Kardiovaskuler Small Class

7/31/2019 Kardiovaskuler Small Class

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THE

SYSTEM

Dr.Ngakan Made Rai Widjaja,drh.,MS

Department of Basic Veterinary Science

Faculty of Veterinary Medicine

Airlangga University

Basic Design and FunctionOf the Cardiovascular

System

The cardiovascular system

consists of the heart and

through which blood flow


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When the erythrocyte ispumpe ou o e e s e

of the heart, it enters the

aorta and passes into the

systemic circulation

The systemic circulationis

a subdivision of the cardiovascular

system consisting of all vessels

associated with all organs

(other than the parts of the lungs

where exchange of gases: O2 & CO2)

takes place.


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When blood returns from the

systemic circulation, it enters

the right side of the heart.

The right side of the heart

pumps oo n o e

pulmonary circulation.

The pulmonary circulation

consists of vessels associated

with the parts of the lungs

takes place.


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From the pulmonary

circulation, blood reenters

the heart on the left side,

and from here it is pumped

out into the systemic

circulation to begin the

loop again.

If the right side of the heart

cannot pump an adequate

amount of blood into the

pulmonary circulation, the left

side of the heart will not receiveenough blood to maintain flow

into the systemic circulation.


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Figure 1: General design of cardiovascular system illustrating the systemic

and pulmonary circulations. Pulmonary circulation is shown in

black. (Reprinted with permission from Reece W.O. Physiology of

Domestic Animals. 2nd ed. Baltimore: Williams & Wilkins, 1997).

Blood flows through the

system because of a driving

force enerated b the contraction of the heart.


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Blood

flow from a point

of

high mean pressure

o

a point of low mean pressure.

In the systemic circulation,

mean blood pressure is

the capillaries and higher in

the capillaries than in the

veins from which bloodreenters the right side of the

heart.


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The driving force of blood

pressure

is necessary to overcome

the vascular resistanceprovided

y e oo vesse s.

The resistance(R) to flow through a

single tube depends on the length

(L) of the tube, the radius(r ) of the

tube, and the character of fluid

ow ng roug e u e

(viscosity,).


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The vessels on the arterial side

the capillaries is an arteriole

have the greatest combined

resistance.

Branching of vessels tends tolower resistance, and the

capillaries in their networks is

responsible for a relatively low

of the small diameter of an

individual capillary).


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Transports

is

the ultimate function

of

the cardiovascular system.

Blood is the transport medium;

the heart provides the force for

movin blood i.e., um

function) around the circulation;

and vessels provide a path for

the movement and permit

interstitial fluids (at the level of

the capillaries).


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The rate

of transport and exchange

is usually determined

by the rate of blood flow

.

Cardiac Cycle

The cardiac cycleis one

complete of cardiac

contraction and relaxation(heartbeat).


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Diastole (dilation, from Gr.

dia,apart; stello, place or put)

refers to the relaxation of a

chamber of the heart just prior

o an ur ng e ng o a

chamber.

Systole (contraction, from Gr.

syn,together; stello, place)

refers to the contraction of a

chamber of the heart that

r ves oo ou o e

chamber.


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Figure 2: Timing of various

events of the

cardiac cycle.

(Reprinted with

permission from

porth C M.

Pathophysiology.5th ed Philadelphia

& Wilkins, 1998)

Two distinc heart sounds

can be heard during each

cardiac cycle in all domestic

species, and these are

typically described as lub(first sound, or S1) and dub

(second sound, or S2).


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These sounds (S1 & S2)

to divide the cardiac cycle

into

The first sound

marks

the beginning of systole,

and the second sound

marksthe beginning of diastole.


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Systole

As the ventricles begin their,

increases in them.

Almost immediately thepressure within each ventricleexcee s t e pressure

differences force the A-Vvalves closed.

The first heart sound(S1)

closure

of

e r g t an e

A-V valves


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The isovolumetric contraction

eriod is the eriod of s stole

during which all valves are

closed (during it the volume of

each ventricle remains

constant).

When ventricular pressures

exceed those in their

respective arterial vessels, the

semilunar valves open to

ejection phaseof systole).


