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