10.7.13 kin 272 class notes- Vagus nerve sends neurotransmitter to location of SA nodeo Causes the SA node to depolarizeo When this happens-sends out action potentialo SA send electrical stimulus to entire atria as well as to the AV nodeo Stimulating the atria, it causes the atria to depolarizeo Leads to action potential, then contractiono AV node Info results in depolarization of AV node Sends action potential Depolarizes Goes to the bundle of His- Releases chemical that stimulates Purkinje fiberso Send message that results in depolarization of the ventricles Action potential  contract Pause between contraction of atria and contraction of ventricle Isovolumic contraction- Waiting for electrical message to contract- Electrical pathway goes at the same time as mechanical pathwayo Week after lab exam we will discuss an ECG Diagram of electrical events in the heart Electrical heart events Image of ECG –graph paper Represents depolarization components, action potential pieces that happen in the heart If we assume-heart gives normal pic of electrical events, it can be assumed that mechanical events are normal as well Atria depolarized – so it contracted- Same with ventricle- Blood vessels o Arteries Blood awayo Veins Blood backo Same three layers… Whats in them & Thickness  Depends on what you are looking at All have…- Tunica intimao Endothelial cellso Identical between arteries and veins- Tunica mediao Different in arteries and veinso Arteries: contains mostly smooth muscle and elastic fiberso Thick component of these vessels – arteries Elastic & smooth muscleo veins collagen & elastin very thin- tunica externao casing that holds everything ino other major differences (the two not talked about in lab) arteries- elastic recoil- in terms of aorta…stuff a large quantity of blood it will stretch and then recoilo allows forward movement of flow veins- no recoil- walls made up of elastin and collagen- not the same stretching capabilities arteries- remain structure after being cut- little tiny squished tubes veins- collapse after being cut- simply because of thickness of walls- big round tubes- veins-no pump system- return flow: rely on…o one way valveso respiratory pump this means that when you breathe you create a vacuum like system in the thoracic cavity – pulls blood upward return flow in veins??? Skeletal muscles – blood vessels go through these! Skeletal muscles work as massaging pumps Move blood back toward heart Sit for a long time – feet are filled with blood (puffy)- Flow= Q- Flow/min = Q with a dot over it- Push blood through the heart to the arteries- Heart works to create the movement of blood flow in one direction- Heart  pump blood to increase flow- Resistance to flow:o Times when each vessel creates resistance to that flowo Is the heart going to have to work harder to get the tissues what they want? Yeaho Exercise creates resistance to flow…?o Total peripheral resistance TPR: total resistance that in the vessels in the periphery Add up all resistance together – equates to how hard the blood has to work Add up all that resistance= total Higher = harder heart has to work What creates resistance?- Vessel length o Alter speed of flow/resistanceo Longer the vessel, more resistance, decrease flow- Vessel diameter  decrease diameter, more resistance, decrease flow- Viscosityo Thickness of bloodo Flows slower the thicker the blood- TPRo More resistance, less flow, more heart worko Vessel lengtho Vessel diametero Viscosityo Turbulance Laminar flow (parabolic flow)- This means that…- Standard tube- Trying to get fluid to go through- Most fluid flows in a parabolic fashion- Fluid in center of tube travels the fastesto No resistance to that fluido Not touching anything- As you get to edges… that flows slower- Bullet shaped- Fastest way to get fluid through a tube Turbulent flow- No parabolic shape- Water just pushes along- Not very quick at all- Has swirls and edie currents that push it against the wall- Movement of water at the end of the ocean (some coming in – some going out)- Water doesn’t move well- Split in the tubes!- Do you think flow is going to go well there? No…- Where regions are dividing- Can’t keep moving forward- Increase turbulent flow, increase resistance- Heart has to work harder to get stuff to the tissure You want laminar flow…look at way that blood vessels divide- Divisions are built a certain way to limit turbulent flow- Elastic arteries – aortao Muscular arterieso Arterioles 10% elastic 90% smooth muscle can change the most… resistance vessels create more restrictiom in vessels  vasomotion – - vasoconstriction - vasodilation dictate direction of flow when you eat blood goes to stomach- this is why hands/ feet get cold after eating