Transcript L5 Cardiac Function and Cycle

Who can put their washing out fastest?
Peg up and place the cards in the right
order – table vs table
EXTENSION – name as many differences
between right and left ventricle?
Learning Outcomes
• Compare the left and right ventricles
• Calculate cardiac output and compare output in different
situations
• Identify the three stages in a heart beat
Left vs. Right Ventricle
• DESTINATION  The left ventricle and the right
ventricle pump out blood from the heart going to the
arteries to supply blood to the different parts of the body.
MISCONCEPTION!!
• BLOOD  The left ventricle receives oxygenated
No difference
volume
(oxygen-rich)
blood and in
pumps
it out topumped!
most of the
systems in the body while the right ventricle receives
deoxygenated (oxygen-poor) blood from the right atrium.
The left and right ventricles pump the
• EFFORT There is also a difference between the effort
same
of blood
through the
exerted
by thevolume
left and right
ventricles.
aorta and
pulmonary
artery.
• STRUCTURAL
 Left
ventricle is actually
thicker than
that of the right ventricle as the person reaches his
teenage to adult years due to exertion requirements
Glossary Terms
Heart Rate (pulse) (HR)
• Number of heartbeats that occurs per minute.
Stroke Volume (SV)
• Volume of blood expelled by each ventricle on
contraction. The stronger the contraction, the greater
the stroke volume.
Cardiac Output (CO)
• Volume of blood pumped out of the ventricle per minute.
of the heart (creates the pulse)
• CO = HR x SV
Cardiac output = pulse rate x stroke volume
1. What is the cardiac output when oxygen uptake is 0.6
2. 16.5 litres per minute is the cardiac output with the
stroke volume was 130, calculate the what is the
oxygen uptake?
What way does blood pass through the
heart?
• Why?
• What is causing that order?
• Hint – what moves blood around the body? What moves
it back towards the heart?
Cardiac Cycle
• Name of the pattern of
contraction (systole) and
relaxation (diastole) in one
complete heartbeat.
DIASTOLE
• During diastole blood
returning to the atria flows
into the ventricles. In
diastole the higher
pressure in the arteries
closes the SL valves
Cardiac Cycle
ATRIAL SYSTOLE
• Atrial systole transfers the
remainder of the blood through
the atrioventricular (AV) valves
to the ventricles.
VENTRICULAR SYSTOLE
• Ventricular systole closes the
AV valves and pumps the blood
out through the semi lunar (SL)
valves to the aorta and
pulmonary artery.
Diastole
Atrial systole
Ventricular systole
Cardiac Cycle
The opening and closing of the AV and SL
valves are responsible for the heart sounds
heard with a stethoscope.
Atrial
Systole
Ventricular
Systole
Diastole
“DUB”
Cardiac cycle
= 0.8 sec
“LUB”
60/0.8 bpm
= 72 bpm
A
Atrioventricular (bicuspid / mitral) valve(s) closes (“snaps shut”– makes 1st
louder heart sound “LUB”
B
Semilunar valve(s) (aortic valve) opens
C
Semilunar valve(s) closes – makes second softer heart sound “DUB”- shut
due to blood accumulating in their pockets
D
Atriioventricular (bicuspid) valve(s) opens
Glossary Definitions
• The chambers of the heart alternatively
contract = SYSTOLE
• The chambers relax = DIASTOLE
• One complete sequence of filling and pumping
blood = CARDIAC CYCLE
• During SYSTOLE, cardiac muscle contracts and
the heart pumps blood. During DIASTOLE, the
cardiac muscle relaxes and the chambers fill
with blood.
So what causes the contraction?
Cardiac Conduction
• The heart beat originates in the heart
itself, it is myogenic.
• However regulated by both nervous and
hormonal control.
• Rate of contraction of cardiac by the
autorhythmic cells of the sinoatrial
node (SAN) or pacemaker
Cardiac Conduction
The timing of cardiac
cells contracting is
controlled by the
impulse from the SAN
spreading through the
atria and then travelling
to the atrioventricular
node (AVN) and then
through the Bundle of
His and Purkyne tissue
to the ventricles.
Cardiac Conduction
The timing of cardiac cells contracting
is controlled by the impulse from the
SAN spreading through the atria and
then travelling to the atrioventricular
node (AVN) and then through the
ventricles. These impulses generate
currents that can be detected by an
electrocardiogram (ECG).
Electrocardiogram (ECG)
Electrodes are placed on the skin over opposite sides of the heart, and the
electrical potentials generated recorded with time. The result is an ECG.
P wave = electrical activity
during atrial systole
QRS complex = electrical activity
during ventricular systole
T wave = ventricular
repolarisation (recovery of
ventricular walls)
Q-T interval – contraction time
(ventricles contracting)
T-P interval – filling time –
ventricles relaxed and filling with
blood
Pattern are studied in different conditions and compared to the standard ECG in
order to diagnose heart conditions, such as arrythmias and fibrillation. Fibrillation
is stopped by passing a strong electric current through the chest wall – the heart
stops for up to 5 seconds after which it begins to beat in a controlled way
A normal ECG trace compared with others indicating an unhealthy heart
During an arrhythmia, the heart can
beat too fast, too slow, or with an
irregular rhythm.
