Human Anatomy and Physiology Blood pressure and regulation of cardiac output

Blood vessels Arteries, arterioles, capillary bed, venules, veins

Changes in blood pressure

Systemic blood pressure Systolic and diastolic pressure Pulse pressure (declines gradually)

Systemic blood pressure Mean arterial pressure MAP = diastolic + pulse pressure pressure 3 MAP = 70 mm Hg + 50 mm Hg = 87 mm Hg 3

Cardiac output Increasing preload pressure increases heart rate and stroke volume

Calculating Cardiac output Cardiac output (CO) = HR x SV HR = 80 beats/min SV = 0.07l/beat or 70 ml CO = 80 x 70 = 5.6 l/min

Starling’s law The greater the filling of the heart, the greater the amount pumped by the heart

Blood pressure Determined by: cardiac output vascular resistance (total peripheral resistance) blood volume

Short Term Regulation Neural control Hormonal control Venous return

Short Term Regulation Chemical control Stimulus: decline in BP Adrenal medulla :norepinephrine (NE) Increases HR Stimulus: increase in BP Atrial natriuretic peptide (ANP) Decreases blood volume and pressure

Short Term Regulation Vascular resistance Altering blood flow by changing vessel diameter Vasodilation/constriction

Short Term Regulation Vasodilation Blood pumped faster Venous return Muscle pump Respiratory pump 100%

Long Term Regulation Changes in blood volume (kidneys) Renal autoregulation Angiotensin II (renin) Hormones ADH Aldosterone

Blood Pressure Regulation Baroreceptors Nerve endings detect stretch Most important (aortic arch, carotid arteries) Information relayed to the brain