Circulation. Primary Principle of Circulation The primary fluid flow principle derives from Newton’s first and second laws of motion: A fluid does not.

CirculationCirculation

Primary Principle of Circulation Primary Principle of Circulation

The primary fluid flow principle derives The primary fluid flow principle derives from Newton’s first and second laws of from Newton’s first and second laws of motion:motion: A fluid does not flow when the pressure is the A fluid does not flow when the pressure is the

same in all parts of itsame in all parts of it

A fluid flows only when its pressure is higher A fluid flows only when its pressure is higher in one area than in another, and it flows in one area than in another, and it flows always from its higher pressure area toward always from its higher pressure area toward its lower pressure areaits lower pressure area

Arterial Blood PressureArterial Blood Pressure

High pressure must be maintained in the arteries High pressure must be maintained in the arteries to keep blood flowing through the cardiovascular to keep blood flowing through the cardiovascular system.system.

The chief determinant of arterial blood pressure The chief determinant of arterial blood pressure is the volume of blood in the arteries. is the volume of blood in the arteries.

Arterial blood volume is directly proportional to Arterial blood volume is directly proportional to arterial pressure.arterial pressure. An increase in arterial blood volume causes an An increase in arterial blood volume causes an

increase in arterial pressure.increase in arterial pressure.

Cardiac OutputCardiac Output

Cardiac output (CO) is determined by the Cardiac output (CO) is determined by the volume of blood pumped out of the ventricles volume of blood pumped out of the ventricles by each beat (stroke volume or SV) and by by each beat (stroke volume or SV) and by heart rate (HR)heart rate (HR)

SVSV(volume/beat) x (volume/beat) x HRHR(beat/min) = (beat/min) = COCO(volume/min)(volume/min)

Peripheral ResistancePeripheral Resistance Peripheral resistance is the resistance to blood Peripheral resistance is the resistance to blood

flow caused by friction of blood passing through flow caused by friction of blood passing through blood vessels.blood vessels.

Friction develops because of a characteristic of Friction develops because of a characteristic of blood—its viscosity, or stickiness—and partly blood—its viscosity, or stickiness—and partly from the small diameter of arterioles and from the small diameter of arterioles and cappilaries.cappilaries.

Viscosity stems mainly from the red blood cells, Viscosity stems mainly from the red blood cells, but also from protein molecules present in the but also from protein molecules present in the blood. blood.

Aortic and Aortic and carotid sinus carotid sinus

pressoreflexespressoreflexes

These These pressoreflexes pressoreflexes

operate in a operate in a feedback loop that feedback loop that

maintains the maintains the homeostasis of homeostasis of

blood pressure by blood pressure by decreasing the decreasing the heart rate when heart rate when

the blood pressure the blood pressure surpasses the set surpasses the set

point. point. 

Relative Blood VolumesRelative Blood Volumes

Blood Pressure Control Blood Pressure Control MechanismsMechanisms

There are many factors that control the There are many factors that control the cardiovascular system.cardiovascular system.

An area in the medulla called the vasomotor An area in the medulla called the vasomotor center or vasoconstrictor center, will, when center or vasoconstrictor center, will, when stimulated, initiate an impulse outflow via stimulated, initiate an impulse outflow via sympathetic fibers that ends in the smooth sympathetic fibers that ends in the smooth muscle surrounding resistance vessels, muscle surrounding resistance vessels, arterioles, venules, and veins, causing their arterioles, venules, and veins, causing their constriction. constriction.

Changes in Local Blood Flow Changes in Local Blood Flow During ExerciseDuring Exercise

Venous Return to the HeartVenous Return to the Heart

Venous Pumps – the blood pumping Venous Pumps – the blood pumping action of respirations and skeletal muscle action of respirations and skeletal muscle contractioncontraction

Total Blood Volume – the greater the total Total Blood Volume – the greater the total volume of blood, the greater the volume of volume of blood, the greater the volume of blood returned to the heart. blood returned to the heart.

Venous ReturnVenous Return

Semilunar ValvesSemilunar Valves

A.A. Local blood Local blood pressure pushes pressure pushes flaps openflaps open

B.B. When pressure When pressure below the valve below the valve drops, blood drops, blood flows backwards flows backwards and the valve and the valve closescloses

Capillary Exchange and Total Capillary Exchange and Total Blood Volume Blood Volume

Capillary exchange – the exchange of Capillary exchange – the exchange of materials between plasma in the materials between plasma in the capillaries and the surrounding interstitial capillaries and the surrounding interstitial fluid of the systemic tissues. fluid of the systemic tissues.

Measuring Blood PressureMeasuring Blood Pressure The sphygmomanometer measures the amount The sphygmomanometer measures the amount

of air pressure equal to the blood pressure in an of air pressure equal to the blood pressure in an artery. artery.

The sounds that one hears when taking a blood The sounds that one hears when taking a blood pressure are called Korotkoff sounds. pressure are called Korotkoff sounds.

The first sound indicates the systolic blood The first sound indicates the systolic blood pressure and the last sound is an indication of pressure and the last sound is an indication of the diastolic pressure. the diastolic pressure.

Normal blood pressure is about 120 over 80 Normal blood pressure is about 120 over 80 (120/80)(120/80)

Mechanism of Pulse Mechanism of Pulse Intermittent injections of blood from the heart Intermittent injections of blood from the heart

into the aorta, which alternately increases and into the aorta, which alternately increases and decreases the pressure in that vessel. If blood decreases the pressure in that vessel. If blood steadily poured out of the heart into the aorta, steadily poured out of the heart into the aorta, there would be no pulse. there would be no pulse.

The elasticity of the arterial walls, which allows The elasticity of the arterial walls, which allows them to expand with each injection of blood and them to expand with each injection of blood and then recoil. If the vessels were fashioned from then recoil. If the vessels were fashioned from rigid material, you would not be able to feel a rigid material, you would not be able to feel a pulse even tough there would still be a pressure pulse even tough there would still be a pressure change. change.

Where the Pulse Where the Pulse Can Be FeltCan Be Felt

The pulse can be The pulse can be felt whenever an felt whenever an artery lies near the artery lies near the surface and over a surface and over a bone or other firm bone or other firm background. background.

Hypertension (High Blood Hypertension (High Blood Pressure)Pressure)

Defined as a blood pressure of 140/90 and Defined as a blood pressure of 140/90 and aboveabove

Risk factors include: genetics, sex, race, Risk factors include: genetics, sex, race, age, stress, high alcohol and caffeine age, stress, high alcohol and caffeine intake, obesity, smoking and lack of intake, obesity, smoking and lack of exerciseexercise