Blood Flow and the Control of Blood Pressure 15

Arteriolar Resistance Sympathetic reflexes Local control of arteriolar resistance Hormones

Arteriolar Resistance

Arteriolar Resistance Myogenic autoregulation Paracrines Active hyperemia Reactive hyperemia Sympathetic control SNS: norepinephrine Adrenal medulla: epinephrine

Hyperemia Figure 15-11a

Hyperemia Figure 15-11b

Norepinephrine Tonic control of arteriolar diameter Figure 15-12

Distribution of Blood Distribution of blood in the body at rest Figure 15-13

Blood Flow Blood flow through individual blood vessels is determined by vessel’s resistance to flow Figure 15-14a

Blood Flow Blood flow through individual blood vessels is determined by vessel’s resistance to flow Flow  1/resistance Figure 15-14b

Precapillary Sphincters Figure 15-15a

Precapillary Sphincters Figure 15-15b

Capillaries: Exchange Plasma and cells exchange materials across thin capillary wall Capillary density is related to metabolic activity of cells Capillaries have the thinnest walls Single layer of flattened endothelial cells Supported by basal lamina Bone marrow, liver and spleen do not have typical capillaries but sinusoids

Two Types of Capillaries Figure 15-16a

Two Types of Capillaries Figure 15-16b

Velocity of Blood Flow Velocity of flow depends on total cross-sectional area of the vessels Figure 15-17

Capillary Exchange Exchange by paracellular pathway or transendothelial transport Small dissolved solutes and gasses by diffusion is determined by concentration gradient Large solutes and proteins by vesicular transport In most capillaries, large proteins are transported by transcytosis

Capillary Exchange Bulk flow Mass movement as result of hydrostatic or osmotic pressure gradients Absorption: fluid movement into capillaries Net absorption at venous end Filtration: fluid movement out of capillaries Caused by hydrostatic pressure Net filtration at arterial end

Fluid Exchange at a Capillary Hydrostatic pressure and osmotic pressure regulate bulk flow PLAY Animation: Cardiovascular System: Autoregulation and Capillary Dynamics Figure 15-18a

Lymphatic System Returning fluid and proteins to circulatory system Picking up fat absorbed and transferring it to circulatory system Serving as filter for pathogens

Fluid Exchange at a Capillary Figure 15-18b

Lymphatic System Figure 15-19

Edema Two causes Inadequate drainage of lymph Filtration far greater than absorption Disruption of balance between filtration and absorption Increase in hydrostatic pressure Decrease in plasma protein concentration Increase in interstitial proteins

Blood Pressure Components of the baroreceptor reflex Figure 15-21 KEY Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic Veins Arterioles Ventricles SA node Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY Figure 15-21

Blood Pressure Figure 15-21 (1 of 10) KEY Stimulus Sensor/receptor Change in blood pressure Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY Figure 15-21 (1 of 10)

Blood Pressure Figure 15-21 (2 of 10) KEY Stimulus Sensor/receptor Carotid and aortic baroreceptors Change in blood pressure Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY Figure 15-21 (2 of 10)

Blood Pressure Figure 15-21 (3 of 10) KEY Stimulus Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY Figure 15-21 (3 of 10)

Blood Pressure Figure 15-21 (4 of 10) KEY Stimulus Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY Figure 15-21 (4 of 10)

Blood Pressure Figure 15-21 (5 of 10) KEY Stimulus Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY Figure 15-21 (5 of 10)

Blood Pressure Figure 15-21 (6 of 10) KEY Stimulus Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic SA node Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY Figure 15-21 (6 of 10)

Blood Pressure Figure 15-21 (7 of 10) KEY Stimulus Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic SA node Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY Figure 15-21 (7 of 10)

Blood Pressure Figure 15-21 (8 of 10) KEY Stimulus Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic Ventricles SA node Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY Figure 15-21 (8 of 10)

Blood Pressure Figure 15-21 (9 of 10) KEY Stimulus Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic Arterioles Ventricles SA node Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY Figure 15-21 (9 of 10)

Blood Pressure Figure 15-21 (10 of 10) KEY Stimulus Medullary cardiovascular control center Carotid and aortic baroreceptors Change in blood pressure Parasympathetic neurons Sympathetic Veins Arterioles Ventricles SA node Integrating center Stimulus Efferent pathway Effector Sensor/receptor KEY Figure 15-21 (10 of 10)

Blood Pressure The baroreceptor reflex: the response to increased blood pressure Figure 15-22

Blood Pressure The baroreceptor reflex: the response to orthostatic hypotension PLAY Animation: Cardiovascular System: Blood Pressure Regulation Figure 15-23

CVD: Risk Factors Not controllable Controllable Gender Age Family History Controllable Smoking Obesity Sedentary lifestyle Untreated hypertension

CVD: Risk Factors Uncontrollable genetic but modifiable lifestyle Blood lipids Leads to atherosclerosis HDL-C versus LDL-C Diabetes mellitus Metabolic disorder contributes to development of atherosclerosis

LDL and Plaque The development of atherosclerotic plaques Figure 15-24

Hypertension The relationship between blood pressure and the risk of developing cardiovascular disease Essential hypertension has no clear cause other than hereditary Figure 15-25

Hypertension Carotid and aortic baroreceptors adapt Risk factor for atherosclerosis Heart muscle hypertrophies Pulmonary edema Congestive heart failure Treatment Calcium channel blockers, diuretics, beta-blocking drugs, and ACE inhibitors

Summary Blood vessels Measuring blood pressure Vascular smooth muscle, metarterioles, venules, and angiogenesis Measuring blood pressure Systolic pressure, diastolic pressure, pulse pressure, MAP, and Korotkoff sounds Resistance in the arterioles Myogenic autoregulation, active hyperemia, and reactive hyperemia

Summary Distribution of blood Capillary exchange Lymphatic system Continuous capillaries, fenestrated capillaries, bulk flow, filtration, absorption, and colloid osmotic pressure Lymphatic system Blood pressure regulation Baroreceptors, baroreceptor reflex, and cardiovascular control center Cardiovascular disease