11: Musculoskeletal system

muscular system

provides support, stability and movement. Enables all physical movement, maintains posture, circulate blood, and generate essential body heat.

muscles

tissue that can contract and relax to produce movement

cardiac muscle

striated and branched for strength. Involuntary control. Uni-nucleated.

smooth muscle

found in blood vessels, digestive tract, uterus etc… Not striated, cells are tapered and action is involuntary

skeletal muscle

contract and relax to bring about movement. Attached to skeleton. Striated for strength, voluntary, multi-nucleated for extra control. Many mitochondria which produce energy for the cell.

joint

a place where two or more bones meet (via ligaments)

tendon

muscles are connected to bones by tissues called _____. They are flexible but inelastic cords of strong fibrous collagen tissue that join bone to muscle.

characteristics of muscle

• contractability: ability to be contracted (shortened)

• extensibility: ability to be stretched (lengthened)

• elasticity: ability to return to original shape after being stretched.

(Important to note: while muscles are able to shorten their length by contraction and can be stretched, they are unable to increase their own length.)

flexor

muscle that draws two parts of the body closer to one another

extensor

muscle that moves two parts of the body further away from one another

antagonistic muscles

pairs of muscles that work against each other to create movement.

as one muscle contract, the other relaxes (lengthens). they swap actions to reverse the movement.

agonist (prime mover)

muscle which creates the desired movement (contracting muscles)

antagonist

yields the movement of the agonist (relaxing muscle)

synergist muscles

aid the prime mover by contracting to help steady a joint or movement.

origin

attachment of a muscle tendon to a stationary bone

insertion

attachment of a muscle tendon to a moveable bone.

muscle tone

• partial contraction tightens the muscle but not enough to create movement

• many different fibres take turns to contract, while others relax.

• posture is dependent on muscle tone.

fascicle

each muscle consists of bundles of fibres held together by a sheath of connective tissue called the perimysium. these bundles are ______.

muscle fibre/cell

• each _____ is cylindrical in shape.

• each is surrounded by a membrance called sarcolemma

• contains multiple nuclei, cytoplasm called sarcoplasm, many mitochondria for maximum energy release and extensive myofibrils which run parrallel to the length of the cell.

myofibril

within the sarcoplasm, threadlike and lie parrallel to each other, running the length of the cell.

each is made up of even smaller units called myofilaments.

can be divided into sub-units along their length, called sarcomeres.

myofilaments

made of protein, are the actual contracting units where the work of movement is done.

arrangement of thick and thin filaments within fibril gives a banded effect and a striated appearance when viewed microscopically.

actin

primarily made of the protein actin and is thinner in structure.

myosin

primarily made of the protein myosin and is thicker in structure.

what happens with myofilaments

when a muscle fibre receives energy and is activated by a nerve, the thick and thin protein filaments slide past each other in a matter which shortens the myofibril.