Download Welcome to BTEC Sports - AS Physical Education

Carbon- dioxide is transported around the body in the
following ways:

5% dissolves in plasma

20% combines with haemoglobin

75% is transported in the blood as hydrogen
carbonate (bicarbonate) ions - The CO2 produced
by the muscles as a waste product diffuses into the
blood stream where it combines with water to form
carbonate acid. This is a weak acid that dissociates
into hydrogen carbonate ions.
Oxygen plays a major role in energy production.
Reduction- detrimental impact on performance.

Oxygen enters the red blood cells and combines with
haemoglobin to form oxyhaemoglobin.

However, this depends on the amount of oxygen
present.

When there is plenty of oxygen available all
haemoglobin carries oxygen- haemoglobin is fully
saturated.

When oxygen supplies are limited oxyhaemoglobin
splits and releases oxygen into the muscles.
FORMING OXYHAEMOGLOBIN...
During exercise
Oxygenated blood to
muscles
In lungs – lots of
oxygen –
Haemoglobin
becomes fully
saturated with O2
In working muscles –
higher temperature
and more CO2 – more
oxygen leaves the
haemoglobin
(dissociates)
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The temperature of our
muscles increase.
As a result more CO2 is
produced.
Both these increase the amount
of O2 in the muscles.



Typically, the PO2 in our arteries is 90100mmHG- blood leaving the lungs is about
97- 98% saturated with haemoglobin.
When this blood reaches the tissues, the
PO2 falls to about 40mmHG, a point where
haemoglobin is about 75% saturated.
As a result a large proportion of the oxygen
being carried by the blood is released into the
tissues.
This release of oxygen occurs in greater
amounts in exercise muscles, where the PO2
may drop to well below 40mmHG, so nearly all
the oxygen is released from the haemoglobin.
 The amount of oxygen released is also affected
by acidity levels.
 In acid conditions (because of more CO2 and
lactic acid- during exercise) oxygen splits more
readily from haemoglobin.
* This effect is seen as a shift of the dissociation
curve to the right, know as the BOHR SHIFT.*

Exam Question
Describe how oxygen is transported to the working muscles and the effect that
strenuous exercise will have on its delivery. Explain why strenuous exercise has
this effect.
(4 marks)
EXAM ANSWER
Simplistic circulation – heart – arteries – muscles;
Oxygen as oxyhaemoglobin;
Exercise increases temperature;
More CO2 in blood/increased acidity;
Both increases release of oxygen from haemoglobin at muscles;
Bohr shift;
(4 marks)



Lots of oxygen- rich blood is delivered to our
muscles.
Consequently, there is a difference between the
oxygen content of the artery approaching the
muscle and the vein leaving the muscle (a- VO2
difference)
During exercise the a- VO2 increases.
A- VO2 DIFFERENCE
Artery carrying
O2 to muscle
Vein carrying O2
away from muscle
Difference in oxygen concentrations
between artery and vein = a-vO2 diff.
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





