Higher Human Biology
Unit 2: The continuation of life
Chapter 20:
Transport Mechanisms: The
cardiac cycle
22/03/2016
Mrs Smith Ch19 The need for
transport
1
Learning
Intentions
Success
Criteria
To understand the
anatomy of the heart, to
find out how the
heartbeat is controlled
and to look at
differences in blood
pressure in the
circulatory system.
1. Describe the cardiac cycle
of the heart
22/03/2016
2. Explain the cardiac cycle
of the heart in relationship
to pressure changes
Mrs Smith Ch19 The need for
transport
2
Cardiac Cycle
The cardiac cycle is the pattern of contraction and
relaxation of the heart during one heartbeat.
The average
heart rate is
75
beats/min
with a
cardiac cycle
of 0.8 secs.
Systole = contraction
Diastole = relaxation
Image source: www.classes.kumc.edu
Heartbeat animation
The average human heart rate at rest
is 75 beats a minute
Each heart beat lasts for
approximately 0.8 of a second at rest
Each heart beat involves a series of
Events referred to as
THE CARDIAC CYCLE
Heartbeat:
Atria & Ventricular diastole
Stage 1:
A heartbeat begins
with the heart muscle relaxed
and valves
closed.
Blood flows into the two atria
and both sides fill up with
blood.
This blood has to be pushed
through the valves to get into
the ventricles. How does this
happen?
Heartbeat: Atrial systole
Stage 2:
The atria contract and the
blood is squeezed which
causes the AV valves leading
to the ventricles to open.
Blood then flows from the atria
into the ventricles.
What happens to the open
valves when the atria are
empty?
Heartbeat: Atrial systole
Stage 2 (continued):
The AV valves between the
atria and the ventricles
close.
This prevents any backflow.
What happens next
to the blood in the ventricles?
Heartbeat: Ventricular Systole
Stage 3:
Almost immediately, the
ventricles contract and the
blood is squeezed again.
The pressure of the blood
forces open the SL valves
leading out of the heart.
Blood is pumped out
of the heart.
What happens to the open
valves when the ventricles are
empty?
Heartbeat: Ventricular Systole
Stage 3 (continued):
When the ventricles are
empty, the SL valves leading
out of the heart close and the
heart muscle relaxes.
This completes the sequence
of contraction and relaxation in
one heartbeat.
What will happen next?
Stages of a heartbeat
Stage 1 (again):
The atria fill up with blood as
the heartbeat sequence
begins again.
Why are the walls
of the atria thinner than the
walls of
the ventricles?
Why is the wall of the left
ventricle thicker than the right
ventricle?
Try this Scholar Animation Fig.3.9
http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&contentGUID=dfaf24ad-00219d39-4277-e967e919c79f
2. Heart Valves & Sounds
Throughout the cardiac cycle, pressure changes take place
in the atria, ventricles and arteries
Pressures in the right and left atrium, right and left ventricle, aorta
and pulmonary arteries can be recorded and illustrated in
graphical form
The graph on the next slide shows pressure changes in the left side
of the heart and the aorta
A similar graph can be drawn for the right side of the heart and the
pulmonary arteries
Such a graph is similar in shape to that obtained for the left side
of the heart but all the pressures readings are of a lower value
Pressure Changes in the Heart
120
SL valve closes
SL
valve
opens
pressure (mm Hg)
100
aortic
pressure
80
left ventricular
pressure
60
40
AV
valve
opens
AV
valve
closes
20
left atrial
pressure
0
0
0.1
0.2
0.3
0.4
0.5
0.6
time (s)
ATRIA
VENTRICLES
= systole
= diastole
0.7
0.8
Pressure Changes in
the Left Side of the
Heart During One
Cardiac Cycle
120
aortic
pressure
pressure (mm Hg)
100
The pressure changes
in the left ventricle,
left atrium and aorta
can be related to the
phases of the cardiac
cycle
80
left ventricular
pressure
60
40
20
left atrial
pressure
0
0
0.1
0.2
0.3
0.4
time (s)
0.5
0.6
0.7
0.8
Pressure Changes in the
Left Side of the Heart
A
WX
A
Z
Y
120
aortic
pressure
DUB
pressure (mm Hg)
Period Z to A represents
the phase of Passive Filling
of the ventricles when the
AV valves are open and 100
the semi-lunar valves are
closed
Period A to W represents
the phase of Atrial Systole
80
when the atria contract
and the ventricles are
filled to full capacity
Period W to X represents
60
the first phase of
Ventricular Systole when
the ventricles contract in an
isometric fashion; the
greatest rise in ventricular 40
pressure occurs during this
phase and the ventricular
volume remains constant
Period X to Y represents the20
second phase of Ventricular
Systole when ejection of blood
takes place and pressure in the
aorta rises
0
Period Y to Z represents relaxation
0
of the ventricles (diastole) when the
ventricular pressure drops sharply
left ventricular
pressure
left atrial
pressure
LUB
0.1
0.2
0.3
0.4
time (s)
0.5
0.6
0.7
0.8
Heart Murmur
Abnormal cardiac blood flow causes abnormal heart
sounds known as heart murmurs.