A heartbeat that is too fast is called
tachycardia. A heartbeat that is too
slow is called bradycardia.
Atrial flutter
SUMMARY
Regulation of the Heart
•Atria relaxed – fill with blood
•RA with deoxygenated blood from vena cava
•LA with oxygenated blood from pulm vein
•SAN sends out 72 impulses/min over atrial wall
– atria contract 72 times/min
•Atria contract to force blood into ventricles
•Atria relax
•Impulse reaches AVN
•Delayed momentarily
•Impulse travels through nerve fibres of the
atrioventricular bundle and its branches into
walls of the ventricles
•Ventricles contract – from apex upwards to
force blood into arteries
•Oxygenated blood from LV to aorta – to body
•Deoxygenated blood from RV to pulmonary
artery – to lungs (to be oxygenated)
Nervous Regulation of SAN
The medulla regulates the
rate of the SAN through
the antagonistic (working
oppositely - both increase
and decrease – for fine
control similar to a car with
a brake and accelerator)
action of the autonomic
nervous system (ANS)
(involuntary control –
however some can be
controlled).
Nervous Regulation of SAN
Sympathetic accelerator nerves release
adrenaline (epinephrine) and slowing
parasympathetic nerves release acetylcholine.
Actual rate is
determined by which
system exerts greatest
influence at the time.
Hormonal Regulation of SAN
If stressed or during
exercise the
sympathetic nervous
system acts on the
adrenal glands,
causing the release
of adrenalin which
increases the heart
rate.
Demonstration
• Place the cards into the correct
category
Review
The cardiac cycle is initiated and controlled by the heart
itself. Cardiac muscle is said to be ......................... since it
will contract and relax of its own accord. The beat is
initiated by the .........................which is situated in the wall
of the ............... Waves of depolarisation travel
through the atria causing atrial .............. The waves of
depolarisation can only travel to the ventricles via the
................... situated at the top of the ventricular septum.
From here the waves travel to the apex of the heart through
the ..................... which is made of specialised
conducting cells called ........................... These then carry
the waves of depolarisation through the ventricle walls
causing both ventricles to contract simultaneously. At this
stage the ..................... are open and the ..........................
are shut so that blood can be forced into the arches.
Review
The cardiac cycle is initiated and controlled by the heart
itself. Cardiac muscle is said to be ..myogenic... since it will
contract and relax of its own accord. The beat is initiated by
the .sinoatrial node (SAN).which is situated in the wall of the
.right atrium.... Waves of depolarisation travel
through the atria causing atrial .systole.. The waves of
depolarisation can only travel to the ventricles via the
..atroventricular node (AVN).. situated at the top of the
ventricular septum. From here the waves travel to the apex
of the heart through the .. bundle of His... which is made of
specialised
conducting cells called .. Pukinje
fibres..These then carry the waves of depolarisation through
the ventricle walls causing both ventricles to contract
simultaneously. At this stage the ...semilunar valve.. are
open and the ...atrioventricular valves... are shut so that
Cardiac Conduction
• The heart beat originates in the heart itself but is
regulated by both nervous and hormonal control. The
autorhythmic cells of the sinoatrial node (SAN) or
pacemaker set the rate at which cardiac muscle cells
contract. The timing of cardiac cells contracting is
controlled by the impulse from the SAN spreading
through the atria and then travelling to the
atrioventricular node (AVN) and then through the
ventricles. These impulses generate currents that can be
detected by an electrocardiogram (ECG).
Cardiac Cycle
• Name of the pattern of contraction (systole)
and relaxation (diastole) in one complete
heartbeat.
• During diastole blood returning to the atria
flows into the ventricles. In diastole the
higher pressure in the arteries closes the SL
valves
• Atrial systole transfers the remainder of the
blood through the atrioventricular (AV)
valves to the ventricles.
• Ventricular systole closes the AV valves and
pumps the blood out through the semi lunar
(SL) valves to the aorta and pulmonary
artery.
1. ATRIAL SYSTOLE:
• Blood under low pressure flows into the atria from
the pulmonary veins and vena cava.
• As the atria fill, the pressure of blood against the
atrioventricular (AV) valves pushes them open and
blood leaks into ventricles. The atria walls contract,
forcing blood into ventricles.
2. VENTRICULAR SYSTOLE:
• The ventricles contract from the bottom of the
heart upwards, increasing the pressure in the
ventricles.
• Blood is pushed through the arteries.
• The pressure of the blood against the AV valves
closes them, preventing back flow.
3. DIASTOLE; (atria and ventricles relax).
• Pressure in atria and ventricles is lowered by the
relaxation of cardiac muscles.
• Blood under high pressure in the arteries is drawn
back towards the ventricles, closing the semi-lunar
valves, preventing back flow.
• The coronary arteries fill during diastole.