Download The Heart

The Heart and Blood Vessels
Chapter 26
Aidhm
The need for a circulatory system
• Organisms that are
only a few cells
thick do not need a
circulatory system.
• Nutrients/oxygen/
waste are
transported by
diffusion
Two types of Circulation System
Open Circulation Systems
Heart pumps blood into vessels that are open
ended
Found in invertebrates e.g. in Insects
Two types of Circulation System
Closed Circulation Systems
Blood remains in a continuous system of
blood vessels
Found in vertebrates e.g. in Humans
Advantages of a Closed Circulation
System
1.
Blood can be pumped faster
Nutrients can be delivered faster to cells
Allows organism to be more active
2.
Blood flow rate to different organs
can be changed
Blood flow can be increased to the leg muscles
when running
Main parts of Human Circulation
System
1.
2
Heart
Blood Vessels
Arteries
Arterioles
Veins
3.
Blood
Venules
Capillaries
Blood Vessels
1. Arteries
a. Carry oxygenated blood away from the heart.
b. Divided into smaller vessels called arterioles
2. Veins
a. Carry deoxygenated blood towards the heart
b. Small veins are called venules
3. Capillaries
a. Tiny vessels, link arteries to veins
Arteries
Veins
Functions of parts
• Inelastic protein: Collagen, prevents over expansion
• Muscle and elastic fibres: Changes size of the vessel (when
exercising, blushing)
• Endothelium: Single layer of cells
Cross section of blood vessel
Collagen
Muscle and
Elastic fibres
Endothelium
Lumen
Blood vessels under the microscope
Arteries
Veins
Thin Wall
Thick Wall
Narrow
lumen
Wide
lumen
Have valves
to prevent
backflow
Blood pressure
• Arteries: blood under high
pressure. Artery expands (pulse)
• Veins: blood under low pressure.
Valves present to prevent
backflow
Capillaries
• Have single layer of endothelium
• Walls are permeable
• There is a capillary close to every body
cell
Capillaries
Did you know….
Learning check
Can you….
Aidhm
The Heart
Location
Between the lungs
slightly to the left side of the
thorax
above the diaphragm
Function
To pump blood around the body
Structure
A hollow structure made of
cardiac muscle, surrounded by a
double membrane (pericardium)
Role of Heart Muscle
1.
The heart wall is made of Cardiac
Muscle
2.
Drives blood around the body
3.
Cardiac Muscle does not fatigue
Human
Two-Circuit
Circulation
• Circuit is short.
• Therefore walls of right ventricle are
thin
• Gains oxygen, loses carbon dioxide
• Circuit is long.
• Therefore walls of left ventricle
are thicker
• Loses oxygen, gains carbon
dioxide
Double Circulation System
• Heart is a double
pump.
• Advantages:
I.
Separation of
oxygen rich and
oxygen poor blood
II.
Blood pressure
can be kept high
• Single circulation
systems have low blood
pressure. E.g.
Pathway of blood Around Body
Vena Cava
Aorta
Pulmonary Artery
Pulmonary Vein
Left Atrium
Bicuspid Valve
Right Atrium
Left Ventricle
Tricuspid Valve
Cardiac muscle
Right ventricle
Semi Lunar Valves
Septum
The Heart
Part
Function
Pericardium
surrounds heart to prevent friction
Septum
separates the right and left side of heart
Tricuspid valve
(right side)
Valves prevent backflow. Held by tendons
(heart strings). Has 3 flaps
Bicuspid valve (left
side)
Valves prevent backflow. Held by tendons
(heart strings). Has 2 flaps
Semilunar valves
Valves prevent backflow. Blood flows into
the 2 main arteries
Right ventricle
pumps blood to lungs by the pulmonary
artery (thin wall – short circuit)
Left ventricle
pumps blood to body by the aorta (thick
wall – long circuit)
From the Junior Cert, can you complete the following
Role of Valves
Semi Lunar
valves
Tricuspid
valve
Prevents
backflow into
right atrium
Prevent
backflow into
heart
Bicuspid
Valve
Prevents
backflow into
left atrium
Blood pathway through heart
Aorta
Vena Cava
Right Atrium
Pulmonary artery
Pulmonary vein
Left atrium
Bicuspid valve
Tricuspid valve
Right ventricle
Left ventricle
Blood supply to the
heart wall
Coronary arteries
Cardiac muscle is
supplied with blood by
the coronary arteries.