This is often
caused by faulty
valves that fail to
open or close
fully.
This is often an
inherited
condition but
can be caused by
illness e.g.
rheumatic fever.
Learning Success Criteria
Intentions
To understand the
anatomy of the
heart, to find out how
the heartbeat is
controlled and to
look at differences in
blood pressure in the
circulatory system.
3. Describe the structures
involved in the conducting
system of the heart
4. Describe the role of the sinoatrio node in the conductivity
of the heart
5. State the sequence of
electrical conductivity of the
heart.
3. Conducting System of the Heart
• The heart is special in
Pace maker
(Sino-atrial
that the electrical
node (SAN))
stimulation necessary for
contraction of its muscles
originates from within
the heart itself
• The sequence of events
which occurs during each
heartbeat is brought
about by the activity of
the PACEMAKER and
the CONDUCTING
SYSTEM of the heart
As well as the Pacemaker the
conduction system consists of...
• Atrio-ventricular node or AV node
• Bundle of conducting fibres, which divides
into left & right branches (Bundle of His)
• Dense network of Conduction fibres in the
ventricle walls (Purkinje fibres)
• The above cells are specialised muscle
cells which join in a network called the
CONDUCTION SYSTEM
• http://www.bbc.co.uk/learningzone/clips/th
e-human-heart/12225.html
The PACEMAKER
AKA – Sino-atrial Node (SAN)
• The pacemaker is located in the wall of the right atrium.
• The pacemaker is specialised tissue which exhibits
spontaneous excitation.
• This means that it initiates electrical impulses which
make the heart contract at a certain rate.
• This rate can then be regulated by other factors to suit
the bodies requirements.
• The pacemaker works automatically and would continue
to function in the absence of nerve connections from the
rest of the body.
http://www.youtube.com/watch?v=te_SY3MeWys&fe
ature=related
Conduction system of the Heart
Understanding these
DEFINITION will help with the
following slides:
SYSTOLE; The phase of the
heartbeat when the heart
muscle contracts and
pumps blood from the
chambers into the arteries.
(the chambers empty).
DIASTOLE; The phase of the
heartbeat when the heart
muscle relaxes and allows
the chambers to fill with
blood
Conduction of the heart:
step by step!
1.The electrical signal originates from the
pacemaker (sino-atrial node) this makes
heart muscle cells contract at a certain
rate.
2. A wave of excitation (from the SA node)
spreads across the muscle cells of the two
atria making them contract (atrial systole).
3.The impulse is picked up by the atrioventricular node (AV node) located near
the base of the atria.
Conducting System of the Heart
4. The impulse passes from the AV node to
the bundle of His. This bundle of
conducting fibres divides into right and left
branches which are continuous with the
Purkinjie fibres in the ventricular walls.
5. Stimulation of these fibres causes
contraction of the two ventricles (Ventricular
systole). The contraction of the ventricles
spreads upwards from the apex.
