Muscles 1 Flashcards
What do muscles do?
Generate force, movement and allow us to express and regulate ourselves
What are the two types of muscles we have in our body?
Smooth and striated
What two types of striated muscles are there?
Skeletal and cardiac
Skeletal muscles forms what structures and describe their nucleus/nuclei
Fibres which a multinucleate
What are the typical dimensions of a skeletal muscle fibre?
10-100 micrometers in diameter and up to 20cm long
Fibres form where and from what?
in utero from mononucleate myoblasts
Do myoblasts replace cells if damaged?
No
What happens to muscle fibres during growth?
They increase in size, not quantity
What encases muscle fibres?
Connective tissue
What cells replace damaged muscle cells after injury?
Satellite cells
How do satellite cells form new muscle cells?
They differentiate (specialisation)
How can other fibres compensate for adjacent fibres being damaged?
Hypertrophy (getting bigger)
Describe the action cycle of a sarcomere
- Muscle action potential propagated
- Calcium ions released from lateral sac
- Calcium binds to troponin - removing the blocking action of tropomyosin
- The myosin head binds to the actin filament and moves to contract the muscle
- ATP binds to the cross bridge to detach the filament linkage
- Calcium ions are pumped into the lateral sac
- Calcium removal from troponin restore blocking action of tropomyosin
What two receptors mediate the movement of calcium ions in the action cycle?
DHP (voltage sensitive calcium channel) and Ryanodine receptor
What is a motor unit?
Motor neurons and muscle fibres as a unit
A force exerted by a muscles is a _____
Tension
A force exerted on a muscle is the _____
Load
Short latent period and longer contraction time is indicative of what kind of contraction
Isometric
Longer latent period and shorter contraction time is indicative of what kind of contraction?
Isotonic
What is the latent period?
The time before excitation contraction begins
Contraction time is what?
The time taken between the start of a contraction and its peak tension
What is the typical range of contraction time?
10-100 microseconds
What is contraction time mediated by?
Calcium ion concentration
As load increases, what happens to contraction velocity and distance?
They’re shortened
What is the typical duration of action potentials in muscles?
1-2 microseconds
Summation occurs when?
When action potentials immediately or just after a previous action potential
Tetanic tension is greater than twitch tension because?
[Calcium ion] never gets low enough to allow troponin/tropomyosin to block myosin binding sites
What does movement at a limb require?
Two antagonistic groups of muscles
What do level systems of muscles accomplish?
Allows muscles to exert an amplified force - shortening velocity producing increases manoeuvrability
