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)
write a note on isotonic contraction
has the same retention, the muscle length changes i.e in bicep curls, bending knee or smiling
how are muscle cramps treated?
stretching, muscle relaxants, hydration, Vit B supplements, cold/heat therapy
write a note on isometric contractoin
muscle length stays the same, tension increases i.e moving against heavy load or immovable objects or lifting heavy weights
what does origin mean in terms of muscle orientation?
where the muscle is attached to immovable or less movable bone
what does insertion mean in terms of muscle orientation
the muscle is attached to movable bone
give the scientific names for muscle direction: parallel, right angles, converging, circular, feather-like, spindle shaped
rectus, transverse/oblique,convergent, obicularis, pennate, fusiform
what are the scientific names for the follow relative sizes of muscles: largest, smallest, long, short
maximus, minimus, longus, brevis
what is the scientific wording for muscles that have two origins and three origins?
biceps and riceps
how might a triangular and a trapezoidal muscle be described?
deltoid and trapezius
what words describe the adduction and extension action of muscles
adductor and extensor
give an example of each of the following muscles: circular, convergent, parallel, unipennate, multipennate, fusiform, bipennate
orbicularis oris, pectoralis major, sartorius, extensor digitorumlongus, deltoid, biceps brachii, rectus femoris
which embryonic cells do muscles develop from?
myoblasts
what happens when myoblasts fuse?
muscle fibres are formed
what % body mass is comprised muscle in men and women?
42% in men and 36% women- due to testosterone
what impact has aerobic or endurance exercise have on the body
stronger, more flexibility, resistance to fatigue. does not increase muscle size. increased blood supply + mitochondria and o2 storage. efficiency of metabolism and heart function
what are the effects of resistance/isometric exercise
this exercise includes muscles vs immovable object. have an increase in muscle cell size as there are more contractile units. increase in muscle size and strength.
what happens to muscle mass with age?
mass decreases and muscles become more sinewy.
by how much does muscle mass decrease by age 80?
50%`
What is a fascicle?
Bundle of muscle cells
What are the layers of membrane?
Epimysium - outer
Perimysium - membrane between fascicles
Endomysium - membrane of fascicles
Blood vessels