6. The muscle cells contract in unison,
and then relax awaiting the next
signal.
Summary: Conduction of the
heart with an ECG.
Such coordination of the heartbeat ensures each type of
systole recieves the combined effect of many muscle cells
contracting and that the ventricular systole occurs slightly
later the atrial systole allowing time for the ventricles to fill
completely before they contract.
& AGAIN Conducting System of the Heart: Explained a little differently.
The origin of the heartbeat is
from within a specialised patch
of cardiac muscle tissue, located
in the wall of the right atrium,
and known as the sino-atrial
node or SA node
SA node
in wall of
right atrium
The AV node connects
with a bundle of large
fibres called the bundle
of His, which divides into
left and right bundle
branches
AV node
Another node of
specialised tissue known
as the AV node is
located in the right
portion of the septum
between the atria
and close to the
AV valves
Bundle of His
with left and right
bundle branches
The left and
right bundle
branches divide
into smaller
branches
called Purkinje
fibres that
spread
throughout the
ventricular muscle
CON’T: Conducting System of the Heart: Explained a little differently.
When the SA node emits spontaneous
electrical impulses, they spread rapidly
across both atria due to the inter-connecting
nature of the cardiac muscle cells
When the electrical
impulses reach the
border between the
atria and ventricles
they are blocked by
a band of nonconducting
fibrous tissue
In order to reach
the ventricles,
electrical impulses
must pass through
the AV node, which
slows down the
speed of electrical
transmission
This delay, called the AV delay,
is extremely important as it
allows the atria to complete their
contraction before the ventricles
begin to contract
As the impulses spread
across the atria, they
stimulate a wave of
contraction within the
atrial walls and
atrial systole is
triggered
Fibrous Tissue
AV
Node
Impulses are
conducted from
AV node along
the bundle of His
The bundle fibres
divide into
numerous
Purkinje fibres
that permeate
throughout the
ventricular
muscles
The spread of
electrical impulses
throughout the
ventricles triggers
ventricular systole
Electrocardiogram (ECG)
The electrical signals of the heart can be detected
by electrodes on the skins surface. They are
displayed on an oscilloscope screen to produce a
pattern called an electrocardiogram (ECG).
The diagram below shows a normal ECG
The ECG trace for each heartbeat displays 3 distinct
waves: A P wave, a QRS complex and a T wave
The waves of an ECG
R
P wave
T wave
Q
S
• P wave - Electrical impulses spreading across the
atria from the SAN; it coincides with atrial contraction
or systole.
• QRS complex - Wave of excitation passing through
ventricles; coincides with ventricular systole.
• T wave - Electrical recovery of the ventricles at the
end of ventricular systole.
ECG waves : The intervals
P–R
interval
R
P wave
T wave
T–P
interval
Q
S
• The P – R interval time between the events of atrial systole and
ventricular systole. This period represents the time taken for the
impulse to spread from the SA node through the atria, plus the
delay in transmission to the AV node, together with the
conduction time through the bundle of His and Purkinje fibres.
• The T – P interval is the time spent by the heart in diastole
before the next atrial systole begins
A
Abnormal ECGs
Heart disease and unusual heart rhythms
can be detected by ECG patterns. The
Normal ECG
diagrams below show identifiable patterns
for some common heart conditions.
http://www.youtube.com/watch?v=x67vRkooZDc&feature=related
Abnormal ECG: Arterial Flutter
• In an arterial flutter the contractions occur
much too rapidly than normal but do
remain coordinated.
• The example shown in the diagram shows
several P waves for ever QRS complex.
Abnormal ECG: Fibrillation
• In a fibrillation, contractions of different groups of
muscle cells occurs at different times making it
impossible for coordinated pumping of the heart
chambers to take place.
• Ventricular fibrillation, for example produces an
ECG with an irregular pattern.
• This condition is lethal if not corrected.
Abnormal ECG: tachycardia.
• During ventricular tachycardia, abnormal cells in
the ventricle walls act like pacemakers and
make these chambers beat rapidly and
independently of the atria.
