Cardiovascular System Question And Answers

Question 1. What is cardiac cycle? Describe events occurring during normal cardiac cycle.
Answer:

Cardiac Cycle Definition:

• The sequence of changes in the pressure flow in the heart chambers and blood vessels in between the two subsequent cardiac contractions is known as cardiac cycle

Cardiac Cycle Events:

• In the beginning of each cardiac cycle.
  1. Both atria and ventricles are relaxed.
  2. A-V valves are open.

1. Artial systole:

Artial systole Definition:

• The contraction of atria is called atrial systole.

Artial systole Duration:

• It lasts for 0.1 sec.

Artial systole Features:

• Intra atrial and intraventricular pressure increases.
• It propel approx 30% additional blood into the ventricles.
• Throughout the atrial systole due to pressure gradient the blood flows from the atria into the ventricles.

2. Ventricular systole:

Ventricular systole Defintion:

• The contraction of ventricle is called ventricular systole.

Ventricular systole Duration:

• Total duration – 0.3 sec.
  1. Isovolumetric ventricular contraction – 0.05 sec.
  2. Ventricular systole proper – 0.25 sec.

Read And Learn More: BDS Previous Examination Question And Answers

Ventricular systole Features:

1. Isovolumetric ventricular contraction.
   • Semilunar valves are already closed.
   • Ventricular pressure exceedes atrial pressure.
   • This causes closure of AV valves.
   • The ventricles are now as closed chambers.
   • There is rapid increase in the pressure of ventricles.
   • However, there is no change in the volume of ventricular chambers.
   • Thus, it is called is volumetric ventricular contraction.
   • It causes bulging of A-V valve
2. Ventricular systole proper.
   • Ventricular pressure exceeds the pressure in aorta and pulmonary artery.
   • Semilunar valves are open.
   • It leads to ejection of blood from the ventricles.
   • Ejection of blood occurs in two stages.
     1. Rapid ejection period – 0.1 sec.
        • Intraventricular pressure rises to maximum. due to opening of semilunar valves, a large amount of blood is rapidly ejected from ventricles.
     2. Slow ejection period – 0.015 sec.
        • Ventricular pressure declines
        • This leads to slow ejection of blood with much less force.

3. Ventricular diastole:

Ventricular diastole Definition:

• The relaxation of ventricles is called ventricular diastole.

Ventricular diastole Duration:

• Total duration -0.5 sec.
  1. Protodiastoe – 0.04 sec.
  2. Isometric ventricular relaxation -0.08 sec.
  3. Ventricular diastole proper – 0.28 sec.
  4. Filling phase – 0.1 sec.

Ventricular diastole Features:

1. Protodiastole.
   • Ventricular pressure reduces
   • Pressure in aorta and pulmonary artery increases
   • Valves are closed.
   • Atrial pressure exceeds that of ventricle.
2. Isometric ventricular relaxation.
   • Ventricles are relax.
   • As all valves are closed, ventricles are again closed chambers.
   • Thus as there is no change in volume of ventricle, it is called isometric ventricular relaxation.
3. Ventricular diastole proper.
   • About 70% of ventricular filling occurs during this stage.
   • It includes.
     1. Rapid filling phase.
        • As A-V valves are open, sudden rush of blood from atrium into ventricles occurs.
        • Ventricular pressure remains low.
        • Atrial pressure also falls.
     2. Slow filling called diastasis.
        • It is due to continuous filling of both atrium and ventricles.
     3. Atrial diastole.
        • Definition:
          • The relaxation of atria is called atrial diastole
        • Duration:
          • 0.7 sec.
        • Features:
          • Atrial pressure gradually increases.
          • A-V valves are opened.

Question 2. What are heart sounds? How are they produced? (or) First heart sound. 
Answer:

Heart sounds:

Heart sounds Definition:

• The mechanical activities of the heart during each cardiac cycle produce some sounds, called heart sounds.

Types and their causes:

1. First heart sound:

• It is prominent.
• Resembles the word `LUBB’.
• Can be heard by stethoscope.
• Occurs during isometric ventricular contraction phase and part of ejection period of each cardiac cycle.
• Causes:
• Simultaneously close of A-V vales other factors include.
  • Valvular factors.
    1. Vibration created in the valvular leaflets and chordate tendinae.
  • Vascular factor.
    1. Blood flow into aorta and pulmonary artery during ejection period.
  • Muscular factor.
    1. Tension produced in myocardium and.
    2. Contraction of ventricular muscle.
  • Atrial factor.
    1. Vibrations set up due to atrial systole.
    2. Duration: 0.10-0.17 sec.

2. Second heart sound:

• It is also prominent and heard by stethoscope.
• It resembles the word ‘DUBB’.
• Occurs during protodiastole and part of isometric ventricular relaxation of cardiac cycle.
  Causes:
• Synchronous and sudden closure of semilunar valves.
  Duration:
• 0.10 to 0.14 sec.

3. Third heart sound:

• It is very mild sound.
• Can be heard by microphone and not by stethoscope.
• It occurs during rapid filling phase of cardiac cycle.
  Causes:
• When there is sudden rush of blood into ventricles during rapid filling phase, vibrations are produced in the ventricular wall.
• These vibrations result in third heart sound
  Duration: 0.07, to 0.10 sec.

