d) Cardiovascular System
Higher Human Biology
What can
you
remember
about the
heart and
blood
vessels?
What is the Cardiovascular System?
• The cardiovascular system, also
known as the circulatory system, is
composed of blood, blood vessels
and the heart.
• The heart functions as a pump to
move blood through the blood
vessels of the body.
• A circulatory system is essential for
large, multi-cellular organisms, such
as humans and animals.
Heart Revision
Learning Intention
• Describe the path of
blood flow through
the heart including
the heart valves
The heart is a DOUBLE PUMP:
1st - blood is pumped to the lungs & returns to the heart,
2nd - blood is pumped to the body & back to the heart again.
1. Deoxygenated
blood from the body
is pumped from the
heart to the lungs
4. The oxygen leaves
the blood to be used
by the body and the
blood goes back to
the heart
2. The blood receives
oxygen in the lungs
and is pumped back
to the heart
3. The oxygenated
blood is then pumped
by the heart to the
body
The Structure of the Heart
• The heart is has 4
chamber
• The upper chambers
are called atria
(atrium singular)
• The lower chambers
are called ventricles
Heart Valves
• Valves prevent
back flow of blood
• Between the atria
and ventricles are
atrioventricular
(AV) valves
• Between the
ventricles and
arteries leaving the
heart are semilunar
(SL) valves
Left SL Valve
Left AV
Valve
Right SL
Valve
Right AV
Valve
LA
RA
RV
LV
Heart Rap
From left ventricle out through the
aorta to the body
Right SL valve
Deoxygenated
blood flows
from the body
into the heart
via the VENA
CAVA
Out via the
pulmonary
artery to the
lungs
LEFT
ATRIUM
RIGHT
ATRIUM
Left SL valve
Oxygenated
blood flows
back from the
lungs via the
PULMONARY
VEIN
LEFT VENTRICLE
RIGHT
VENTRICLE
Left AV valve
Right AV valve
Parts of heart musical quiz
Pig heart dissection
Who Am I?
1. I leave the right ventricle and go to the lungs
Pulmonary Artery
2. I take deoxygenated blood to the heart
Vena Cava
3. I prevent backflow of blood into the left atrium
Left AV Valve
4. I come from the lungs and go back to the heart
Pulmonary Vein
5. I prevent backflow of blood into the right ventricle
Right SL Valve
6. I leave the left ventricle of the heart
Aorta
Learning Intentions
• State what is meant by the terms cardiac
output, heart rate and stroke volume
• Explain the calculation of cardiac output
Learning Intention
• Compare the structure and function of arteries,
capillaries and veins
Blood Vessels
• Blood leaves the
heart in arteries
• It then flows
through capillaries
in the tissues and
organs
• And returns to the
heart in veins
• There is a decrease
in blood pressure as
the blood moves
away from the
heart.
Layers in Blood Vessels
• The endothelium lining the central lumen of the
blood vessels is surrounded by layers of tissue.
• These surroundings layer differ in each type of
blood vessel
endothelium
Arteries
• Arteries have an outer layer of connective tissue
containing elastic fibres which stretch
• They have a middle layer containing smooth muscle with
more elastic fibres
• Endothelium lines the central lumen where the blood
flows through
Connective
tissue
Muscle tissue
Endothelium
Arteries
• The elastic walls of the arteries stretch and recoil to
accommodate the surge of blood that enters them after
each contraction of the heart.
• The smooth muscle can contract causing vasoconstriction
and less blood to flow
• The smooth muscle can relax causing vasodilation and
more blood to flow
Capillaries
• Transport blood
between arteries and
veins
• Exchange of materials
between blood and
cells
• Their walls are only one
cell thick, allowing
nutrients and waste to
diffuse through with
ease
Veins
• Veins have an outer layer of connective tissue containing
elastic fibres but a much thinner muscular wall than
arteries.
• Endothelium lines the central lumen where the blood flows
through
• They contain valves which prevent the backflow of blood.
Connective
tissue
Muscle tissue
Endothelium
Learning Intentions
• Describe the exchange of materials between
tissue fluid and cells
• State how lymph is formed and what happens to
it
Blood
• Blood consists of red and
white blood cells, platelets
and plasma
• Plasma is a watery yellow
liquid containing dissolved
substances such as glucose,
amino acids, respiratory
gases, plasma proteins and
useful ions
Tissue Fluid
Blood at low
pressure
Blood at high
pressure
Fluid squeezed out
• Blood arriving at the arteriole end of a capillary bed is at
a higher pressure than blood in the capillaries
• As blood is forced into the narrow capillaries, it
undergoes pressure filtration and much of the plasma is
squeezed out through the thin walls
Tissue Fluid
• This plasma which has
been squeezed out
through the thin walls of
the capillaries into the
surrounding tissues is
called tissue fluid
• The only difference
Tissue Fluid
between plasma and
tissue fluid is that plasma
has proteins and tissue
fluids do not
Tissue
Fluid
Tissue Fluid
• The cells exchange molecules with the tissue fluid by
diffusion down a concentration gradient
• Useful molecules such as food and oxygen diffuse into
the cells from the tissue fluid
• Carbon dioxide and other metabolic wastes diffuse out
of the cells and into the tissue fluid to be excreted
Lymph
• Most of the tissue fluid goes back by into the blood
capillary by osmosis
• The fluid that does not return to the blood is now
referred to as lymph and is collected by the
lymphatic system
Lymph passes
into lymphatic
system
Blood
arriving in
the arteriole
high
pressure
Lymph
vessel
Blood
leaving in
venule
low
pressure
Some tissue fluid
enters capillary
by osmosis
capillary
Some tissue
fluid enters
lymphatic
system
Some plasma
forced out of
capillary
Tissue fluid
Lymph
• Lymph is collected by a vast
network of lymph vessels
• These vessels eventually
return their contents to the
main circulation near the
heart via osmosis
• The lymphatic system has
no pump- the contraction
of skeletal muscles
squeezes lymph along the
vessels
Try these questions . . .
