Cardiovascular system. General pattern of blood flow.

Cardiovascular Cardiovascular systemsystem

General pattern of blood General pattern of blood flowflow

HeartHeart Atria- upper chambersAtria- upper chambers

Receive blood returning to the heartReceive blood returning to the heart Ventricles- lower chambersVentricles- lower chambers

Receive blood from the atria and contract to Receive blood from the atria and contract to force blood out of the heart into the arteriesforce blood out of the heart into the arteries

Right ventricle is thinner than the leftRight ventricle is thinner than the left Right pumps short distance to the lungs, little Right pumps short distance to the lungs, little

resistanceresistance Left must force blood to all other parts of the body, high Left must force blood to all other parts of the body, high

resistanceresistance Septum- solid, wall like separation between Septum- solid, wall like separation between

the atrium and the ventricle on the right the atrium and the ventricle on the right with those on the leftwith those on the left Blood never mixes with blood from the other sideBlood never mixes with blood from the other side

valvesvalves Atrioventricular valve-right tricuspid and left Atrioventricular valve-right tricuspid and left

bicuspid ensure one-way blood flow bicuspid ensure one-way blood flow Tricuspid valve- blood flows from right atrium Tricuspid valve- blood flows from right atrium

to right ventricle, prevents back flowto right ventricle, prevents back flow Right ventricle contracts, pressure increases, Right ventricle contracts, pressure increases,

valve closesvalve closes Pulmonary valve- allows blood to leave the Pulmonary valve- allows blood to leave the

right ventricle,prevents back flow right ventricle,prevents back flow Bicuspid valve- blood passes from left atrium Bicuspid valve- blood passes from left atrium

to left ventricle, prevents back flowto left ventricle, prevents back flow Aortic valve-opens when ventricle contracts Aortic valve-opens when ventricle contracts

allows blood to leaveallows blood to leave When closed prevents blood from backing up in When closed prevents blood from backing up in

ventricleventricle

Path of bloodPath of blood Blood low in OBlood low in O2 2 enters right atrium through vena enters right atrium through vena

cavae and coronary sinuscavae and coronary sinus Right atria wall contracts, blood enters right Right atria wall contracts, blood enters right

ventricleventricle Right ventricle wall contracts and blood moves Right ventricle wall contracts and blood moves

into pulmonary trunk and its branchesinto pulmonary trunk and its branches From pulmonary arteries blood enters capillaries From pulmonary arteries blood enters capillaries

associated with lungsassociated with lungs Oxygenated blood returns to heart through Oxygenated blood returns to heart through

pulmonary veins through left atriumpulmonary veins through left atrium Left atrial wall contracts and blood moves into left Left atrial wall contracts and blood moves into left

ventricle, left ventricle contracts blood moves to ventricle, left ventricle contracts blood moves to aortaaorta

trtr

Heart blood supplyHeart blood supply

Coronary arteries supply blood to Coronary arteries supply blood to the heart’s tissue the heart’s tissue

Cardiac veins drain blood that has Cardiac veins drain blood that has passed through the myocardial passed through the myocardial capillaries capillaries

Join coronary sinus on the heart’s Join coronary sinus on the heart’s posterior surface which empties into posterior surface which empties into the right atriumthe right atrium

Cardiac cycleCardiac cycle

When atria relax blood flows into When atria relax blood flows into themthem

Increases pressureIncreases pressure Most of the blood goes directly to Most of the blood goes directly to

ventriclesventricles Atrial systole– atrial contractionAtrial systole– atrial contraction

Forces the rest of the blood into Forces the rest of the blood into ventricles ventricles

Atrial diastole– atrial relaxationAtrial diastole– atrial relaxation

Cardiac conduction Cardiac conduction systemsystem Sinoatrial node (S-A node)-Sinoatrial node (S-A node)-

Can reach threshold on their ownCan reach threshold on their own Spread to surrounding myocardium and stimulates Spread to surrounding myocardium and stimulates

fibers fibers RhythmicRhythmic

Referred to as pacemakerReferred to as pacemaker Left and right contact almost simultaneouslyLeft and right contact almost simultaneously

Atrioventricular node (A-V node)Atrioventricular node (A-V node) Provides normal conductionProvides normal conduction Fibers have small diameters that slows the impulse Fibers have small diameters that slows the impulse Allows more time for atria to empty and ventricle Allows more time for atria to empty and ventricle

fill with bloodfill with blood Muscles are whorls which cause twisting motion when Muscles are whorls which cause twisting motion when

contractcontract

Cardiac conduction Cardiac conduction system system During ventricular contraction A-V valves During ventricular contraction A-V valves

remain closed, atrial pressure increasesremain closed, atrial pressure increases Ventricles relax- vemtricular diastoleVentricles relax- vemtricular diastole A-V valves openA-V valves open Blood flows to ventriclesBlood flows to ventricles Pressure decreases while filling Pressure decreases while filling Atria contracts increasing pressure in ventricleAtria contracts increasing pressure in ventricle When pressure exceeds atrial pressure A-V When pressure exceeds atrial pressure A-V

closescloses Pressure increases until valves of pulmonary Pressure increases until valves of pulmonary

trunk open and blood flows to arteriestrunk open and blood flows to arteries

Electrocardiogram (ECG)Electrocardiogram (ECG) Recording of the electrical changes in the Recording of the electrical changes in the

myocardium during a cardiac cyclemyocardium during a cardiac cycle 11stst change– P wave change– P wave

