Viva Cardiovascular Flashcards
What structural characteristics of
cardiac muscle enable its continuous
rhythmic contractions?
These are: Presence of pacemaker cell that
initiates autorhythmicity, presence of special
conductive tissue and presence of free
branchings between the muscle fibres
(syncytium) ensure the quick passage of
impulse from pacemaker cell to all parts of
heart to initiate continuous rhythmic
contractions.
Name the special conducting tissues
of heart.
SA node, AV node, bundle of His and Purkinje fibers (Fig. 15.1
What is cardiac pacemaker?
SA node is called as the cardiac pacemaker
because it is made up of ‘P’cells which can
generate the impulse more rapidly than any
of the pacemaker tissue of heart and
thereby determine the rate at which the
heart beats
What is law of heart muscle?
It states that the size of muscle fibers,
glycogen content and rate of conduction
increases from nodal to Purkinje’s fiber
whereas length of systole, duration of
refractory period and rhythmicity increases
in the reverse direction.
What is intercalated disc and what is
its importance?
At the point of contact of two cardiac muscle
fibers, extensive folding of cell membrane
occurs which is known as intercalated discs.
They provide a strong union between fibers
so that the pull of one contractile unit can be
transmitted to the next, thereby helps in
increasing force of contraction.
What is the role of gap junction in
cardiac muscle?
Gap junction is present in the intercalated
disc of cardiac muscle fibers and helps in
rapid transferring of electrical currents, ions,
etc. from one cell to another without coming
in contact with ECF. Thus they provide low
resistance bridge for the rapid spread out
of electrical impulse, thereby helps the
cardiac muscle to act as syncytium
(functional)
Name the valves and their location
There are 4 valves—two in between the atria
and ventricles known as atrioventricular
valves (A-V valves) and two are at the
opening of the blood vessels arising from
the ventricles (semilunar valves).
• A-V valves: These are present in between
the atria and ventricles. The valve present
in between right atria and right ventricle
is known as Tricuspid valve and the
valve present in between left atria and
left ventricle is known as Bicuspid valve.
• Semilunar valves: There are two semilunar
valves namely Pulmonary valve and
Aortic valve. The pulmonary valve is
present at pulmonary orifice which leads
from RV to pulmonary artery and the
aortic valve is present at aortic orifice
which leads from LV to the aorta
Name the special junctional tissues
and their conduction rate.
The special junctional tissues and their rate of impulse generating capacity are: Special junctional tissues Impulse generating capacity S A Node 75 ± 5 times/min A V Node 60 times/min Bundle of His 40 times/min Purkinje’s fiber 20 times/min
What do you mean by pacemaker
potential or diastolic depolarization?
The pacemaker tissue is characterized by
unstable RMP due to slow depolarization
resulting from leakage of Na+ from outside
to inside through Na
+ leak channels. This
show leakage of Na+ inside the cell causes
increase in electropositively inside the
cell which ultimately enables to induce
another action potential easily. This slow
polarization in between action potential is
known as prepotential or pacemaker
potential or diastolic depolarization.
Why SA node is called as cardiac
pacemaker?
A node acts as a pacemaker of heart
because the rate of impulse generation in
normal heart is determined by this node
because of its highest rate of impulse
generating capacity (75 ± 5 times/min) than
other junctional tissues. This is why it is
known as cardiac pacemaker.
What is ectopic pacemaker?
When the pacemaker is other than SA Node
(e.g. AV node, etc.) it is called as ectopic
pacemaker.
What is the duration of refractory
period in cardiac muscle?
Refractory period is very long in cardiac
muscles. It is about 0.53 seconds. In this, the
absolute refractory period is 0.27 seconds
and relative refractory period is 0.26
seconds
What is the significance of long
refractory period in cardiac muscles?
Due to the long refractory period, the
complete summation of contractions,
fatigue and tetanus do not occur in cardiac
muscle.
What do you mean by nodal and
idioventricular rhythm?
The AV node takes the charge of generating
impulse rhythmically when SA node does
not work. In this condition atria and
ventricles beat almost simultaneously at the
rate of 60 times per min. This rhythm of
heart is known as Nodal rhythm. Whereas
2nd Stannius ligature applied over the A-V
groove makes the atria to continue beating
with it’s own rhythm whereas the ventricle
stops beating due to blockade of impulse
from atria to ventricles. After sometime
ventricle generates it’s own impulse and
starts beating at much slower rate. This
rhythm of heart beat in which atria and
ventricular beating do not follow any specific
pattern is known as idioventricular
rhythm.
