Transcript File

Higher Human Biology
Unit 2
Physiology & Health
KEY AREA 6: Structure and Function of the heart
Higher Human Biology
We are going to build on the knowledge and skills that you developed during N5 and will
learn about the following Physiology & Health key areas : -
Key Area 1 – Reproductive Organs
Key Area 2 –Hormonal Control of Reproduction
Key Area 3 – Biology of Controlling Fertility
Key Area 4 – Ante- and Postnatal Screening
Key Area 5 – Structure and Function of Arteries, Capillaries and Veins
Key Area 6 – Structure and Function of the heart
Key Area 7 – Pathology of Cardiovascular Disease (CVD)
Key Area 8 – Blood Glucose Levels and Obesity
N5 Revision - Circulatory System
Blood is transported
in the Circulatory
System.
The heart is made up of cardiac
muscle tissue.
The 4 chambers of the heart
are:Right Atrium
Right Ventricle
Left Atrium
Left Ventricle
The right ventricle pumps blood
to the lungs.
The left ventricle pumps blood
to the WHOLE BODY!
Therefore the muscle of the
left ventricle is much thicker
than the right ventricle muscle
N5 Revision - Pathway of Blood
1. Blood from the Body
2. Vena cava vein
3. Right Atrium
4. Right Ventricle
5. Pulmonary Artery
6. LUNGS
7. Pulmonary Vein
8. Left Atrium
9. Left Ventricle
10. Aorta artery
11. Blood to the Body
12. Arteries
13. Capillaries
14. Veins
Vena
Cava
Vein
N5 Revision - Heart Structure
Semi-lunar Valves
Tricuspid Valve
Bicuspid Valve
Valves STOP the blood from flowing backwards
Bitesize Heart Function (0:40)
Bitesize animation of heart
N5 Revision - Coronary Arteries
Coronary Arteries supply the heart muscle with blood containing oxygen
and nutrients (e.g. glucose)
Coronary Veins take carbon dioxide and wastes away from the heart
Physiology & Health Learning Intentions
KEY AREA 6 – Structure & Function of the Heart
a) Cardiac function and cardiac output
b) Cardiac Cycle
c) Structure and function of the Cardiac Conducting System
d) Blood pressure
6a) Structure and function of the heart
Atrio-ventricular (AV) valves prevent
black flow of blood from ventricles to
atria
Semi-lunar (SL) valves prevent
backflow of blood at the entrance of
the pulmonary and aorta arteries.
These valves open during ventricular
contraction allowing blood into the
arteries, and close when arterial
pressure exceeds ventricular
pressure
6b) Cardiac function and Cardiac Output
At each contraction of the heart, the right ventricle pumps the same volume of blood
through the pulmonary artery (and round to the lungs) as the left ventricle pumps through
the aorta (and round the body)
Heart Rate (Pulse) is the number of heartbeats that occurs per minute
Stroke Volume is the volume of blood expelled by each ventricle on contraction. The
stronger the contraction, the greater the stroke volume.
Cardiac output is the volume of blood pumped out of a ventricle per minute. Thus:-
CARDIAC OUTPUT (CO) = HEART RATE (HR) X STROKE VOLUME (SV)
6c) Cardiac Cycle
The cardiac cycle refers to the pattern of contraction (systole) and relaxation (diastole)
shown by the heart during one complete heartbeat
The average cardiac cycle is 0.8seconds, which is based on a heart rate of 75 beats per
minute
6d) Atrial and Ventricular Diastole (relaxing)
The blood returning from the vena cava
and pulmonary veins going into the atria
causes the volume of blood in the atria to
increase and some of the blood flows into
the ventricles
AV valves open
SL valves closed
6e) Atrial systole (atria contracting) & ventricular
diastole (ventricles relaxing)
Atrial systole causes the remainder of the blood
to go through the AV valve to the ventricle.
This is due to the fact that atrial pressure
exceeds ventricle pressure, so the AV valves are
pushed open and blood then enters the
ventricles.
During atria systole(contraction) and ventricular
diastole (relaxing), the two atria contract
simultaneously and send the remainder of the
blood down into the ventricles through the open
AV valves. The ventricles fill up with blood and
the SL valves remain closed
AV valves open
SL valves closed
6f) Ventricular systole (ventricles contracting) & atrial
diastole (atria relaxing)
Closes the AV
valves and pumps
the blood out
through the SL
valves to the aorta
and pulmonary
artery
6g) Cardiac Conducting System
The sequence of events that occurs during each heartbeat is brought about by
the activities of the pacemaker and the conducting system of the heart
The auto-rhythmic cells of the sino-atrial node(SAN)(pacemaker) is located in
the wall of the right atrium and sets the rate at which the cardiac muscle cells
contract
6h) Cardiac Conducting System
1.
