Skeletal Muscle Flashcards
The muscular compromises how much of our total body weight?
40-60%
What are the functions of the muscular system?
Movement
Posture
Storing/moving substances
Generating heat (shivering)
What structure covers the entire muscle?
Epimysium
What structure is made of connective tissue and encapsules fascicles?
Perimysium
What are fascicles?
Bundles of muscle fibres
Sarcoplasm is the site of what?
Anaerobic respiration (enzymes)
What are satellite cells?
Stem cells that differentiate into myoblasts and then myofibrils
Sarcomeres are the smallest unit of skeletal muscle and are compromised of what?
Myofilaments.
Actin forms in a what type of strand?
Double helical strand
What is the role of tropomyosin?
Interacts with actin, covers binding site, myosin heads cannot bind to actin.
As well as tropomyosin, what other myofilament is associated with actin?
Troponin
What three parts make up the thick myosin filament?
Globular head
Flexible region
Tail
How many myosin molecules are there per thick filament?
300
What are the three extra structural proteins in a sarcomere? Explain their role.
- Titin - molecular spring, associates with myosin and actin.
- Nebulin - attachment subunits of actin, gives helical structure, avoids separation.
- Desmin - Z line, joins sarcomeres.
What is the definition of a sarcomere?
Smallest unit of a muscle cell, contains myofilaments which contract to form tension within a muscle.
Give a general outline of the sliding filament theory created by Huxley in 1954.
Filaments slide past each other, both filaments remain relatively unchanged in length, despite changes in gross muscle lengths.
H zone consists of what?
Myosin only.
During concentric contraction, actin is pulled along myosin, what happens to the sarcomere structure?
Z lines move closer.
H zone reduces.
I band reduces.
A band remains the same.
What is the sarcolemma?
Excitable membrane that depolarises to pass on AP.
What is the sarcoplasmic reticulum?
Interconnecting tubules which surround the myofibrils and regulate calcium levels within the muscle cell.
What are T-Tubules?
Branch from sarcolemma and pass on AP to muscle fibre.
Describe the cross-bridge cycle.
- Tropomyosin covers binding site on actin.
- AP arrives.
- Calcium released from SR, binds to troponin = conformational change.
- Tropomyosin uncovers binding site.
- Hydrolysis of ATP on myosin head.
- Cross-bridge formed.
- Pi released from head, changes angle, facilitates power stroke.
- Head picks up another ATP, binding breaks cross bridge.
- Repeats until calcium levels drop.
What is fat max?
The maximum amount of fat an athlete can burn per hours - endurance trained people utilise fat at a higher rate.
If a fibre appears to have a deep red colour, what is there a high concentration of?
Myoglobin