4. Fourth heart sound:

• It is an audible sound.
• Can be studied by phonocardiogram.
• It occurs during atrial systole.
• During atrial sysole, vibrations are produced in.
  1. Atrial musculature
  2. Flaps of atrioventricular valves.
  3. Some of ventricular myocardium.
• These vibrations results in fourth heart sound.
  Duration: 0.02-0.04 sec

Question 3. Define electrocardiogram. Draw a neat diagram and briefly describe different waves. What is the significance of P-R interval? (or) Draw and label a normal electrocardiogram. What is P-R interval?
Answer:

Electrocardiogram (ECG):

Electrocardiogram Definition:

• It is the graphical registration of the electrical fluctuations of the heart occurring during each cardiac cycle.

Waves: of Normal Electrocardiogram (ECG):

• The waves of normal ECG are represented by letters P, Q, R, S,T and U.

1. ‘P’ wave:
Synonym:

1st wave:

It is positive wave.

Direction and shape:

Directed upwards.

It is rounded or pointed.

Causes:

It is produced due to depolarization of atrial musculature.

Duration: 0.1 sec.

Significance:

Represents the spread of cardiac impulse from SA node to atrial muscle.

Peak – represents invasion of AV node by excitation process.

Height – represents functional activity of atrial muscles.

2. QRS complex:

• Synonym: Initial ventricular complex.
• Q-is small negative deflection.
• Ris prominent, pointed positive wave.
• S-Negative deflection following ‘R’ wave.
  Causes:
• QRS complex – Due to depolarization of mid-portion of the interventricular septum.
• ‘R’ – due to depolarization of apical portion of the inteventricular septum and that of ventricular muscle.
• S’-due to depolarization of more basal portion of ventricular musculature.
• Duration: 0.08 to 0.12 sec.
  Significance:
• If its duration exceeds 0.12 sec, it leads to heart block.

3. T wave:

• It is positive wave.
• It is rounded.
• It is final ventricular complex.
  Causes:
• Repolarization of ventricular musculature.
  Duration: 0.27 Sec.
  Significance:
• End of T wave coincides with the closure of semilunar valves.

4. ‘U’ wave:

• It is rarely seen.
• It is positive small round wave.
  Cause:
• May be due to slow repolarization of papillary muscles.
• Duration: 0.08 sec.
  Significance:
• It is insignificant wave of ECG.

Significance of PR interval:

• PR interval is the interval from the beginning of `P wave to the beginning of Q and R wave.
• It denotes the time interval between completion of atrial depolarization and beginning of ventricular depolarization.
• It signifies the conduction of impulses through AV node.
• It also indicates the duration of conduction of the impulse from the SA node to ventricles.
• Its normal duration is 0.12-0.16 sec.
• Duration decreases with increases in heart rate.
• If duration is more than 0.2 sec. it indicates delayed conduction, and if it is less than 0.12 sec – it indicates that impulse must have arise in AV node.

Question 4. What is cardiac output? Mention factors effecting cardiac output? Add a note on venous return. (or) Enumerate any three factors influencing venous return to the heart. Explain any one of them.
Answer:

Cardiac output:

• Definition:
• The amount of blood pumped out by each ventricle into the circulation per minute is called cardiac output.

Factors effecting cardiac output:

1. Venous return:

Venous return Definition:

• It is the amount of blood, which is returned to the heart from different parts of the body.

Effect on cardiac output:

• When venous return increases, cardiac output also increases.
• But when it decreases and heart rate also decreases then the cardiac output does not decrease.
• Venous return is directly proportional to cardiac output if other factors remains constant.

Factors effecting venous return:

1. Thoracic pump or respiratory pump.
   • During inspiration the following changes occur.
     1. Expansion of thoracic cavity.
     2. Decrease in intra-throacic pressure.
     3. Increase in diameter of inferior vena cava.
     4. This is turn increases venous return.
2. Cardiac pump.
   1. Vis A tergo-A force from behind.
      • It is imparted by the contraction of the heart.
   2. Vis A fronte-force acting from front.
      • It attracts blood in the veins towards the heart.
3. Muscle pump:
   1. On contraction of muscle:
      • Veins in between muscles are squeezed.
      • The valves present proximal to the muscle is opened.
      • This propels the blood towards heart.
   2. On relaxation of muscle.
      • The valves proximal to the muscle is closed.
      • This prevents back flow of blood.
      • When muscular activity increases the venous return also increases.
4. Total blood volume.
   • Increase in blood volume increases venous return.
5. Sympathetic tone.
   • Increase in sympathetic activity causes constriction of venules.
   • This, the turn, increases venous return.
6. Gravity.
   • Gravitational force reduces the venous return.
7. Venous pressure.
   • Pressure in venules is 12-18 mm Hg.
   • Pressure in inferior and superior venacava – 5.5 mmHG
   • At the junction of vena cava and right atrium pressure is 4.6 mm Hg.
   • Pressure in atrium falls to zero during atrial diastoles.
   • This pressure gradient helps in venous return.

2. Force of Contraction:

• The cardiac output is directly proportional to the force of contraction only if other factors remains constant.
• This in turn depends on diastolic period and ventricular filling.

3. Heart rate:

• It is directly proportional to cardiac output if other factors remains constant.
• Marked increase in heart rate, increases cardiac output.
• Marked decrease in heart rate, decreases cardiac output.

4. Peripheral resistance:

• It is the resistance against which the heart has to pump the blood.
• Thus, cardiac output is inversely proportional to peripheral resistance.

Question 5. Define the terms cardiac output and cardiac index. Mention methods for mention the factos measuring cardiac output that influence cardiac output? (or) Explain Fick’s Principle. (or) What is normal cardiac output? How it is determined in man?
Answer:

Definitions:

1. Cardiac Index:

• It is defined as the amount of blood pumped out of ventricle per minute per square meter of the body surface area.

