SS 1 Filtration Secretion Reabsorption

Circulatory System Circulates Nutrients: glucose, amino acids, fatty acids, ketones, etc Wastes: Hormones: bound & free Gases: CO 2 and O 2 Formed Elements: Cells and Cell Fragments –Erythrocytes, Leukocytes, Thrombocytes = Platelets Other roles of the Cardiovascular System Thermoregulation Blood Clotting Reproduction (ex: penile erection) S 2

Figure Blood volume ~ 5 liters Serum = plasma – clotting factors Formed elements Components…… Blood doping & erythropoietin (hormone that stimulates erythrocyte production in bone marrow) to increase hematocrit Entering and Exiting the blood Discontinuous capillaries in bone marrow, spleen, & liver permit erythrocytes to enter and exit blood. Hct = percentage of blood volume occupied by RBCs Anemia EPO and “The Scoop on Tissie” S 3

Fig Arteries..away from heart Veins..return to heart Regional blood flow determined by arteries and arterioles. Resting Cardiac Output = 5L/min for each side! When left heart can’t pump all the blood it receives from pulmonary circuit (due to high aortic pressure and/or damage to left ventricle) blood accumulates in pulmonary circuit. This is congestive heart failure. Symptom: shortness of breath. S 4

Figure CO = 5L/min for each circuit Up to 35 L/min in strenuous exercise S 5

What’s missing? Microcirculation Pulmonary circuit Systemic Circuit CO = 5 liters/min Exchange Vessels Resistance Vessels Capacitance vessels S 6 Recall Portal Systems!Arterial Blood Pressure

Pulmonary circuit Systemic Circuit S 7 Pressure gradients makes fluids move. Moving fluids flow, but flow is limited by resistance. Resistance creates pressure. Arterioles establish Mean Arterial Pressure

F=Q=ΔP/R Flow = Pressure gradient/Resistance from Ohm’s Law (V=IR) R = 8Lη/πr 4 Q= ΔP πr 4 8Lη Poiseulle’s equation Smooth muscles determine radius Double radius … 16x flow Half radius….1/16 th flow Radius of arterioles regulates Q to organs S 8

MAP = CO x TPR Mean Arterial Pressure = Cardiac Output x Total Peripheral Resistance MAP = (HR x SV) x TPR S 14

Cardiac Output = Heart Rate X Stroke Volume What regulates heart rate? CO = HR x SV 5L/min = 72 beat/min x 70 ml/beat The Cardiac Cycle animation S 1 What regulates Stroke Volume?

Figure Bicuspid =Mitral Tricuspid Problems with valves: ….Stenosis (narrowing) →Heart Murmurs (turbulent flow past a constriction) note: origin of neonatal heat murmurs (foramen ovale) ….Prolapse (eversion) allows backflow (also generates murmurs) Semilunar Valves Heart sounds produced by valve closings Animation Heart murmurs ≠ heart sounds S 4

Figure Cardiac Myofiber Plateau phase Cardiac Myofiber action potential Long refractory period prevents summation in cardiac myofibers S 3

Figure SA node cells do not have stable resting membrane potential, spontaneously produce AP, are Pacemaker cells S 5 S 4

Figure Pacemaker Cells in Conducting System: SA Node and Bundle of His Ectopic Pacemaker Locations other than SA Node S 5 Cardiac Pacemaker action potential These cells set the rhythm & control Heart Rate.

Figure Intrinsic Rate = 100 beat/min S 15 2 effects of Parasymp: hyperpolarization & slower depolarization

Figure Effect of “Beta blockers” NEEPIACh mAChR Effect of atropine Beta-adrenergic receptors S 6

Fibrous connective tissue between atria and ventricles prevents the conduction of action potential. Only route is via AV node, bundle of His, bundle branches, Purkinje fibers, and to ventriclular myofibers. What prevents the AP from being conducted from ventricles back to atria? S 7

1 st Heart Sound = Closure of Atrioventricular (AV) valves at beginning of Ventricular Systole 2nd Heart Sound = Closure of Semilunar valves at beginning of Ventricular Diastole S 8 “Sis-toe-lee” “die-ass-toe-lee”

Figure Systolic Diastolic Ejection Fraction = SV/EDV Atrial Fibrillation Ventricular Fibrillation & Defibrillation Stroke Volume Animation S 9

Events are same for Cardiac Cycle for Right Side of Heart; only difference is lower systolic pressures in right atrium and right ventricle. S 10

CO = HR x SV 5L/min = 72 beat/min x 70 ml/beat 35 L/min = ? beat/min x ? ml/beat S 1 So far, we’ve dealt with the factors that control Cardiac Output by changing heart rate. + sympathetic - parasympathetic 2 1 3

Figure Stroke Volume Animation S 2

Frank-Starling Law of the Heart FS LoH = SV is proportional to EDV Ventricular Function Curve Does not depend on hormones or nerves Assures that the heart adjusts its output based on VENOUS RETURN Ways to enhance Venous Return: 1) muscle contractions 2) “respiratory pump” 3) venoconstriction S 3 ↑VR→ ↑EDV → ↑SV

Fig Low EDV High EDV Length-tension “curve” for Cardiac muscle Overinflation of ventricles leads to less effective pumping S 4

Overinflation of ventricles results in reduction in stroke volume S 5 Treatments? …..diuretics

Contractility NE from Symp postganglionics & EPI from Adrenal medulla acting via B-adrenergic receptors on cardiac myofibers. Note: cardiac myofibers NOT innervated by parasympathetic division Increase Ejection Fraction S 6

3 Effects of Sympathetic Stimulation 1: Increase rate of contraction 2: Increase peak tension 3: Decrease twitch duration S 7 Why should the contraction be shorter?

Afterload is analogous to trying to pump more air into a tire that is already fully inflated (heart contracting to overcome diastolic pressure.) High blood pressure increases the workload of the heart….. Cardiac hypertrophy….increase chance of irregular conduction of AP through heart S 9 Hypertrophic cardiomyopathy

Summary: Control of Stroke Volume End diastolic volume (preload) Contractility (strength of ventricular contraction due to adrenergic stimulation) Pressure in arteries that must be overcome = Afterload FS LoH S 8

CO = HR x SV 5L/min = 72 beat/min x 70 ml/beat 35 L/min = ? beat/min x ? ml/beat S 11 Factors that control Cardiac Output by changing heart rate and stroke volume. + sympathetic - parasympathetic EDV (FSLoH) contractility Afterload (MAP)

Fig Even persons with heart transplants can adjust CO in the absence of innervation of heart. Summary of Factors that Regulate Cardiac Output S 12

S 13 Heart is pump that generates pressure gradient. Blood flows through vessels, which have resistance. Arterioles have greatest resistance and create “backpressure” in the arteries and aorta. Mean Arterial Pressure = diastolic +1/3(systolic – diastolic) = /3(120-70) = = 87 mm Hg