physiology of the heart

2. DEFINITION : -
• THE HEART IS A MUSCULAR ORGAN IN MOST ANIMALS, WHICH PUMPS BLOOD
THROUGH THE BLOOD VESSELS OF THE CIRCULATORY SYSTEM.
• THE PUMPED BLOOD CARRIES OXYGEN AND NUTRIENTS TO THE BODY, WHILE
CARRYING METABOLIC WASTE SUCH AS CARBON DIOXIDE TO THE LUNGS.

3. FUNCTIONS OF THE HEART?
THE CARDIOVASCULAR SYSTEM HAS THREE MAIN FUNCTIONS:
i. TRANSPORT OF OXYGEN, CARBON DIOXIDE AND NUTRIENTS.
ii. CLOTTING OF OPEN WOUNDS.
iii. REGULATION OF BODY TEMPERATURE.

4. LOCATION OF THE HEART : -
• IT LIES IN THE FRONT AND MIDDLE OF YOUR CHEST, BEHIND AND SLIGHTLY TO
THE LEFT OF YOUR BREASTBONE.
• IT IS A MUSCLE THAT PUMPS BLOOD TO ALL PARTS OF YOUR BODY TO PROVIDE IT
WITH THE OXYGEN AND NUTRIENTS IN NEEDS TO FUNCTION.
• YOUR HEART HAS THE RIGHT AND LEFT SEPARATED BY A WALL.

5. PHYSIOLOGICAL FUNCTION OF
THE HEART?
• THE HUMAN HEART IS AN ORGAN THAT PUMPS BLOOD THROUGHOUT THE BODY VIA
THE CIRCULATORY SYSTEM, SUPPLYING OXYGEN AND NUTRIENTS TO THE TISSUES
AND REMOVING CARBON DIOXIDE AND OTHER WASTES.
• PUMPING OXYGENATED BLOOD TO THE OTHER BODY PARTS.
• PUMPING HORMONES AND OTHER VITAL SUBSTANCES TO DIFFERENT PARTS OF
THE BODY.
• RECEIVING DEOXYGENATED BLOOD AND CARRYING METABOLIC WASTE PRODUCTS
FROM THE BODY AND PUMPING IT TO THE LUNGS FOR OXYGENATION.
• MAINTAINING BLOOD PRESSURE.

6. PHYSIOLOGICAL STRUCTURE OF THE HEART : -

7. PARTS OF THE HEART WITH
FUNCTION : -
• SUPERIOR VENA CAVA -RUNNING TOWARDS THE RIGHT ATRIUM OF THE HEART,
RETURNING DEOXYGENATED BLOOD FROM THE BODY. THE SVC IS ONE OF THE 2 LARGE
VEINS BY WHICH BLOOD IS RETURNED FROM THE BODY TO THE RIGHT SIDE OF THE
HEART.
• CORONARY SULCUS -THE ATRIAARE SEPARATED FROM THE VENTRICLES BY THE
CORONARY SULCUS (AURICULOVENTRICULARGROOVE); THIS CONTAINS THE TRUNKS OF
THE NUTRIENT VESSELS OF THE HEART, AND IS DEFICIENT IN FRONT, WHERE IT IS
CROSSED BY THE ROOT OF THE PULMONARY ARTERY.

8. • BRACHIOCEPHALIC TRUNK - ALSO CALLED THE BRACHIOCEPHALIC OR
INNOMINATE ARTERY, IS THE SECOND BRANCH TO ARISE FROM THE AORTA. ...
THE BRACHIOCEPHALIC TRUNK GIVES OFF THE RIGHT SUBCLAVIAN ARTERY,
SUPPLYING THE RIGHT UPPER LIMB; AND THE RIGHT COMMON CAROTID ARTERY,
SUPPLYING THE RIGHT SIDE OF THE BRAIN, HEAD AND NECK.
• LIGAMENTUM ARTERIOSUM - ACTS AS A TETHER THAT HOLDS
THE AORTA AND PULMONARY ARTERY CLOSE TO EACH OTHER.
• PULMUNARY TRUNK - THE PULMONARY TRUNK IS THE MAJOR ARTERIAL TRUNK THAT
CARRIES DEOXYGENATED BLOOD FROM THE RIGHT VENTRICLE TO THE LUNGS.