Depolarization of atrial fibers will lead to Depolarization of atrial fibers will lead to contractioncontraction

Fibers reach ventricular fibers and depolarize Fibers reach ventricular fibers and depolarize rapidlyrapidly

QRS complex– Q wave, R wave, and S waveQRS complex– Q wave, R wave, and S wave Corresponds to depolarization of ventricular fibers Corresponds to depolarization of ventricular fibers

just prior to contraction of ventricular wallsjust prior to contraction of ventricular walls T waveT wave

Electrical change as ventricular muscle fibers Electrical change as ventricular muscle fibers repolarize repolarize

Atrial repolarization is at the same as ventricular Atrial repolarization is at the same as ventricular fibers depolarizefibers depolarize

Arteries and arteriolesArteries and arterioles

ArteryArtery Innermost layer helps prevent blood clotting Innermost layer helps prevent blood clotting

by providing a smooth surface and secreting by providing a smooth surface and secreting biochemicals that inhibit platelet biochemicals that inhibit platelet aggregationaggregation

May also regulate local flow by secreting May also regulate local flow by secreting substances that dilate or constrict blood substances that dilate or constrict blood vesselsvessels

Arteries progressively divide into thinner Arteries progressively divide into thinner tubes and eventually give rise to arteriolestubes and eventually give rise to arterioles Walls thin as they near the capillariesWalls thin as they near the capillaries

Capillaries Capillaries

The smallest diameter of blood vesselsThe smallest diameter of blood vessels Connect the arterioles and venulesConnect the arterioles and venules Extensions of the inner linings of arteriolesExtensions of the inner linings of arterioles Area where exchange of materials occursArea where exchange of materials occurs

Exchange in capillariesExchange in capillaries Gas, nutrients, and metabolic by productsGas, nutrients, and metabolic by products The substances exchanged move through The substances exchanged move through

capillary walls through diffusion, filtration, and capillary walls through diffusion, filtration, and osmosisosmosis

Filtration forces molecules through a membrane with Filtration forces molecules through a membrane with hydrostatic pressurehydrostatic pressure

Capillary exchange cont.Capillary exchange cont.

Blood pressure moves blood through Blood pressure moves blood through arteries and arteriolesarteries and arterioles Pressure decreases as the distance from Pressure decreases as the distance from

the heart increasesthe heart increases Greater in the arteries than arterioles, Greater in the arteries than arterioles,

arterioles greater than capillaries, etc.arterioles greater than capillaries, etc. Filtration effect primarily at arteriolar endFiltration effect primarily at arteriolar end

Veins and Venules Veins and Venules Venules are microscopic vessels that continue Venules are microscopic vessels that continue

from the capillaries and merge to form veinsfrom the capillaries and merge to form veins Veins contain flaplike valves Veins contain flaplike valves

Valves close if blood begins to back yup in a veinValves close if blood begins to back yup in a vein Aid in returning blood to the heart because they Aid in returning blood to the heart because they

open if blood flow is toward the heart and close if it open if blood flow is toward the heart and close if it is in the opposite directionis in the opposite direction

Also function as blood reservoirs Also function as blood reservoirs If a hemorrhage causes a drop in arterial blood pressure, If a hemorrhage causes a drop in arterial blood pressure,

veins are stimulated to constrict and help maintain blood veins are stimulated to constrict and help maintain blood pressure by returning more blood to the heartpressure by returning more blood to the heart

Ensures a nearly normal blood flow even when as much as 25% Ensures a nearly normal blood flow even when as much as 25% is lostis lost

Blood pressure Blood pressure Blood pressure is the force blood exerts Blood pressure is the force blood exerts

against the inner walls of the blood vesselsagainst the inner walls of the blood vessels Arterial pressure rises and falls in a Arterial pressure rises and falls in a

pattern corresponding to the cardiac cyclepattern corresponding to the cardiac cycle The maximum pressure during ventricular The maximum pressure during ventricular

contraction is called the systolic pressurecontraction is called the systolic pressure The lowest pressure that remains in the The lowest pressure that remains in the

arteries until the next venticular arteries until the next venticular contraction is diastolic pressurecontraction is diastolic pressure

The alternating expanding and recoiling of The alternating expanding and recoiling of the artery wall is felt as the pulsethe artery wall is felt as the pulse

Blood pressure factorsBlood pressure factors Heart actionHeart action

Determines how much blood enters the arterial Determines how much blood enters the arterial systemsystem

Stroke volume-the amount of blood that is Stroke volume-the amount of blood that is discharged from the left ventricle with each discharged from the left ventricle with each contractioncontraction

