Component 1 ‒ 1.1.b. Cardiovascular and
respiratory systems
© OCR 2019
Learning outcomes
By the end of this topic you should be able to demonstrate
knowledge and understanding of the cardiovascular and
respiratory systems at rest, during exercise and during
recovery including:
• heart rate, stroke volume and cardiac output
• cardiac cycle – conduction system
• neural, intrinsic and hormonal regulation of HR
• the vascular shunt mechanism
• mechanisms of venous return
• respiratory volumes
• mechanics of breathing at rest and during exercise
• neural and chemical control of breathing
• gaseous exchange at the alveoli and muscles.
© OCR 2019
Timings
Topic
Allocated time
Heart rate, stroke volume and cardiac output
1 Hour
Cardiac Cycle – Conduction System
1 Hour
Neural, Intrinsic and Hormonal regulation of HR
2 Hours
The Vascular Shunt Mechanism
2 Hours
Mechanisms of Venous Return
1 Hour
Respiratory volumes
1 hour
Mechanics of breathing at rest and during exercise
3 hours
Neural and Chemical control of breathing
1 hour
Gaseous Exchange at the alveoli and muscles
3 hours
Total
15 hours
© OCR 2019
The circulatory systems
The Cardiovascular system is responsible
for delivering oxygen extracted from the air
around us to the muscle tissues for
respiration. It includes the heart, a dualaction pump, the blood vessels and the
blood which actually transports the oxygen.
Oxygenated blood exits the left side of the
heart and is transported to muscle tissues
via the SYSTEMIC circulatory system.
Oxygen is released to the muscles and
deoxygenated blood returns to the right side
of the heart. It then travels to the lungs via
the PULMONARY circulatory system to take
on more oxygen and the process continues.
© OCR 2019
Structure of the heart
The heart is a network of blood vessels,
valves and chambers directing blood
flow around the circulatory system.
The top two chambers are known as
ATRIA. They receive blood from the
circulatory systems.
The bottom two chambers, the
VENTRICLES, receive blood from the
atria to pump onwards to the next stage
of the cycle.
© OCR 2019
Cardiac cycle
The heart is a dual-action pump responsible for the transport of blood around the
body.
The right and left side of the heart will contract at the same time delivering blood
to the two circulatory systems. The right side of the heart to the pulmonary
circulatory system and the left side to the systemic circulatory system.
ATRIAL SYSTOLE – the phase when both
atria contract to force blood into the
ventricles through the bicuspid and
tricuspid valves.
VENTRICULAR SYSTOLE – the phase
when both ventricles contract to eject
blood into the pulmonary artery and aorta
for transportation around the circulatory
systems.
DIASTOLE – the relaxation phase of the
cardiac cycle, no contraction takes place
and blood enters the atria from the vena
cava and pulmonary vein
© OCR 2019
Conduction system
The cardiac cycle is controlled by the conduction system of the heart. The heart is
MYOGENIC which means it has the capacity to generate its own electrical
impulse. The impulse is transmitted through the cardiac muscle to stimulate
contraction.
The SINO-ATRIAL (SA) NODE initiates the impulse
which is transported through both atria where it is
received by the ATRIO-VENTRICULAR (AV)
NODE. This causes Atrial Systole. Blood is ejected
out of both atria and into the ventricles.
The AV node delays the impulse briefly then
releases it onwards to the BUNDLE OF HIS. The
bundle of His splits the impulse down the left and
right bundle branches where they reach the
PURKINJE FIBRES. Once the impulse reaches
these fibres both ventricles will contract causing the
blood to be ejected into the circulatory systems.
There is a brief break where no impulse is
generated allowing blood to enter the atria.
© OCR 2019
Conduction system
STAGE
1
CYCLE / Blood movement
Blood enters the atria from the vena cava
and the pulmonary vein.
Atria and Ventricles are relaxed
CONDUCTION
No impulse
DIASTOLE
2
Both Atria contract.
Blood is forced from the atria to the
ventricles.
ATRIAL SYSTOLE
3
Blood is forced from the ventricles to the
Aorta and Pulmonary Artery.
