Download THE HEART

THE HEART
The Heart- structure
Double Circulatory System
The Heart

This is a muscular organ divided by the
septum in to 2 separate pumps:

Right side:
pumps blood to the lungs

Left side:
pumps blood to the body
The Heart

Each side has 2 chambers…



Atrium:
Ventricle:
Upper chamber (pl: Atria)
Lower chamber
… and 2 valves:



Atrioventricular:
In the centre of the heart
between the atrium and the ventricle
Semi lunar valves: In the arteries
Valves ensure the blood flows the correct way
around the heart.

Coronary arteries supply the heart muscle
with blood
Name the parts:
The heart - function




The heart is a hollow muscle
It collects blood returning in veins
It pumps blood into arteries
Direction of blood controlled by valves
Veins drain into….
Atria pump blood into…
Atrio-ventricular (biscuspid & tricuspid) valves direct
blood into …
Ventricles pump blood through …
Arterial/semi-lunar valves direct blood into…
Arteries carry blood away to the tissues.
© 2008 Paul Billiet ODWS
Heart actions
Action
Atria
Ventricles
(contract/relax)
(contract/relax)
Atrial
Systole
Ventricular
Systole
Diastole


Systole – contraction
Diastole - relaxation
A-V
valves
S-L
Valves
(open/closed)
(open/closed)
1. Isometric relaxation




In the first phase the heart
is in a state of relaxation.
All the valves are closed
Blood enters the atria from
the veins
The pressure in the atria
slowly rises as a result of
the increase of blood in
them.
2. Rapid filling




Eventually the pressure in the
atria becomes higher than the
pressure in the ventricles
causing the AV valves to open
and the blood to flow into the
ventricles.
This is called rapid filling
The heart is still in diastole
The SL valves are still shut
3.Diastasis



In this phase, the heart is still
in diastole.
The pressure in the heart
equals the pressure in the
veins and there is no
movement of blood
The AV valves are open but
the SL valves remain shut
4. Atrial Systole



The atria then contract
forcing all the remaining
blood into the ventricles.
The pressure rises in the
ventricles as a result
stretching the walls.
The ventricles are still in
diastole and the SL valves
are still shut.
5. Isometric contraction


As soon as the atria relax,
their pressure falls to below
that of the ventricles which
forces the AV valves shut.
This is the “lub” sound of the
heart beat.
The pressure in the
ventricles then begins to rise
even further as they begin to
contract (isometric
contraction).
6. Ejection


As the ventricles continue
contracting, the pressure in
them becomes greater than
the pressure in the arteries
and the SL valves open.
The blood can then move
into the arteries.
Homework

Phase
Isometric
Relaxation
Rapid Filling
Diastasis
Atrial Systole
Isometric
contraction
Ejection
Fill in this table to show the movement of blood (if any), if the valves are
open or closed and if the chambers are in diastole or systole:
Movement of
blood
SL Valves
AV Valves
Atria
Ventricles
Homework