9. SOUNDS OF THE HEART : -
• THE PULMONARY TRUNK IS THE MAJOR ARTERIAL TRUNK THAT CARRIES
DEOXYGENATED BLOOD FROM THE RIGHT VENTRICLE TO THE LUNGS.
 NORMAL HEART SOUNDS : - IN HEALTHY ADULTS, THERE ARE TWO SOUND ,
OFTEN DESCRIBED AS A LUB (FIRST)AND A DUB (SECOND) THAT OCCUR IN
SEQUENCE WITH EACH HEARTBEAT. THESE ARE THE FIRST HEART SOUND (S1)
AND SECOND HEART SOUND (S2), PRODUCED BY THE CLOSING OF THE
ATRIOVENTRICULAR VALVES AND SEMILUNAR VALVES, RESPECTIVELY.

10. • THIRD HEART SOUND : - RUSHING OF BLOOD INTO VENTRICLES DURING THIS PHASE
CAUSES PRODUCTION OF THIRD HEART SOUND.
• FOURTH HEART SOUND - FOURTH HEART SOUND IS AN INAUDIBLE SOUND. IT
BECOMES AUDIBLE ONLY IN PATHOLOGICAL CONDITIONS. IT IS STUDIED ONLY BY
GRAPHICAL RECORDING, I.E. BY PHONOCARDIOGRAPHY. THIS SOUND IS PRODUCED
DURING ATRIAL SYSTOLE (LATE DIASTOLE) AND IT IS CONSIDERED AS THE PHYSIOLOGIC
ATRIAL SOUND. IT IS ALSO CALLED ATRIAL GALLOP OR PRESYSTOLIC GALLOP.

12. CARDIAC MURMUR: -
• CARDIAC MURMUR IS THE ABNORMAL OR UNUSUAL HEART SOUND. IT IS ALSO
CALLED ABNORMAL HEART SOUND OR CARDIAC BRUIT. CARDIAC MURMUR IS
HEARD BY STETHOSCOPE, ALONG WITH NORMAL HEART SOUNDS.
• CARDIAC MURMUR IS HEARD BY PLACING CHEST PIECE OF STETHOSCOPE OVER
THE AUSCULTATORY AREAS. MURMUR DUE TO DISEASE OF A PARTICULAR VALVE
IS HEARD WELL OVER THE AUSCULTATORY AREA OF THAT VALVE.

13. CLASSIFICATION OF MURMUR: -
• CARDIAC MURMUR IS CLASSIFIED INTO THREE TYPES:
A. SYSTOLIC MURMUR
B. DIASTOLIC MURMUR
C. CONTINUOUS MURMUR

14. • „SYSTOLIC MURMUR SYSTOLIC MURMUR IS THE MURMUR WHICH IS
PRODUCED DURING SYSTOLE. IT IS PRODUCED IN THE FOLLOWING CONDITIONS:
1. INCOMPETENCE OF ATRIOVENTRICULAR VALVES ; WHEN THE
ATRIOVENTRICULAR VALVES BECOME WEAK, THESE VALVES CANNOT CLOSE
COMPLETELY. IT CAUSES REGURGITATION OF BLOOD FROM VENTRICLES TO THE
ATRIA DURING VENTRICULAR SYSTOLE, PRODUCING THE MURMUR. IT IS A HARSH
BLOWING SOUND WITH HIGH FREQUENCY

