Dr. Jim Stallworth from the University of South Carolina School of Medicine will answer questions and provide information about med school admissions.   The talk will commence at 6:30 in RMSC 122.

Ch 12 Cardiovascular Physiology 3 November 2008 Finish Section B The Heart Begin Section 3 The Vascular System Lab this Week: EKGs and Blood Pressure. Wear shoes and clothes for running. Abstract due Friday.

Frank-Starling Law of the Heart 12.25.jpg Does not depend on hormones or nerves Assure that the heart adjusts its output based on venous return

Fig. 09.21 Length-tension “curve” for Cardiac muscle High EDV Low EDV Overinflation of ventricles leads to less effective pumping 09.21.jpg

Figure 12.25 Contractility

3 Effects of Sympathetic Stimulation 1: Increase rate of contraction 2: Increase peak tension 3: Decrease twitch duration

Control of Stroke Volume End diastolic volume (preload) Contractility (strength of ventricular contraction due to adrenergic stimulation) Afterload (pressure in arteries that must be overcome) FS LoH High blood pressure increases the workload of the heart….. Cardiac hypertrophy….increase chance of irregular conduction of AP through heart

CO = HR x SV 5L/min = 72 beat/min x 70 ml/beat 35L/min =. beat/min x CO = HR x SV 5L/min = 72 beat/min x 70 ml/beat 35L/min = ? beat/min x ? ml/beat

Summary of Factors that Regulate Cardiac Output Fig. 12.28 Even persons with heart transplants can increase CO in the absence of innervation of heart. 12.28.jpg Notice: No Parasymp innervation of Cardiac Muscle

Mean Arterial Pressure = Cardiac Output x Total Peripheral Resistance MAP = CO x TPR

Figure 12.02 CO x TPR = MAP

Properties of Blood Vessels All vessels and heart chambers lined with ENDOTHELIAL cells (simple squamous) Arteries Arterioles Capillaries Venules Veins Elastic, low compliance, large diameter, low resistance vessels Resistance vessels Exchange Wall = simple squamous endothelium Capacitance vessels, high compliance, low pressure, valves for unidirectional flow

Fig. 12.29 Aorta Brachial or Femoral artery Pusatile flow Damage to artery vs vein 12.29.jpg

6 Fig. 12.39b Analogy: river width and flow 12.39b.jpg

Fig. 12.30 Elastic recoil of stretched arterial walls during ventricular systole maintains arterial pressure during diastole as blood drains into arterioles. Atherosclerosis 12.30.jpg Point of Confusion: Smooth muscles in arterial walls DO NOT rhythmically contract!

Arteries and Arterial Pressure Mean Arterial Pressure Arteriole Arterioles have two main functions: 1) regulate flow to tissues and organs and 2) responsible for Total Peripheral Resistance which influences Blood Pressure. MAP = CO x TPR Poiseulle’s Equation

Fig. 12.50 12.50.jpg

Receptors for other ligands Alpha receptors more common except in skeletal muscle arterioles which have more B2 receptors

3 Fig. 12.36 12.36.jpg Metabolic autoregulation, flow autoregulation, myogenic autoregulation