VENTRICULAR SYSTOLE
Impulse from SA
NODE to
AV NODE
AV NODE to
BUNDLE OF HIS to
PURKINJE FIBRES
© OCR 2019
Heart rate, stroke volume and cardiac output
Definition
Rest
Maximal
Heart Rate
The number of beats of the heart
per minute
60-75
220 - age
Stroke Volume
The volume of blood ejected from
the left ventricle per beat
70ml/beat
100- 120ml
Cardiac
Output
The volume of blood ejected from
the left ventricle per minute
5l/min
20-30l/min
Rest
Maximal
50
220 - age
Stroke Volume
100ml/beat
160- 200ml
Cardiac Output
5l/min
30-40l/min
Heart Rate
© OCR 2019
Heart rate regulation – neural control
SYMPATHETIC NERVOUS SYSTEM
The body systems must adapt to the environment around it to allow them to
perform as efficiently as possible. When exercise is undertaken, the muscles
require greater volumes of oxygen to help in the breakdown of fats and glucose to
produce ATP for muscular contractions. The sympathetic nervous system
responds by stimulating the SA node to increase heart rate.
PARASYMPATHETIC NERVOUS SYSTEM
Once exercise has finished and the body begins to recover the parasympathetic
nervous system will act to reduce stimulation of the SA node reducing heart rate.
This will eventually return to resting levels.
© OCR 2019
Sympathetic nervous system
SYMPATHETIC NERVOUS SYSTEM
The sympathetic nervous system is responsible for increasing heart rate. This is
controlled by the CARDIAC CONTROL CENTRE situated in the MEDULLA
OBLONGATA of the brain.
The Cardiac Control Centre receives information from receptors concerning
various changes in the body as a result of exercise being undertaken.
The CCC then sends impulses down the ACCELERATOR NERVE to increase the
firing rate of the SA Node, thus increasing heart rate meaning more oxygen is
delivered to the working muscles.
© OCR 2019
RECEPTORS
BARO
CHEMO
PROPRIO
DETECT WHAT?
INCREASE
IN
PRESSURE
INCREASE IN
ACIDITY/
DECREASE IN
pH
MOVEMENT
WHERE?
IN THE BLOOD
VESSELS
IN THE BLOOD
IN TENDONS
AND MUSCLE
FIBRES
© OCR 2019
Parasympathetic nervous system
PARASYMPATHETIC NERVOUS SYSTEM
The parasympathetic nervous system is responsible for reducing heart rate. This
is also controlled by the CARDIAC CONTROL CENTRE situated in the
MEDULLA OBLONGATA of the brain.
The Cardiac Control Centre receives information from receptors concerning
various changes in the body as a result of exercise ceasing.
The CCC then sends impulses down the VAGUS NERVE to decrease the firing
rate of the SA Node, thus decreasing heart rate meaning less oxygen is delivered
to the working muscles.
© OCR 2019
Heart rate regulation – hormonal control
In response to exercise the
ADRENALIN and NOR-ADRENALIN
are released from the ADRENAL
GLAND. These hormones have a
direct effect on the force of
contraction of the heart muscle, thus
increasing Stroke Volume and the
firing rate of the SA node, thus
increasing Heart Rate. The combined
effect will increase Cardiac Output
and delivery of oxygenated blood to
the working muscles.
© OCR 2019
The vascular system
The vascular system is a dense
network of blood vessels. It includes
the blood which travels through the
system transporting oxygen, carbon
dioxide and essential nutrients
throughout the body.
The blood vessels include:
ARTERIES – transport oxygenated
blood from the heart. The largest of
these is the AORTA which receives
blood from the LEFT VENTRICLE.
VEINS – larger blood vessels
carrying deoxygenated blood back
towards the heart. The largest of
these is the VENA CAVA which
delivers deoxygenated blood back to
the RIGHT ATRIA of the heart.
© OCR 2019
The vascular system
ARTERIOLES – smaller arteries which have a large layer of smooth muscle
allowing the lumen diameter to be altered.
CAPILLARIES – are vessels of a single layer of cells which penetrate the muscle
and organ cells. They allow for gas, nutrient and waste exchange.
VENULES – the smaller blood vessels carrying deoxygenated blood back towards
the heart.
© OCR 2019
Venous return mechanisms
POCKET VALVES – one way valve located in the veins which prevent the
backflow of blood.
MUSCULAR PUMP – the contraction of skeletal muscle during exercise which
compresses the veins forcing blood back towards the heart.
RESPIRATORY PUMP – During inspiration and expiration a pressure difference
between the thoracic and abdominal cavities is created which squeezes blood
back towards the heart.
SMOOTH MUSCLE – The layer of smooth muscle in the walls of the veins
venoconstricts to create VENOMOTOR TONE maintaining pressure in the vein
and thus helping the transport of blood back to the heart.
