week 5- cardiac mechanic Flashcards
what can a single ventricular cell do?
contract and glow on calcium transport
coupling of electrical to contractile event
what does skeletal muscle need to contract?
intracellular calcium
what does muscle cell need to contract?
extracellular calcium
function of T tubules
carry surface depolarisation deep into the cell
structure of muscle cell components
myofibrils, mitochondria, sarcoplasmic reticulum, nucleus and others
explain the excitation-contraction coupling in the heart
L-type calcium channel sense depolarisation by AP and open
causes Ca influx down conc gradient in sarcoplasm
mechanical link to SR receptor to release of calcium
calcium binding to troponin causing contraction
calcium recycled into SR and Ca exit to maintain Ca concentration within cell no ATP used
describe relationship between force production and intracellular calcium
between 1-10micromol calcium rapid increase in force produced
beside sigmoid shape of graph
describe the length-tension relationship in cardiac muscle
increase increase stretching followed by stimulation increase the active force output up to a maximum then decrease but the passive force just increase
why cardiac muscle have more passive force than skeletal muscles?
because the cardiac muscle are more resistant and less compliant due to properties of ECM and cytoskeleton
forms of contraction in the heart?
isometric and isotonic
what is isometric contraction
increase in pressure in the ventricles but no change in length of muscle fibres
what is isotonic contraction
shortening of muscle fibres to eject blood from ventricles
what is preload
weight that stretches the muscle before contraction stimulation
what is afterload
weight not apparent to muscle in resting but should be overcome once contraction starts
relationship between shortening and afterload
the greater the after load the more reduced a shortening is- linear relationship
longer muscles > shorter muscles