Phase
Isometric
Relaxation
Rapid Filling
Diastasis
Atrial Systole
Isometric
contraction
Ejection
Fill in this table to show the movement of blood (if any), if the valves are
open or closed and if the chambers are in diastole or systole:
Movement of
blood
SL Valves
AV Valves
Atria
Ventricles
None
closed
closed
diastole
diastole
Atrium 
Ventricle
closed
open
diastole
diastole
None
closed
open
diastole
diastole
Atrium 
Ventricle
closed
open
systole
diastole
None
closed
closed
diastole
systole
Ventricle 
arteries
open
closed
diastole
systole
Pressure in the Atria:
PRESSURE / kPa
Atrial Systole
16
12
8
4
The atria are full of blood
from rapid filling and at high
pressure.
The pressure rises further as
they contract.
0
Atrial Systole
TIME
Pressure in the Ventricles:
PRESSURE / kPa
Atrial Systole
16
12
8
The ventricles are slowly
filling with blood. Their
pressure increases…
4
0
Atrial Systole
TIME
Pressure in the Atria:
PRESSURE / kPa
Ventricular contraction
16
12
8
After systole,
the atria start to
relax (diastole)
and their
pressure falls.
4
0
Atrial Systole Ventricular Systole
TIME
Pressure in the Ventricles:
PRESSURE / kPa
Ventricular contraction
16
12
8
4
Meanwhile, the
ventricular pressure
continues to rise as
the ventricles start
to contract
0
Atrial Systole Ventricular Systole
TIME
Pressure in the Ventricles:
Ventricular contraction
PRESSURE / kPa
At this point,
16
12
8
4
0
the rising
pressure in the
ventricles
exceeds the
pressure in the
atria and the AV
valve snaps
shut.
The pressure in
the ventricles
increases
rapidly as they
contract
Atrial Systole Ventricular Systole
TIME
Pressure in the Atria:
PRESSURE / kPa
Ejection
16
12
8
4
The Atria are in
diastole so are
already starting to
fill with blood
again. This
increases the
pressure inside
them
0
Atrial Systole Ventricular Systole
TIME
Pressure in the Ventricles:
PRESSURE / kPa
Ejection
16
12
8
4
0
The pressure
continues to rise
as the ventricles
contract. As
they eject their
blood into the
arteries the
pressure starts
to level off and
eventually fall.
Atrial Systole Ventricular Systole Atrial and
Ventricular
Diastole
TIME
Pressure in the Atria:
PRESSURE / kPa
Atrial and Ventricular Diastole
16
12
8
The atria continue
to fill with blood
which increases
the pressure
inside them.
4
0
This happens until…
Atrial Systole Ventricular Systole Atrial and
Ventricular
Diastole
TIME
Pressure in the Ventricles:
PRESSURE / kPa
Atrial and Ventricular Diastole
16
12
8
4
…the
pressure in
the
ventricles
falls below
the
pressure in
the atria.
0
Atrial Systole Ventricular Systole Atrial and
Ventricular
Diastole
TIME
Pressure in the Atria:
PRESSURE / kPa
Atrial and Ventricular Diastole
16
12
8
When this
happens,
the AV valve
opens
4
0
And the pressure in the atria
temporarily drops as blood leaves.
Atrial Systole Ventricular Systole Atrial and
Ventricular
Diastole
TIME
Pressure in the Atria:
PRESSURE / kPa
Atrial and Ventricular Diastole
16
12
8
The pressure in
both the atria
and ventricles
then starts to rise
again during
rapid filling
4
0
Atrial Systole Ventricular Systole Atrial and
Ventricular
Diastole
TIME
PRESSURE / kPa
Pressure in the Aorta:
16
We can add the
pressure changes in
the aorta during the
cardiac cycle to this
graph
12
8
These are generally
higher than the
pressures in the heart
as the blood has to
flow through a smaller
space.
4
0
Atrial Systole Ventricular Systole Atrial and
Ventricular
Diastole
TIME
PRESSURE / kPa
Pressure in the Aorta:
16
Try to work out when
the semi lunar valves
open and close…
12
Hint:
8
At this point the
pressure in the left
ventricle rises above
that of the aorta…
4
0
Atrial Systole Ventricular Systole Atrial and
Ventricular
Diastole
TIME
And at this point, the
pressure in the aorta is
higher than the left
ventricle. The blood
would start to flow
backwards….
PRESSURE / kPa
Pressure in the Aorta:
16
You should have
worked out that the
semi lunar valves open
at this point
12
8
And close at this point
4
Now let’s look at a
slightly different graph
of all the events…
0
Atrial Systole Ventricular Systole Atrial and
Ventricular
Diastole
TIME
What happens at 1,2,3 and 4?
THE CARDIAC CYCLE



Diastole
= muscles relaxed
= low pressure in the heart
Systole
= muscles contracted
= high pressure in the heart
Sound: LUB DUB or LUP DUP
© 2008 Paul Billiet ODWS
What happens at 1,2,3 and 4?
THE MAJOR FACTORS
CONTROLLING HEART BEAT

The heart muscle tissue shows an inherent
contraction without connection to nervesMYOGENIC

The heart beat is initiated and controlled at
the SINO-ATRIAL NODE (the pacemaker)
© 2008 Paul Billiet ODWS
Sino Atrial Node





The heartbeat is controlled by electrical
signals that cause the muscle to contract.
These electrical signals start in the
“pacemaker” or Sino Atrial Node.
This is a region of the heart that contracts
rhythmically on its own, releasing an impulse
across the heart.
Look at these clips:
You tube 1 You tube 2
The control of the heart beat
The Sino-atrial node


The Sino-atrial node is
situated in the wall of
the right atrium.
When it produces an
impulse, a “wave of
excitation” spreads
through the specialised
cardiac muscle cells
causing the atria to
contract (atrial systole)
The atrioventricular node


The impulse is stopped
by a layer of connective
tissue called the
“insulating sheath”
which is between the
atria and the ventricles.
However, on this
sheath is another node
called the
atrioventricular node.
Purkyne fibres and the Bundle
of His


When the AVN is stimulated
it sends the impulse down
special conductive muscle
fibres called Purkyne fibres.
Collectively, these fibres are
called the bundle of His
(hissssss). This runs
through the septum of the
heart and (rather cleverly)
does not affect the muscle
in this area.
Bundle of His
Ventricular Systole

When the impulse reaches
the bottom of the heart, it
divides into two and sends
the impulse through
Purkyne fibres across both
the ventricles.
•The muscle contraction
starts at the bottom of the
heart and radiates
upwards. This is needed to
push blood upwards into
the arteries.
Extrinsic control of the heart rate

Extrinsic = outside (in this case, outside the heart)

The heart rate can be increased or decreased by
hormones and by nervous input from the brain.