What is AV delay? What is its
significance?
When the impulse reaches to AV node, there
is a delay of about 0.1 sec to pass the impulse
to bundle of His. This time gap is known as
AV delay. It allows the atria to contract just
ahead of ventricular contraction thereby
atria is emptied before ventricular ejection.
What is Frank-Starling’s law
Within the physiological limit the larger the
initial length of muscle fiber (end diastolic
fiber length), the greater will be the force of
contraction of the heart which is known as
Frank-Starling’s law of heart.
What is the ionic basis of plateau
phase of cardiac action potential?
Immediately after depolarization voltage
gated Na+ channel‘s used to close resulting
stoppage of entry of Na+ ions and voltage
gated K+ channel start opening resulting exit
of K+. These results in rapid fall of
electropositivity initially known as rapid
repolarization. Afterwards, the rate of
repolarization becomes slower due to
prolonged opening of voltage gated Ca+2
channel through which Ca+2 enters inside.
Thus the exit of K+ is almost counterbalanced by entry of Ca+2 resulting sustained
depolarization known as plateau phase in
(Fig. 15.2).
Enumerate the properties of cardiac
muscle.
• Excitability • Rhythmicity • Conductivity • Contractility Contractility includes: – All or none law – Staircase phenomenon – Summation of subliminal stimuli – Refractory period.
all or none law applicable in heart?
All or none law which states that if a
stimulus is applied, whatever may be the
strength of stimulus, the cardiac muscle
responds maximally or it does not give any
response at all (Fig. 15.2). Of course, it is
applicable only in whole atrial muscle (i.e.
atrial syncytium) or in whole ventricular
muscle (i.e. ventricular syncytium) not to a
single cardiac muscle fiber.
Define staircase phenomenon. Why
does it occur?
If stimuli are applied repeatedly, with an
interval of 2 seconds to the cardiac muscles,
the force of contraction increases gradually
for the first few contractions. Later the force
remains the same. The gradual increase in
the force of contraction is known as staircase
phenomenon or treppe response. It occurs
because of the short interval of 2 seconds in
between the stimuli. During this period, the
beneficial effect is produced and this
facilitates the force of successive contraction
Why left ventricular subendocardial
region is more prone to myocardial
infarction?
The blood supply to the cardiac muscle in
different areas of heart is not same. On the
surface of the cardiac muscle there are large
epicardial arteries supplying more blood to
those areas whereas in the subendocardial
region blood supply is less because it is
supplied by smaller intramuscular arteries
and plexus of subendocardial artery the
diameter of which are less. This blood supply
to the subendocardial plexus is further
reduced during systole. Therefore the
subendocardial region is more prone to
myocardial infarction. Again as the left
ventricular thickness is much more than that
of right ventricle the occlusion is more
severe in left ventricle. For this region LV
subendocardial region is more prone to MI.
What are the importance of anastomotic channels in heart muscle?
In the normal heart there are some
collaterals among the smaller arteries which
become active under abnormal conditions
like myocardial ischemia. They open up
within a few seconds after the sudden
occlusion of larger artery and become
double in number by the end of 2nd or 3rd
day and reach to normal by one month.
When atherosclerosis causes constriction of
coronary arteries slowly over a period of
many years, collateral vessels develop
restoring normal blood and thus the patient
never experiences acute episode of cardiac
dysfunction.
What is the importance of autoregulation in blood supply in heart muscle?
Like some other organs the heart has the
capacity to regulate it’s own blood flow up
to a certain limit in order to maintain an
almost constant blood flow to the cardiac musculature in spite of any alteration of
systemic blood flow. This is known as
autoregulation of coronary blood supply
What is the importance of autoregulation in blood supply in heart muscle?
Like some other organs the heart has the
capacity to regulate it’s own blood flow up
to a certain limit in order to maintain an
almost constant blood flow to the cardiac
musculature in spite of any alteration of
systemic blood flow. This is known as
autoregulation of coronary blood supply.
