• 2 The cardiovascular system
• (a) The structure and function of arteries, capillaries
and veins to include endothelium, central lumen,
connective tissue, elastic fibres, smooth muscle and
valves. The role of vasoconstriction and vasodilation
in controlling blood flow.
Structure of the Cardiovascular
System
What is the Cardiovascular system?
• The cardiovascular system, also
known as the circulatory system, is
composed of blood, blood vessels
and the heart.
• The heart functions as a pump to
move blood through the blood
vessels of the body.
• A circulatory system is essential for
large, multi-cellular organisms, such
as humans and animals, and provide
at least five major functions that are
necessary for life.
The five major functions of the cardiovascular
system are:
• Transporting oxygen and removing
carbon dioxide
• Transporting nutrients and removing
wastes
• Fighting disease
• Transporting hormones
• Regulating body temperature
Cardiovascular system
• http://www.youtube.com/watch?v=CjNKbL_-cwA
Components of the CVS
• The CVS consists of
a double pump (the
heart) and a complex
system of blood
vessels.
The cardiovascular system
• The cardiovascular system is made up
of the heart along with the blood
vessels.
Blood vessels
A layer of cells called the endothelium lines the
central lumen of all blood vessels. It is surrounded by
layers of tissue. These surrounding layers differ in
each type of blood vessel.
The middle of the vessel is called the central lumen.
ARTERIES
• Carry blood away from
the heart
• Endothelium
• One cell thick
• Elastic tissues & smooth muscles
• Rebounds
• Evens flow
• Fibrous tissue
• Tough
• Resists stretch
Contraction of the smooth muscle:
vasodilation and vasoconstriction
Arteries
• Arteries carry blood away from the heart. The further the blood
travels away from the heart, the lower the blood pressure gets.
• They have an outer layer of connective tissue containing elastic
fibres and a middle layer containing smooth muscle with more elastic
fibres. The elastic walls of the arteries stretch and recoil to
accommodate the surge of blood after each contraction of the
heart.
• The smooth muscle can contract, called vasoconstriction. This
decreases the blood flow. It can also relax, causing vasodilation.
This increases blood flow. Movement of these muscles controls
blood flow.
VEINS
• Carry blood towards the
heart
• Endothelium
• Larger lumen than
arteries
• Thinner muscle layer &
few elastic fibres
• Blood at lower pressure
• Fibrous tissue
VEINS
• Contain valves
• Prevents backflow of
blood
• Situated between
skeletal muscles
• Muscle compresses vein
when contracted
• Blood “squirted” towards
heart
Veins
• Veins have an outer layer of connective tissue
containing elastic fibres but a much thinner
muscular wall than arteries. They contain
valves to prevent back flow of blood as blood
is at a lower pressure in veins than arteries.
CAPILLARIES
• Transport blood between
arteries and veins
• Form large networks
(capillary beds)
• Exchange of materials
between blood and cells
• Their walls are only one cell
thick, allowing nutrients and
waste to diffuse through
with ease.
Capillaries
Arteriole
Capillaries
(capillary bed)
Venule
Capillaries
• Capillaries are only one cell thick to allow
exchange of substances with tissues.
• (i) The exchange of materials between tissue fluid and
cells through pressure filtration and the role of lymph
vessels.
• Similarity of tissue fluid and blood plasma with the
exception of plasma proteins.
Tissue Fluid and the Lymphatic system
Lymphatic system
• http://www.youtube.com/watch?v=Q530H1WxtOw
Comparison of contents of plasma and tissue fluid
Plasma
Tissue fluid
Protein e.g. red blood cells
No protein
Oxygen and carbon dioxide
Oxygen and carbon dioxide
glucose, amino acids
glucose, amino acids
water
water
Tissue fluid
• Dissolved substances move out through the
capillary walls by pressure filtration, forming
tissue fluid. Tissue fluid is similar to blood
plasma except it does not contain plasma
proteins e.g. red blood cells. Tissue fluid
surrounds cells and supplies them with glucose,
amino acids, oxygen and other useful
substances. Carbon dioxide and other
metabolic waste (waste produced by chemical
reactions in the cell) diffuse out of the cells
and into the tissue fluid to be excreted.