GRAVITY – Blood from above the heart returns towards the heart with the help of
gravity.
© OCR 2019
Redistribution of cardiac output
Cardiac output at rest is approximately 5 litres per minute. During maximal
exercise this can increase to 25-40 litres per minute depending on fitness levels.
To further aid performance during exercise the increased cardiac output is
redistributed to areas of the body which need it most, namely the working
muscles. This is done by the VASCULAR SHUNT MECHANISM.
The redistribution of blood is controlled by the VASOMOTOR CONTROL
CENTRE in the medulla oblongata.
The VCC receives information from CHEMORECEPTORS about increases in
blood acidity and BARORECEPTORS regarding pressure changes on arterial
walls.
This causes the VCC to alter stimulation of arterioles in different areas of the body
via the vasomotor nerves.
© OCR 2019
Vasomotor control
VASOCONSTRICTION is where
increased stimulation from the
vasomotor nerve causes the smooth
muscle layer to contract reducing
lumen diameter and therefore blood
flow.
VASODILATION is where decreased
stimulation from the vasomotor nerve
causes the smooth muscle layer to
relax increasing lumen diameter and
therefore blood flow.
© OCR 2019
Vascular shunt mechanism
Distribution
To organs
To working
muscles
Effect
At rest
During exercise
Arterioles
Pre-Capillary
Sphincters
Arterioles
Pre-Capillary
Sphincters
Vasodilate
Relaxed
Vasoconstrict
Contract
Arterioles
Pre-Capillary
Sphincters
Arterioles
Pre-Capillary
Sphincters
Vasoconstrict
Contract
Vasodilate
Relaxed
More blood travels to organs
than muscles
More blood travels to
muscles than organs
© OCR 2019
Structure of the respiratory system
The respiratory system has two
main functions:
•
•
•
Pulmonary ventilation – the
inspiration and expiration of air
from the atmosphere around us.
Gaseous exchange – the
extraction of oxygen from the air
into the blood stream and then
into the muscle tissues.
The respiratory muscles work to
cause volume changes within
the thoracic cavity to cause air to
be inhaled and exhaled.
© OCR 2019
Gas transport
Blood consists of 55% plasma
and 45% blood cells. Once
oxygen as passed from the alveoli
into the blood it is carried in two
ways:
97% combines with haemoglobin
to produce oxyhaemoglobin
HbO2
3% is dissolved within the blood
plasma.
© OCR 2019
Gas transport
The waste product of aerobic respiration Carbon Dioxide is also
transported in the blood this time in three ways:
70% Dissolved in water and carried as Carbonic Acid
23% Combines with haemoglobin to create Carbaminohaemoglobin
7% Dissolved in blood plasma
© OCR 2019
Breathing frequency, tidal volume and
minute ventilation response to exercise
There are three main measures of
respiration:
BREATHING FREQUENCY –
represents the number of breaths
taken per minute.
TIDAL VOLUME – is the volume of
air INSPIRED or EXPIRED per
breath measured in ml or litres.
MINUTE VENTILATION – is the
volume of air INSPIRED or EXPIRED
per minute measured in ml or litres.
© OCR 2019
Breathing frequency, tidal volume and
minute ventilation
Tidal volume
Frequency
Minute
ventilation
(Pulmonary)
Definition
Volume of air
breathed in or out
per breath
Number of breaths
per minute
Volume of air
breathed in or out
per minute
Resting
value
0.5 litres
12 -16
6 – 8 litres
Maximal
value
3 - 5 litres
40+
200+ litres
© OCR 2019
Mechanics of breathing: rest
•
•
•
•
•
•
The Diaphragm contracts and
flattens.
External Intercostal muscles
contract.
Rib cage moves up and out
Volume of the Thoracic Cavity
increases.
Pressure of the Thoracic Cavity
decreases.
Air moves from higher pressure
outside to lower pressure in the
lungs.
© OCR 2019
Mechanics of breathing: rest
•
•
•
•
•
•
•
The Diaphragm relaxes and
returns to a dome shape.
External Intercostal
muscles relax.
Rib cage moves down and in
Volume of the Thoracic
Cavity decreases.
Pressure of the Thoracic
Cavity increases.
Air moves from higher
pressure inside to lower
pressure outside lungs.
The process is PASSIVE.
© OCR 2019
Mechanics of breathing: exercise
•
•
•
•
•
•
•
•
•
The Diaphragm contracts and flattens MORE
than at rest.
