Cardiovascular physiology Flashcards
what are the actions of the heart?
-chronotropic action
-inotropic action
-dromotropic action
-bathmotropic action
what is the chronotropic action
The frequency of the heart beat/ heart rate.
TACHYCARDIA: increase in heart rate
BRADYCARDIA: decrease in heart rate
what is inotropic action
the force of contraction of the heart.
POSITIVE INOTROPIC ACTION: increase in force of contraction
NEGATIVE INOTROPIC ACTION: decrease in force of contraction
what is dromotropic action
The conduction of impulses through the heart.
POSITIVE DROMOTROPIC ACTION: increase in velocity of contraction
NEGATIVE DROMOTROPIC ACTION: decrease in the velocity of contraction
what is bathmotropic action
The excitability of cardiac muscle
POSITIVE BATHMOTROPIC ACTION: increase in cardiac muscle excitability
NEGATIVE BATHMOTROPIC ACTION: decrease in cardiac muscle excitability
what is the cardiac cycle
The cardiac cycle a succession of coordinated events taking place in the heart during each heart beat. These events are classified into 2:
-SYSTOLE
-DIASTOLE
During systole, heart contracts and pumps the blood through arteries.
During diastole, heart relaxes and blood is filled in the heart. All these changes are repeated during every heartbeat, in a cyclic manner.
The heart beats 72 times a minute and the cardiac cycle duration is 0.8 SECONDS
what are the atrial event durations in the cardiac cycle
- Atrial systole = 0.1 sec
- Atrial diastole = 0.7 sec.
what are the ventricular event durations in the cardiac cycle
- Ventricular systole = 0.3 sec
- Ventricular diastole = 0.5 sec
draw that diagram to show the cardiac cycle
check the booklet
what are the events of the cardiac cycle
=> Artrial events
-Atrial systole
-Atrial diastole
=>Ventricular events
VENTRICULAR SYSTOLE (0.3s)
-Isovolumetric contraction phase
-Rapid ejection phase
-Slow ejection phase
VENTRICULAR DIASTOLE (0.5s)
-Protodiastole
-isovolumetric relaxation phase
-rapid passive filling phase
-reduced filling phase (diastasis)
-Last rapid filling phase
describe the atrial systole
-Atrial systole or the atrial contraction phase lasts for 0.1 s
-It coincides with the last rapid filling phase of ventricular diastole
- Before the beginning of atrial systole, the ventricles are relaxing, AV
valves are open and blood is flowing from the great veins into the atria
and from the atria into the ventricles. Thus the atria and ventricles are
forming a continuous cavity. - When the atrial contraction begins, about 75% of the blood has already
flown into the ventricles. Thus, atrial contraction usually causes an
additional 25% filling of the ventricles.
-Therefore, even if the atria fail to function, there is little disturbance to the cardiac cycle.
describe the atrial diastole
-After the atrial systole, there occurs atrial diastole (0.7 s).
-This period coincides with the ventricular systole (for 0.3s) and most of the ventricular diastole (for 0.4s)
- During atrial diastole, atrial muscles relax and there occurs gradual
filling of the atria due to continuous venous return and the pressure
gradually increases in the atria and drops down to almost zero with
the opening of AV valves.
-Then the pressure again rises and follows the ventricular pressure during the rest of atrial diastole.
describe the atrial diastole
-After the atrial systole, there occurs atrial diastole (0.7 s).
-This period coincides with the ventricular systole (for 0.3s) and most of the ventricular diastole (for 0.4s)
- During atrial diastole, atrial muscles relax and there occurs gradual
filling of the atria due to continuous venous return and the pressure
gradually increases in the atria and drops down to almost zero with
the opening of AV valves.
-Then the pressure again rises and follows the ventricular pressure during the rest of atrial diastole.
what are the phases of the v
what are the phases of the ventricular systole
=>Isovolumetric contraction phase (0.05s)
=>Ejection phase (0.25s)
-Rapid ejection phase (0.1s)
-slow ejection phase (0.15s)
comment on the isovolumetric contraction phase
- lasts for 0.05s
- With the beginning of ventricular contraction, the ventricular pressure
exceeds atrial pressure very rapidly causing closure of AV valves (this
event is responsible for production of first heart sound). - Since the AV valves have closed and semilunar valves have not opened, the ventricles contract as a closed chamber and the pressure inside the ventricles rises rapidly to a high level.
- As the ventricles contract, the volume of blood in the ventricles does
not change; hence this phase is called isovolumic contraction phase. - During this phase, due to sharp rise in ventricular pressure, there
occurs bulging of AV valves into the atria producing a small but sharp
rise in intra-atrial pressure called c-wave. - This phase lasts for 0.05 s, until the pressure in the left and right
ventricles exceeds the pressure in the aorta (80 mmHg) and pulmonary
artery (10 mmHg) and the aortic and pulmonary valves open.
comment on the isovolumetric contraction phase
- lasts for 0.05s
- With the beginning of ventricular contraction, the ventricular pressure
exceeds atrial pressure very rapidly causing closure of AV valves (this
event is responsible for production of first heart sound). - Since the AV valves have closed and semilunar valves have not opened, the ventricles contract as a closed chamber and the pressure inside the ventricles rises rapidly to a high level.
