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UNC-Chapel Hill EXSS 376 - Exam 2 Study Guide

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EXSS 376 1st Edition Exam #2 Study GuideCardiovascular SystemOverview- Three major circulatory elementso Pump (heart)o Channels or tubes (blood vessels)o Fluid medium (blood)- Heart generates pressure to drive blood through vessels- Blood flow must meet metabolic demandsStructure- Heart is a dual pump containing 4 chambers- 2 upper chambers = atriao Receive blood from blood vessels returning blood to the heart (veins)- 2 lower chambers = ventricleso Eject blood from heart into blood vessels (arteries)- Note: left ventricle more hypertrophied than right because it pumps blood through the entire bodyValves- 2 valves situated between the atria and ventricles = AV valveso right = tricuspid; left = bicuspid - 2 valves guard blood flow from ventricles = semilunar valves o aortic (left) and pulmonary (right)Heart Layers- Wall has 3 distinct layerso Epicardium: outer layer Formed with visceral pericardiumo Myocardium: middle layer Composed of cardiac tissue (what makes heart pump) 95% of heart layer cardiac muscle fibers are interconnected by intercalated discs to form a functional syncytia- mechanically and electrically interconnected cells acting as 1 unit 2 cell junctions are present in an intercalated disc- desmosome: binds sarcolemmas together (mechanical)- gap junction: allow action potentials to move from 1 cardiac muscle cell to another (electrical) o Endocardium: inner layer Provides smooth lining for the chambers of the heart and covers the valves of the heartCardiac Conduction System- Sinoatrial (SA) node: pacemaker of the heart initiates action potentialso Located on right atrial wallo On its own, SA would fire AP’s every 0.6 sec (100 per min), with parasympathetic tone ~75 per min If you took the heart out of the body, would beat at 100 bpmo Causes atria to contract- Action potential reaches atrioventricular (AV) nodeo Action potential slows downo Provides time for blood to enter ventricles- From AV nodes, AP enters bundle of his- AP travels down right and left bundle branches- Purkinje fibers rapidly conduct the AP throughout ventricleso Ventricles contract Cardiac Cycle- Cardiac cycle = all events associated with 1 contraction- Can be divided into 3 phaseso Relaxation period: all 4 chambers in diastoleo Atrial systole: atria contracto Ventricular systole: ventricles contract- 1. Relaxation Periodo end of cardiac cycle when all 4 chambers in diastole (relaxed)o what happens in atria?  Blood flows into relaxed atriao What happens in ventricles? Ventricles relax Pressure drops in ventricles Semilunar valves close When ventricular pressure drops below atrial pressure, ventricles begin tofill- Accounts for 75% of ventricular fillingo  majority of blood entering ventricles occurs during relaxation period- 2. Atrial Systoleo atrial contraction forces remaining blood (25%) in atria into relaxed ventricles tricuspid and bicuspid valves open- 3. Ventricle Systoleo at first, ventricular contraction pushes tricuspid and bicuspid vales closed prevents back flow, increased pressure closes valveso ventricular pressure increases and then open semilunar valves o blood is ejected to aorta and pulmonary arteries Cardiac Output- CO = volume of blood pumped by each ventricle per min (L/min)- At rest = 5 L/min- Cardiac output at rest does not change- 2 determinates: HR (bpm) and SV (volume of blood pumped per beat)- typical valueso predicted HR max = 220 – ageo at rest, trained vs. untrained: same cardiac output trained = lower HR but higher SVo at max exercise: max HR is same, but trained has higher SV => higher Q (cardiac output)Stroke Volume- SV = EDV – ESVo EDV: End Diastolic Volume Amount of blood in the ventricle at the END of diastole – right before it contractso ESV: End Systolic Volume Amount of blood in ventricle at end of SYSTOLE – what is left over after contraction Cardiac Output Control- Heart rateo ↑ Parasympathetic activity: rest/digest Increasing PARASYMPATHETIC activity will DECREASE HR Resting threshold starts LOWERo ↑ Sympathetic activity: fight or flight Increasing SYMPATHETIC activity will INCREASE HR Threshold is reached more RAPIDLY- Stroke volumeo ↑ Sympathetic activity Increased force of contraction = less blood left over = lower ESV Squeezes more blood out of the chambero ↑ EDV ↑venous return ↑EDV ↑length of cardiac muscle fibers- Frank-starling mechanism: greater the stretch = greater subsequent contraction ↑strength of contraction ↑EDV stretches cardiac fibers ↑SVVascular System- arteries: carry blood away from heart- arterioles: control blood flow, feed capillaries- capillaries: site of nutrient and waste exchange- venules: collect blood from capillaries- veins: carry blood from venules back to heartBlood Pressure- force per unit area that blood places on the inside of the wall of a blood vessel (mmHg)- primary cardiovascular variable being regulated is MEAN ARTERIAL PRESSUREo ensures adequate BLOOD FLOW to tissues- systolic: highest pressure in artery (during systole); top number- diastolic: lowest pressure in artery (during diastole); bottom number - MAP: average blood pressure in arteries o Diastolic + 1/3(systolic-diastolic) - BP = systolic / diastolic - No blood flow going through when at 140…slowly release, hear tapping – initial sound = blood intermittently going through vessel, keep releasing it until hear nothing – diastolic (flowing freely w/out constriction)- Pressure greatest near the heart; just enough in veins to bring back to heart - Pressure = force that drives flowDeterminants of MAP- 1. Total peripheral resistance (TPR)o resistance in peripheries- 2. Blood Volumeo decrease blood volume = decrease blood pressureo minor decrease in blood volume has only minimal effect on BPo >10% blood loss decreases BPo water retention may increase blood volume and INCREASE BP- 3. Cardiac Output o any increase in CO (or Q) will increase MAP IF TPR remains constant Total Peripheral Resistance- TPR: opposition to blood flow due to FRICTION between blood and walls of the blood vessels- Depends on:o Vessel radius (MOST IMPORTANT) Decrease in diameter increases resistance to blood flow Influenced by:- Local (tissue) metabolic controlso Increase O2 = vasoconstrictor (because already meeting O2 needs)o Increase CO2, H+ =


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UNC-Chapel Hill EXSS 376 - Exam 2 Study Guide

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