Methods for measuring cardiac output:

1. Direct methods – used in animals.

• By using cardiometer.
• By using flow meter.

2. Indirect methods – used in animals and humans.

• By using Fick’s principle.
• Indicator or dye dilution method.
• Thermodilution technique.
• Ballistocardiography.

Direct fick method:

• According to Fick’s principle, the amount of a substance taken up by an organ (or by the whole body) or given out in a given unit of time is the product of amount of blood flowing through the organ and the arteriovenous difference of the substances across the organ.
• Amount of substance taken or given = Amount of blood flow/min arteriovenous differene.
• This principle can be used to determine cardiac output.
• Cardiac output = \(\frac{Amount of substance taken/given by organ/minute}{Arteriovenous difference of substance across the organ}\)

Dye-dilution method:

• A solution containing 5 mg of dye is injected rapidly into a vein.
• Immediately after the injection, samples of arterial blood are taken serially at intervals of 0.5 – 2 sec.
• Each is analysed for concentration of dye.
• Values are plotted on semi-logarithmic paper with concentration of dye on Y-axis and time on X-axis.
• The resultant curve shows.
  1. Initial increase in concentration of dye till it reaches a peak.
  2. Then steadily declines.
  3. Next, rises again indicating recirculation of the blood containing the dye.

Question 6. What is normal heart rate? Describe variation and regulation of heart rate.
Answer:

Heart rate:

• Normal heart rate in adults in 70-80 beats per minute.

Variations:

1. Physiological variations:

1. Age.
   • After birth, heart rate decreases with age.
   • However, in old age it is high.
2. Sex.
   • Heart rate is slightly higher in females.
3. Surface area.
   • Heart rate is inversely proportional to surface area.
4. Body temperature.
   • For each 1oF rise in body temperature, heart rate increase by about 10 beats per minutes.
5. Emotions.
   • Excitement, fear, anger – increases heart rate.
   • Shock, grief decreases heart rate.
6. Exercise.
   • Heart rate increases with severity of exercise.
7. Respiration.
   • During inspiration, heart rate increases while during expiration, heart rate decreases.
8. Metabolic rate.
   • An increase in metabolic rate, increases heart rate.

2. Pathological variations:

1. Increase in intracranial tension, heart rate decreases.
2. Thyrotoxicosis – increases heart rate.
3. In fever, anaemia, hypoxia – heart rate increases.
4. In jaundice, hypothyroidism- heart rate decreases.

3. Drugs:

• Epinephrine – increases heart rate.
• Nor epinephrine causes reflex brady cardia.

Regulation of heart rate:

• Heart rate is regulated by the nervous mechanism.
• It consists of three components.

1. Vasomotor center:

Situation:

• Bilaterally in the reticular formation of medulla oblongata and lower part of the pons.

Areas:

1. Vasodilator area/depressor area.
   • Forms medial portion of vasomotor center controlled by cerebral cortex and hypothalamus.
   • Functions:
   • Decreases heart rate
   • Decreases BP
   • Decreases stroke volume
   • Decreases venous return.
   • Causes vasodilation.
2. Vasoconstrictor/pressor area.
   • Forms lateral portion of vasomotor center.
   • Controlled by cerebral cortex and hypothalamus.
     Functions:
   • Incraeses heart rate
   • Increases BP.
   • Increases stroke volume.
   • Increases venous return.
3. Sensory areas.
   • Causes vasoconstriction.
   • Forms posterior part of vasomotor center.
   • It receives sensory impulses via. glossopharyngeal and vagus nerve.
     Function:
   • Controls vasoconstrictor and vasodilator area.

2. Motor (Efferent) Nerve Fibres:

3. Sensory (Afferent) nerve fibers:

• These fibers pass through the inferior cervical sympathetic nerve.
  Function:
• Carries pain and stretch sensations from the heart to the brain.

Question 7. What is normal arterial blood pressure and physiologic variations? Describe the role of sinoaortic mechanism in regulation of blood pressure. (or) Role of sino-aortic mechanism in regulation of blood pressure.
Answer:

Arterial blood pressure:

Definition:

• It is defined as lateral pressure exerted by the moving column of blood on the walls of arteries.

Normal value:

• In adult 120 mm Hg (100-130 mm Hg) – systolic BP
• Diastolic BP-80 mm Hg (70-85 mm Hg)

Physiologic variations:

1. Age.
   • Arterial blood pressure, increases with age.
2. Sex.
   • In females, BP is less than males before menopause.
   • BP is more than males after menopause.
3. Body built.
   • BP is directly proportional to surface area.
   • Thus, BP is more in obese persons.
4. Diurnal variation.
   • Peak values are observed during afternoon.
   • In early morning, it is lowest.
   • Gradually increases in afternoon and again reduces in evening.
5. After meals.
   • Due to sympathetic stimulation, BP increases after intake of food.
6. Sleep.
   • Due to low metabolic rate, BP decreases during sleep.
   • However, it increases during sleep associated with dreams.
7. Emotions.
   • Excitement and anger increases blood pressure.
8. Exercise.
   1. After moderate exercise.
      • Systolic pressure increases, no effect on diastolic pressure.
   2. After severe exercise.
      • Systolic pressure increases, diastolic pressure reduces.
9. Posture.
   • When an individual stands up venous return is decreased, leads to reduced cardiac output which in turn diminishes blood pressure.
10. Climate.
    1. Exposure to cold.
       • Produces vasoconstriction.
       • This increases BP.
    2. Exposure to heat.
       • Produces vasodilation.
       • This decreases BP.

