Transcript How your Heart beats…

How your Heart beats…
In this Power-point:
• The structure of the Heart
• How a valve works
• The Cardiac Cycle
• Control of the beat
• Parts of the blood
http://www.giraffe-pictures.net/giraffe-heart-cartoon.jpg
http://www.heart-valvesurgery.com/Images/heartcartoon.jpg
External view of the heart
http://2.bp.blogspot.com/_gVhO17PeNI0/SLDDCGZnw9I/AAAAAAAAADo/lDX1D1QY2pw/s320/human+heart+diagram.jpg
The internal structure of the heart
Simple diagram of the heart
http://upload.wikimedia.org/wikibooks/en/1/1c/Heart_diagram_corrected_labels.JPG
How a valve works……
The heart valves work in
much the same way. (esp.
the semi lunar valves)
The bi-cuspid and tri-cuspid
valves have tendons to stop
them being pushed insideout.
http://wiki.nus.edu.sg/download/attachments/22053011/one_way_vein_valves.jpg.jpg
Watch the whole thing first before splitting it into sections…….
Left Atrium
Right Atrium
Right Ventricle
Left Ventricle
Now look at the flow of the blood. The blood comes into the atria from the Vena cava
Notice
how
atria
at the
same
time,the
then
both
ventricles
fillwith
then
empty
at the
andlook
pulmonary
vein,fill
goes
into
the ventricles
and
isco-ordinate
then pumped
past
the
semilunar
Next
atboth
the valves.
Try
to
follow
how
valves
the
beating
of the
same
valves intoatria
the
aorta
or pulmonary artery
and time
ventricles
The heart beats on average 70 times every minute and is
continuous. The beat is Myogenic – It beats without external
impetus. (Remember the scene from Indiana jones and the temple of doom
where the priest removes the heart and it continues to beat………..)
.
http://img2.timeinc.net/ew/dynamic/imgs/080715/Death-scenes/Indiana-Jones-heart_l.jpg
• The periods of contraction are called
systole. There are 2 periods of systole –
atrial followed by ventricular.
• The periods of relaxation are called
diastole. The whole heart – atria and
ventricles go into diastole at the same
time.
• Atrial Systole →Ventricle systole→
Diastole→ Atrial Systole →Ventricle
systole→ Diastole……….
Atrial Systole
• The Atria contracts
• The blood is pushed
against the AV valve
which opens.
• Vena Cava and
pulmonary vein valves
are shut.
• The blood flows into
the ventricle.
http://upload.wikimedia.org/wikipedia/commons/thumb/3/34/Heart_systole.svg/200px-Heart_systole.svg.png
Ventricular Systole
• The ventricle
contracts.
• This pushes blood
against the AV valve
and closes it.
• The semi lunar valves
open,
• Blood flows into the
Aorta or Pulmonary
artery.
http://upload.wikimedia.org/wikipedia/commons/thumb/3/34/Heart_systole.svg/200px-Heart_systole.svg.png
Diastole
• All the muscles relax.
• The semi-lunar valves
close.
• Pulmonary vein and
vena cava valves
open.
• Blood flows into the
atria AND ventricles.
http://upload.wikimedia.org/wikipedia/commons/thumb/3/34/Heart_systole.svg/200px-Heart_diastole.svg.png
Or in more depth………
•
•
•
•
•
•
•
•
•
The cardiac cycle
One cardiac cycle consists of the atria and then the ventricles contracting so
that the blood that has entered the heart is pumped out. This occurs about
We shall start when the atria and ventricles are in diastole.
Blood at a low pressure in the veins flows into the atria. This increases the
pressure inside the empty atria as they fill. Some of the blood trickles
through the open atrioventricular valves into the relaxed ventricles below.
When the atria are full, they go into atrial systole, their walls contract and
blood is pushed through the valves into the ventricles. The pressure in the
atria is increased due to the contractions and the pressure is increasing in
the ventricles as they fill with blood.
When the atria contract, blood cannot flow back into the veins because the
pressure of the blood pushes on the valves in the veins to shut them.
After a short delay the ventricles contract from the apex (base) upwards.
The pressure inside the ventricles increases due to the ventricular systole.
As the pressure increases to a higher level than the pressure in the atria,
blood pushes against the atrioventricular valves, shutting them (the first
heart sound) and preventing backflow.
The semilunar valves open under the pressure and blood leaves the heart.
The ventricles relax - ventricular diastole - and the semilunar valves snap
shut behind the blood (the second heart sound).
So how does the pattern of beat
work?
Click on the link below. Turn off the sound and watch.
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter22/animation__conducting_system_of_the_heart.html
You need to know about:
The flow of impulse from the Sino-Atrial Node or
Pacemaker across the atria.
