Download Chapter 3 Answers (part I) - Pearson Schools and FE Colleges

AS PE for OCR Teacher Resource File 2nd Edition
3.I.1
3 The cardiovascular and respiratory systems
Chambers of the heart –
answers
1.
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3 The cardiovascular and respiratory systems
3.I.2
AS PE for OCR Teacher Resource File 2nd Edition
The conduction system of the
heart – answers
1.
Adapted from: Seeley and Tate
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AS PE for OCR Teacher Resource File 2nd Edition
3.I.3
3 The cardiovascular and respiratory systems
Cardiac cycle – answers
Briefly describe, in order, the events during the cardiac cycle in the diagrams below.
Diastole
Relaxation/passive filling phase lasting
0.5 seconds.
Deoxygenated blood enters right atria
from superior and inferior vena cavae..
Oxygenated blood enters left atrium
from pulmonary veins.
Rising pressure of blood against AV
valves forces blood through into
ventricles.
Past tricuspid valve on the right side of
the heart.
Past bicuspid valve on the left side of
the heart.
Volume of blood after filling is termed
end diastolic volume (EDV).
Atrial systole
Contraction of left and right atria.
Increased pressure in atria forces the
remaining blood into the left and right
ventricles.
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3 The cardiovascular and respiratory systems
AS PE for OCR Teacher Resource File 2nd Edition
Ventricular systole
Contraction of both left and right
ventricles.
Lungs
Lungs
Body
Increases ventricle pressure, forcing
blood out of both ventricles (stroke
volume).
Right ventricle forces blood out of
pulmonary valve into pulmonary artery
to the lungs.
Left ventricle forces blood out of aortic
valve into aorta to the body tissues.
A reserve volume of blood may be left
in ventricles (ESV).
Tricuspid and bicuspid valves remain
shut.
Aortic and pulmonary valve close after
ventricular systole to prevent blood flow
back into ventricles. Next diastole phase
begins.
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3.I.4
3 The cardiovascular and respiratory systems
Distribution of cardiac output at
rest: answers
‘Approximately 5 litres of blood is pumped out of the heart every minute.’
•
Look at the distribution of cardiac output during resting conditions in the diagram below.
•
To simplify the diagram, let us split all the divisions into:
(a) muscles
(b) organs (liver, kidneys, heart, brain and others).
Muscles (20%)
1000ml
Liver (27%)
1350ml
Heart (4%)
200ml
Skin (6%)
300ml
Kidneys (22%)
1100ml
Brain (14%)
700ml
Other (7%)
350ml
1 Where is the greatest percentage of cardiac output distributed during resting
conditions?
Greatest % distributed to organs. Only 20% distributed to muscles.
2 In relation to their overall mass compare the percentage of cardiac output
distributed to the kidneys, and that distributed to the muscles.
% distributed to kidneys is much the same as muscles and yet kidneys are very
small compared with muscle mass.
3 Why is the distribution of cardiac output to muscles so low during resting
conditions, despite the larger surface area of muscle?
During rest muscles are mostly inactive and do not require a large % of cardiac
output to supply the oxygen for their energy demands.
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3 The cardiovascular and respiratory systems
3.I.5
AS PE for OCR Teacher Resource File 2nd Edition
Distribution of cardiac output
during exercise – answers
1. Fill in the missing spaces with the following words:
supply
cardiac output
oxygen
demand
increased
During exercise the muscles’ demand for oxygen increases in line with exercise intensity.
If the supply of oxygen is to be met then the % of cardiac output distributed to the working
muscles will need to be increased.
2. Show your understanding of the redistribution of cardiac output during exercise by filling in
the spaces to label the graph below. Use the labels provided.
80%
REST
MUSCLES
ORGANS
EXERCISE
20%
Redistribution of cardiac output from rest to exercise
Cardiac output Q
Approx
80% Q
MUSCLES
ORGANS
Approx
20% Q
AT REST
DURING EXERCISE
Intensity
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AS PE for OCR Teacher Resource File 2nd Edition
3.I.6
3 The cardiovascular and respiratory systems
Stroke volume response to
exercise – answers
1. Stroke volume is determined by four main factors:
•
Venous return volume (Starling’s Law of the Heart)
•
ventricular stretch (EDV)
•
ventricular contractility/force of contraction (ESV)
•
and pulmonary artery pressure.
Stroke volume (SV) increases with exercise intensity
2. What happens to SV as exercise intensity increases?
SV increases with increase in intensity but only up to exercise intensities between 40–
60% of an individual’s maximal working capacity.
3. What happens to SV before exercise intensity approaches maximal working capacity?
After this, stroke volume is thought to plateau or fall slightly.
4. Why does SV not continue to increase towards maximal capacity as exercise intensity
increases?
Heart rate increases as exercise intensity increases; therefore there is less time for
diastole/venous return to fill the heart. The physical size of the heart also
limits/prevents SV from continuing to increase. SV changes with heart rate to ensure
the most efficient supply of cardiac output to the working muscles.
5. What is the benefit of an increased SV during exercise?
Increased SV increases Q and therefore increases supply of O2 to the working muscles,
increasing aerobic endurance and delaying fatigue.
