7/28/2019 bio heartB

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1) when atria and ventricle are both open/relaxed … AV valve=opensemilunar valve= closed

2) when atria is contracted (all blood in atria go into ventricle)AV valve=openSemilunar valve=closed

3) when ventricle is contractedAV valve=closed

Semilunar valve=open-------Systole: contraction phase of cardiac cycleDiastole: relaxation phase of cardiac cycle-------Cardiac output: volume of blood each ventricle pumps per minute1) heart rate = # of beats per minute2) stroke volume - amount of blood pumped by a ventricle in a singleconstruction-------(carry blood away) Arteries -> arterioles -> capillaries (stuff are exchangedbetween blood and interestial fluid) -> venules -> veins (blood goes back toheart)-------Arteries are elastic and stretch as they fill with blood. They are wrapped insmooth muscle that is innervated by the SNS. (Epinephrine is a powerfulvasoconstrictor causing arteries to narrow) Large arteries have less smoothmuscle per volume than medium size arteries. Arterioles are very smalland wrapped by smooth muscle. Constriction and dilation of arterioles canbe used to regulate blood pressure and reroute blood. Capillaries aremicroscopic blood vessels (1 cell thick). *nutrient and gas exchange takeplace!! Four methods for materials to cross capillary walls: 1)pinocytosis 2)

diffusion or transport through capillary cell membranes 3) movementthrough pores in cells called fenestrations 4) movement through spacebetween the cells. As blood flows through capillary, hydrostatic pressure isgreater than osmotic pressure. In arerole end of capillary, net fluid flowout of capillary and into interstitium. Near the venule end of a capillary,

net fluid flow is into the capillary and out of the interstituim. Vein lumenare bigger than lumen of arteries and veins have greater volume of blood.Blood moves the slowest through capillaries.-------Pressure: blood pressure increases near the heart and decreases to itslowest in the capillaries

Velocity: a single artery is much bigger than a capillary but there are farmore capillaries than arteries. The total cross-sectional area of all thosecapillaries put together is much greater than the cross sectional of a singleaorta or a few arteries. Blood flow follows the continuity equation, Q = Av

well so velocity is greatest in the arties where cross-sectional area issmallest and velocity is lowest where cross sectional area is the greatest-------1) SA Node is pacemaker located in RA and it contracts by itself at regularintervals and spreads its contractions to the surrounding cardiac musclesvia electrical synapses made from gap junctions.2) pace of SA node is faster than normal heartbeats but parasympatheticvagus nerve innervates the SA node, slowing the contractions.3) action potential generated by SA node spreads around both atriacausing them to contract and at the same time spreads to the AV nodelocated in the wall of cardiac muscle between the atria.4) there is a delay at AV node which allows the atria to finish theircontraction and to squeeze their contents into the ventricles before theventricles begin to contract.5) from the AV node, action potential moves down bundle of His (locatedin the wall separating the ventricles).6) Action potential branches out through the ventricular walls vaiconductive fibers called Purkinje fibers7) from the Purkinje fibers, the action potential is spread through gap

junctions from one cardiac muscle to the next. The fibers in the ventriclesallow for a more unified and stronger contraction.