Cardiovascular physiology Flashcards

Question

comment on the isovolumic (isometric) contraction phase

Answer 1

-It lasts for 0.06s * This phase begins with the closure of semilunar valves and lasts for about 0.06 s. * Since semilunar valves have closed and the AV valves have not yet opened, the ventricles continue to relax as closed chambers in this phase. This causes rapid fall of pressure inside the ventricles (from 80 mmHg to about 2–3 mmHg in left ventricle. * As in this phase, the ventricular volume remains constant, so this phase is called isovolumic or isometric relaxation phase. * This phase ends when the AV valves open

Answer 2

-It lasts for 0.11s * During ventricular systole, the atria are in diastole and venous return continues so that the atrial pressure is high when the AV valves open. * The high atrial pressure causes a rapid, initial flow of blood into the ventricles. * The rapid passive filling phase produces the 3rd heart sound (S3), which is not normally audible in adults but may be heard in children. * Once the AV valves open, the atria and ventricles are a common chamber and pressure in both cavities falls as ventricular relaxation continues.

Answer 3

-It lasts for 0.19s -In this phase, pressure in atria and ventricles reduces slowly and remains little above zero. -This decreases the rate of blood flow from atria to ventricle causing a very slow filling or virtually cessation of ventricular filling called diastasis.

Answer 4

-The last rapid filling phase of ventricular diastole coincides with the atrial systole. -As described in the beginning, the atrial systole brings about the last rapid filling phase and pushes the additional 25% blood in the ventricles. -With this phase, the ventricular cycle is completed.

Answer 5

Ejection fraction refers to the fraction (or portion) of end diastolic volume that is ejected out by each ventricle per beat. From 130 to 150 mL of end diastolic volume, 70 mL is ejected out by each ventricle (stroke volume). Ejection fraction (Ef) is the stroke volume divided by end diastolic volume expressed in percentage. Stroke volume (SV) is, end diastolic volume (EDV) minus endsystolic volume (ESV). Normal ejection fraction is 60% to 65%.

Answer 6

Ejection fraction is the measure of left ventricular function. Clinically, it is considered as an important index for assessing the ventricular contractility. Ejection fraction decreases in myocardial infarction and cardiomyopathy

Answer 7

It is the Amount of blood remaining in ventricles at the end of ejection period (i.e. at the end of systole) is called endsystolic volume. It is 60 to 80 mL per ventricle.

Answer 8

End diastolic volume is the amount of blood remaining in each ventricle at the end of diastole. It is about 130 to 150 mL per ventricle.

Answer 9

-Henderson Calorimeter -Angiograph

Answer 10

Heart sounds are the sounds produced by mechanical activities of heart during each cardiac cycle. Heart sounds are produced by: 1. Flow of blood through cardiac chambers 2. Contraction of cardiac muscle 3. Closure of valves of the heart.

Answer 11

1. Auscultation with stethoscope. The first and second heart sound can be heard normally with the help of stethoscope. 2. By using microphone, the amplified heart sounds (first, second and third) can be heard using a loudspeaker. 3. Phonocardiogram is the graphical record of all the four heart sounds. This is achieved by placing an electronic sound transducer over the chest and connecting it to a recording device like polygraph.

Answer 12

CAUSE First heart sound is produced by vibrations set up by the sudden closure of AV valves at the start of ventricular systole, during phase of isovolumic contraction CHARACTERISTICS. The 1st heart sound is long and soft when heart rate is low, and loud when the heart rate is high. Its duration is about 0.15 s and frequency is 25–45 Hz. It sounds like the spoken word ‘LUBB’. SITE FOR AUSCULTATION It can be heard by auscultation of the chest with stethoscope, microphone and phonocardiograph. It is best heard over mitral and tricuspid areas. CORRELATION WITH ECG 1st heart sound coincides with peak of R wave in ECG.