The inability of the impulse to pass directly to the
ventricles……
…..but the Pick up of the impulse at the Atrio-ventricular
node.
The passing of the impulse down the Purkinje fibers to the
bottom of the heart…
…Causing the contraction of the ventricle upwards
In Summary
Within the right atrium there are a specialise group of
cells called the Sino Atrial Node.(SAN).
These cells can generate an electrochemical potential
across the cell membrane and once threshold is
reached this can be propagated across the other cells
of both atria.
The speed of conduction across the two atria is fast
enough that both effectively contract together.
However the cell membrane structure alters across a
line rough consistent with the diagram and effectively
prevents the conduction of the contraction stimuli
traveling down into the ventricles
http://click4biology.info/c4b/6/hum6.2.htm
A) The impulse is picked up by a specialised group
of cells in the right atrium wall called the AtrioVentricular Node (AVN).
B) The AVN conducts the impulse down through the
central septum of the heart along specialised fibres
called the Purkinje fibers. The fibres are insulated
from the muscle and do not cause contraction.
C) The impulse emerges into the muscle at the
apex of the heart so that the ventricular contraction
begins at the apex.
D) The impulse travels on emerging into the heart
muscle higher up the ventricle wall in this way the
contraction spreads upwards.
Note that this direction of contraction pushes the
blood towards the semi-lunar valve and also not
that the transmission time down the Purkinje tissue
creates a delay between atrial and ventricular
systole. This delay maintains the correct directional
flow of blood through the different chambers.
http://click4biology.info/c4b/6/hum6.2.htm
What controls how fast or slow the
heart beats?
• Accelerator Nerve into the Sino-Atrial Node
speeds up the pulse from resting beat, The
Decelerator Nerve (Vagus) slows down the
pulse rate. These nerves are controlled by the
cardiac center in the Medulla Oblongata of the
brain.
http://scienceaid.co.uk/biology/humans/images/heartnerves.jpg
• Adrenalin released from the adrenal
glands also acts on the Sino-atrial Node to
speed up the pulse from resting beat, this
is a Fight or Flight response.
The adrenalin is
carried to the
heart in the blood
stream.
http://www.coolschool.ca/lor/BI12/unit13/U13L02/adrenalglands.png
The blood is made up of 3 main
types of cell
1. Red blood cells
(erythrocytes)
- are responsible for the
carriage of oxygen.
- have no nucleus so they
can carry more
haemoglobin.
- are small and able to pass
through small
capillaries.
http://www.topnews.in/health/files/blood-vessels.jpg
White blood cells (leukocytes)……
2. Phagocytes – gobble up large invaders
such as bacterial cells and amoeba by
process of phagocytosis (“cell eating”- like a
pac-man!) They have a multi-lobed nucleus
so that they can pass out of the blood
vessels to fight infection. These form the
majority of Pus!
http://www.fazaclo.com/Images/red_white_blood_cells.jpg
3. Lymphocytes – produce antibodies to
fight off the smaller invaders such as
viruses. The large nucleus is highly
active in producing the antibodies.
These cells stay in the blood vessels
and lymph vessels.
http://www.immunesupportonline.com/Images/lymphocyte%20and%20nutrophil.jpg
Blood plasma
The rest of the blood is Plasma and
platelets. This is responsible for
the other functions of the blood:
• Carriage of dissolved products of
digestion
• Carriage of dissolved waste
products of metabolism
• Carriage of dissolved hormones
– chemical messengers
• Carriage of heat
• Carriage of Carbon Dioxide
•http://www.clarian.org/ADAM/doc/graphics/images/en/19432.jpg
Structure of Blood vessels
Why is it important to have elastic fibers in the arteries?
http://trc.ucdavis.edu/biosci10v/bis10v/week10/arteries.gif
Structure of Arteries
•
•
•
•
Thick walls
No valves
Elastic tissue
Keep blood at
high pressure
• Always Away
from the heart
http://greenfield.fortunecity.com/rattler/46/images/artery1.JPG
Structure of Veins
• Veins have valves and thin
walls because the blood
pressure is low and they
need to stop “backflow”!
• They have much less elastic
fiber to resist the pressure.
http://www.teachpe.com/images/500structure_of_vein2.JPG
Structure of Capilliaries
• Very thin walls to allow
easy diffusion.
• Narrow to allow cells
through in single file
• Very many capillaries to
deliver blood to all the
tissue.
• Are leaky – to allow the
tissue fluid with all its
disolved nutrients to bath
the body cells.
http://www.biosbcc.net/doohan/sample/images/CO%20and%20MAP/bulk%20flow.jpg