Cardiac output- volume discharged/minuteCardiac output- volume discharged/minute Stroke volume x heart rateStroke volume x heart rate

Blood volumeBlood volume Equals the sum of formed elements and plasma Equals the sum of formed elements and plasma

volumes in vascular systemvolumes in vascular system Varies with age and sex and directly with body sizeVaries with age and sex and directly with body size

Normally directly proportional to blood Normally directly proportional to blood volumevolume

Can fall if fluid balance is upset Can fall if fluid balance is upset

Factors cont.Factors cont. Peripheral resistancePeripheral resistance

Produced from friction between blood and vessel Produced from friction between blood and vessel wallswalls Slows blood flowSlows blood flow

Contraction of smooth muscles in arteriolar Contraction of smooth muscles in arteriolar walls increases pressurewalls increases pressure

Dilation lessens resistance and drops the Dilation lessens resistance and drops the pressure in responsepressure in response

Blood viscosityBlood viscosity The greater the viscosity, the greater the The greater the viscosity, the greater the

resistance resistance Blood cells and plasma proteins increase blood viscosityBlood cells and plasma proteins increase blood viscosity Blood pressure increases as viscosity increases and Blood pressure increases as viscosity increases and

drops as viscosity decreasesdrops as viscosity decreases

Control of blood pressureControl of blood pressure

Two important mechanisms for Two important mechanisms for maintaining normal arterial pressure maintaining normal arterial pressure are:are: Regulation of cardiac outputRegulation of cardiac output Regulation of peripheral resistanceRegulation of peripheral resistance

Cardiac outputCardiac output Volume of blood discharged from the left Volume of blood discharged from the left

ventricle and heart rateventricle and heart rate Starling’s law of the heart--Greater the Starling’s law of the heart--Greater the

length of myocardial fibers the greater the length of myocardial fibers the greater the contractional force contractional force

Baroreceptors sense changes in pressureBaroreceptors sense changes in pressure Increases Increases nerve impulse travels to brain, nerve impulse travels to brain,

heart rate decreasesheart rate decreases Triggers cardioinhibitor reflex—cardiac output Triggers cardioinhibitor reflex—cardiac output

falls and blood pressure moves to normal levelfalls and blood pressure moves to normal level Cardioaccelerator reflex triggered by Cardioaccelerator reflex triggered by

decreasing arterial pressuredecreasing arterial pressure Causes heart to beat faster, increases heart rate, Causes heart to beat faster, increases heart rate,

and pressureand pressure

Peripheral resistancePeripheral resistance

Changes in the arteriole diameters Changes in the arteriole diameters regulate peripheral resistanceregulate peripheral resistance Small diameters offer greater resistance to Small diameters offer greater resistance to

blood flowblood flow Vasomotor center controls impulses sent Vasomotor center controls impulses sent

to arteriole wallsto arteriole walls Certain chemicals also influence Certain chemicals also influence

peripheral resistance by affecting peripheral resistance by affecting precapillary sphincters and smooth precapillary sphincters and smooth muscle in arteriole wallsmuscle in arteriole walls

Venous blood flowVenous blood flow Blood pressure decreases as blood moves Blood pressure decreases as blood moves

through the arterial system and into the through the arterial system and into the capillary networkscapillary networks Depends on skeletal muscle contraction, Depends on skeletal muscle contraction,

breathing movements, and vasoconstriction of breathing movements, and vasoconstriction of veinsveins

Contracting skeletal muscles- thicken and Contracting skeletal muscles- thicken and press on nearby vessels squeezing blood press on nearby vessels squeezing blood insideinside

Respiratory movements- causes pressure Respiratory movements- causes pressure changes in thoracic cavity changes in thoracic cavity Inspiration- pressure decreases in thoracic cavity Inspiration- pressure decreases in thoracic cavity

and rises in abdominal cavity which squeezes and rises in abdominal cavity which squeezes blood out of veinsblood out of veins

Venous blood cont.Venous blood cont.

Vasoconstriction returns venous blood to Vasoconstriction returns venous blood to the heartthe heart Venous pressure is low, sympathetic reflexes Venous pressure is low, sympathetic reflexes

stimulate smooth muscle in veins to contractstimulate smooth muscle in veins to contract veins provide blood reservoir that can veins provide blood reservoir that can

adapt its capacity to changes in blood adapt its capacity to changes in blood volumevolume If blood is lost and blood pressure falls, If blood is lost and blood pressure falls,

venoconstriction can force blood out of venoconstriction can force blood out of reservoirreservoir

Paths of circulationPaths of circulation

Two major pathwaysTwo major pathways Pulmonary circuitPulmonary circuit

Consist of vessels that carry blood from the Consist of vessels that carry blood from the heart to the lungs and back to the heartheart to the lungs and back to the heart

Systemic circuitSystemic circuit Carries blood from the heart to all parts of Carries blood from the heart to all parts of

the body and back againthe body and back again