Summary Tissue Fluid and
Lymphatic System
Lymph passes
into lymphatic
system
Lymph
vessel
Blood
leaving in
venule
low
pressure
Some tissue fluid
enters capillary
by osmosis
Some tissue
fluid enters
lymphatic
system
Blood
arriving in
the arteriole
high
pressure
capillary
Some plasma
forced out of
capillary
Respiring cell
Tissue fluid
• Case study on disorders of the lymphatic system. Suitable examples
include the effect of kwashiorkor on fluid balance and elephantiasis.
Lymphatic system
• Excess tissue fluid is absorbed by lymphatic
vessels which are found around cells in each
tissue, forming lymph fluid. The lymph fluid
eventually returns to the blood.
• (b) The structure and function of the heart.
• (i) Cardiac function and cardiac output.
• Definition of cardiac output and its calculation.
Cardiac Function and Cardiac Output
Heart Rate (HR)
• Number of times heart beats in one minute
• Normal values around 72bpm
• Normal range is between 60-90
Stroke Volume (SV)
• Volume of blood ejected by each ventricle during
contraction
• The heart pumps the same volume of blood through
the ventricles during each beat.
• ~ 70ml
Cardiac Output
Cardiac Output is the volume of blood pumped by
each ventricle per minute and is the function of
two factors:
• Heart rate (beats per minute)
• Stroke volume (the volume of blood ejected by
each ventricle during each contraction)
CO = HR x SV
• Measuring pulse rate in arteries using pulsometer. Calculate cardiac
output under different conditions.
Some typical values for cardiac output at varying levels of
activity
Activity
Level
Heart rate
(bpm)
Stroke
Volume (ml)
Cardiac
Output
(l/min)
Rest
72
70
5
Mild
100
110
11
Moderate
120
112
13.4
Heavy
(athlete)
200
150
30
Cardiac output
• Heart rate (HR) = number of beats of the heart
per minute (bpm)
• Stroke volume (SV) = volume of blood ejected by
each ventricle during contraction (ml).
The left and right ventricles pump the same
volume of blood through their arteries each time.
• Cardiac output (CO) measures the volume of
blood pumped out by each ventricle per minute.
To calculate this:
CO = HR x SV
• http://www.phschool.com/science/biology_place/labbench/lab10/int
ro.html
Cardiac function
The Heart
Atrioventricular valve
Semi-lunar valve
Atrioventicular valve
Semi-lunar valve
• The opening and closing of the AV and SL
valves are responsible for the heart sounds
which can be heard with a stethoscope.
• (ii) The cardiac cycle to include the functions atrial
systole, ventricular systole, diastole. Effect of pressure
changes on atrio-ventricular (AV) and semi lunar (SL)
valves.
THE CONDUCTING SYSTEM OF
THE HEART
Stuart brown – stooibrown@yahoo.com
• Cardiology. As a youngster I had a cardiac pacemaker. Two,
actually. I still have one of them, plus the x-ray of the damn thing in
my chest. So I can talk a bit about what it did for me (and what it
didn't do) and the sorts of tests which were done on me to examine
my heart's performance.
Cardiac cycle
•
1.
2.
3.
The cardiac cycle consists of three stages:
Atrial systole
Ventricular systole
Diastole
Cardiac cycle
1.
Atrial systole
Pressure in the atria builds up as muscles of the atria walls contract,
forcing blood through the AV valves into the ventricles. AV valves open, SL
valves shut.
2. Ventricular systole
Pressure in the ventricles build up as muscles of the ventricle walls
contract, forcing blood through the SL valves into the arteries. SL valves
open, AV valves shut.
3. Diastole
Pressure decreases in both atria and ventricles as muscles relax.
Blood flows back into the atria and starts to flow into the ventricles. The
higher pressure in the arteries closes the SL valves. AV valves open, SL
valves shut.
Pure Science Specials - Of Hearts and Minds
• https://www.youtube.com/watch?v=Xwx5fbElMfk
• 50 mins
• (iii) The structure and function of cardiac conducting
system including nervous and hormonal control.
• Control of contraction and timing by cells of the sinoatrial node (SAN) and atrio-ventricular node (AVN).