15. • 2. STENOSIS OF SEMILUNAR VALVES DURING STENOSIS OF AORTIC VALVE, THE LEFT
VENTRICULAR PRESSURE RAISES UP TO 300 MM HG DURING SYSTOLE. IT CAUSES A
GREATER TURBULENCE IN THE BLOOD FLOW. THE VIBRATIONS OF THIS SOUND CAN BE
FELT AS ‘THRILLS’ BY PALPATION OVER LOWER NECK REGION AND UPPER CHEST. IN
SEVERE CONDITIONS, THE SOUND IS HEARD EVEN A FEW FEET AWAY FROM THE AFFECTED
PERSON. IT IS A HARSH AND A LOUD SOUND.
• 3. MURMUR DUE TO ANEMIA A SYSTOLIC MURMUR IS HEARD IN SEVERE ANEMIA
BECAUSE OF REDUCED VISCOSITY AND ACCELERATED FLOW OF BLOOD.
• 4. SEPTAL DEFECT DURING INTERVENTRICULAR SEPTAL DEFECT, BLOOD FLOWS FROM
LEFT VENTRICLE TO RIGHT VENTRICLE DURING SYSTOLE. IT PRODUCES A SYSTOLIC
MURMUR. SEPTAL DEFECT IS A RARE DISORDER.
• 5. COARCTATION OF AORTA COARCTATION OF AORTA IS A CONGENITAL DISORDER,
CHARACTERIZED BY THE NARROWING OF A PART OF SYSTEMIC AORTA. A LOUD MURMUR
IS PRODUCED DURING SYSTOLE AND IT IS HEARD IN THE EARLIER PART OF DIASTOLE
ALSO.

16. • DIASTOLIC MURMUR DIASTOLIC MURMUR IS THE MURMUR THAT IS PRODUCED
DURING DIASTOLE. IT IS PRODUCED IN THE FOLLOWING CONDITIONS:
1. STENOSIS OF ATRIOVENTRICULAR VALVES WHEN THE ATRIOVENTRICULAR VALVES BECOME
NARROW, THE TURBULENCE OF BLOOD FLOW OCCURS DURING DIASTOLE, I.E. WHEN BLOOD ENTERS
THE VENTRICLES FROM ATRIA. MURMUR DUE TO STENOSIS OF MITRAL VALVE IS HEARD BETTER AT
MITRAL AREA. MURMUR DUE TO STENOSIS OF TRICUSPID VALVE IS HEARD BEST AT TRICUSPID AREA. IT
IS A WEAK SOUND WITH LOW FREQUENCY. SOMETIMES, MURMUR DUE TO MITRAL STENOSIS CANNOT BE
HEARD BY STETHOSCOPE, DUE TO LOW FREQUENCY. BUT IT CAN BE FELT AS A MILD THRILL OVER
MITRAL AREA OF THE CHEST.
2. INCOMPETENCE OF SEMILUNAR VALVES MURMUR IS PRODUCED DURING THE REGURGITATION
OF BLOOD FROM AORTA INTO THE VENTRICLE, THROUGH INCOMPETENT SEMILUNAR VALVE DURING
DIASTOLE. IT IS LIKE A BLOWING SOUND WITH LOW FREQUENCY.

17. • CONTINUOUS MURMUR CONTINUOUS MURMUR IS THE MURMUR THAT IS HEARD IN
CONDITIONS SUCH AS PATENT DUCTUS ARTERIOSUS.
1. PATENT DUCTUS ARTERIOSUS INTACT DUCTUS ARTERIOSUS IS CALLED PATENT DUCTUS
ARTERIOSUS (CHAPTER 114). A CONTINUOUS MURMUR IS HEARD IN THIS CONDITION. HOWEVER,
INTENSITY OF THE SOUND IS MORE DURING SYSTOLE AND LESS DURING DIASTOLE. BECAUSE OF THIS, IT
IS ALSO CALLED MACHINERY MURMUR. IT IS A HARSH BLOWING SOUND AND IS HEARD BEST IN THE
PULMONARYAREA. THE MURMUR IS HEARD 1 YEAR AFTER BIRTH.

