Muscular System Flashcards
what are the functions of muscles?
movement, maintaining posture, protects organs, generates heat, stabilise joints, valves, pupil dilation, raising hair
what are the 4 characteristics of muscles
excitability (responding to stimuli), contractility, extensibility, elasticity (can recoil to resting length after being stretched)
which type of tissue wraps and reinforces muscles?
connective
what are the three types of muscle
smooth, skeletal, cardiac
describe the structure of smooth muscle
visceral- meaning it lines hollow organs. it is non-striated and involuntary
describe the structure of skeletal muscle
voluntary, striated and multinucleated
describe the structure of cardiac muscle
striated and involuntary
what’s a sacromere?
single contractile unit
write a note on muscle fibres
are a multinucleated cell. may be up up to 30cm in length. the cell membrane of the muscle fibre is called the sarcolemma. the sarcoplasm is the muscle fibre cytoplasm, and the myofibril is the rod like organelle containing contractile elements (sarcomeres). myofibrils have alternating Light (I) and Dark (A) bands
write a note on sarcomeres
smallest contractile unit of muscle fibres. they are the region between two successive Z discks and have thick filaments (myosin) and thin filaments (actin)
what function has the myosin head, tropomyosin and troponin?
myosin head forms cross bridges with thin filaments to contract muscle cells.
Tropomyosin is a protein strand that stabilises actin.
Troponin is bound to actin and is affected by Ca2+.
*learn the diagram for this
What is the sliding filament model?
during contraction thin filaments slide past thick ones so that they overlap. Myosin heads latch to active sites on actin forming a cross bridge. Tiny rachets propel thin filaments to centre of the sarcomere
What is the process of muscle contraction
- Action potential travels down axons and arrives at neuromuscular junction where there is a release of acetylcholine (ACh) into the synaptic cleft.
- ACh diffuses across the cleft and attaches to ACh receptors on the sarcolemma of muscle fibre.
- A rush of sodium into the sarcoplasm produces action potential in the sarcolemma where ACh is broken down.
describe what happens at a neuromuscular junction and then how this results in muscle contraction
action potential travels down the sarcolemma where calcium is released from SR. Calcium binds to troponin resulting in a change of shape, as myosin binding sites are exposed on actin. The myosin cross bridge forms with actin. Myosin head pivots and pulls the actin filament to the M line. ATP attaches to myosin and the cross bridge detaches. the myosin can be reactivated
what is a muscle cramp?
sudden or involuntary contraction of muscles due to long periods of exercise, medications, dehydration, muscle strain nerve/kidney/thyroid disorders, inadequate blood supply, nerve compression or mineral depletion (Ca, K, Mg)