Angina pectoris
Due to myocardial ischemia there is
stimulation of nociceptors present in heart
muscle resulting in pain sensation which is
normally referred to upper sternum, left
forearm, left shoulder, neck and side of the
face. This clinical condition is known as
angina pectoris.
Why cardiac muscle cannot be
tetanized?
It is because of it’s long absolute refractory
period and thus summation of contractile
response is not possible which is essential
for tetanization of heart muscle.
Cardiogram
The record of the mechanical activity of the
heart is known as cardiogram
Define and give normal values of
end diastolic volume, stroke volume and
end systolic volume.
During ventricular diastole the intraventricular volume is increased which results
filling of the ventricles. At the end of diastole
the amount of blood filled by the ventricle
is known as end diastole volume (EDV). It
is about 120-130 ml.
During ventricular systole intraventricular
volume decreases which results increase in
pressure thus ejection of blood out of
ventricles. During each systole the amount
of blood pumped out by each ventricle is
known as stroke volume (SV). Normal
value:70 ml/beat.
At the end of systole however some
amount of blood is remained in each
ventricle which is known end systolic
volume (ESV). The normal volume: 50-60
ml/ beat.
What do you mean by vagal escape?
What is its cause?
If strong vagal stimulation to heart is
continued then after a pause the ventricles resume to beat at a slow rhythm which is
called as vagal escape represented by
Figure 15.3.
During prolonged vagal stimulation right
auricle stops beating and distends due
to blood overflow which leads to fall of
BP → afferent impulse from carotid sinus to
cardiac centers → stimulate ventricles to start
its beat.
Q.30 What is the action of sympathetic
nerves on heart?
Sympathetic nerves increase the rate and
force of contraction of heart by secreting
noradrenaline
What is sympathetic tone?
Continuous stream of accelerator impulses
that arises from cardio accelerator center
and reaches the heart via sympathetic
nerves is known as sympathetic tone or
cardio accelerator tone. However, under
resting conditions, the vagal tone is more
dominant over the sympathetic tone.
Define apex beat
Apex beat is the impulse or throb which is
felt and seen on the chest wall normally in
the left 5th intercostal space just medial to
left nipple.
What is protodiastole? Is it part of
systole or diastole?
Protodiastole is the very brief phase before
diastole in which ventricular systole has
ceased but relaxation yet to start.
It can not be well defined whether the
protodiastole is a part of systole or diastole
as some workers include it in diastole as
muscle contraction is stopped at this phase
whereas some others believe that it is a part
of systole as muscle relaxation has not yet
started
Define cardiac cycle.
he sequence of events (mechanical,
electrical, etc.) associated with consecutive
heart beat
is repeated cyclically which is
known as cardiac cycle (Fig. 15.4). Normal
dura
tion is 0.8 sec if heart rate is 75 beats/
min.
What are the causes of 1st heart
sound?
These are: • Closure and vibrations of AV valves at the beginning of ventricular systole. • Vibrations of blood surrounding the AV valves. • Vibrations of major blood vessels around the heart. • Vibrations of walls of heart.
What are the characteristics of 1st
heart sound? (Fig. 15.4)
It is: • Soft, prolonged with low pitch. • Duration is 0.12 sec and occurs in peak or downstroke of R wave in ECG and just before onset of ‘c’ wave in jugular pulse tracing. • Best heard at apex beat area and is associated with onset of ventricular systole.
What is the significance of 1st heart
sound?
It indicates force of contraction, condition
of myocardium and competence of AV
valves.
What are the causes of 2nd heart
sound?
These are: Closure and vibration of semilunar valves at the end of ventricular systole. Vibrations of blood surrounding these valves. Vibrations of walls of aorta and pulmonary artery. Vibrations of the wall of ventricles to a little extent.
What are the characteristics of 2nd
heart sound
It is:
• Sharp, short and high pitched.
• Duration is 0.08 sec and follows T wave in
ECG and coincides with ‘v’ wave in
jugular venous pulse tracing.
• Best heard at 2nd right costal cartilage for
aortic component and 2nd intercostal
space at left sternal border for pulmonary
component.
• Associated with onset of ventricular
diastole.
1 What is the significance of 2nd heart
sound?
It indicates the competence of semilunar
valves
When and how 3rd heart sound is
produced?
