skeletal muscles

what are the 3 types of muscle

cardiac

skeletal

smooth

what is cardiac muscle

performs coordinated contractions that allow your heart to pump blood through your circulatory system

what is skeletal muscle

produces movement, maintains posture, stabilises joints and generates heat

what is smooth muscle

pushes fluids and solids along digestive tract, regulates diameter of arterioles and bronchioles

what type of muscle can we control

can control the contraction and relaxation of skeletal muscle

different architectures of skeletal muscles

parallel

fusiform

circular

convergent

multipennate

unipennate

bipennate

what does the skeletal muscles do

contract

what does muscle contraction mean

reduction in volume and shortening

what happens when muscles are stimulated

muscles generate force when attempt to shorten which causes either shortening, lengthening or no change in length

what are the types of muscle action

concentric

eccentric

isometric

what is concentric muscle action

when the muscle shortens

e.g. the curl of a bicep curl

what is eccentric muscle action

lengthening of muscle

when move arm down

what is isometric muscle action

no movement of muscle

what is the structure of skeletal muscle

70-80% muscle volume composed of myofibrils (contain actin and myosin)

contains muscle tissue, connective tissue, blood vessels and nerves

what is the microscopic structure of the muscle cell

thin, elongated cylinder

multinucleated cells

striated apperance

what are multinucleated cells

genes within control production of enzymes and structural proteins required for normal muscle action

what are sarcomeres

repeating functional units that make up myofibrils

how many sarcomeres are there per myofibril

thousands

what are sarcomeres made up of

thick and thin filaments aswell as stabalising and regulating proteins

what is the A band

the dark band with thick myosin filaments and overlap of actin and myosin

what is the I band

thin actin filament only

what are Z lines

separate the different sarcomeres

what is thick filament

made up of 300 myosin molecules and a core of titin

long tail and free head that binds to the active sites on thin filaments

the head contains ATPase

what is thin filament

contains 4 proteins:

filamentous actin

nebulin

tropomysosin

troponin

how does the muscle generate tension

sliding filament theory

what is the sliding filament theory

thick and thin filaments slide past each other

what is the cross bridge cycle

molecular mechanism where myosin and actin myofilaments slide over each other. During muscle contraction  the heads of myosin myofilaments quickly bind and release in a ratcheting fashion, pulling themselves along the actin myofilament

what is stage 1 of the cross bridge cycle

binding - ADP and Pi bind to myosin which causes calcium ions to be released into the sarcoplasmic reticulum and they then bind to troponin which exposes the active sites

what is stage 2 of the cross bridge cycle

power stroke - ADP and Pi released from myosin, myosin swivels causing displacement of actin filament towards the M line

what is stage 3 of the cross bridge cycle

dissociation - ATP binds to myosin, actin and myosin dissociate

what is stage 4 of the cross bridge cycle

activation - energy from hydrolysis of ATP used to re-energise the myosin head, ADP and Pi remain bound to myosin

what do the number of cross bridges determine

how much force the muscle can produce