Download - Blood Flow and the Control of Blood Pressure

POWERPOINT® LECTURE SLIDE PRESENTATIONby LYNN CIALDELLA, MA, MBA, The University of Texas at AustinAdditional Text by J Padilla Exclusively for physiology at ECC

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

HUMAN PHYSIOLOGYAN INTEGRATED APPROACH FOURTH EDITION

DEE UNGLAUB SILVERTHORN

UNIT 3UNIT 3

PART A

15 Blood Flow and the Control of Blood Pressure


Overview: Cardiovascular System

Figure 14-1

Arteries take blood away from the heart and veins return it.

Arteries connect to arterioles, that connect to capillaries, that connect to venules, that connect to veins

Two portal systems shown here have two sets of capillaries connected

Arteries take blood away from the heart and veins return it.

Arteries connect to arterioles, that connect to capillaries, that connect to venules, that connect to veins

Two portal systems shown here have two sets of capillaries connected


Functional Model of the Cardiovascular System

Figure 15-1

Systemic Arteries maintain pressure during ventricular relaxation by changing vessel diameter

Arteries and veins are for travel and capillaries for exchange

Systemic Arteries maintain pressure during ventricular relaxation by changing vessel diameter

Arteries and veins are for travel and capillaries for exchange

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-2

Blood Vessel Structure

Blood vessels vary in diameter and wall thickness.

Veins have a larger diameter and thinner walls than arteries.

Capillaries are thin enough to allow for diffusion and narrow to restrict RBC to flow in single file

Blood vessels vary in diameter and wall thickness.

Veins have a larger diameter and thinner walls than arteries.

Capillaries are thin enough to allow for diffusion and narrow to restrict RBC to flow in single file


Metarterioles

Capillaries lack smooth muscle and elastic tissue reinforcement which facilitates exchange

The walls are thin enough to allow WBC and plasma to scape. Plasma that leaves the capillaries and bathes the tissues will be called lymph and will be collected by lymphatic capillaries.

The walls are thin enough to allow WBC and plasma to scape. Plasma that leaves the capillaries and bathes the tissues will be called lymph and will be collected by lymphatic capillaries.

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-15a

Precapillary Sphincters


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


Continous Capillary Fenestrated Capillary

Sinusoidal Capillary

Two Types of CapillariesTwo Types of Capillaries


Angiogenesis

New blood vessel development- after birth, happens to accommodate tissue growth like when one gains weight

Necessary for normal development- growth needed during childhood

Wound healing and uterine lining growth- blood vessel formation needed in adulhood

Controlled by cytokines- chemical signal that induce mitosis Mitogens: VEGF and FGF- vascular endothelial growth factor

and fibroblast growth factor

Inhibit: angiostatin and endostatin- these natural occuring chemicals are being used to treat cancer and coronary disease

Coronary heart disease Collateral circulation- natural formation of additional blood

vessels to supplement flow of blocked vessels


Velocity of Blood Flow

Velocity of flow depends on total cross-sectional area of the vessels. The greater the total cross-sectional area the slower the velocity. Velocity is slowest at the capillaries. Although the diameter of a capillary is smaller than any other vessel its total cross-sectional area is greater than any other.


Review of Blood Flow

Flow is inversely proportional to resistance. Resistance is influenced by vessel diameter. The larger the diameter the slower the speed as long as the flow rate is constant.

Flow is inversely proportional to resistance. Resistance is influenced by vessel diameter. The larger the diameter the slower the speed as long as the flow rate is constant.


Pressure Differences in Static and Flowing Fluids

Pressure falls over distance as energy is lost because of friction. In circulation the further away the blood is from the heart the lower the pressure. Pressure is lower is veins than in arteries


Fluid Flow through a Tube

Flow ∆P

Pressure gradient cause a fluid to flow . Blood vessels create pressure gradients by altering diameter size


The Role of Radius in Determining Resistance to Flow

A small change in diameter can use a great change in resistance and flow. Thus blood vessels can dramatically alter blood flow when they vasoconstrict or vasodialate

A small change in diameter can use a great change in resistance and flow. Thus blood vessels can dramatically alter blood flow when they vasoconstrict or vasodialate


Fluid Rate Versus Velocity of Flow

The velocity of flow is influenced by cross-sectional area. Although a large cross-sectional area may allow more fluid to pass at one time, it also causes it to slow down. Don’t think of cross-sectional area as the diameter of the blood vessel.


Pressure throughout the Systemic CirculationBlood pressure is highest in the arteries and decreases continuously as it flows through the circulatory system.

Systolic pressure is exerted on vessel walls when the heart contracts

Diastolic pressure is pressure during heart relaxation.

Pulse pressure measures strength of pressure wave systolic P – diastolic P

Mean arterial pressure measures driving pressure diastole P + 1/3 pulse pressure.


Elastic Recoil in Arteries

(a) Ventricular contraction

Ventricle contracts.

Aorta and arteries expand and store pressure in elastic walls.

Semilunar valve opens.