Sinoaortic Mechanism:

Action of baroreceptors and chemoreceptors in carotid and aortic region constitute in carotid and aortic region constitute sinoaortic mechanism.

1. Action of baroreceptors:

2. Action of chemoreceptors:

Question 8. Explain the regulation of blood pressure brought about by the baroreceptor mechanism. (or) Baroreceptors.
Answer:

Baroreceptors:

• They are the receptors that give response to change in blood pressure.
• They are sensitive to stretch.
• Also called pressorreceptors.

Situation:

1. In carotid sinus.

2. In aorta in the wall of the arch of aorta.

Nerve supply:

1. Carotid sinus baroreceptors.

• Supplied by hering’s nerve, branch of the glossopharyngeal nerve.

2. Aortic baroreceptors.

• Supplied by aortic branch of vagus nerve.

Mechanism of action:

1. Action of baroreceptors on increase in arterial blood pressure.

2. Action of baroreceptors on decrease in arterial blood pressure.

Question 9. What is systolic, diastolic and pulse pressure? Give an account of factors that maintain blood pressure.
Answer:

Definition:

1. Systolic Blood Pressure:

• It is defined as the maximum pressure exerted in the arteries during systole of the heart.
  Normal value:
• 120 mm Hg.
• It ranges between 100-130 mm Hg.

2. Diastolic blood pressure:

• It is defined as the minimum pressure exerted in the arteries during diastole of the heart.
  Normal value:
• 80 mm Hg
• It ranges between 70 – 85 mm Hg.

3. Pulse pressures:

• It is the difference between the systolic pressure and diastolic pressure.
  Normal values:
  • 40 mm Hg.

Factors maintaining blood pressure:

1. Central factors:

Cardiac output:

Effect on blood pressure:

• Systolic pressure is directly proportional to the cardiac output.
• Thus, increases in cardiac output, increases systolic pressure.
• If increase in cardiac output is due to increase in heart rate, it increases diastolic blood pressure.
• If increase in cardiac output is due to increase in stroke volume, it increases systolic blood pressure.

2. Peripheral factors:

1. Peripheral resistance:

Definition:

• It is the resistance by which blood has to overcome while passing through the periphery.
  Effect on blood pressure:
• The diastolic pressure in directly proportional to peripheral resistance
• It depends on.
  1. Velocity of blood.
     • Peripheral resistance is directly proportional to the velocity of blood.
  2. Viscocity of blood.
     • When the viscosity of blood increases it offers more resistance.
  3. Blood volume,
     • If the blood volume is more, it increases venous return and cardiac output.
     • This increases blood pressure.
  4. Elasticity of the vessel wall.
     • Total peripheraì resistance is inversely proportional to the elasticity of vessel wall.

2. Venous return:

• Blood pressure is directly proportional to venous
• When venous return increases there is increases in ventricular filling and cardiac output.
• This, in turn increasses blood pressure.

Question 10. Define systolic and diastolic blood pressure. Give their normal values. Describe the medullary control of blood pressure.
Answer:

Definitions and their normal values:

Medullary control of blood pressure:

• Medullary control of blood pressure is brought about by vasomotor center.

Vasomotor center:

Location:

• Bilaterally in the reticular formation of medulla oblongata.

Components:

• It consists of

1. Vasoconstrictor area/pressor area:

• Present in anterior part of vasomotor center.

Actions:

• Send impulses to blood vessels through sympathetic fibers.
• Stimulation of this area causes vasoconstriction.
• This causes increases in BP.

2. Vasodilator area/depressor area:

• Present in upper part of medulla.

Actions:

• Suppresses the vasoconstriction area
• This causes vasodilatation.
• Results in decrease in BP.

3. Sensory area:

• Present in the nucleus of tractus solitaries

Actions:

• Receives impulse from the periphery via glossopharyngeal and vagal nerves.
• It controls vasoconstrictor and vasodilator area.

Mechanism of Action:

• Vasomotor center is regulated by following.

1. Baroreceptor mechanism:

• They are receptors that give response to change in blood pressure.

Action on vasomotor center:

• With increase in blood pressure, baroreceptors are stimulated.
• These receptors causes.
  1. Inhibition of vasoconstrictor area.
  2. Stimulation of vasodilator area.

2. Chemoreceptor mechanism:

• Chemoreceptors give response to change in chemical constituents of blood.

3. Higher centers:

• The vasomotor center is controlled by the impulses from the cerebral cortex and hypothalamus.

4. Respiratory centers:

• During beginning of expiration BP increases.
• During later part of expiration and inspiration – BP decreases.

Question 11. Properties of cardiac muscle. (or) Name the specialized conducting tissues of heart.
Answer:

1. Excitability:

Definition:

• The ability of a tissue to give response to a stimulus is called excitability.

Features:

• Excitability is increased by the stimulation of sympathetic or catecholamine activity
• It is inhibited by stimulation of vagus nerve or acetylcholine secretion.

2. Rhythmicity:

Definition:

• Rhythmicity is the ability of a tissue to produce its own impulses regularly.

Features:

• This property is present in all the tissues of the heart.
• The sinoartrial node (SA node) has the highest rhythmicity.
• If the SA node is destroyed, next AV node takes over the function.
• Stimulation of SA node accelerates heart rate.

3. Conductivity:

• This property is highly developed in a specialized conductive system of myocardium.
• It comprises of
  1. AV node.
     • Present in the right posterior portion of intra-atrial septum.
  2. Bundle of his.
     • Arises from AV node.
  3. Right and left bundle branches.
     • They are branches of bundle of his.
  4. Purkinje fibers.
     • They arise from each branch of bundle of His.
     • Thus impulses is conducted and spread all over the ventricular myocardium through this conductive system.

