Structure of skeletal muscle Flashcards
What are parallel muscles best at
Can shorten the most
What are convergent muscles best at
like a fan, can go various directions
what are pennate muscles best at
can produce most tension
what are circular muscles best at
open and close things
What is the epimysium continuous with
tendon and periosteum
what is the perimysium continuous with
epimysium
What is the endomysium continuous with
the perimysium
what is the sarcolemma
the cell membrane
what is the sarcoplasmic reticulum
ER with calcium pumps
what is a myofibril
actin and myosin packed and organized into bundles, responsible for contraction and relaxation
what is a sarcomere
1 contractile unit (Z disc to Z disc)
what are titin proteins
elastic, connect thick filaments to Z disc.
What happens to the H zone during contraction
Thin filaments slide into Hzone decreasing it.
1000s of sarcomeres end to end
myofibril
Striation
100s of myofibrils lined up together
What are the factors affecting strength of muscle contraction
1) frequency of stimulation
2) number of muscle fibres contracting
3) Type of muscle fiber
Explain frequency of stimulation
single AP = weak muscle twitch (not useful)
many consecutive= tetanus
- more Calcium released than can be pumped in, enough musc tension to pull on tendon
Explain number of muscle fibres contracting
-1 motor unit = motor neuron plus all the muscle fibres it innervates.
Small unit - percise
large unit- powerful
-Number of motor units recruited, only a few = weak
many = strong, asynchronous recruitment
What is asynchronous recruitment
shifts of motor units to avoid fatigue
happens during sub maximal contraction
Explain the 2 Types of sources of energy
-ATP stores only last 2 seconds, so body needs other sources
there is intermediate and sustained
What are intermediate sources
Lasts about 1 min, 1 step transfer of energy and phosphate from creatine phosphate
What are sustained sources
There is aerobic and aerobic
What are aerobic sources of energy
They require oxygen. The make many ATP but are slow.
what are anaerobic energy sources
No oxy. But less ATP, fewer steps, create lactic acid.
What are the 3 types of muscle fibres
1) Slow oxidative
2) Intermediate fibers
3) Fast-glycolytic fibers
What are slow oxidative fibres
- slow to contract, slow to fatigue
- marathon, or posture
- Use aerobic respiration (need oxygen)
- Red, many mitochondria, many capillaries,
What are intermediate fibres
- Medium resistance to fatigue
- Aerobic resp.
- some mitochondria, some capillaries, low myoglobin, pink
What are fast-glycolytic fibres
-fast to contract, fast to fatigue sprinter, power lifter -Glycolysis (anaerobic) produces lactic acid -more myosin & actin = larger -white
What causes muscle fatigue (4)
1) Decreased energy reserve 2) damage 3) decreased ph. which causes decreased calcium binding 4) central fatigue which is mental, decreases muscle recruitment
What is oxygen debt
After exercise, elevated O2 consumption continues until the debt is repaid.
It is the amount of O2 required to restore ATP, creatine, phosphate and glycogen
remove lactic acid and power sweat glands
