L9/10- Skeletal muscle Flashcards
function of skeletal muscle
- To contract and cause movement
- To keep joints stable
- Homeostasis- generate heat
structure of skeletal muscle
- Each skeletal muscle fibre is made up of many single cylindrical muscle cells
- Muscle fibres are bundled together to form muscle fascicles
- An individual skeletal muscle may be made up of thousands of muscle fibres bundled together in fasicals
o Wrapped in a connect tissue covering (fascia)
what covers muscle fasicles
fascia- loose connective tissue
connective tissue which covers skeletal muscle
1) epimysium
2) perimysium
3) endomysium
- Epimysium:
wraps each muscle, providing structural support, maintaining structural integrity (connective tissue). Also separates muscle from other tissues
- Perimysium:
separates muscle fascicles-organising individual muscle fibres which form muscles
- Endomysium:
inside each fascicle, each muscle fibre is encased in a thin connective tissue layer of collagen and reticular fibres. Contains nutrients to support the muscle fibre- supplied by blood vessels
muscles are attached to bone via
tendons
movement is dependent on the
direction of muscle fibre contraction
point of origin
- is the attachment site that doesn’t move during contraction
- Usually proximal (closer to the body)
point of insertion
- the attachment site that does move when the muscle contracts
- Usually distal (further away from the body)
skeletal muscles are well supplies with blood vessels for
for nourishment (glucose) , oxygen delivery (for respiration- ATP) and waste removal (lactic acid).
somatic motor neurones signal
fibres to contract
- nervous impulse from somatic NS
thin muscle fibres require
less blood supply
thick muscle fibres require
more blood supply
three types of striated muscle
- slow twitch
- intermediate
- fast twitch
what type of muscle is slow twitch
type 1
what type of muscle is intermediate
type 2A
type of muscle is fast twitch
type 2B
what type of respiration does slow twitch (T1) muscle do
aerobic
what type of respiration does fast twitch (T2A) muscle do?
anaerobic
what type of respiration does intermediate muscle do?
aerobic
slow twitch features
o Rich capillary supply
o Fatty acids- lots of ATP/CO2
o Aerobic- lots of myoglobin to provide oxygen – red
o Many mitochondria
o Many cytochromes
o Fatigue resistant
o Endurance type activities, standing and walking
intermediate features
o Rich capillary supply o Fatty acids and glycogen- lactase o Aerobic o High myoglobin- red to pink o Many intermediate mitochondrial numbers o Many cytochromes o Moderate fatigue resistant o Standing/walking- assist type 1 and 2B activities
fast twitch features
o Poor capillary supply o Glycogen- lactate/little ATP o Anaerobic o Low myoglobin levels (white) o Few mitochondria and cytochromes o Rapidly fatigues o Strength and anaerobic type activities o Sprinting etc
what is produced in fast witch fibres
lactate - no oxidative phosphorylation and only small production of ATP
- insufficient oxygen supply
colour of slow twitch
red (myoglobin)
why does slow twitch need myoglobin
in constant need of oxygen- sustained exercise e.g. endurance
colour of intermediate
pink (some myoglobin)
colour of fast twitch
white
extrinsic muscle
have insertions in bone or cartilage e.g. protruding the tongue, retracting is and moving it from side to side
intrinsic muscle
Not attached to bone- attached to other muscle.
e.g. allows the tongue to change shape but not position- aids swallowing
skeletal muscle is
striated
Innervation of skeletal muscle- Neuromuscular junctions (NMJs)
- Small terminal swellings of the axon which contain Ach
o Nerve impulses release acetylcholine
o Ach binds to receptors on the sarcolemma and initiated AP to be propagated along the muscle (T-tubule- deep into the muscle)
myasthenia graves is what type of disease
autoimmune
in myasthenia gravis antibodies are directed against
ACh receptor
- blocking it
30% reduction in receptor number
sufficient for symptoms
- endplate invaginations reduced
- reduced synaptic transmission
what does myasthenia gravis cause
intermittent muscle weakness