1. What is tissue fluid?
2. Name a substance that passes from body cells into tissue
fluid
3. Tissue fluid surrounds the muscle cells. Some of this fluid is
reabsorbed into the bloodstream. How else is tissue fluid
removed from around the cells?
4. Describe the means by which lymph is forced along through
the lymphatic system
Answers . . .
1. It is the liquid consisting of plasma and small, dissolved
molecules that is squeezed out of capillaries during pressure
filtration
2. Carbon dioxide
3. It is absorbed into the lymphatic system via thin-walled
lymphatic vessels and returned to blood capillaries by
osmosis
4. When the vessels are pressed during muscular contraction,
the lymph is pushed along the lymph vessels
Heart Rate (HR)
• Number of heart beats in one minute
• Normal values around 72bpm
• Normal range is between 60-90
What is your HR?
Stroke Volume (SV)
• Volume of blood pumped out by each
ventricle during contraction
• Normal values are around 70ml
Cardiac Output (CO)
• Cardiac output is the volume of blood
pumped out of a ventricle per minute
• It is calculated by the following equation –
CO = HR X SV
• Normal values are around 5 litres/min
a) At rest: HR = 72bpm
SV = 70ml
What is the CO of this individual?
CO = 72 x 70
= 5040 ml/min
= 5 litres/min
b) During exercise: HR = 200bpm
SV = 150ml
What is the CO of this individual?
CO = 200 x 150
= 30000ml/min
= 30 litres/min
Some typical values for cardiac output at varying levels of activity:
Activity
Level
Heart rate
(bpm)
Stroke
Volume (ml)
Cardiac
Output
(l/min)
Rest
72
70
5
Mild
100
110
11
Moderate
120
112
13.4
Heavy
(athlete)
200
150
30
Learning Intention
• Describe the events of the cardiac cycle
The Cardiac Cycle
• The cardiac cycle refers to the pattern of contraction
and relaxation of the heart during one complete
heartbeat.
• Contraction of the heart muscle is known
as systole while relaxation is known as diastole.
• This lasts about 0.8 secs (0.3s systole,0.5s diastole)
Two Phases of the Cardiac Cycle
• Systole: contraction of the heart (atrial
first, the ventricular). Blood forced out
of chambers
• Diastole: relaxation of all chambers of
the heart. The chambers fill with blood
The Cardiac Cycle
1. Atrial & ventricular
diastole
2. Atrial systole
(ventricular diastole)
3. Ventricular systole
(atrial diastole)
Animation
Atrial and Ventriclar Diastole
• The atria fill with
blood from the vena
cava and pulmonary
vein, and some of
the blood flows into
the ventricles.
• AV valves open
Atrial Systole
• Both atria contract and
transfer the remainder of
the blood through the open
AV valves to the ventricles
Ventricular Systole
• About 0.1s after atrial systole the
ventricles contract
• Ventricular systole closes the AV
valves and pumps the blood out
through the open semi lunar (SL)
valves to the aorta and pulmonary
artery.
• Semi-lunar valves close when
pressure in arteries exceeds
pressure in ventricles and the
cardiac cycle begins again!
Cardiac Cycle Summary
Cardiac Cycle Summary
Ventricular Volume Graph
Atrial systole
Ventricular systole
Heart Sounds
• The opening and closing of the AV and SL valves
are responsible for the heart sounds heard with a
stethoscope (lubb dubb)
Learning Intention
• Describe the structure of the cardiac conducting
system
Conducting System of Heart
• The heart beat starts in the heart
itself
• Heart muscle cells are selfcontractile. This means they are
able to contract and produce an
electrochemical signal, which is
passed on to other cardiac muscle
cells, causing them to contract.
• It is regulated by the nervous
system and hormones which
ensures that it beats in a coordinated manner.
Inside human body
SA Node
• The SAN is found at the top of the right atrium.