Answer 13

CAUSE It is caused by vibrations associated with closure of the semilunar valves just at the onset of ventricular diastole. CHARACTERISTICS The second heart sound is a short, loud, high pitched sound. Its duration is 0.12 s and frequency is 50 Hz. It sounds like the spoken word ‘DUBB’. SITE FOR AUSCULTATION It can be heard by auscultation of the chest with stethoscope, microphone and phonocardiograph. It is best heard over the aortic and pulmonary areas. CORRELATION WITH ECG. Second heart sound usually coincides with end of T wave in ECG

Answer 14

CAUSE Third heart sound is caused by vibrations set up in the cardiac wall by the inrush of blood during rapid filling phase of ventricular diastole. CHARACTERISTICS Third heart sound is a short, soft and low pitched sound. Its duration is 0.1 s. Normally, it cannot be heard by auscultation with stethoscope, BUT IT CAN BE heard by phonocardiogram and microphone CORRELATION WITH ECG. The 3rd heart sound appears between T and P waves of ECG.

Answer 15

Cause. It is caused by vibrations set up during atrial systole which coincides with last rapid filling phase of ventricular diastole. Characteristics. It is normally not audible. Sometimes it can be heard immediately before the first sound when atrial pressure is high or when ventricle is stiff in condition such as ventricular hypertrophy. It is a short and low pitched sound. Its duration is about 0.03 s and frequency about 3 Hz. It can be recorded only with the phonogram Correlation with ECG. Fourth heart sound coincides with the interval between the end of P wave and onset of Q wave

Answer 16

ABNORMAL HEART SOUNDS -TRIPLE HEART SOUND (GALLOP RHYTHM): It is characterized by distinctive sounds at each beat, i.e aside the 1st and 2nd heart sounds. This is called Gallop rhythm. It is indicative of myocardial infarction and serious hypertension -QUADRUPLE HEART SOUND: It is characterized by 4 heart sounds. It is seen in myocardial infarction. If there is no 3rd heart sound, the 3rd and 4th sounds may merge, resembling gallop rhythm

Answer 17

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 murmurs are produced by a turbulent blood flow or by change in the direction of blood flow. Normally, the blood flows through the heart and blood vessels as laminar flow which is streamlined and silent. The turbulent flow, on the other hand, produces vibrations in the tissues that are heard as murmurs.

Answer 18

* Systolic murmur, which is produced during systole, * Diastolic murmur, which is produced during diastole and * Continuous murmur, which is produced continuously.

Answer 19

Systolic murmur is produced during the systole, It includes the following: 1. Incompetence of atrioventricular valves (Regurgitation): Incompetence refers to weakening of the heart valve. When the valve becomes weak, it cannot close properly. It causes back flow of blood, resulting in turbulence 2. Stenosis of semilunar valves: Stenosis means narrowing of heart valve. Blood flows rapidly with turbulence through the narrow orifice of the 3. Anemia: systolic murmur is heard in severe anemia because of reduced viscosity and accelerated flow of blood. 4. Septal defect: Due to interventricular septal defect, blood flows from left ventricle to right ventricle during systole 5. Coarctation of aorta: congenital narrowing of systemic aorta

Answer 20

This is a cardiac murmur produced during diastole, it include the following: 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 2. Incompetence of semilunar valves: Murmur is produced during the regurgitation of blood from aorta into the ventricle, through incompetent semilunar valve during diastole

Answer 21

It is a murmur which is produced continuously. it includes: Patent ductus arteriosus (PDA), i.e. a congenital disorder in which there is backward flow of blood from aorta into the pulmonary artery.