18. CARDIAC CYCLE
TO BEGIN WITH, ALL THE FOUR CHAMBERS OF HEART ARE IN A RELAXED STATE, I.E., THEY
ARE IN JOINT DIASTOLE. AS THE TRICUSPID AND BICUSPID VALVES ARE OPEN, BLOOD
FROM THE PULMONARY VEINS AND VENA CAVA FLOWS INTO THE LEFT AND THE RIGHT
VENTRICLE RESPECTIVELY THROUGH THE LEFT AND RIGHT ATRIA. THE SEMILUNAR
VALVES ARE CLOSED AT THIS STAGE.
THE SAN NOW GENERATES AN ACTION POTENTIAL WHICH STIMULATES BOTH THE ATRIA
TO UNDERGO A SIMULTANEOUS CONTRACTION – THE ATRIAL SYSTOLE. THIS INCREASES
THE FLOW OF BLOOD INTO THE VENTRICLES BY ABOUT 30 PER CENT. THE ACTION
POTENTIAL IS CONDUCTED TO THE VENTRICULAR SIDE BY THE AVN AND AV BUNDLE
FROM WHERE THE BUNDLE OF HIS TRANSMITS IT THROUGH THE ENTIRE VENTRICULAR
MUSCULATURE.

19. • THIS CAUSES THE VENTRICULAR MUSCLES TO CONTRACT, (VENTRICULAR SYSTOLE), THE ATRIA
UNDERGOES RELAXATION (DIASTOLE), COINCIDING WITH THE VENTRICULAR SYSTOLE
• VENTRICULAR SYSTOLE INCREASES THE VENTRICULAR PRESSURE CAUSING THE CLOSURE OF
TRICUSPID AND BICUSPID VALVES DUE TO ATTEMPTED BACKFLOW OF BLOOD INTO THE ATRIA.
• AS THE VENTRICULAR PRESSURE INCREASES FURTHER, THE SEMILUNAR VALVES GUARDING
THE PULMONARYARTERY (RIGHT SIDE) AND THE AORTA (LEFT SIDE) ARE FORCED OPEN,
ALLOWING THE BLOOD IN THE VENTRICLES TO FLOW THROUGH THESE VESSELS INTO THE
CIRCULATORY PATHWAYS. T
• THE VENTRICLES NOW RELAX (VENTRICULAR DIASTOLE) AND THE VENTRICULAR PRESSURE
FALLS CAUSING THE CLOSURE OF SEMILUNAR VALVES WHICH PREVENTS THE BACKFLOW OF
BLOOD INTO THE VENTRICLES. AS THE VENTRICULAR PRESSURE DECLINES FURTHER, THE
TRICUSPID AND BICUSPID VALVES ARE PUSHED OPEN BY THE PRESSURE IN THE ATRIA EXERTED
BY THE BLOOD WHICH WAS BEING EMPTIED INTO THEM BY THE VEINS. THE BLOOD NOW ONCE
AGAIN MOVES FREELY TO THE VENTRICLES.

20. THE VENTRICLES AND ATRIA ARE NOW AGAIN IN A RELAXED (JOINT DIASTOLE)
STATE, AS EARLIER. SOON THE SAN GENERATES A NEW ACTION POTENTIAL AND THE
EVENTS DESCRIBED ABOVE ARE REPEATED IN THAT SEQUENCE AND THE PROCESS
CONTINUES THIS SEQUENTIAL EVENT IN THE HEART WHICH IS CYCLICALLY
REPEATED IS CALLED THE CARDIAC CYCLE AND IT CONSISTS OF SYSTOLE AND
DIASTOLE OF BOTH THE ATRIA AND VENTRICLES.
AS MENTIONED EARLIER, THE HEART BEATS 72 TIMES PER MINUTE, I.E., THAT MANY
CARDIAC CYCLES ARE PERFORMED PER MINUTE. FROM THIS IT COULD BE DEDUCED
THAT THE DURATION OF A CARDIAC CYCLE IS 0.8 SECONDS.
DURING A CARDIAC CYCLE, EACH VENTRICLE PUMPS OUT APPROXIMATELY 70 ML OF
BLOOD WHICH IS CALLED THE STROKE VOLUME. THE STROKE VOLUME MULTIPLIED
BY THE HEART RATE (NO. OF BEATS PER MIN.) GIVES THE CARDIAC OUTPUT.
THEREFORE, THE CARDIAC OUTPUT CAN BE DEFINED AS THE VOLUME OF BLOOD
PUMPED OUT BY EACH VENTRICLE PER MINUTE AND AVERAGES 5000 ML OR 5 LITRES
IN A HEALTHY INDIVIDUAL.