3rd heart sound is produced during the first
1/3 of ventricular diastole. It occurs due to
the vibrations set up by the rushing of the
blood during the rapid filling phase of
ventricular diastole.
What is murmur
It is the sound produced by turbulence produced in the blood by a forward flow through a stenosed (narrowed) valve or back flow (regurgitation) through a deformed or incompetent valve
How do you classify murmur?
It will be classified on the basis of their
relationship with main heart sounds like
presystolic, systolic, diastolic and also to and
fro murmurs
What are the maximum and
minimum pressure in heart?
• Maximum pressure in left ventricle is
above 120 mm Hg.
• Max pressure in right ventricle is above
25 mm Hg
• Minimum pressure in left ventricle is 80
mm Hg.
• Minimum pressure in right ventricle is
few mm Hg
What is the normal heart rate? What
are the factors affecting heart rate (HR)?
Normal value of HR is 72 beat/min with
the normal range 60-90 beat/min.
The factors are: age, sex, body temperature, hypoxia, emotion, exercise, etc. and
drugs like epinephrine and norepinephrine.
Why HR is slightly higher in
females than males?
It is because of two reasons:
• Lower systemic BP
• More resting sympathetic tone
What is Cushing reflex?
It is represented by following sequential events: Increased intracranial pressure → decreases blood supply to medullary hypoxia and hypercapnia → stimulation of medullary vasomotor center → increase of systemic BP → stimulation of baroreceptors → stimulation of vagus nerve → decrease of HR and respiration. This reflex mechanism by which increased intracranial pressure results bradycardia is known as Cushing reflex.
What do you mean by sinus
arrhythmia?
Heart rate increases with inspiration and
decreases during expiration. This phenomenon is known as sinus arrhythmia.
State Marey’s law
If the other conditions remain constant then
the HR is inversely related with systemic
BP (Fig. 15.5
Define cardiac output, stroke volume
and cardiac index.
Cardiac output: The amount of blood pumped out by each ventricle per min is called as cardiac output. The normal value is 5 lit/min/ventricle. Stroke volume: The amount of blood pumped out by each ventricle in each beat is known as stroke volume. Normal value is 70 ml/beat/ventricle. Cardiac index: It is the cardiac output per square meter of body surface area. The normal value is 3.2 L/m2 /min.
What do you mean by extrinsic
and intrinsic autoregulation of cardiac
output?
If cardiac output is controlled by controlling
only heart rate (as CO = HR × SV) it
is known as extrinsic autoregulation of
cardiac output whereas if it is regulated by
regulating only stroke volume, it is known
as intrinsic autoregulation.
What is the difference between
heterometric and homometric regulation
of cardiac output?
To control cardiac output when ventricular
contraction is regulated by controlling initial
length of the muscle fiber, i.e. EDFL, then it
is called as heterometric regulation which is
independent of cardiac nerves. Whereas
when cardiac nerves regulate the myocardial
contractility to control the cardiac output, it
is known as homometric regulation of
cardiac output.
What is Frank-Starling’s law of heart?
What is its relation with venous return?
It states that within the physiological limit,
the force of ventricular contraction is
directly proportional to the initial length of
muscle fibers (EDFL).
If venous return is increased the EDFL of
the ventricular muscle is also increased
resulting in more force of ventricular
contraction thereby more cardiac output.
What do you mean by Vis A Tergo
and Vis A Fronte in relation to cardiac
pump?
Vis A Tergo is the force which drives the
blood forward from behind, e.g. the
contraction of the heart drives the blood in
forward direction, whereas Vis A Fronte is
the force acting from front that attracts
blood in the veins towards the heart, e.g.
ventricular systolic and diastolic suction
pressure.
Enumerate the factors affecting
venous return.
The factors are: Thoracic or respiratory
pump, cardiac pump, muscle pump, total
blood volume and increased sympathetic
activities on veins
Two methods cardiac output is measured
Direct Fick method and
• Indirect dye dilution method
Ficks principle
It states that the amount of a substance
taken up by an organ or by whole body
per unit time is equal to the arterial level of
that substances minus the venous level
(i.e. A-V difference) times the blood flow,
i.e. amount of substance taken/min = A-V
difference of the substance × blood flow/
min
What are the disadvantages of Fick’s
method?
