Transcript File - Ms Curran`s Leaving Certificate Biology

Open Vs Closed Circulatory System

Open
Open ended vessel which blood leaves
Blood flows around cells
Enters heart through openings

Closed
Blood remains in vessels
Materials exchanged by diffusion
More efficient then open system, Faster
and flow can be increased/decreased
Blood Vessels
3 main types
1. Arteries (A for Away from heart)
divide into smaller vessels- Arterioles
2. Veins (to heart)
divide into smaller veins- Venules
3. Capillaries
tiny vessel (1 cell in thickness), link
arteries & veins
Arteries Vs Veins
What have they both got in common? What is different?
Arteries Vs Veins
Both have the same 3 layers.
Main difference is in the middle layer.
 3 layers
1. Outer, is tough, made of protein called collagen
which prevents wall from over expanding.
2. Middle, is muscle and elastic, it can alter the size of
the vessel
3. Inner, are living cells called endothelium.
Valves
Blood pressure is the force blood applies
against the wall of a blood vessel.
 Blood pressure is highest in arteries, this
causes the arteries to expand, which causes
our pulse.

Pressure in veins is very weak. Ordinary
muscles help push the blood by contracting and
squeezing to return blood to the heart.
 Because pressure is low, must prevent backflow
 Valves control direction of blood flow

Artery
Carries blood away from
heart
Vein
Carries blood to heart
Blood under high pressure Blood under low pressure
Thick walls
Thin walls
Small Lumen
Large Lumen
Blood flows in pulse
No pulse
Blood rich in oxygen
Blood low in oxygen
Valves absent
Valves present
Capillaries
Tiny, branched vessels
 Walls are permeable, allow materials to
move across the walls
 100,000 km

The Heart
Made of cardiac (slow to fatigue) muscle,
surrounded by a double membrane called
Pericardium.
 It contracts 100,000 times a day
 Pumps 5-20 litres of blood per minute
 Why such a difference? 5-20

Structure of the Heart
Divided into 2 side by a wall called Septum.
4 chambers,
2 upper = Atria, 2 lower = Ventricles
 Atria & ventricles are separated by valves
 These valves are held in place by tendons
 These tendons are held in place by Papillary Muscles.

Valve on right has 3 flaps, tricuspid valve
 Valve on left has 2 flaps, bicuspid valve
 Semilunar valves prevent blood returning to heart

Pulmonary artery
Semilunar valve
Superior vena cava
Aorta
Semilunar valve
Pulmonary vein
Pacemaker
Left atrium
Right atrium
Bicuspid valve
Inferior
vena cava
Tendon
Tricuspid valve
Right ventricle
Cardiac Muscle
Pericardium
Papillary Muscle
Left ventricle
Septum
Blood flow in the heart
Step 1
 Deoxygenated blood enters the right atrium
through 2 venae cavae.
Superior - head, arms, chest.
Inferior – Lower part of body.
 The right atrium contracts forcing blood into
right ventricle
 The venae cavae close to prevent backflow
Blood flow in the heart
Step 2
 When the right ventricle contracts the
tricuspid valve is forced closed
 Blood is then forced out of the heart and
into the lungs through the semilunar valve
in the pulmonary artery.
Blood flow in the Heart
Stage 3
 Oxygenated blood returns to the heart
from the lungs and enters the left atrium
through the pulmonary veins (only vein to
ever carry oxygen rich blood)
 Pumped through bicuspid valve into the
left ventricle
Blood flow in the heart
Stage 4
 When the left ventricle contracts the
bicuspid valve closes.
 Blood is pumped out of the heart through
the semilunar valve in the aorta
 When the ventricles relax these valves
close to stop backflow
Double Circulation
Heart is really a double pump. The 2 sides of
the heart are divided by the septum.
 Why is this necessary?
 Answer=

Hence humans have a 2-circuit circulatory
system.
The Pulmonary Circuit & The Systemic Circuit

Double Circulation
Pulmonary circuit
Right ventricle pumps de-oxygenated blood
around the pulmonary circuit.

This circuit is short so the walls of the
ventricle are thin
Double Circulation
Systemic Circuit
The Left ventricle pumps oxygenated blood
to head, arms, trunk and legs.

This is a much longer route so the walls are
much thicker and stronger.
Double Vs Single Circulation

Allows oxygen rich and poor blood to be
kept separate.

Ensures the blood pressure is high enough
to reach all parts of the body.

Single circulation system can only produce
low pressure, this restricts activities of
animal i.e. worm
Blood supply to the Heart itself

supplied by the coronary arteries
These are connected by the aorta

coronary veins drain blood into the right
atrium

Blockage of the coronary arteries is a common
cause for heart attacks
What Controls the Heartbeat

The pacemaker or SA (Sino-atrial node),
located in the wall at the top of the right atrium

It sends out a regular electrical impulse which
causes the atria to contract, followed by the
ventricles.

Frequency of these impulses are controlled by
the brain & can speed up or slow down.
Pulmonary artery
Superior vena cava
Pacemaker
Inferior
vena cava
Pulmonary vein
Aorta
Stages of heartbeat
Diastole = Chambers relax
Systole = Chambers contract
1. Blood enters heart (Atrial Diastole)
both Ventricles & Atria are relaxed. All valves
are closed.
Stages of Heartbeat
2.Blood is pumped from atria to ventricles
(Atrial systole)
PM cause atria to contract
(how?), this pumps blood
into ventricle.
The tri & bi-cuspid valves
open while the venae
cava & pulmonary veins
close. Semi-lunar valves
remain closed.
Stages of heartbeat
3. Blood leaves the heart (Ventricular Systole)
Atria relax, impulses from AV (atrio-ventricular) nodes
cause ventricles to contract. This forces blood out
through the pulmonary artery & Aorta
The pressure forces open
semi-lunar valves & closes
the tri & bi-cuspid valves
Ventricles relax, closing the
semi-lunar valves.
Sound of Heartbeat

“Lub-dub” sound

Caused by valves being forced shut

Lub due to bi & tri-cuspid valves closing

Dub due to semi-lunar valves snapping shut
Pulse

When left (thick) ventricle contracts,
pressure of blood forced in the aorta causes
it to expand & then contract

This forms a wave down the arteries called
pulse
Average adult pulse rate is 72 beats/min
Most people between 60-100

Blood Pressure

This is the force exerted by the blood against
the walls of the blood vessels

Human blood pressure is measured by finding
the amount of pressure needed to stop the
flow of blood
This produces 2 readings
1. When there is a pulse 2. When no pulse

Blood Pressure

Typical blood pressure in adults is 120/80 mm
of mercury. These values rise with age.

If the lower value goes over 95 mm of Hg the
person suffers from high blood pressure

High blood pressure is caused by blockages in
arteries.
Effects of smoking on Heart

Tabacco contains 400 harmful chemicals,
including nicotine (more addictive then heroin)

Nicotine causes increased heart rate & blood
pressure

Carbon monoxide reduces O2 carried by blood

In Ireland 7000 people a yr die form smoking
Effects of exercise on Heart

When we exercise our muscles get bigger &
stronger this is the same for our heart

Exercise improves circulation and reduces body
weight

Most beneficial exercise is aerobic exercise e.g.
Walking, jogging, running, swimming and
Dancing so get your feet moving.
Effects of Diet on Heart

3 main factors = salt, fat & being overweight

Harmful fats found in red meat & dairy, they
contain Cholesterol which forms blockages

1 packet of processed foods contains your
entire days intake of salt

Obesity causes high blood pressure & heart
attacks