Transcript module 3 3.1.2 transport in animals heart and circulationx

Module 3 - 3.1.2 Transport in
Animals
Heart and Circulation
By Ms Cullen
What are the features of a good
transport system?
• a fluid to carry nutrients and gases around the
body – the blood.
• a pump to create pressure and cause the fluid
(blood) to flow around the body- the heart.
• exchange surfaces which allow nutrients and
gases to enter and leave the blood where
needed.
• tubes or vessels to carry the blood.
• 2 circuits, one to pick up oxygen and nutrients,
the other to deliver them to tissues.
Open or Closed Circulatory Systems?
• Vertebrates have closed circulatory systems – all
the blood is enclosed in the blood vessels.
• Insects have an open circulatory system.
• In insects blood is pumped by a heart and flows
out of the heart in arteries into a body cavity
which is called the haemocoel (‘blood space’).
• In insects blood does not transport oxygen,
instead they have tubes, trachea, which carry air
directly from the atmosphere deep into the
tissues.
Insect
Single and Double Circulatory Systems
Fish have a twochambered heart in
which a single-loop
circulatory pattern takes
blood from the heart to
the gills and then to the
body.
Humans, birds, and
mammals have a fourchambered heart that
completely separates
oxygen-rich and
oxygen-depleted blood.
Amphibians
• Amphibians have a three-chambered heart with two atria and one
ventricle. A loop from the heart goes to the pulmonary capillary beds,
where gas exchange occurs. Blood then is returned to the heart. Blood
exiting the ventricle is diverted, some to the pulmonary circuit, some to
systemic circuit.
• The disadvantage of the three-chambered heart is the mixing of
oxygenated and deoxygenated blood.
Reptiles
• Some reptiles have partial separation of the ventricle.
• Other reptiles, plus, all birds and mammals, have a four-chambered heart,
with complete separation of both systemic and pulmonary circuits.
Single and Double Circulatory Systems
• Humans and mammals have a double
circulatory system.
• The pulmonary circulation is the part of the
circulatory system connected to the lungs.
• The systemic circulation serves the rest of the
body.
• As there are two circuits, it is known as a
double circulatory system, however, it is more
like a figure of ‘8’.
Evolution of the circulatory system
Single and Double Circulatory Systems
Task:
Using P. 172-173 in Kerboodle
• Explain the differences between the single
circulatory system of fish and the double
circulatory system of mammals.
• Explain the advantages of the double
circulatory system to humans.
The Mammalian Heart
Week 8
The internal structure of the heart
The heart
• The heart is made of
CARDIAC MUSCLE.
• Cardiac muscle fibres
have INTERCALATED
DISCS holding the muscle
cells together tight and
sheet like. This speeds up
nervous stimulation of
the whole tissue.
Cardiac muscle
• The muscle is STRIATED
as voluntary muscle is.
• Mitochondria are
numerous.
• It is MYOGENIC – able
to contract and relax of
it’s own accord.
PAG 2.1 - Heart Dissection
• Be careful with scalpels!
• Wear goggles and gloves.
• Wash hands after dissection.
When you have finished complete the Qs at the
bottom of the page.
Questions:
• Describe the function of the atrioventricular
valves
• Describe the roles of the tendinous cords
• Explain why the wall of the left ventricle needs to
be much thicker than the right
• Why might it be harmful if the right ventricle
creates too much pressure
Keywords you need to know: make a card match activity!
Single circulatory system. Double circulatory system. Diffusion.
Respiration. Pulmonary circulation. Systemic circulation.
Deoxygenated. Oxygenated.
Atrium. Ventricle. Coronary artery. Constrict. Vena cava.
Pulmonary vein.
Atrioventricular valve. Tendinous cords. Septum. Semilunar
valve. Alveoli. circulatory system, erythrocyte, facillitated
diffusion, pulmonary circulation, systemic circulation,
The Cardiac Cycle
Sequence of Contraction
Cardiac Cycle
1. Atrial Systole= Atrial
contraction
2. Ventricular Systole =
Ventricular contraction
3. Ventricular Diastole=
Filling phase
Normal cardiac cycles
(at rest) take 0.8
seconds
The Cardiac Cycle
Ventricular systole opens the SL valves,
forcing blood out of the ventricles through
the pulmonary artery or aorta.
Ventricular diastole is the
filling of the ventricles
with blood. Atria and
ventricles relax. Blood
from the body flows into
the vena cava, which
empties into the right
atrium. At the same time,
oxygenated blood from
the lungs flows from the
pulmonary vein into the
left atrium.
The muscles of both atria contract, forcing blood downward through each AV
valve into each ventricle.
Feel the beat...
• The sound of the heart
contracting and the valves
opening and closing produces
a characteristic "lub-dub"
sound.
• Lub is associated with closure
of the AV valves,
• dub is the closing of the SL
valves.
The Cardiac Cycle
• http://www.youtube.com/watch?v=fZT9vlbL2
uA
A single heart cell beating!
Control of heart rate
Cells contract rhythmically – Intrinsic rhythmicity
60 beats per minute
Rhythm maintained by a wave of electrical
excitation similar to a nerve impulse that spreads
through special heart tissue.
Hearts’ own rhythm means your body doesn't
waste resources on this continuous activity.
You do also have nerves and hormones to speed up or slow
down heart rate which are controlled by cardiovasular centre
in your brain.
-sympathetic nerves to heart accelerate heart rate
- vagus nerve decelerates heart rate
The rhythmic sequence of contractions is coordinated by the
sinoatrial (SA) {pacemaker} and atrioventricular (AV) nodes.
Human heartbeats originate from SA node near the right atrium.
SA gives electrical stimulation that initiates atrial contraction by
creating an action potential.
Modified muscle cells contract,
sending a signal to other muscle
cells in the heart to contract.
The signal spreads to the
atrioventricular node (AV
node). Small delay at the
AV node
Signals carried from the AV node,
slightly delayed, (allows blood to
fill ventricles) through bundle of
His fibers and Purkinjie fibers
cause the ventricles to contract
simultaneously
Electrical impulses in the heart originate in the sinoatrial node and travel through the
intrinsic conducting system to the heart muscle.
The impulses stimulate the myocardial muscle fibres to contract and thus induce
systole.
http://www.youtube.com/watch?v=fZT9vlbL2uA
The heart in action
Electrocardiograms
• The electrical impulses controlling the heart
can be detected and measured using an
electrocardiogram (ECG).
• Electrodes are placed on the skin at opposite
sides of the heart and electrical potentials are
recorded.
• A graph of voltage against time is produced.
• An echocardiogram allows Drs to look at the
heart working using ultrasound.
http://www.youtube.com/watch?v=TwA0LM5_1dE
Electrocardiograms
• One full heartbeat- 0.8s
• P wave is caused by
contraction (depolarisation)
of the atrium.
• QRS complex is caused by
contraction (depolarisation)
of the ventricles.
• T wave is the relaxation
(repolarisation) of the
ventricles.
Remember!
Depolarise = loses electrical charge – contracts
Repolarise = regains charge – relaxes
A normal ECG trace compared with others indicating an unhealthy heart
Week 8
Electrocardiograms
http://www.youtube.com/watch?v=v3b-YhZmQu8
Pressures changes in the aorta, left ventricle and left atrium during one
heartbeat
Using this diagram in your
handbook and P.188 in
your textbook annotate
the graph to explain what
is happening to
-aortic pressure
-ventricular pressure
-atrial pressure
-ventricular volume
Q Why is atrial pressure
always lower than
ventricular?