External Intercostal muscles
contract MORE than at rest.
Additional muscles are recruited.
Sternocleidomastoid, scalenes
and pectoralis minor.
Rib cage moves up and out FURTHER than
at rest.
Volume of the Thoracic Cavity
increases MORE than at rest.
Pressure of the Thoracic Cavity decreases
MORE than at rest.
MORE air than at rest moves from higher
pressure outside to lower pressure in the
lungs.
© OCR 2019
Mechanics of breathing: exercise
•
•
•
•
•
•
•
•
•
The Diaphragm relaxes.
External Intercostal muscles relax.
Additional muscles are recruited.
Rectus Abdominus, External
Obliques, Internal Obliques contract
Rib cage moves down and in
FURTHER than at rest.
Volume of the Thoracic Cavity
decreases MORE than at rest.
Pressure of the Thoracic Cavity
increases MORE than at rest.
MORE air moves from higher pressure
outside to lower pressure in the lungs
The process is ACTIVE.
© OCR 2019
Mechanics of breathing: rest
INSPIRATION
.
REST
EXERCISE
DIAPHRAGM
EXTERNAL INTERCOSTALS
DIAPHRAGM
EXTERNAL INTERCOSTALS CONTRACT
HARDER
EXTRA MUSCLES
INCREASE VOLUME OF THORACIC
CAVITY
DECREASE PRESSURE
GTER INCREASE VOLUME OF THORACIC
CAVITY
AIR MOVES IN
GTER DECREASE PRESSURE
MORE AIR MOVES IN
EXPIRATION
PASSIVE
INTERNAL INTERCOSTALS CONTRACT
DIAPHRAGM
EXTERNAL INTERCOSTALS
DECREASE VOLUME OF THORACIC
CAVITY
RECTUS ABDOMINUS CONTRACTS
INCREASE PRESSURE
GTER INCREASE PRESSURE
AIR MOVES OUT
ID:
MORE AIR MOVES OUT
GTER DECREASE VOLUME OF THORACIC
CAVITY
228014470
© OCR 2019
Control of breathing: exercise
Much like the neural control of the
heart, increased contraction of the
respiratory muscles during exercise
occurs as a response to information
received in the receptors.
Chemical Control
Increased acidity in the blood and
decreased pH is detected by the
CHEMORECEPTORS.
They send messages to the
INSPIRATORY CONTROL
CENTRE in the Medulla Oblongata
to increase INSPIRATION.
© OCR 2019
Control of breathing: exercise
Neural Control
Movement in the joints is detected
by the PROPRIORECEPTORS.
THERMORECEPTORS detect an
increase in temperature which
causes an increase in respiratory
rate.
BARORECEPTORS (stretch
receptors) detect stretch in the
lungs stimulating the EXPIRATORY
CONTROL CENTRE to increase
EXPIRATION.
© OCR 2019
Gaseous exchange carbon
dioxide: alveoli
External respiration
There is a low partial pressure
of carbon dioxide in the
alveoli.
High Partial Pressure of
carbon dioxide in the
pulmonary capillary/blood.
Steep concentration gradient
between alveoli and capillary
Carbon Dioxide diffuses from
the blood into the alveoli.
© OCR 2019
Gaseous exchange oxygen:
alveoli
External respiration
There is a high partial pressure of
oxygen in the alveoli.
Low partial pressure of oxygen in
the pulmonary capillary/blood.
Steep concentration gradient
between alveoli and capillary.
Oxygen diffuses from the alveoli
into the blood.
© OCR 2019
Gaseous exchange oxygen:
Alveoli during exercise
External respiration
There is a high partial pressure of
oxygen in the alveoli. The same as at
rest.
Due to internal respiration consuming
oxygen in the muscle cell there is a
Lower Partial Pressure of oxygen in the
pulmonary capillary/blood returning to
the alveoli.
Steeper concentration gradient between
alveoli and capillary than at rest.
More oxygen diffuses from the alveoli
into the blood.
© OCR 2019
Gaseous exchange carbon
dioxide: alveoli during exercise
External respiration
•
There is a low partial pressure of
carbon dioxide in the alveoli. The same
as at rest.
•
•
•
Due to internal respiration producing
more carbon dioxide in the muscle cell
there is a higher partial pressure of
carbon dioxide in the pulmonary
capillary/blood returning to the alveoli.
Steeper concentration gradient
between alveoli and capillary than at
rest.
More carbon dioxide diffuses from the
blood into the alveoli.
