Structure & Functions of skeletal muscle Flashcards
1
Q
Myofibrils
A
- made up of myofilaments; myosin and actin
- smallest unit is a sarcomere
2
Q
Myosin and Actin
A
- myosin fibres; consists of several myosin molecules
- centred by titin (protein)
- actin molecules are attached to nebulin; ensures uniformity in length
3
Q
T tubules
A
- run through fibres either side of Z-disc
- rapid conductions of action potentials
- in close contact with sarcoplasmic reticulum
4
Q
Muscle contraction
A
- myosin heads bind to actin; crossbridge
- myosin has ATP binding site ATP —> ADP + Pi
- energy released
- calcium released from the sarcoplasmic reticulum allows heads to bend; Powerstroke
- ATP reformed; resumes original shape
5
Q
Muscle contraction
A
- myosin heads bind to actin; crossbridge
- myosin has ATP binding site ATP —> ADP + Pi
- energy released
- calcium released from the sarcoplasmic reticulum allows heads to bend; Powerstroke
- ATP reformed; resumes original shape
6
Q
What are the two molecules involved in the control of muscle contractions?
A
Troponin
Tropomyosin
7
Q
What happens when an action potential arrives at a neuromuscular junction?
A
- calcium released from the sarcoplasmic reticulum
- calcium binds to troponin
- tropomyosin changes position exposes myosin-binding site on actin
8
Q
Rigor Mortis
A
- ATP production stops upon death
- calcium levels aren’t maintained
- calcium leaks into cytosol
- binding of myosin heads
- low ATP means these bonds don’t break
9
Q
Hypocalcemia
A
- in dogs; tetany
- in ruminants; paresis
- in cows; no transmission
- in dogs; ACH is higher, transmission still occurs. Involuntary contraction occurs
10
Q
Creatine Phosphate
A
ATP + Creatine —> ADP + Creatine Phosphate
- catalysed by creatine kinase
- Concentrations of ATP and ADP determine the direction of the reaction
- As soon as contractions start, ATP concentration decreases