Impulses from the SAN spreads through the muscle cells in the wall of the two
atria making them contract simultaneously (atrial systole).
2.
The impulses are then picked up by the Atrio-Ventricular node (AVN) which
located is centrally near the base of the atria
3.
The impulses pass from the AVN into a bundle of conducting fibres which divide
into left and right branches into each ventricular wall, causing contraction of
the two ventricles (ventricular systole).
**This ensures that ventricle systole occurs slightly later than atrial systole –
which allows for the ventricles to fill completely before they contract**
4.
The timing of cardiac cells contracting is controlled by the impulse from the
SAN spreading through the ventricles – these impulses generate currents that
can be detected by an electrocardiogram (ECG)
The heart beat originates in the heart itself but is regulated by both nervous and
hormonal control
6i) Autonomic Nervous Control of the Heart
• Control centres in the medulla of the brain regulate the rate of
the SAN through the antagonistic action of the autonomic
nervous system (ANS)
6j) Autonomic Nervous Control of the Heart
1. The cardio-accelerator centre sends its nerve impulses via sympathetic
nerves to the heart
2. The cardio-inhibitor centre sends its information via a parasympathetic
nerve to the heart
3.
The two pathways are antagonistic to one another in that they have
opposite effects on heart rate:a)An increase in the number of nerve impulses arriving at the SAN
(pacemaker) via the sympathetic nerve results in an increase in heart
rate due to the sympathetic accelerator nerves releasing the
neurotransmitter noradrenaline
b)An increase in the number of nerve impulses arriving at the SAN
(pacemaker) via the parasympathetic nerve results in a decrease in
heart rate due to the slowing parasympathetic nerves releasing the
neurotransmitter acetylcholine
6k) Hormonal Control of the Heart
During exercise or stress, the sympathetic nervous
system acts on the adrenal glands in the kidneys, making
them release the hormone epinephrine (adrenaline) into
the bloodstream.
On reaching the SAN (pacemaker), this hormone causes
the pacemaker to generate cardiac impulses at a higher
rate, and brings about an increase in heart rate
6l) Interpretations of Electrocardiograms
•
•
(1)
(2)
(3)
The electrical activity of the heart
generates tiny currents that can
be picked up by electrodes placed
on the skin surface
Normal ECG patterns consist of 3
distinct waves:-
P wave – is the electrical
impulses spread over the atria
from the SAN
QRS wave complex – is the
electrical impulses passing
through the ventricles
T wave – is the electrical
recovery of the ventricles
near the end of the
ventricular systole
6m) Blood Pressure Changes
• Blood pressure is the force exerted by blood against
the walls of the blood vessels
• BP is measured using a BP sphygmomanometer in units
of millimetres of mercury (mmHg)
• BP is generated by the contraction of the ventricles
and is highest in the aorta and pulmonary artery
• As the heart goes through systole and diastole during
each cardiac cycle, the arterial pressure rises and
falls
• During ventricular systole, the pressure of blood in
the aorta rises to a maximum e.g. 120mmHg
• During ventricular diastole, the pressure of blood in
the aorta drops to a minimum e.g. 70mmHg
• Normal BP is written as 120/70 mmHg
6n) Measurement of blood pressure
Using a sphygmomanometer
1. The cuff is inflated until it stops blood flow
2. The cuff is allowed to deflate gradually until the pressure in the artery
is greater than the pressure in the cuff. The blood starts to flow(
detected by a pulse) at systolic pressure
3. More air is released from the cuff until no pulse detected – this is at
diastolic pressure
6o) Measurement of blood pressure
Hypertension (high blood pressure) is the prolonged elevation of blood
pressure when at rest e.g. above 140/90mmHg
Hypertension is a major risk factor for many diseases that have a
relatively high incidence later in life e.g. coronary heart disease and
strokes
Hypertension is commonly found in people that are:
- overweight
- not taking enough exercise
- eating high fat diet
- eating too much salt
- under continuous stress
- smokers
Physiology & Health Questions
KEY AREA 6 – Structure and function of the heart
1. Testing Your Knowledge 1
Page
2.
What you should know
Page
2.
Quick Quiz
172
172
Q’s 1-4
Q1-15