© OCR 2019
Gaseous exchange oxygen:
muscle cell
Internal respiration




There is a high partial pressure of
oxygen in the blood.
Low Partial Pressure of oxygen in
the muscle cell
Steep concentration gradient
between blood and muscle cell.
Oxygen diffuses from the blood into
the muscle cell.
© OCR 2019
Gaseous exchange carbon
dioxide: muscle cell
Internal respiration
•
•
•
•
There is a high partial pressure of
carbon dioxide in the muscle cell
Low partial pressure of carbon dioxide
in the pulmonary capillary/blood.
Steep concentration gradient between
blood and muscle cell.
Carbon dioxide diffuses from muscle
into the blood.
© OCR 2019
Gaseous exchange oxygen:
muscle cell during exercise
Internal respiration
There is a high partial pressure of
oxygen in the muscle. The same as at
rest.
Due to internal respiration consuming
oxygen in the muscle cell there is a
lower partial pressure of oxygen in the
muscle cell than at rest.
Steeper concentration gradient between
blood and muscle cell than at rest.
More oxygen diffuses from the blood into
the muscle cell.
© OCR 2019
Gaseous exchange carbon dioxide:
muscle cell during exercise
Internal respiration
There is a low partial pressure of carbon
dioxide in the blood. The same as at
rest.
Due to internal respiration producing
more carbon dioxide in the muscle cell
there is a higher partial pressure of
carbon dioxide in the pulmonary muscle
cell than at rest.
Steeper concentration gradient between
alveoli and capillary than at rest.
More carbon dioxide diffuses from the
blood into the alveoli.
© OCR 2019
Gaseous exchange
.
EXTERNAL
INTERNAL
FROM
Alveoli
Blood
Capillary
TO
Blood
Capillary
PARTIAL PRESSUREAT
REST
Alveoli
Capillary
High
Low
Capillary
High
DIFFUSION
GRADIENT
AT REST
PARTIAL PRESSURE
EXERCISE
DIFFUSION
GRADIENT
EXERCISE
Alveoli
Capillary
Steep
High
LOWER
STEEPER
Muscle
DIFFUSION
GRADIENT
AT REST
Capillary
Muscle
DIFFUSION
GRADIENT
EXERCISE
Low
Steep
High
LOWER
STEEPER
Muscle Cell
© OCR 2019
Oxygen dissociation from haemoglobin
In order for efficient transport of oxygen in the blood it has a high
attraction to haemoglobin.
This is known as AFFINITY.
However oxygen must release from haemoglobin when it is required at
the muscle cell. During exercise the volumes of oxygen released
increases.
As the partial pressure of oxygen in the blood reduces so does the affinity
of oxygen to haemoglobin.
© OCR 2019
Bohr's Shift
During exercise there is an increase in blood acidity due to the increased
production of Lactic Acid and Carbonic Acid. This reduces the blood pH.
The reduction in blood pH also causes a reduction in the affinity of blood to
haemoglobin.
This allows more oxygen to be released to the muscle cell during exercise.
The graph shows the increased release of oxygen during exercise. The graph
shifts down and to the right.
This is known as BOHR'S SHIFT.
© OCR 2019
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4: Cardiovascular system/Olga Bolbot/Shutterstock.com
5: Internal anatomy of the heart/Alila Medical Media/Shutterstock.com
6: Heart/Studio BKK_Shutterstock.com
7: Conduction system of heart/Blamb/Shutterstock.com
14: Kidneys adrenal glands/Double Brain/Shutterstock.com
15: Difference between artery and
vein/Shutterstock/NelaR/Shuttertock.com
16: Capillaries/NelaR_Shutterstock.com
19: Vasomotor control/Alila Medical Media/Shutterstock.com
21: Respiratory system/Alila Medical Media/Shutterstock.com
22: Hemoglobin carrying oxygen_Sakurra_Shutterstock.com
24: Pulmonary function tests/Sudio BKK_Shutterstock.com
26, 27: Ribs and diaphragm/Blamb/Shutterstock.com
28: Facial muscles/DeryaDraws/Shutterstock.com
29: Abdominal muscle/medicalstocks/Shutterstock.com
31, 32: Respiratory control centers/Blamb/Shutterstock.com
33, 34, 35, 36: Alveolus gas exchange/Designua/Shutterstock.com
37, 38, 39, 40: Breathing and gas exchange in mitochondria
cells//Nasky/Shutterstock.com
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