4. Contractibility:

Contractibility Definition:

• It is ability of the tissue to shorten in length after receiving a stimulus.

Properties of contractibility:

1. All or none law:

• According to it, when a stimulus is applied, whatever may be strength, the whole cardiac muscle responds to the maximum or it does not give response at all.

2. Staircase phenomenon:

• The force of contraction increases gradually for the first few contractions and then it remains same.

3. Refractory period:

• It is the period in which the muscle does not show any response to a stimulus.
• It is of two types:
  • Absolute refractory period.
  • Relative refractory period.

Question 12. Explain origin and spread of cardiac impulse.
Answer:

• The conducting system of the heart is responsible for the origin and spread of cardiac impulse.

Origin of impulse:

• Cardiac impulses are generated in the pacemaker which is sino-atrial node i.e., SA Node.
• SA node is situated in right-atrium just below the opening of superior vena cava.

Spread of impulse:

• Impulses is spread from SA node to AV nodes first through internodal pathway.
• This includes.
  • Anterior internodal fibers of bachman.
  • Middle internodal fibers of wenkebach.
  • Posterior internodal fibers of thorel.
• All these fibers from SA node converge on AV node.
• From here, the impulse are spread through conductive system of heart.
• It comprises of
  1. AV node
  2. Bundle of his
  3. Right and left bundle branches
  4. Purkinje fibers.

Question 13. What are heart sounds? How are they produced? Mention their clinical significance.
Answer:

Heart Sounds Significance:

• Heart sounds is of diagnostic value to detect cardiac diseases involving the valves of heart.
• In the valvular lesions and septal defects alteration in the nature of heart sounds occur.
• Splitting of first heart sound occurs due to asynchronous closure and AV valves.
• Splitting of second heart sound occurs due to asynchronous closure of semilunar valves.
• Graphical recording of heart rate provides useful information about the underlying defect.

Question 14. How many heart sounds are heard and how are they positioned in a normal cardiac cycle?
Answer:

Question 15. List the difference between first and second heart sounds.
Answer:

Question 16. Electrocardiograph.
Answer:

• The instrument or the ECG machine by which the electrical activities of the heart are recorded is called electrocardiograph.

Electrocardiographic grid [ECG grid]:

• Electrocardiograph records the electrical signals produced from the heart on a moving strip of paper.
• The markings on this paper is called ECG grid.
• It consists of horizontal and vertical lines at regular intervals of 1 mm.

Lines of ECG Grid:

1. Vertical lines:

• It indicates duration of different waves of ECG.
• Interval between two thin lines (1mm) = 0.04 sec.

2. Horizontal lines:

• It indicates amplitude of ECG waves.
• Interval between two thin lines (5 mm) = 0.5 MV
• Interval between two thin lines (1 mm) = 0.1 MV

Speed of the paper:

• The movement of paper is adjusted in 25 mm/sec and 50 mm/sec.
• Usually, it is 25 mm/sec.
• If heart rate is very high, the speed of the paper is changed to 50 mm/sec.

Question 17. Regulation of cardiac output.
Answer:

Cardiac output is controlled by two main regulatory process:

1. Control of heart rate or extrinsic autoregulation:

• It is governed by vasomotor center located in the medulla.
• Vasomotor center

2. Control of stroke volume or intrinsic autoregulation:

• It is governed by
• Heterometeric regulations
• It is based on Frank Starling’s law.
• It states that the force of contraction of heart is directly proportional to the initial length of muscle fibres before the onset of contraction.

Preload:

• During diastole due to the ventricular filling, the muscle fibers are stretched.
• This increases the length of the fibers.
• This, in turn, increases the end diastolic pressure in the ventricle.
• This is called preload.

Afterload:

• At the end of isometric contraction period, the semilunar valves are opened.
• Blood is ejected into the aorta and pulmonary artery.
• Due to this, pressure in these vessels increases.
• This is called afterload.

Homometric regulation:

• Here myocardial contractibility increases without an increase in initial length of cardiac muscle fibers.

Question 18. Define stroke volume, describe the factors effecting cardiac output.
Answer:

Stroke volume:

Definition:

• The amount of blood pumped out by each ventricle during each beat is called stroke volume.
• Normal stroke volume is 80 ml.

Modified Fick’s Principle:

• It is used to measure cardiac output.

Cardiac output is measured in two ways:

1. Using oxygen consumption:

• Cardiac output is measured by determining the amount of oxygen consumed in thebody in a given period of time and dividing this value by the arteriovenous difference across the lungs.
• Cardiac output = O₂ Consumed ÷ Arteriovenous O₂ difference.

2. Using carbon dioxide:

• Cardiac output is measured by determining arteriovenous difference of carbon dioxide and the amount of carbon dioxide evolved from lungs.

Question 19. Factors effecting heart rate. (or) Draw and label the special conductive tissues of heart.
Answer:

1. Age:

• After birth, as age increases, vagal tone increases and heart rate decreases.
• In old age, heart rate is high due to fall in vagal tone.

2. Sex:

• Heart rate is slightly higher in females.

3. Body temperature:

• Every 1° F rise in body temperature, heart rate increases by about 10 beats/minute.
• Fall in body temperature decreases heart rate.

4. Drugs:

1. Epinephrine:
   • Directly increases heart rate.
2. Nor-epinephrine.
   • By its direct action, increases heart rate.
   • But by its pressor effect, decreases heart rate.