- As the ventricles contract, the volume of blood in the ventricles does
not change; hence this phase is called isovolumic contraction phase. - During this phase, due to sharp rise in ventricular pressure, there
occurs bulging of AV valves into the atria producing a small but sharp
rise in intra-atrial pressure called c-wave. - This phase lasts for 0.05 s, until the pressure in the left and right
ventricles exceeds the pressure in the aorta (80 mmHg) and pulmonary
artery (10 mmHg) and the aortic and pulmonary valves open.
comment on the rapid ejection phase
-Lasts for 0.1s
-As soon as the semilunar valves open, the blood is rapidly ejected out for
about 0.13s.
-About 2/3rds of the stroke volume is ejected in this rapid ejection phase.
-Pressure rises to 120 mmHg in the left ventricle and to 25mmHg in the right ventricle.
-The right ventricular ejection begins before that of left and continued even after left ventricular ejection is complete.
-As both the ventricles almost eject the same volume of blood, the velocity
of right ventricular ejection is less than that of the left ventricle.
comment on the slow ejection phase
-It lasts for 0.15s
-It refers to when rate of ejection declines.
-About 1/3rd of the stroke volume is ejected during this phase.
-The intraventricular pressure starts declining and falls to a value slightly lower than in aorta, but for a short period momentum keeps the blood flowing forward
comment on the slow ejection phase
-It lasts for 0.15s
-It refers to when rate of ejection declines.
-About 1/3rd of the stroke volume is ejected during this phase.
-The intraventricular pressure starts declining and falls to a value slightly lower than in aorta, but for a short period momentum keeps the blood flowing forward
comment on the slow ejection phase
-It lasts for 0.15s
-It refers to when rate of ejection declines.
-About 1/3rd of the stroke volume is ejected during this phase.
-The intraventricular pressure starts declining and falls to a value slightly lower than in aorta, but for a short period momentum keeps the blood flowing forward
comment on the slow ejection phase
-It lasts for 0.15s
-It refers to when rate of ejection declines.
-About 1/3rd of the stroke volume is ejected during this phase.
-The intraventricular pressure starts declining and falls to a value slightly lower than in aorta, but for a short period momentum keeps the blood flowing forward
what are the phases of the ventricular diastole
- Protodiastole (0.04 s),
- Isovolumic (isometric) relaxation phase (0.06 s),
- Rapid passive filling phase (0.11 s),
- Reduced filling phase or diastasis (0.19 s) and
- Last rapid filling phase which coincides with the
atrial systole (0.1 s).
comment on the protodiastole
-It lasts for 0.04s
-When the ventricular systole ends, the ventricles start relaxing and
intraventricular pressure falls rapidly.
-This phase lasts for 0.04 s.
-During this phase, the elevated pressure in the distended arteries (aorta and pulmonary artery) immediately pushes the blood back towards
ventricles which snaps the semilunar valves to close.
-Closure of semilunar (i.e. aortic and pulmonary) valves prevents the movement of blood back into the ventricles and produces the second heart sound (S2).
comment on the isovolumic (isometric) contraction phase
-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
comment on the rapid filling phase
-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.
comment on the reduced filling phase (diastasis)
-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.
comment on the last rapid filling phase
-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.
comment on ejection fraction
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%.
what is the significance of determining ejection fraction
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
what is end systolic volume
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.
what is end diastolic volume
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.
what devices can be used to measure ventricular volume
-Henderson Calorimeter
-Angiograph
what are Heart sounds
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.
what is used to listen to the heart sounds
- Auscultation with stethoscope. The first and second heart sound can be
heard normally with the help of stethoscope. - By using microphone, the amplified heart sounds (first, second and
third) can be heard using a loudspeaker. - 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.
comment on the first heart sound
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.
COMMENT on the second heart sound
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
Comment on the 3rd heart sound
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.
COMment on the 4th heart sound
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
comment on some abnormal heart sounds
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
what is a 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 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.
what are the types of cardiac murmurs
- Systolic murmur, which is produced during systole,
- Diastolic murmur, which is produced during diastole and
- Continuous murmur, which is produced continuously.
Comment on systolic murmur
Systolic murmur is produced during the systole, It includes the following:
- 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
- Stenosis of semilunar valves: Stenosis means narrowing of heart valve. Blood flows rapidly with turbulence through the narrow orifice of the
- Anemia: systolic murmur is heard in severe anemia because of reduced viscosity and accelerated flow of blood.
- Septal defect: Due to interventricular septal defect, blood flows from
left ventricle to right ventricle during systole - Coarctation of aorta: congenital narrowing of systemic aorta
comment on diastolic murmur
This is a cardiac murmur produced during diastole, it include the following:
- 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 - Incompetence of semilunar valves: Murmur is produced during the regurgitation of blood from aorta into the ventricle, through incompetent
semilunar valve during diastole
comment on continous murmur
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.
comment on cardiac output
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
what is cardiac index
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
comment on the distrubution of cardiac output
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
what are physiological factors that affect cardiac output
- 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.
what are the pathological factors that affect cardiac output
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.
what factors maintain cardiac input
*venous return,
*force of contraction,
*peripheral resistance and
*heart rate
comment on venous return as a factor that maintains Cardiac output
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
comment on peripheral resistance as a factor that maintains Cardiac output
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.
comment on heart rate as a factor that maintains Cardiac output
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.
comment on force of contraction as a factor that maintains cardiac output
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
how is cardiac output measured
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.