• The P (atrial) waves are absent and the wide
QRS waves are abnormal.
Pacemakers
Abnormal heart
rhythms can be
controlled by
fitting an artificial
pacemaker. This
stimulator
regulates the heart
beat by sending out
small electrical
impulses to the
heart making it
beat normally.
Task: Torrance-TYK pg152 Qu’s 1&4
22/03/2016
Mrs Smith Ch18 Birth & Post-natal
development
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Essay Questions:
SQA 2010
Discuss the conducting
system of the heart and
how it is controlled.
(10)
22/03/2016
Mrs Smith Ch19 The need for
transport
42
Learning
Intentions
Success
Criteria
To understand the
anatomy of the heart, to
find out how the
heartbeat is controlled
and to look at
differences in blood
pressure in the
circulatory system.
6. Describe the changes in
blood pressure as blood
flows through the circulatory
system.
7. Explain these changes in
blood pressure in reference
to peripheral resistance.
8. Explain the role of elastic
walls of the main arteries.
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Mrs Smith Ch19 The need for
transport
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4. Blood Pressure
Contraction of the ventricles creates pressure which causes
the blood to flow. The pressure in the arteries rises and falls
as the heart goes through systole & diastole.
Ventricular systole = maximum ~120 mm Hg
Ventricular diastole = minimum ~80 mm Hg
Blood Pressure Con’t
• During ventricular systole (contraction) the
pressure of the blood in the aorta rises to
a maximum e.g. 120 mmHg
• During ventricular diastole (relaxing) it
drops to a minimum e.g. 80 mm Hg
Measurement of the blood pressure
Try the Scholar
Animation 3.4.7
Measuring Blood
Pressure
http://courses.s
cholar.hw.ac.uk/v
le/scholar/sessi
on.controller?act
ion=viewContent
&contentGUID=
06fbef35-81055747-fc8955365ca328af
Systolic and diastolic blood pressures are measured
using a sphygmomanometer and varies widely
from person to person.
The graph below shows arterial
blood pressure trace
The graph below shows arterial
blood pressure trace
5. Role of Elastic walls
Large arteries are elastic
They conduct blood from the heart to medium
sized arteries
When the heart contracts and ejects blood, the
walls stretch to accommodate the surge of blood.
The stretched fibres store some of the energy.
During the diastole phase the arteries recoil,
causing the blood to move forward in a continuous
flow.
Diagram of the Elastic walls
6. Decreasing Blood Pressure
• Although the pumping
action of the heart
causes fluctuations in
aortic blood pressure
(e.g. Systolic 120mm Hg
and diastolic 80mm Hg),
the average pressure in
the aorta remains fairly
constant at 100mm Hg.
• The diagram shows how a progressive decrease in
pressure occurs as blood travels round the circulatory
system dropping to almost zero by the time it reaches
the right atrium again
Why does the Blood Pressure
decrease?
• The pressure of the
blood decreases as the
blood moves away from
the heart.
• Changes are due to the
peripheral resistance as
the vessels become
narrower.
• Blood pressure is also
related to the volume of
blood present.
• e.g
increase in
volume
increase in blood
pressure
Peripheral Resistance
• Peripheral resistance means the
resistance to the blood flow caused by
friction between the blood and the walls of
the vessels.
• This friction occurs because blood is sticky
and the arterioles and capillaries through
which it passes are narrower in diameter
and present a large surface area of wall in
contact with blood.
Peripheral resistance:
Greatest in the arterioles
The arterioles
present the greatest
resistance to blood
flow and bring about
the largest drop in
pressure (around
50mm Hg).
LARGE DROP IN
THE
ARTERIOLES
Changes in blood pressure, velocity, and the area
of the arteries, capillaries, and veins of the
circulatory system
Changes in blood pressure
• Blood pressure is also directly related to
volume of blood present in the arteries. An
increased arterial volume leads to an
increase in arterial pressure.
High Blood Pressure
Caused by:
• Any factor that increases the rate and
force of contraction of the heart tend to
increase the arterial blood pressure
For example
•High levels of stress
•Excessive salt in the
diet.