• It sends out a electrical impulses which are carried
through the muscular walls of both atria
• This ensures that both atria contract simultaneously and
results in atrial systole
• The electrical impulse is then
passed to the atrioventricular
node (AVN)
Bundle of
HIs
AV Node
• The AVN is found lower part of the right atrium
• When the impulse reaches the AVN it is passed into
a bundle of conducting fibres.
• These fibres split left and right
into the ventricles. This causes
the ventricles to contract at
the same time.
Pathway
(1) Impulse is generated in the
SA node
(2)The AVN then picks up the
impulse from SAN
(3)Passes to bundle of
conducting fibers and travels
down the septum
(4)Passes to the bundle
branches (right & left)
(5)Passes to the ventricles
contract from bottom up
SAN
Bundle of
conducting
fibers
AVN
septum
Learning Intention
• Describe the autonomic and hormonal
regulation of the cardiac conducting system
Regulation of Heart Rate
• The SAN alone initiates
each heartbeat, and the
timing of each is controlled
by the impulse from the
SAN travelling to the AVN
and then through the
ventricles.
• However, heart rate is not
fixed as it is altered by
nervous and hormonal
activity
Autonomic Nervous System Regulation
• The medulla regulates the
rate of the SAN through the
antagonistic action of the
autonomic nervous system
(ANS)
• The autonomic nervous
system consists of 2 opposing
(antagonistic) branches
– Sympathetic pathway
– Parasympathetic pathway
Sympathetic Nerve
• An increase in the
number of nerve
impulses at the SAN via
the sympathetic nerve
increases heart rate
• Sympathetic accelerator
nerves release
norepinephrine
(noradrenaline)
Parasympathetic Nerve
• An increase in the
number of nerve
impulses at the SAN via
the parasympathetic
nerve decreases heart
rate
• Parasympathetic nerves
release acetylcholine
Hormonal Regulation of the Heart
• Under certain circumstances
e.g. stress or exercise the
sympathetic nervous system
causes the adrenal glands to
produce the hormone
adrenaline
• This travels in the blood to
act on the SAN, which
generates impulses at a
higher rate, increasing heart
rate
Autonomic Nervous System &
Hormonal Regulation
Control centre in
medulla
adrenalin
Starter Questions
1. What structure initiates the heartbeat?
2. Name the two parts to the autonomic nervous system.
3. Which nerve in the autonomic nervous system speeds up
heart rate?
4. Which nerve in the autonomic nervous system slows down
heart rate?
5. Which part of the brain sends messages to via the
sympathetic nerve to speed up heart rate and the
parasympathetic nerve to slow down heart rate?
6. Name the hormone secreted by the adrenal glands.
7. Under what circumstances is adrenaline released by the
adrenal glands?
8. What neurotransmitter is released by the sympathetic
nerve?
9. What neurotransmitter is released by the
parasympathetic nerve?
Electrocardiogram
• In an ECG(electrocardiogram)
test, the electrical impulses
made while the heart is
beating are recorded and
shown on a piece of paper
• It can show any problems with
the heart's rhythm, and the
conduction of the heart beat
through the heart which may
be affected by underlying
heart disease
Animation
• The P wave = the wave
of excitation
spreading over the
atria from the SAN
• The QRS Complex =
the wave of
excitation passing
through the
ventricles.
The T wave = the recovery of the ventricles
towards the end of ventricular systole
Abnormal Heart Rhythms
• Some forms of heart disease can be
detected and diagnosed using ECGs
because they produce unusual but
identifiable patterns such as:
– Ventricular Tachycardia
– Ventricular fibrillation
– Atrial Flutter
Abnormal ECG - Ventricular Tachycardia
Abnormal cells in the
ventricle walls act like
pacemakers and beat
rapidly and
independently of the
atria
Abnormal ECG - Ventricular
fibrillation
• Uncoordinated electrical activity
• Coordinated pumping of the chambers cannot
take place
• Fatal if not corrected by defibrillation
(Defibrillation consists of delivering a
therapeutic dose of electrical energy to the
heart with a device called a defibrillator).
Abnormal ECG - Atrial Flutter
• Rapid rates of electrical excitation occur which
leads to an increase in the contraction of either
the atrium or ventricles.
• The contractions remain coordinated
Learning Intention
• Discuss the measurement and typical
readings for blood pressure
Blood Pressure
• This is the force exerted by blood against
the walls of the blood vessels. It is
measured in millimetres of mercury (mmHg)
Blood Pressure
• The blood needs to be under
pressure to travel round the body
and for pressure filtration (as
mentioned at the capillaries)
• As the heart contracts and
relaxes blood pressure rises and
falls.
• Measure 2 values – systolic BP
(pressure during ventricular
contraction) and diastolic BP
(pressure during ventricular
relaxation)
Measurement of BP
Both systolic and diastolic BP can be
measured by an inflatable instrument
called a sphygmomanometer which is
wrapped around the upper arm.
• Normal values are around 120mmHg
for systolic pressure and 70mmHg for
diastolic pressure (120/70)
Hypertension
• High blood pressure is called hypertension
• Hypertension is a major risk factor for many diseases
including coronary heart disease.