In the muscle, oxygen is stored by
myoglobin.
*Myoglobin is a protein that stores oxygen in
the muscle*
This has a high affinity for oxygen and stores
the oxygen until it can be transported from
the capillaries to the mitochondria.
*The mitochondria are the sites in the
muscle where aerobic respiration takes place
(power stations of the cells*
Energy is produced in the form of ATP.
*ATP is a molecule of energy*
ARTERIES:
CAPILLARIES: VEINS:
 Thick elastic walls
 Thin walls
 Tiny, very thin
 Small lumen
 Take blood back
walls
 Take blood away
to the heart
 Diffusion of O2
from the heart
 High pressure
and CO2
TASK: Read the paragraph and answer the
questions.
• When the heart contracts it creates pressure in the blood vessels
and pushes blood through the arteries.
• This pressure and velocity depends on the blood vessels.
ARTERIES
CAPILLARIES
VEINS
High pressure and velocity.
Low pressure and slow velocity.
Low pressure but higher velocity.
Blood
pressure
Blood
velocity
Crosssectional
area
Arteries
arterioles
capillaries
venules
veins
Velocity
falls then
rises increasing
&
decreasing
crosssectional
area
Pressure
falls friction &
increasing
crosssectional
area
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TASK: Complete the missing words
using the word bank.
Valves in the veins prevent the
backflow of blood and ensures that
blood only flows towards the heart.
There is a contraction of the skeletal
muscles to force the blood back
through to the heart.
The suction pressure of the heart
helps the blood to flow back to the
heart.
ACTION OF THE VALVES......
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MUSCLE PUMP...
17
Exam Question
(i) Arteries, capillaries and veins form part of the circulatory system. Explain the
main features of capillaries in relation to their function.
(3 marks)
(ii)
Blood supply is maintained by the venous return mechanisms. Explain
how these mechanisms ensure the return of blood to the heart.
(3 marks)
EXAM ANSWER
(i)One cell thick / think walls;
Large surface area for the diffusion of gases;
Narrow diameter single blood cell / short diffusion pathway;
3 marks
(ii)Veins have one-way pocket valves;
Muscle contractions (muscle pump) compress veins and push blood towards the
heart;
Breathing movements / respiratory pump alters pressure in thorax and assist flow
back to the heart;
Sympathetic nerves cause venous tone / veins contract to aid return of blood during
exercise;
Suction pump of the heart;
3 marks
Vasodilation and Vasoconstriction
• During exercise our blood flow needs to be redistributed to accommodate for this.
Vasodilation
• During exercise we need more oxygen to go to our working muscles and the carbon
dioxide needs to be removed.
• Vasodilation means that our blood vessels dilate and get bigger to allow this process
to occur.
• This process happens around the muscles that our needed during exercise.
• For example, during a football match this would occur to those blood vessels
surrounding the quadriceps, hamstrings, and gastrocnemius.
• This is controlled by the sympathetic nerve impulseS from the brain.
Vasoconstriction
• This is the process of the blood vessels getting smaller to restrict the blood flow to
certain muscles, to accommodate for the process of vasodilation.
• This would happen in the blood vessels that surround those muscles that aren’t
required during exercise such as the gut muscles.
LESSON OBJECTIVE
LESSON OBJECTIVE
• To understand the structure
and function of the
cardiovascular system.
LESSSON OUTCOME
• To be able to explain the structure
and function of the cardiovascular
system.
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• The heart is a two sided pump.
• The right side pumps blood to the lungs to collect
oxygen.
• The left side is slightly bigger and pumps blood to
our muscles to deliver oxygen.
• The right and left halves are separated by the
septum.
• The pumping parts (the bottom parts of the heart)
are called the ventricles.
• The blood collects in the atria.
The Cardiovascular System
The four chambers of the heart have special names:
An upper chamber is called an atrium (plural: atria).
right
atrium
right
ventricle
left
atriu
m
left
ventricle
A lower chamber is called a
ventricle.
The Cardiovascular System
Deoxygenated
blood is
pumped from
the heart to the
lungs through
the pulmonary
artery.
Deoxygenated
blood returns to
the heart
through the
vena cava.
lungs
body’s
cells
Oxygenated
blood returns
to the heart