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3 The cardiovascular and respiratory systems
3.I.7
AS PE for OCR Teacher Resource File 2nd Edition
Heart rate, stroke volume and Q
response to changes in posture
and exercise – answers
1. What happens to heart rate (HR) as exercise intensity increases?
HR increases in line with exercise intensity.
2. What happens to SV from supine to sitting and then to standing? Why?
SV decreases from supine to sitting, and decreases further to standing. Blood pooling
does not occur in the supine position so VR is easily returned to the heart. In sitting and
standing VR has to return against gravity, increasing blood pooling, which reduces VR
and therefore SV (Starling’s Law).
3. What happens to cardiac output (Q) from supine to sitting and standing?
Q is a product of SV and therefore decreases in line with SV from sitting and standing.
4. What happens to HR, SV and Q from walking to jogging and running?
HR and SV increase and consequently increase Q as exercise intensity increases.
5. Why does the swimmer have the highest SV?
Swimmer is in a supine position so there is less blood pooling in the legs.
6.
Why does the cyclist have the lowest SV from the three exercise activities?
Cycling position causes the most blood pooling, and fewer muscles are active, reducing
muscle pump action.
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3.I.8
3 The cardiovascular and respiratory systems
Resting cardiac output, stroke
volume and heart rate – answers
1. Fill in the missing information to provide definitions and volumes for HR, SV and Q.
Heart Rate
(HR)
The number of ventricular
contractions in one minute.
Untrained
70bpm
Trained
50bpm
Stroke
Volume (SV)
The amount of blood
ejected from the heart
each time the ventricles
contract
Untrained
71ml
Trained
100ml
Cardiac
Output (Q)
The amount of blood
ejected from the heart in
1 minute
Untrained
4970ml
(4.97 litres)
Trained
5000ml (5 litres)
Cardiac output (Q) SV × HR
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3 The cardiovascular and respiratory systems
3.I.9
AS PE for OCR Teacher Resource File 2nd Edition
Stroke volume – answers
1. End-Diastolic Volume EDV (before/filling)
The volume of blood in the ventricles when it has completed its relaxation phase.
End-Systolic Volume ESV (after)
The volume of blood remaining in the ventricles when it has completed its contraction
phase.
Stroke Volume SV (difference)
The volume of blood ejected from the heart ventricles per beat.
2. EDV – ESV = SV
3. (See below in the glasses.)
4. Only up to 40–50% of the blood in the ventricles is pumped out at rest.
5. Heart has a reserve volume (ESV), which can be used during exercise to increase SV.
At rest:
Before
After
SV
EDV =
130ml
ESV =
60ml
SV =
70ml
–
=
Notice that around 40–50% of the blood in the ventricles is pumped out at rest.
During exercise:
Before
After
SV
EDV =
130ml
ESV =
10ml
SV =
120ml
–
88
=
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AS PE for OCR Teacher Resource File 2nd Edition
3.I.10
3 The cardiovascular and respiratory systems
Cardiovascular drift – answers
1. Cardiovascular drift is the gradual decrease in SV and increase in HR during prolonged
exercise.
2. Arterial (systemic/pulmonary) pressure also declines.
This effect is generally associated with an increase in body temperature, which causes an
increase in Q redirected to the skin to reduce body temperature and a decrease in blood plasma
volume as a result of sweating. Together, these decrease VR, which in turn decreases EDV,
which in turn decreases SV. The HR increases to compensate for the decrease in SV to maintain
the required Q. Relate the control mechanisms to HR response e.g. anticipatory rise due to effect
of adrenaline on SA node.
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3 The cardiovascular and respiratory systems
3.I.11
AS PE for OCR Teacher Resource File 2nd Edition
Control of heart rate – answers
1. Put the following words into the appropriate space within the following section.
involuntary
medulla oblongata
intrinsic
cardiac
neural
motor
timings
sympathetic
number
The medulla oblongata in the brain
This contains the following three control centres:
•
the cardiac control centre
•
the respiratory control centre
•
the vasomotor control centre.
The cardiac control centre
This controls the timings/number of heart contractions (HR), which are altered by three
factors:
•
neural control (most important)
•
hormonal control
•
intrinsic control.
The autonomic nervous system
This is:
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•
under involuntary control
•
made up of sensory/receptor and motor nerves
•
motor nerves are referred to as the sympathetic and parasympathetic nerves.
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AS PE for OCR Teacher Resource File 2nd Edition
3 The cardiovascular and respiratory systems
Summary of factors affecting
cardiac control centre –
answers
3.I.12
Fill in the boxes to complete the summary.
During exercise
Neural
Chemoreceptors
In muscles, aorta &
carotid arteries
1. Decrease in pH
2. Increase in pp CO2
3. Decrease in pp O2
Neural
Baroreceptors
In aorta &
carotid arteries
Increase in blood
pressure =
decrease in HR
but neutralised
due to demand
Intrinsic
for O2
Venous return
Increase in VR
(Starling’s Law) =
increase in HR & SV
Key + increases HR
Key – decreases HR
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Neural
–
+
Cardiac
control
centre in
medulla
oblongata
+
Intrinsic
+
Hormonal
+
Proprioreceptors
e.g. Golgi tendon organs,
muscle spindles/joint
receptors
Increase in motor activity =
increase in HR & SV
Temperature
Increase in
temperature =
increase in HR
Adrenaline
From adrenal glands
Stimulates SA node
directly via blood =
increases in HR & SV
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