5. Diseases:

1. Increase in intracranial tension.
   • Decreases blood supply to medulla.
   • Stimulates medullary centre which causes decreases in heart rate.
2. Thyrotoxicosis.
   • It is associated with high resting heart rate.
3. Hypoxia.
   • Causes stimulation of chemoreceptors.
   • This in turn increases heart rate.

6. Emotions:

• Excitement, fear, anger – increases heart rate
• Shock, grief-decreases heart rate.

7. Exercise:

• Heart rate increases with severeity of exercise.

8. Painful stimuli:

1. Superifical pain causes activation of sympathetic stimulation.
   • This produces increases in heart rate.
2. Deep pain causes sympathetic inhibition.
   • This produces decrease in heart rate.

9. Respiration:

• Heart rate increases with inspiration.
• It decreases during expiration.

Question 20. Specialised junction tissues of heart.
Answer:

Synonym:

• Conductive tissues.

Junctional tissues of heart:

• It comprises of

1. AV node:

Location:

• Posteriorly on right side of the interatrial septum near the opening of coronary sinus.

Nerve supply:

• It is supplied by left vagus nerve and sympathetic nerve supply.

2. Internodal atrial pathways:

• They arise from SA node and converge on AV node.
• They conduct impulses from SA node to AV node.
• They are arranged as
  1. Anterior internodal fibers of bachman.
  2. Middle internodal fibers of wenckebach.
  3. Posterior internodal fibers of thorel.

3. Bundle of his:

• Arises from AV node.
• Runs upwards to the posterior margin of the membranous interventicular system.
• Then it runs forward below it.

4. Right and left bundle branches:

• They are branches of bundle of His.
  1. Left branch.
     • Divides into anterior and posterior fascicle.
  2. Right branch.
     • Passes down the right side of the septum.

5. Purkinje fibres:

• They arise from branches of bundle of His.
• Penetrate the ventricular wall.
• Transmit impulse at a fast velocity.

Question 21. Define circulatory shock. Describe its various stages.
Answer:

Circulatory Shock Definition:

• It is a clinical syndrome characterized by impairment of adequate tissue perfusion primarily due to low cardiac output or acute circulatory failure.

Circulatory Shock Stages:

• According to Winters, circulatory shock occurs in 4 stages.

1. Circulatory Shock Initial stage:

Circulatory Shock Initial stage Features:

• Slight reduction in the blood volume.

2. Compensatory stage:

Circulatory Shock Compensatory stage Features:

• Further reduction in the blood volume.
• Blood pressure is maintained due to reflex vasoconstriction.
• Blood supply to vital organs is not affected.
• Decrease in blood supply to non-vital organs.

3. Progressive stage:

Circulatory Shock Progressive stage Features:

• Reduction in blood pressure and pulse pressure due to reflex tachycardia and vasoconstriction.
• Decreased in myocardial activity and arteriolar tone.
• Hypotension occurs.

4. Circulatory Shock  Irreversible state:

• Brain fails to function due to servere cerebral ischemia.
• Blood pressure falls.
• Due to decrease in the myocardial activity and arteriolar tone, cardic failure occurs.

Question 22. ECG-its causes and waves.
Answer:

Electrocardiogram (ECG):

• It is the graphical registration of the electrical fluctuations of the heart occurring during each cardiac cycle

ECG Waves:

• The waves of normal ECG are P, Q, R, S, T and U

Question 23. Sino-aortic mechanism
Answer:

• Action of baroreceptos and chemoreceptos in carotid and aortic region constitute sino-aortic reflex.

1. Action of baroreceptor:

2. Action of chemoreceptors:

Question 24. Explain baroreceptor mechanism of regulation of blood pressure.
Answer:

• Baroreceptors are the receptors that give response to change in blood pressure
• They are sensitive to stretch

Action of baroreceptors:

1. Action on increase in arterial blood pressure

• Increase in arterial blood pressure
• Causes stimulation of baroreceptors
• Impulses are send to nucleus of tractus solitarius
• This acts on

1. Vasoconstrictor

• Inhibits it
• Reduces vasomotor tone
• Causes vasodilation

2. Vasodilator area

• Stimulates it
• Increases vasomotor tone
• Causes vasoconstriction

2. Action on decrease in arterial blood pressure

• Decrease in arterial blood pressure
• Causes inhibition of baroreceptors
• This inhibits nucleus of tractus solitarius
• Acts on
• Both normalizes the blood pressure

1. Vasoconstrictor

• Inhibits it
• Reduces vasomotor tone
• Causes vasodilation

2. Vasodilator area

• Stimulates it
• Increases vasomotor tone
• Causes vasoconstriction

Question 25. Short term regulation of blood pressure.
Answer:

• Neural regulation of blood pressure is term as short term regulation.
• It is brought about by vasomotor centers

Vasomotor centers:

Location:

• Bilaterally in the reticular formation of medulla oblongata

Components:

• It consists of

1. Vasoconstrictor area/pressor area

• Present in anterior part of vasomotor center

Actions:

• Send impulses to the blood vessels through sympathetic fiber’s
• Stimulation of this area causes vasoconstriction

2. Vasodilator area / depressor area

• Present in upper part of medulla

Actions:

• Suppresses the vasoconstriction area
• This causes vasodilation
• Results in decrease in arterial blood pressure

3. Sensory area

• Present in the nucleus of tractus solitarius

Actions:

• Receive impulse from the periphery via glossopharyngeal and vagal nerves
• It controls Vasoconstrictor and vasodilator area

Mechanism of action:

• Vasomotor center is regulated by following

1. Baroreceptors mechanism

• They are receptors that give response to change in blood pressure

Action on vasomotor center:

• With increase in blood pressure, baroreceptors are stimulated
• These receptors causes
  • Inhibition of Vasoconstrictor area
  • Stimulation of vasodilator area

2. Chemoreceptors mechanism

• Chemoreceptors give response to change in chemical constituents of blood

3. Higher centers

• The vasomotor center is controlled by the impulses from the
  cerebral cortex and hypothalamus

4. Respiratory centers

• During beginning of expiration blood pressure increases
• During later part of expiration and inspiration blood pressure decreases

Question 26. Pacemaker/Sinoarotic node. (SA node). (or) Name the specialized conducting tissue of heart. (or) Properties of cardiac muscle.
Answer:

Sinoarotic Node Location:

• Sinoarotic node is situated in the right atrium just below the opening of superior vena cava.

Sinoarotic Node Pacemaker:

• It is defined as the part of the heart from which the impulses for heartbeat are produced.
• In mammalian heart, this pacemaker is sinoatrial node.

Sinoarotic Node Dimensions:

• Length – 15 mm
• Width 2 mm
• Thickness – 1 mm

Sinoarotic Node Innervation:

• SA node is supplied by right vagus nerve.
• It receives sympathetic nerve fibers from the cervical sympathetic ganglia via the cardiac nerves.

Question 27. Cardiac cycle.

Answer:

Cardiac cycle Events:

• It consists of
  1. Atrial systole
  2. Ventricular sysole
  3. Atrial diastole
  4. Ventricular diastole.

Question 28. Heart sounds.
Answer:

Heart sounds Types:

1. First heart sound.
2. Second heart sound
3. Third heart sound
4. Fourth heart sound.

Question 29. ECG.
Answer:

Waves of Normal ECG:

• `P’ Wave
• QRS’ Complex
• T Wave
• ‘U’ Wave

Intervals and segments of ECG:

• P-R interval
• QT interval
• S-T segment
• R – R interval

Question 30. Draw a neat diagram of ECG and label it. What is the importance of recording ECG?
Answer:

ECG Importance:

• ECG gives information about the rate, rhythm and conductivity of myocardium.
• It is essential diagnostic aid for.
  1. Any conduction defects
  2. Any arrhythmias.
  3. Detection of myocardial infarction.
  4. Detection of ischaemia.

Question 31. ECG is lead I.
Answer:

• To record ECG, the surface of the body is connected to the ECG machine by means of electrodes called ECG leads.

Lead-I:

• It is obtained by connecting right arm and left arm.
• The right arm is connected to the negative terminal of the instrument.
• The left arm is connected to the positive terminal of the machine.

Question 32. Anaphylactic shock.
Answer:

• It is a rapidly developing severe allergic reaction.
• It occurs when an individual who has previously been sensitive to an antigen is re-exposed to it.

Anaphylactic shock Mechanism:

Occurence of generalized antigen-antibody reactions.
↓
This causes release of large amount of histamine
↓
Vasodilation increases
↓
Leads to increase in capillary permeability.
↓
Causes loss of proteins and water from blood.
↓
Results in shock.

Question 33. Immediate effects of moderate haemorrhage.
Answer:

• During moderate haemorrhage occurs compensatory changes take place and normal condition is restored.
• These change are
  1. Blood pressure decreases slightly and soon it returns back to normal.
  2. Tachycardia.
     • Produces rapid pulse.
  3. Generalised vasoconstriction.
     • This increases the peripheral resistance.
     • Causes reflex venoconstriction.
     • Venoconstriction enhances venous return, ventricular filling and stroke volume.
  4. Stimulation of adrenal medulla.
     • Causes increase in catecholamine release.
  5. Stimulation of respiratory centre.
     • Leads to rapid shallow breathing.
  6. Stimulation of reticular system.
     • Produces restlessness, apprehension.
  7. Renal vasoconstriction results in.
     • Renal ischaemia.

Question 34. Intra atrial pressure cruve.
Answer:

It has three positive waves – a, c & v and three negative waves – x, x₁, & y.

Question 35. Intraventricular pressure curve.
Answer:

It has seven segments:

Question 36. Cardiac murmur.
Answer:

Abnormal heart sounds are called cardiac murmurs:

• They are produced during valvular diseases and septal defects.

Types:

1. Systolic murmur.

• Produced during systole of heart.

2. Diastolic murmur.

• Produced during diastole of heart.

3. Continuous murmur.

• It is produced continuously.

Question 37. ECG leads:
Answer:

• To record ECG, the surface of the body is connected to the ECG machine by means of two electrodes called ECG leads.

Types:

1. Bipolar leads:

• Two limbs are connected to obtain these leads and both the electrodes are active.
• It subtypes are:
  1. Limb lead I
  2. Limb lead II
  3. Limb lead III

2. Unipolar leads:

• In it, one electrode is active and other is an indifferent electrodes.
• It is subtypes are:
  1. Unipolar limb leads.
  2. Unipolar chest leads.

Question 38. Arrhythmia.
Answer:

Arrhythmia refers to disturbance to heart rhythm or irregular heart beat.

Types:

1. Normotopic arrhythmia:

• Here, SA nodes is pacemaker.

Subtypes:

1. Sinus arrhythmia.
   • Increase in heart rate during inspiration and decrease during expiration is called sinus arrhythmia.
2. Sinus tachycardia.
   • Increase in the discharge of impulse from SA node is called sinus tachycardia.
3. Sinus bradycardia.
   • Reduction in the discharge of impulse from SA node is called sinus bradycardia.