through the
pulmonary
vein.
Oxygenated
blood is pumped
at high pressure
from the heart to
the body through
the aorta.
The Cardiovascular System
The pulmonary circulation carries:
deoxygenated blood from the
heart to the lungs
lungs
oxygenated blood back from
the lungs to the heart, ready
to be pumped out to the body.
The systemic circulation carries:
oxygenated blood to the rest
of the body through the
arteries
deoxygenated blood back to
the heart through the veins.
body’s
cells
Right atria
Left atria
Left ventricle
Right ventricle
Septum
25
The valves in our heart stop the backflow of blood.
The blood flows from the atria to the ventricles through the artio- ventricular valves (A- V valves).
The blood flows from the ventricle to the arteries through the semi- lunar valves (S- L valves).
vein valve
open
blood
to the
heart
The valves allow
blood to flow in the
correct direction…
backflow
prevented
vein valve
closed
…but close if blood
starts to flow in the
wrong direction.
Right S-L valve
Right atria
Left atria
Right A-V valve
Left ventricle
Left A-V valve
Right ventricle
Septum
2
7
THE ARTIA....
•
•
•
•
The artia collects the blood.
The left atria receives blood from the lungs through
the pulmonary veins.
The right atria receives blood from the body from
the vena cava.
There is an upper (superior) vena cava and a lower
(inferior) vena cava.
Superior vena cava
Right S-L valve
Pulmonary veins
Right atria
Left atria
Right A-V valve
Left ventricle
Left A-V valve
Right ventricle
Inferior vena cava
Septum
2
9
THE VENTRICLES...
•
•
•
The ventricles pump the blood around the body.
The left ventricle pumps blood to the body through
the aorta.
The right ventricle pumps blood to the lungs
through the pulmonary artery.
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Superior vena cava
Aorta
Pulmonary artery
Right S-L valve
Pulmonary veins
Right atria
Left atria
Right A-V valve
Left ventricle
Left A-V valve
Right ventricle
Inferior vena cava
Septum
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THE HEART.....
TASK....
• Complete the paragraph on how the blood flows
through the heart, using the word bank.
HEART BEAT
• The chambers of the heart can contract and relax.
• The period of contraction is called systole.
• The period of relaxation is called diastole.
• The atria and ventricles contract at different times and
this is what makes the cardiac cycle.
HEART BEAT
1.
Impulse for contraction is generated by a
small mass of specialised cardiac muscle –
sino- atrial node (SAN)
2. Artia contracts
3. Can’t get through to the ventricles
4. Atrio- ventricular node
5. Artria fully contracts
6. Septum
7. Bundle of His
8. Purkinje fibres
9. Ventricular wall
10. Ventricles contract
CONTROL OF HEART RATE...
Spreads through atria
first - systole
Sino-atrial
node
Picked up by AVN
Then down septum
Sets heart rate intrinsic
Then from tip of
ventricle systole
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SAN sets
heart rate
Impulses spread
through atria
Impulses picked
up by AVN
Valves act
as barrier
Down ventricle
via bundle of His
Ventricles contract
via Purkinje fibres
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EXAM QUESTION...
EXAM QUESTION
Describe how the sinoatrial node (SAN) and the
atrioventricular node (AVN) control the increase in
heart rate during exercise.
(6 marks)
ANSWER
SAN initiates heart beat/sends impulses;
intrinsic/myogenic/pacemaker;
spread of impulses through atria;
atria contracts/systole;
role of valves as non-conducting material;
impulse reaches AVN;
initiation of impulse down interventricular
septum/reduced delay of spread of impulses;
Bundle of His;
Purkinje fibres conducting impulses;
ventricular systole/contraction;
period of diastole/relaxation for filling;
release of (nor) adrenaline from SAN
(6 marks)
HEART RATE RANGE...
During exercise our heart rate increases, as our body needs
more energy for muscle contracts, so there is a higher demand
for oxygen and when we finish exercising it needs to return to
our resting heart rate.
Our nerves act as a brake and an accelerator.
Vagus nerve
Slows the heart rate
down
Sympathetic nerve
Speeds the heart
rate up
During exercise, more CO₂ is produced.
This increases the acidity of our blood
and lowers the PH.
This is detected by the chemoreceptors,
which sends a message to the medulla.
This leads to changes in the heart rate
via the vagus and sympathetic nerves.
Exercise - blood CO2 levels rise
Medulla
Detected by chemoreceptors
