z line 
H zone - just myosin - thick 
I band - just actin - thin 
A band - one sarcomere - z to z
M line - middle
10
Q

What are stages of muscle contraction?

A
  1. Release Calcium Sarcoplasmic reticulum
  2. Calcium binds to troponin C
  3. Confrontational change in troponin complex
  4. Troponin I released from actin, troponin T moves from the myosin binding site
  5. Myosin head free to interact the actin
11
Q

Explain the stages of cross bridge cycling…

A
  1. ATP binds to myosin head and releases it
  2. Myosin dissociates from actin
  3. ATP hydrolysed and releases energy - myosin moves to a cocked state
  4. Myosin then binds to a new place on the actin
  5. Phosphate released - myosin performs power stroke and filaments slide
  6. ADP released