2. Ectopic arrhythmia:

• In it, the structure of heart other than SA node is the pacemaker.

Subtypes:

1. Hemotopic arrhythmia in which impulses arise from any part of conductive system.
2. Heterotopic arrhythmia in which impulses arise from musculature of heart.

Question 39. Heart block.
Answer:

• It refers to the blockage of impulses generated by SA nodes.

Types:

1. Sinoatrial block:

• When the impulses from SA node are not transmitted to AV node, it is called sinoatrial block.

2. Atrioventricular block:

• In it impulses are not transmitted from atria to ventricles.

Question 40. Atrial flutter.
Answer:

• It is an atrial arrhythmia associated with atrial paroxysmal tachycardia.
• During atrial flutter, both the atria beat rapidly like the wings of bird.
• The atrial rate is about 250-350/minute.
• Second degree of heart block occurs during atrial flutter.
• The maximum conduction rate by AV node increases to 230-240 impulse/min.

Question 41. Fibrillation.
Answer:

1. Atrial fibrillation:

• In this, the atria shows irregular and rapid beats.
• Rate reaches 300-400 beats/minute.

Cause:

• Due to circus movement of impulses within atrial musculature.

2. Ventricular fibrillation:

• In this, ventricles beat very rapidly and irregularly.
• Rate reaches 400-500 beats/minute.

Cause:

• Circus movement of impulses within ventricular, musculature.

Question 42. Tachycardia and bradycardia.
Answer:

Question 43. Brain-bridge reflex.
Answer:

It is the reflex arising from right atrium that regulates the vagal tone.

Mechanism:

Question 44. Enumerate hormones regulating BP.
Answer:

Question 45. Stroke.
Answer:

Definition:

• It is the condition characterized by reversible or irreversible paralysis due to damage to group in brain caused by lack of oxygen.

Types:

1. Ischaemic stroke:

• It occurs due to interruption of blood flow.

2. Hemorrhagic stroke:

• It occurs due to rupture of a blood vessel.

Question 46. Hemorrhage.
Answer:

Definition:

• Haemorrhage refers to excess loss of blood due to the rupture of blood vessels.

Types:

1. Acute haemorrhage – sudden loss of large amount of blood.

2. Chronic haemorrhage.

• Continuous loss of blood for a long time.

Question 47. Define cardiac output and blood pressure.
Answer:

Cardiac Output:

• The amount of blood pumped out by each ventricle into the circulation per minute is called cardiac output

Blood Pressure:

• It is defined as lateral pressure exerted by the moving column of blood on the walls of arteries

Question 48. Hypertension.
Answer:

Definition:

• It is sustained increase of systemic arterial blood pressure

Types:

1. Primary/ essential hypertension

• It is of unknown cause
• Arterial blood pressure is more than 150/90 mm Hg
• It has two forms
  • Benign
  • Malignant

2. Secondary hypertension

• It is due to some underlying causes
• Causes are
  • Renal hypertension Thyrotoxicosis
  • Pill hypertension
  • Hypertension in pregnancy
  • Tumour of adrenal medulla
  • Adrenal cortex tumour
  • Neurogenic hypertension

Question 49. Define blood pressure and give its normal value.
Answer:

Definition:

• Blood pressure is defined as the lateral pressure exerted by the moving column of blood on the walls of arteries.

Normal value:

• Systolic BP 120 mm Hg (100-130 mm Hg)
• Diastolic BP-80 mm Hg (70-85 mm Hg)

Question 50. Give the causes of first and second heart sounds.
Answer:

Question 51. Structure of cardiac muscle
Answer:

• Cardiac muscle is involuntary, striated muscle
• The fibres are branched and interlock freely with each other
• Each is surrounded by a cell membrane called sarcolemma
• Intercalated discs occurs at the contact of two muscle fibres
• Gap junction is present in the intercalated discs along the sides of the adjacent myocardial cells
• The cardiac muscle fibres are highly vascular
• They are surrounded by a rich capillary network
• Sarcoplasmic reticulum shows plenty of cytoplasm, mitochondria and is rich in glycogen.

Question 52. Marey’s law
Answer:

• According to Marey’s law, the pulse rate is inversely proportional to blood pressure.
• The baroreceptors produce the Marey’s law only during resting conditions.
• During exercise there is an increase in both blood pressure and heart rate.

Question 53. Name any two factors that alter the heart rate
Answer:

Question 54. P-R interval
Answer:

• PR interval is the interval from the beginning of P wave to the beginning of Q and R wave
• It denotes the time interval between the completion of atrial
  depolarisation and beginning of ventricular depolarisation
• It signifies the conduction of impulses through AV node
• It also indicates the duration of conduction of impulses from the SA node to ventricle
• It’s normal duration is 0.12-0.16 sec
• Duration decreases with increase in heart rate
• If duration is more than 0.2 sec it indicates delayed conduction and if it is less than 0.12 sec it indicates that impulse must have arise in AV node

Question 55. Sinoaortic chemoreceptors
Answer:

Action of chemoreceptors:

Question 56. Baroreceptor reflex
Answer:

1. Action on increase in arterial blood pressure

• Increase in arterial blood pressure
• Causes stimulation of baroreceptors
• Impulses are send to nucleus of tractus solitarius
• This acts on
• Both normalizes the blood pressure

2. Action on decrease in arterial blood pressure

• Decrease in arterial blood pressure
• Causes inhibition of baroreceptors
• This inhibits nucleus of tractus solitarius
• Acts on