21. THE BODY HAS THE ABILITY TO ALTER THE STROKE VOLUME AS WELL AS THE
HEART RATE AND THEREBY THE CARDIAC OUTPUT. FOR EXAMPLE, THE CARDIAC
OUTPUT OF AN ATHLETE WILL BE MUCH HIGHER THAN THAT OF AN ORDINARY
MAN.
DURING EACH CARDIAC CYCLE TWO PROMINENT SOUNDS ARE PRODUCED
WHICH CAN BE EASILY HEARD THROUGH A STETHOSCOPE. THE FIRST HEART
SOUND (LUB) IS ASSOCIATED WITH THE CLOSURE OF THE TRICUSPID AND
BICUSPID VALVES WHEREAS THE SECOND HEART SOUND (DUB) IS ASSOCIATED
WITH THE CLOSURE OF THE SEMILUNAR VALVES.
THESE SOUNDS ARE OF CLINICAL DIAGNOSTIC SIGNIFICANCE.

22. DOUBLE CIRCULATION; -
• THE BLOOD FLOWS STRICTLY BY A FIXED ROUTE THROUGH BLOOD VESSELS—
THE ARTERIES AND VEINS.
• BASICALLY, EACH ARTERY AND VEIN CONSISTS OF THREE LAYERS: AN INNER
LINING OF SQUAMOUS ENDOTHELIUM, THE TUNICA INTIMA, A MIDDLE LAYER OF
SMOOTH MUSCLE AND ELASTIC FIBRES, THE TUNICA MEDIA, AND AN EXTERNAL
LAYER OF FIBROUS CONNECTIVE TISSUE WITH COLLAGEN FIBRES, THE TUNICA
EXTERNA. THE TUNICA MEDIA IS COMPARATIVELY THIN IN THE VEINS

25. AS MENTIONED EARLIER, THE BLOOD PUMPED BY THE RIGHT VENTRICLE
ENTERS THE PULMONARY ARTERY, WHEREAS THE LEFT VENTRICLE PUMPS
BLOOD INTO THE AORTA. THE DEOXYGENATED BLOOD PUMPED INTO THE
PULMONARY ARTERY IS PASSED ON TO THE LUNGS FROM WHERE THE
OXYGENATED BLOOD IS CARRIED BY THE PULMONARY VEINS INTO THE LEFT
ATRIUM.
THIS PATHWAY CONSTITUTES THE PULMONARY CIRCULATION.
THE OXYGENATED BLOOD ENTERING THE AORTA IS CARRIED BY A NETWORK OF
ARTERIES, ARTERIOLES AND CAPILLARIES TO THE TISSUES FROM WHERE THE
DEOXYGENATED BLOOD IS COLLECTED BY A SYSTEM OF VENULES, VEINS AND
VENA CAVAAND EMPTIED INTO THE RIGHT ATRIUM. THIS IS THE SYSTEMIC
CIRCULATION

26. • THE SYSTEMIC CIRCULATION PROVIDES NUTRIENTS, O2 AND OTHER ESSENTIAL
SUBSTANCES TO THE TISSUES AND TAKES CO2 AND OTHER HARMFUL
SUBSTANCES AWAY FOR ELIMINATION.

27. THANK YOU