The hormone ADRENALINE (epinephrine) increases
heart rate. It is released from adrenal glands and its
function is to prepare the body for fight or flight.
NORADRENALIN in the blood indirectly causes a
slowing of the heart beat

Extrinsic control of the heart rate



The brain will send out signals to the heart
using the autonomous nervous system.
This part of the nervous system controls
involuntary actions (e.g. breathing)
It is based in the medulla oblongata in the
bottom of the brain stem
Autonomous control of the heart
rate

The autonomous nervous system can be divided
into the:


Parasympathetic nerves
Sympathetic nerves

If impulses travel the parasympathetic nerves the
heart rate will SLOW DOWN.

If impulses travel the sympathetic nerves the heart
rate will SPEED UP.
Autonomous control of the heart rate
Confused?
Brain
Medulla
Heart
Sympathetic
nerves
Cardiovascular
centre
Parasympathetic
nerves
SAN
Hurrah!!!
Blood VesselsBasic Organisation
Artery
Arteriole
Capillary
Venule
Vein
6.2.5 Blood Vessels




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There are three types of blood vessel that
transport blood around the body:
Arteries
Veins
Capillaries
Their different structures relate
directly to their different functions.
Basic Structure of blood vessels: Layers
Basic Structure: Layers
Smooth
Muscle
Endothelium
(lining cell
layer)
LUMEN
Fibrous
Connective
tissue
Elastic
tissue
Blood vessels
Cross section through
arteries and veins
Arteries


Arteries carry
oxygenated blood
AWAY from the heart
under high pressure
and high speed.
Features:



Thick wall of elastic
fibres and muscle
Small lumen
No valves
NB The pulmonary artery
carries deoxygenated
blood
Arteries

Thick layer of elastic tissue




Stretched during systole
Recoils during diastole (maintenance of blood
pressure and smoothing of surges)
Pulse
Oxygenated blood
Arterioles


Thick muscle fibres
Control points for blood flow to vessels



Vasodilation
Vasoconstriction
Decrease in blood pressure due to greater
cross-sectional area
Capillaries


Capillaries carry blood
very close to cells and
allow substances to be
exchanged.
Features


Very thin walls
Numerous
Capillaries




Single layer of endothelial cells (<1μm)
Diameter of 8μm
Slow blood flow (amount of blood) and
velocity (speed of blood)
Exchange of oxygen, carbon dioxide, food,
waste etc between blood and cells occurs by
diffusion through fenestrations (small holes)
Veins

Features



Thin walls
Valves
Veins carry deoxygenated NB The pulmonary vein
blood back to the heart
carries oxygenated blood.
under low pressure.
The Hepatic Portal Vein
carries blood from the small
intestine to the liver.
Veins


Thinner walls – less elastic and muscle tissue
Low pressure





Small pressure from capillaries
Secondary heart
Low pressure in atria at atrial diastole
Valves
Deoxygenated blood
Varicose Veins… And the
treatment
Blood





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

One function of blood is to transport
substances around the body:
Nutrients
Oxygen
Carbon Dioxide
Hormones
Antibodies
Urea
Heat
Composition of Blood

55% Plasma (mainly water)

Plasma proteins:






Albumins, Globulins, Fibrinogen
Dissolved food (nutrients) from digestion
Urea and other waste
Hormones
Antibodies
45% Blood cells

Red blood cells, white blood cells and platelets
Erythrocytes


Red blood cells are
properly called
Erythrocytes.
They transport oxygen
and carbon dioxide (!!)
around the body.
Amazing blood cells …..
The heart beats around 3 billion times in the averages person's
life.
About 8 million blood cells die in the human body every second,
and the same number are born each second. Within a tiny droplet
of blood, there are some 5 million red blood cells.
It takes about 20 seconds for a red blood cell to circle the whole
body.
Red blood cells make approximately 250,000 round trips of the
body before returning to the bone marrow, where they were born,
to die.
Red blood cells may live for about 4 months circulating throughout
the body, feeding the 60 trillion other body cells
http://www1.bellevuepublicschools.org/curriculum/k6web/fifthgrade/bodysys/amzcirsystem.html
Leucocytes
Phagocytes
(70%)
Lymphocytes
(30%)
Destroy microbes with
phagocytosis
Destroy microbes with
antibodies
Thrombocytes
Quick revision questions on
the heart…
Heart Problems- Atherosclerosis

Plaque is made up of fat, cholesterol, calcium, and other substances
found in the blood. Over time, plaque hardens and narrows your
arteries. The flow of oxygen-rich blood to your organs and other
parts of your body is reduced.



If a blood clot develops in one of these arteries, the blood supply to that
area of the heart muscle will stop. This is known as a heart attack, or in
medical terms a coronary thrombosis or myocardial infarction.
A heart attack will cause severe chest pains behind the breast bone,
often radiating towards the left arm.
If the blockage (thrombosis) is not dissolved quickly with medication,
the area of heart muscle that isn't getting enough oxygen will stop
working properly.
Risk Factors for CAD (coronary
arterial diseases:
Risk factors for a heart attack include:
 a family history of atherosclerosis
 high cholesterol levels
 high blood pressure
 smoking
 being male
 diabetes Type 1 or Type 2
 being overweight
 stress
 lack of exercise.