Arterioles1

1 2

2

3

3

This process explains how pressure is transferred to blood vessels when the heart contracts

This process explains how pressure is transferred to blood vessels when the heart contracts

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-4b

Elastic Recoil in Arteries

(b) Ventricular relaxation

Isovolumic ventricularrelaxation occurs.

Elastic recoil of arteries sends blood forward into rest of circulatory system.

Semilunar valve shuts, preventing flow back into ventricle.

1

2

3

3

21

This process explains how pressure is maintained in blood vessels while the heart relaxes

This process explains how pressure is maintained in blood vessels while the heart relaxes


Measurement of Arterial Blood PressurePulse Pressure = systolic P – diastolic PValves ensure one-way flow in veinsMAP = diastolic P + 1/3(systolic P – diastolic P)

Pulse Pressure = systolic P – diastolic PValves ensure one-way flow in veinsMAP = diastolic P + 1/3(systolic P – diastolic P)


Pressure Change Pressure created by contracting muscles of the heart and blood

vessels is transferred to blood Driving pressure is created by the ventricle. Thus usually

blood pressure reading focus on left ventricular systole and diastole and arterial pressure not venous pressure.

If blood vessels constrict, blood pressure increases because the diameter decreases and the muscle exerts more pressure on the blood.

If blood vessels dilate, blood pressure decreases because the opposite happens.

Blood volume changes are major factors for blood pressure in CVS. Drinking a lot of fluid increases blood volume, blood loss and dehydration decreases blood volume. The kidneys try to regulate blood volume via fluid loss or retention. The CV system cause changes in diameter to help compensate when posible.


Blood Pressure

Blood pressure control involves both the cardiovascular system and the renal system

Increase or decrease in blood volume is compensated by CV and kidney changes

Increase or decrease in blood volume is compensated by CV and kidney changes


Stroke Volume and Cardiac Output Stroke volume

Amount of blood expelled by one ventricle during a contraction EDV – ESV = stroke volume

Force of contraction Stroke volume increases of decreases based on contraction force Affected by length of muscle fiber and contractility of heart

Frank-Starling law Stroke volume increase as EDV increases

EDV determined by venous return Skeletal muscle pump Respiratory pump Sympathetic innervation

Cardiac output Volume of blood pumped by one ventricle in a given period of time CO = HR SV (heart rate times stroke volume) Average = 5 L/min


Factors that Affect Cardiac Output


Blood Pressure

Mean arterial pressure is a function of cardiac output and resistance in the arterioles= the volume produced by the heart times vessel radius (vasodilation/vasoconstriction)


Arteriolar Resistance (vasoconstriction) Sympathetic reflexes- control blood distribution as needed to maintian

homeostasis such as body temperature Local control of arteriolar resistance- based on metabolism of tissue and tissue

needs for blood flow, can override CNS control in heart and muscle Hormones- those that bind to kidney cells and control salt and water levels. Myogenic autoregulation- increased blood flow causes increase pressure that

stretches the walls. The smooth muscle responds by contracting thus increasing resistance and reducing flow. Therefore, no neural input is needed

Paracrines –secreted by endothelium, allows for local control Active hyperemia- increase blood flow accompanies increased metabolic

activity. As more paracrines accumulate, they call for more blood. Reactive hyperemia- increase blood flow after a state of abnormally low

metabolic rate due local hypoxia. Nitric oxide is made for vasodilation Sympathetic control

SNS: norepinephrine; tonic release maintains myogenic tone, increase release causes vasoconstriction

Adrenal medulla: epinephrine: heart, liver, and skeletal muscle vasodilate


Hyperemia

Figure 15-11a


Norepinephrine

Tonic control of arteriolar diameter


Factors that Influence Mean Arterial Pressure


Blood Pressure

Medullary cardiovascular

control center

Carotid and aorticbaroreceptors

Change in blood

pressure

Integrating center

Stimulus

Efferent pathway

Effector

Sensor/receptor

KEY

Components of the baroreceptor reflexComponents of the baroreceptor reflex

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-21 (5 of 10)

Blood Pressure


control center


Change in blood

pressure

Parasympatheticneurons

Sympatheticneurons

Integrating center

Stimulus

Efferent pathway

Effector

Sensor/receptor

KEY


Blood Pressure


control center


Change in blood

pressure


Sympatheticneurons

Ventricles

SA node

Integrating center

Stimulus

Efferent pathway

Effector

Sensor/receptor

KEY


Blood Pressure


control center


Change in blood

pressure


Sympatheticneurons

Veins

Arterioles

Ventricles

SA node

Integrating center

Stimulus

Efferent pathway

Effector

Sensor/receptor

KEY


Blood Pressure

The baroreceptor reflex: the response to increased blood pressure


Blood Pressure

The baroreceptor reflex: the response to orthostatic hypotension


Distribution of Blood

Distribution of blood in the body at rest


Cardiovascular disease (CVD): Risk Factors Risk factors that are not controllable

Gender Age Family History

Risk factors that are controllable Smoking Obesity Sedentary lifestyle Untreated hypertension

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


Hypertension

Graph shows the relationship between blood pressure and the risk of developing cardiovascular disease

Essential hypertension has no clear cause other than hereditary

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

Download - Blood Flow and the Control of Blood Pressure

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