Interpretation of electrocardiograms (ECG).
• The medulla regulates the rate of the SAN through
the antagonistic action of the autonomic nervous
system (ANS). Sympathetic accelerator nerves release
adrenaline (epinephrine) and slowing
parasympathetic nerves release acetylcholine.
Regulation of the Cardiac Cycle
Sino-atrial node (SAN) and Atrial Ventricular node
(AVN)
Electrical activity of the heart
• http://www.youtube.com/watch?v=v3b-YhZmQu8&feature=related
Cardiac conducting system
• The heart beat is regulated by both nervous
and hormonal control.
• Nervous control:
• Cells of the sino atrial node (SAN), also known
as the pacemaker, in the right atrium set the
pace at which cardiac cells contract without
conscious thought. They are called
autorhythmic.
• The SAN generates an electrical impulse which
spreads throughout the atria, causing atrial
systole. The impulse reaches the AVN which
then carries the impulse across the ventricles,
causing ventricular systole.
Autonomic Nervous System
• The autonomic nervous system (ANS) consists
of 2 antagonistic (opposing) branches
• Sympathetic nerve
• Parasympathetic nerve
Sympathetic
Sympathetic accelerator
nerves
Release adrenaline
(epinephrine)
Increases heart rate
Parasympathetic
Parasympathetic slowing
nerves
Release acetylcholine
Decreases heart rate
The medulla region in the brain regulates the rate of
the SAN through the Autonomic Nervous System
(ANS). It contains two branches which work in
Antagonistic (opposing) ways.
Sympathetic accelerator nerves release
adrenaline (epinephrine) which increases heart rate.
Slowing parasympathetic nerves release
acetylcholine which decreases heart rate.
ABPI schools
• Adrenaline animation:
• http://www.abpischools.org.uk/page/modules/hormones/horm8.cfm
?coSiteNavigation_allTopic=1
Hormonal Regulation of the Heart
• Under certain circumstances
e.g. stress or exercise the
sympathetic nervous system
causes the adrenal glands to
produce adrenaline which
travels in the blood to act on
the SAN, which generates
impulses at a higher rate,
increasing heart rate
Hormonal Regulation of the Heart
• Under certain circumstances
e.g. stress or exercise the
sympathetic nervous system
causes the adrenal glands to
produce adrenaline which
travels in the blood to act on
the SAN, which generates
impulses at a higher rate,
increasing heart rate
• Hormonal control:
• Under circumstances such as stress and exercise, the
sympathetic nervous system causes the adrenal glands to
produce the hormone adrenaline which acts on the SAN to
increase heart rate.
• The impulses generated by the SAN creates
currents that can be detected by an
electrocardiogram (ECG).
• P wave – atrial systole
• QRS waves – ventricular systole
• S wave - diastole
ABNORMAL ECG’S
• Atrial flutter
• Rapid contraction of the atria
• Atria contract 3 times for every
ventricular contraction
ABNORMAL ECG
• Ventricular tachycardia
• Ventricles beat rapidly and
independently of the atria
ABNORMAL ECG’S
• Ventricular fibrillation
• Unco-ordinated electrical activity
• Pumping cannot take place
• Fatal if not corrected
• Defibrillation
• (iv) Blood pressure changes, in response to cardiac
cycle, and its measurement.
• Blood pressure changes in the aorta during the
cardiac cycle. Measurement of blood pressure using a
sphygmomanometer. A typical reading for a young
adult is 120/70 mmHg. Hypertension is a major risk
factor for many diseases including coronary heart
disease.
blood pressure measurement
• http://www.youtube.com/watch?v=ElCbQMiBC6A&NR=1
Blood pressure
• Blood pressure changes in the aorta during the cardiac
cycle. It can be measured using a sphygmomanometer.
• An inflatable cuff stops blood flow and deflates gradually.
The blood starts to flow (detected by a pulse) at systolic
pressure. The blood flows freely through the artery (and a
pulse is not detected) at diastolic pressure.
• A typical reading for a young adult is 120/70 mmHg.
High blood pressure, known as hypertension, is a
major risk factor for many diseases including
coronary heart disease.