Decreased vagus
impulses to SAN - lets
heart beat faster
Increased sympathetic
impulses to SAN - lets
heart beat even faster
Medulla
Stop exercise – CO₂ levels drop
Detected by baroreceptors
Increased vagus
impulses to SAN - lets
heart beat slower
Decreased
sympathetic impulses
to SAN - allows heart
rate to slow
HEART RATE VALUES
TASK...
• Use the internet to help you find the correct
definitions of the key words.
Stroke
volume
The volume of blood pumped
out of one ventricle per beat
Heart rate
The number of times the heart
contracts per minute
Cardiac
output
The volume of blood pumped
out of one ventricle per minute
Cardiac
output
=
Stroke
volume
x
Heart
rate
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TASK...
• Use the internet to find any short term and long term effects
of exercise on the cardiovascular system.
Short Term Effects
Long Term Effects
• Heart rate increases; faster contractions
of the heart to make the blood flow around
the body quicker.
• Stroke volume increases; stronger
contraction of the heart, increasing the
volume of blood being pumped around the
body.
• Cardiac output increases; more blood is
delivered to the working muscles.
• Heart gets bigger and walls of the heart
get thicker (hypertrophy).
• Decrease in resting heart rate
(bradycardia).
• Increase in resting stroke volume.
• Resting cardiac output stays the same.
•Increased volume of blood, leading to a
more efficient delivery of oxygen, which
improves stamina.
• Bigger capillary network.
• High a- vO₂ difference.
• More efficient gas exchange.
EXAM QUESTION...
EXAM QUESTION
(i) Explain the terms cardiac output and stroke
volume and the relationship between them.
(3 marks)
(ii) What are the effects of training on resting cardiac
output and stroke volume? (2 marks)
ANSWER
(i)Cardiac output is the amount of blood leaving the
heart/left ventricle per minute;
Stroke Volume is the amount of blood leaving the
heart/left ventricle per beat;
Cardiac output = Stroke Volume x Heart rate/ Q = SV
x HR/Pulse rate equiv.
(3 marks)
(ii)Cardiac output does not change;
Stroke volume increases/equiv.
(2 marks)
• The more blood that enters the blood during diastole, then the
walls of the ventricle will stretch and contract with more force.
• As a result of an increased blood flow to the heart there is a
increased venous return because more blood is flowing around
the body.
• As a result of this higher workload the cardiac muscle contracts
with greater force, giving a greater ejection of blood.
• This occurs to make up for the shorter period of diastole,
meaning that there is less time for the heart to fill with blood.
THE GREATER THE VENOUS RETURN, THE GREATER THE
STRENGTH OF CONTRACTION.
Changes to cardiac output, stroke volume and heart rate during a
period of steady state exercise
180
160
140
120
Heart rate (bts/min)
Cardiac output (l/min)
Stroke volume (mls)
100
80
60
40
20
0
0
5
10
15
20
25
30
35
40
45
50
55
60
time (mins)
WHAT DOES THE GRAPH REPRESENT?
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• During a steady state of exercise (60 minutes) the
heart rate increases.
• However, the cardiac starts to plateau and as a
result the stroke volume needs to decrease.
• This is thought to be caused by a reduction in fluid
in the blood (due to sweating and loss of fluids
because of the heat generated by muscle
contraction), which in turn decreases the venous
return and thus the stroke volume (Starling’s Law).
EXAM QUESTION
EXAM QUESTION
(i)
Explain why a performer’s stroke volume decreases during a run of constant pace
and workload. (4 marks)
(iii)
Explain how it is possible for a trained and an untrained individual to have the
same cardiac output for a given workload.(2 marks)
ANSWER
(i) During exercise - loss of fluid at sweat;
Hence reduced blood/plasma volume;
Reduced venous return;
Stroke volume decreases;
Starling’s Law of the heart;
Heart rate increases/beats more
Maintain cardiac
‘Cardiovascular Drift’.
(4 marks)
(ii) Same physique/size/frame/weight;
Untrained high heart rate and low stroke volume;
Trained low heart rate large stroke volume;
Can only occur at sub maximal workloads;
At higher workloads untrained will not be able to increase their heart rate sufficiently;
(2 marks)
What have you learnt in today’s
lesson?
LESSSON OUTCOME
• To be able to explain Starling’s Law
and the cardiovascular drift and apply
this knowledge to exam questions.
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