These are:
• As it is the invasive method the subject is
exposed to all risk of hemorrhage,
infection, etc.
• As the subject is conscious of the whole
technique cardiac output may be higher
than normal.
Bundle of kent
n the individuals with WPW syndrome,
there is one additional nodal connecting
tissue in between atria and ventricles besides
AV node which conducts the impulse more
rapidly than AV node. This additional
conducting pathway is known as Bundle of
KENT.
Define blood pressure (BP)
It is the lateral pressure exerted by the
moving column of blood on the wall of
blood vessels during its flow.
Define systolic, diastolic, mean and
pulse pressure with each of their normal
average values
Systolic pressure (SP): It is the maximum
pressure exerted during systole of the heart.
Normal value = 120 mm Hg (Normal
range:110-140 mm Hg).
Diastolic pressure (DP): It is the minimum
pressure during diastole of the heart.
Normal value = 80 mm Hg (Normal range:
60-90 mm Hg).
Pulse pressure (PP): Pulse pressure is the
difference between systolic and diastolic
pressure. Normal value = 40 mm Hg.
Mean pressure: It is average pressure
during each cardiac cycle. Normal value
= 93.3 mm Hg.
Q.66
Enumerate the significance of SP,
DP, PP and MP.
• Systolic pressure indicates the extent of
work done by the heart and also the force
with which the heart is working. It also
indicates the degree of pressure the
arterial wall have to withstand.
• Diastolic pressure is the measure of the
total peripheral resistance and it indicates
the constant load against which heart has
to work.
• Pulse pressure determines the pulse
volume. Whereas mean pressure indicates
the perfusion pressure head which causes
the flow of blood through the arteries,
arterioles, capillaries, veins and venules.
Why does systolic pressure increase
after meal?
After meal pressure over heart increases due
to distended abdomen which in turn
increases heart rate and also there is a
release of epinephrine which also increases
systolic blood pressure.
What do you mean by baroreceptors?
Where are they located
Baroreceptors are the pressure receptors
stimulated in response to change of pressure
around them.
These are located in the wall of blood
vessels (e.g. arterial baroreceptor–present in carotid sinus, aortic arch, root of right
subclavian artery, junction of thyroid artery
with common carotid artery, also
pulmonary trunk) and also in the walls of
the heart (e.g. atriocaval receptors, atrial
receptors)
What do you mean by buffer nerves?
Why they are so called?
Carotid sinus nerve originated from carotid
sinus and aortic nerve arised from arch of
aorta are collectively known as buffer
nerves as they prevent any change in
systemic BP and thus help the BP to keep
normal.
What is Bain-bridge reflex?
Rapid injection of blood or saline in
anesthetized animals produces a rise in
heart rate if the initial heart rate is low. This
is called as Bain-bridge reflex (Fig. 15.6). This
is due to the stimulation of stretch receptors
in the wall of right atrium.
Name different chemoreceptors
responsible for BP regulation. What are
their stimulants?
These are carotid bodies and aortic
bodies. They get stimulated by hypoxia,
hypercapnia, asphyxia and also acidemia.
What is the effect of chemoreceptors
on heart rate?
In conditions like hypoxia, hypercapnia and
increased hydrogen ion concentration, the
chemoreceptors send inhibitory impulses to
vasodilator area (cardioinhibitory center).
Now, the vagal tone is reduced and heart
rate is increased.
What is plateu phase
During some pathological conditions like
aortic stenosis the pulse wave rises slowly,
followed by delayed and sustained peak and
then the pulse faded slowly. Such type of
pulse is known as plateau pulse as
represented by Figure 15.8.
Define ecg
It is the record of electrical activities of heart
by electrocardiograph during different
periods of cardiac cycle (Fig. 15.9)
What do you mean by Einthoven’s
triangle?
The equilateral triangle obtained by
connecting the right arm, left arm and right
leg, by means of electrical wires with current
source as the heart at its center is known as
Einthoven’s triangle (Fig. 15.10).
What is Einthoven’s law?
It states that if the electrical potentials of
any two of the three bipolar leads are known
at any given instant, the 3rd one can be
determined mathematically from the 1st two
by simply summing the 1st two by
Difference between flutter and fibrillation