These branch from the
aorta just above the semi
lunar valves ot the aorta
Coronary veins
Drain blood from heart
wall into the right atrium
Portal systems
A blood pathway that
begins and ends in
capillaries
Vessels do not
connect to the heart
Example: Hepatic
Portal System.
This connects the
stomach and
intestines to the liver
Heartbeat and its control
http://www.youtube.com/watch?v=qYBtchCqPao
The heart beat
• contraction and relaxation of the cardiac
muscle
• controlled by the pacemaker
• The sound is the closing of the heart valves
Did you know….
Factors affecting heart rate
Heart rate is increased by
Exercise
Stress
Heart rate is decreased by
Sleep
Alcohol
Ordinary Level
Higher Level
Heart Rate Control
Pacemaker ( SA Node)
• Located in the right atrium wall
• The SA node emits an electrical impulse and causes the atria to
contract
AV node
•• Located further down the right atrium
wall
• Picks up signal from SA node
• Sends a signal to the ventricles
• Causing the ventricles to contract
Heart Rate Control
Stages of the heartbeat
Contraction of heart muscle is called SYSTOLE
Relaxation of heart muscle is called DIASTOLE
1
Blood enters the two atria. All valves are closed
All chambers are relaxed. (diastole).
Stages of the heartbeat
Contraction of heart muscle is called SYSTOLE
Relaxation of heart muscle is called DIASTOLE
2. The atria contract (systole), tricuspid and bicuspid valves
open, blood is forced down into ventricles
Stages of the heartbeat
Contraction of heart muscle is called SYSTOLE
Relaxation of heart muscle is called DIASTOLE
3. Atria relax ( diastole), ventricles contract (systole), Bicuspid
and tricuspid valves close, semi lunar valves open and blood
is forced into the pulmonary artery and aorta
Stages of the heartbeat
Contraction of heart muscle is called SYSTOLE
Relaxation of heart muscle is called DIASTOLE
4. Ventricles relax (diastole), semi lunar valves close.
The cycle starts again
Higher Level
Can you…
Aidhm
Pulse
The expansion and contraction of arteries due to
pumping of the heart.
A wave of expansion passes down the walls
of arteries following a contraction of the
left ventricle. The elastic fibres in the artery
walls then bring about a contraction of the
artery wall.
Average pulse rate is 72 beats per
minute, found in the neck and wrist
Blood Pressure
As blood passes from arteries to veins pressure drops
Blood pressure is
measured with an
instrument that records the
pressure it takes to stop
the blood flow in an artery
of the upper arm
Blood Pressure
Average Human Blood Pressure: 120/80
Two measurements are taken when recording
blood pressure:
1. Systole pressure (higher number): the pressure
of blood as a pulse passes through the artery.
2. Diastole value (lower number):the pressure
when there is no pulse
Did you know….
Effect of Exercise on the circulation system
Exercise
• strengthens the heart
• increases the size of the
heart
• increases our ability to
transport oxygen
Effect of smoking on the circulation system
1.
Nicotine increases the heart rate, blood pressure and
cholesterol.
Causes strain on the heart
2.
CO2 reduces the amount of O2 carried by the blood
This reduces energy levels
Effect of Diet on the circulation system
• Fat: causes a build up of
cholesterol, which blocks
arteries and lead to stroke
or heart attack
• Salt intake: Raises blood
pressure which can
cause heart attack
• Overweight: Raises
blood pressure which
can cause heart attack
Learning check
Can you…..
Mock Question
(a) (i)
(ii)
(b) (i)
Blood/heart/blood vessels (3 × 2marks)
Diffusion
(3marks)
Absence of nucleus
Absence of nucleus mitochondria
Affinity for oxygen
Biconcave shape
Circulate for days
(2 × 3marks)
(ii)
Transport oxygen
(iii)
Haemoglobin
(iv)
More red blood cells
No Nucleus
Smaller
Reach more places
(3marks)
(3marks)
(Any 1 - 3marks)
END