Dangers of High Blood Pressure
Prolonged high blood
pressure is dangerous
because it
• Requires the ventricles to
work harder (in order to
eject the blood into the
arteries).
• Makes arterial walls more
prone to atherosclerosis.
• May damage blood
vessels (e.g. In cerebrum
leading to a ‘stroke’).
Image source:
www.healthygoodies.ca
Task: Torrance-TYK pg156 Qu’s 1&2
22/03/2016
Mrs Smith Ch18 Birth & Post-natal
development
59
Learning
Intentions
To understand how
the various vessels
involved in the
transport are related
and how materials are
exchanged between
these vessels, tissue
fluid and body cells.
Success
Criteria
9. Describe the structure and
function of the vessels in the
lymphatic system
10. Describe the method of
movement of lymph through the
lymphatic circulation
11. Describe the absorption of lipid in
relation to the lymphatic
circulation
12. Describe the structure and
function of lymph nodes
9. Lymphatic System
Image source: http://trc.ucdavis.edu
9. Lymphatic Vessels
The lymphatic system is considered a specialised part of
the circulatory system because lymph fluid is derived from
blood and lymph vessels return lymph to the bloodstream.
Tiny lymphatic vessels
have porous walls that
lets them absorb
excess tissue fluid
(lymph) filtered from
the bloodstream at the
capillary beds. This is
collected by lymph
capillaries which join
to form larger
lymphatic vessels.
10. Lymphatic Circulation
• Flow of lymph is dependent
upon the vessels becoming
periodically compressed
when muscles contract
during breathing and
movement
• Backflow of lymph is
prevented by valves
• Lymph fluid is returned to
the bloodstream by 2
lymphatic ducts in the veins
of the arms
11. Absorption of lipids
Each finger-like villus in the small intestine has a tiny
lymphatic vessel called a lacteal.
The epithelial cells on
the surface of the villus
absorb the products of
fat digestion (lipids).
Droplets of lipid then
pass to the lacteal and
to the lymphatic system
where they become part
of the lymph.
12. Lymph Nodes
Lymph nodes are oval or bean-shaped structures
found in the lymphatic system, particularly where
lymph vessels meet.
They are
usually found
in groups
(glands) at
the neck,
armpit and
groin.
The Lymphatic System
Task label the diagram from
page 155 - Torrence
Answer: Are your labels correct?
Summary: Function of Lymph Nodes
• Engulf microbes by phagocytosis.
• Filter unwanted debris and toxins from lymph.
• Produce lymphocytes which make antibodies
Swollen Lymph Nodes
During illness, if many micro-organisms enter the
nodes they swell up and can even become infected.
Oedema
This occurs when tissue fluid gathers in the spaces
between cells and blood capillaries causing tissues
to swell.
This can be caused by
• Malnutrition
Low levels of plasma proteins result in
the tissue fluid and blood water
concentration being equal, therefore,
no net movement of water
• High Blood Pressure
Tissue fluid produced at a faster rate
than it can be drained away.
e.g. kwashiorkor
Oedema
Oedema can also be caused by parasites
e.g. larvae of the filarial worm,
transmitted by mosquitoes, which
invade the lymphatic system then when
they mature, blocking lymph vessels.
This causes excessive
growth of tissue – a
condition called
elephantiasis.
http://www.youtube.com/watch?v=pwfdTndbNfA&feature=related
Task: Torrance-TYK pg156 Qu 3
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Mrs Smith Ch18 Birth & Post-natal
development
73
Testing Your Knowledge….
• Pg 156 Q 3
• 3a i) Describe the means by which lymph in a lymph vessel is
forced along through the lymphatic system
• ii) what structures prevent backflow of lymph?
• iii) which structures along lymph to return to the blood
circulatory system?
• 3b) which type of food is absorbed into the body via the
lymphatic system?
• 3c i) which type of white blood cell is produced in the germinal
centre of the lymph nodes?
• ii) Which type of white blood cell removes micro-organisms
from lymph as it passes through the spaces in a lymph node?