Answer 22

cardiac output refers to the amount of blood ejected by each ventricle per minute. The stroke volume is the amount of blood pumped out by each ventricle per beat or per contraction. Therefore, cardiac output (CO) can be calculated by multiplying the stroke volume (SV) by the heart rate (HR). Under normal conditions, the average heart rate is about 70 beats/min and stroke volume is about 80 ml and thus cardiac output is 80 × 70 = 5.6L. The cardiac output is expressed in litres per minute and normally varies from 5–6 L/min

Answer 23

Cardiac index is the cardiac output expressed in relation to the body surface area. The normal cardiac index is about 3.2 l/min/m2

Answer 24

Of the total cardiac output, about 75% is distributed to the vital organs of the body and rest 25% to the skeletal muscle, other organs of the body and skin. The distribution of the cardiac output to various organs of the body is shown in your booklet

Answer 25

* Age. Because of less body surface area, children have less cardiac than adults. * Sex. Since the body surface area is less in females, they have more cardiac index than the males. * Diurnal variation. In the early morning, cardiac output is low which increases in the day time depending upon the basal condition of the individual. * Environmental temperature. Moderate change in environmental temperature does not cause any change in cardiac output. A high environmental temperature is associated with an increase in the cardiac output. * Anxiety and excitement are reported to increase the cardiac output by 50–100%. * Eating is associated with an increase in cardiac output approximately by 30%. * Exercise may increase the cardiac output up to 700% depending upon the vigorousness of exercise. * Pregnancy. An increase in cardiac output to the tune of 45–60% is reported during the later months of the pregnancy. * High altitude. The cardiac output is increased at high altitude due to release of adrenaline as a consequence to hypoxia. * Posture change. Sitting or standing from lying down position may decrease the cardiac output by 20–30% because of pooling of blood in lower limbs.

Answer 26

INCREASE IN CARDIAC OUTPUT IS CAUSED BY: * Fever, due to increased oxidative processes, * Anaemia, due to hypoxia and * Hyperthyroidism, due to increased metabolism. DECREASE IN CARDIAC INPUT IS CAUSED BY: * Rapid arrhythmias, due to incomplete filling, * Congestive cardiac failure, due to weak contractions of heart, * Cardiac shock, due to poor pumping and circulation, * Incomplete heart block, owing to defective pumping action of the heart, * Hemorrhage, because of decreased blood volume and * Hypothyroidism, due to decreased basal metabolism.

Answer 27

*venous return, *force of contraction, *peripheral resistance and *heart rate

Answer 28

Venous return is the amount of blood which is returned to heart from different parts of the body. When it increases, the ventricular filling and cardiac output are increased. Thus, cardiac output is directly proportional to venous return, provided the other factors (force of contraction, heart rate and peripheral resistance) remain constant

Answer 29

Peripheral resistance is the resistance offered to blood flow at the peripheral blood vessels. Peripheral resistance is the resistance or load against which the heart has to pump the blood. So, the cardiac output is inversely proportional to peripheral resistance.

Answer 30

Cardiac output is directly proportional to heart rate provided, the other three factors remain constant. Moderate change in heart rate does not alter the cardiac output. If there is a marked increase in heart rate, cardiac output is increased. If there is marked decrease in heart rate, cardiac output is decreased.

Answer 31

Cardiac output is directly proportional to the force of contraction, provided the other three factors remain constant. According to Frank-Starling law, force of contraction of heart is directly proportional to the initial length of muscle fibers, before the onset of contraction

Answer 32

It is either measured by direct or indirect methods: DIRECT METHOD: Cardiac output, in experimental animals, can be measured directly with the help of an electromagnetic flowmeter placed on the ascending aorta. It is not employed in human, due to the following disadvantages: * It is an invasive technique, so there are risks of infection and haemorrhage. * The cardiac output estimated may be somewhat higher than normal as the patient becomes conscious of the whole technique. * A fatal complication like ventricular fibrillation may occur if the indwelling catheter irritates the ventricular walls, especially when the cardiac output is being measured during heavy exercise. INDIRECT METHODS: * Methods based on Fick’s principle (INDIRECT) * Indicator or dye dilution method, * Thermodilution method, * Method employing inhalation of inert gases and * Physical methods such as: * Doppler technique echocardiography, * Ballistocardiography and * Cineradiographic technique.