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When the blood pressure in

the aorta and pulmonary

vessels are greater than the

pressure in their associated

ventricles, the pressure

differences close the

semilunar valves.

Closure of the aortic and

pulmonary valves isassociated with the second

heart sound(S2).

S2 is used to mark the endof systole and thebeginning of diastole.


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While the A-V valves are closed

during systole and early diastole,

blood continues to flow into the

right and left atria from the

circulation, respectively.

The accumulation of blood withinthe atria increases atrial blood

pressure.

When the A-V valves open, much

of the accumulated blood flows

rapidly into ventricles.

Most ventricular filling occurs

during this periode prior to any

atrial contraction.


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Blood continues to flow into the

atria throughout diastole, and-

open, blood flows directly

through the atria into the

ventricles.

So slow heart rates provide a

long period for ventricular filling.

Atrial contraction (atrialsystole) occurs during

ventricular diastole forcin

an additional volume of

blood into the ventricles,

but this amount is relatively

sma per aps

compared to the volume

already in the ventricles.


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The end-diastolic volume(EDV)

the volume of blood

in each ventricle

at the end of diastole

During systole each ventricle

EDV, typically 40-60%.

The percentage of EDV that isejected is the ejection fraction.


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Heart Sounds and Murmurs

Third and fourth heart sounds may beheard in some normal horses and

cattle with relatively slow heart rate.

The third sound is associated with the

rapid ventricular filling phase after the

n a open ng o e - va ves.

The fourth sound is associated withatrial contractions.

Heart murmur

is

a general term

for

any abnormal

heart sound.


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Murmurs may occur when a valve

fails to close completely (valvularinsufficiency) and blood flow goesin the wrong direction at the wrong

time.

Murmurs may also occur when a

valve fails to o en com letel

(valvular stenosis) and blood is

forced through a smaller thannormal opening.

Electrical Activity of theHeart

In the heart, the initial action potential

occurs spontaneously in a specialized

group of myocardial cells found in the

sinoatrial (SA) node of the heart, from

which the action otential ispropagated around the heart to bring

about contraction of all cardiac

muscle cells.


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Sinoatrial Node and Heart Rate

A unique feature of the electricalactivit of SA node cells is that the

resting membrane potential is

unstable.

This instability permits SA node

ce s o epo ar ze spon aneous y o

threshold, where an action potentialis generated.

The SA node is termed the

pacemakerof the heart because each

develops in the SA node is

propagated around the heart to

myocardial cells and produce a

contraction.


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During light exercise or with

excitement, the parasymphateticinhibition is reduced first to ermits an

increase in heart rate.

With greater excitement or more

stimulation increase, further

increasing heart rate.

Highly trained athletic

animals, such as racing

thoroughbreds, have

relatively high levels of

parasymp a e c s mu a on

to their hearts at rest.


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Atrioventricular Node and OtherSpecialized Conductive Cells in theHeart

The atrioventricular node (A-V

node) and the common bundle, or

bundle of His, are also m ocardial

cells specialized for conducting

action potentials.

The A-V node is in theintraatrial septum, and the

u x

from the A-V node into the

ventricle through thefibrous connective tissue of

the cardiac skeleton.


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The common bundle divides

into several branches that

potentials throughout the

ventricle.

make up these branches are

the Purkinje fibers.

Figure 3. Impulse generation and conduction system of the

mammalian heart


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Cells of the A-V node are specialized

to conduct action potentials more

slowly than other myocardial cells.

This characteristic allow enough

time for the atria to depolarize

completely and contract before

ventricles to stimulate their

contraction.

The slow conduction

through the A-V node

is

.


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Electrocardiography andArrhythmias

Electrocardiography is the recording ofelectrical activit on the surface of the

body that reflects the electrical activity in

the heart.

The lead is a specific combination ofsites where the recording electrodes are

placed on the body.

An electrocardiogram is the actualrecording.


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The P wave is associated with atrialdepolarization.

ventricular depolarization.

The T wave is associated withventricular repolarization.

The period between the P and Q

waves is associated with A-V nodedelay.

Arrhythmiais a general term

for an abnormalit

in cardiac electrical activity,

including

rate, rhythm,

an e propaga on o

action potentials

around the heart.


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