Respiratory System during exercise/recovering

Question 1

Breathing rate response to sub-maximal exercise (2 parts)

Answer 1

• Breathing rate increases in proportion to the intensity of the exercise. This will continue until we reach out maximum point – breathing rate will be between 50-60 breaths a minute.
• Sub-maximal exercise may see a plateau in breathing rate, due to the supply of oxygen meeting the demand from the working muscles.

Question 2

Tidal volume response to sub-maximal exercise (2 parts)

Answer 2

• During sub-maximal exercise tidal volume will increase in proportion to exercise intensity up to approximately 3 litres.
• It plateaus because increased breathing rate towards maximal intensities do not allow enough time and requires too much muscular effort.

Question 3

Minute ventilation response to increasing intensity (2 parts)

Answer 3

• VE increases due to increase in breathing rate and tidal volume
• VE can plateau during sub-maximal intensity exercise; happens when we reach a steady state.

This represents supply meeting demand for oxygen delivery and waste removal.

Question 4

Minute ventilation response to exercise and recovery at different levels (4 parts)

Answer 4

• Initial anticipatory rise in VE – due to adrenaline
• Rapid increase in VE at start of exercise due to breathing rate and tidal volume to increase O2 delivery and waste removal.
• Steady state of VE throughout sustained intensity exercise as O2 meets demand
• During recovery rapid and gradual decrease in VE to resting levels.

Question 5

Transport of oxygen methods (2 methods)

Answer 5

Method 1:

• 97% is carried in a chemical combination with haemoglobin

Method 2:

• 3% is dissolved in the blood plasma – oxygen is not very soluble in water and therefore, this figure is relatively low

Question 6

Oxygen and haemoglobin

What do they form when combined?
Affinity?
How many oxygen molecules for each Hb and what is this dependent on?

Answer 6

• When O2 combines with haemoglobin it form oxy-haemoglobin.
• Haemoglobin has a high affinity for oxygen
• For every one molecule of haemoglobin four molecules of oxygen combine with it - how much depends on partial pressure of oxygen

Question 7

Oxygen and myoglobin

What is it?
Affinity?
What does it do?

Answer 7

• Myoglobin is an iron based protein found in the muscles
• This has a much higher affinity for O2 than Hb
• It acts as an O2 store, by saturating itself with O2 which has disassociated itself from haemoglobin

Question 8

Chain of events O2 being taken up by Hb in the lungs and released to the muscle site (7 steps)

Answer 8

1. At lungs there is a high pO2 and a low pO2 in the blood
2. O2 diffuses across the alveolar membrane into the bloodstream
3. O2 readily combines with haemoglobin until it almost fully saturated
4. Oxy-haemoglobin then travels to the muscles
5. At muscles there is a low pO2 and a high pO2 in the blood
6. Oxygen is released by the haemoglobin (disassociates) and is used by the respiring tissues and muscles

Question 9

Transport of carbon dioxide (3 methods)

Answer 9

• Dissolved in water as carbonic acid - 70%
• In combination with haemoglobin (carbaminhaemoglobin) - 23%
• Dissolved in blood plasma - 7%

Question 10

Partial pressure

Answer 10

The pressure that is exerted by an individual gas when it exists within a mixture of gases

Question 11

Diffusion

Answer 11

The movement of respiratory gases from areas of higher partial pressure to areas of lower partial pressure

Question 12

Exchange of respiratory gases (2 sites)

Answer 12

• External respiration - Between the air in the alveoli of the lungs and the blood in the surrounding alveolar capillaries
• Internal respiration - Between the tissues/muscles of the body and the surrounding capillaries

Question 13

External Respiration

What is it?
What does it involve?
The object of gaseous exchange here is to?

Answer 13

• gaseous exchange at the alveoli
• involves the movement of oxygen and carbon dioxide between the alveoli of the lungs and the surrounding capillaries.
• convert deoxygenated blood returning from the body into oxygenated blood

Question 14

External Respiration - Diffusion of gases in the alveoli is facilitated by several structural features: (4 things)

Answer 14

Respiratory membrane is very thin:

• meaning diffusion distance is very small

Numerous alveoli:

• create a large surface area over which diffusion can take place

Alveoli surrounded by a large capillary network:

• also provides a large surface area for gaseous exchange

Diameter of capillaries is slightly narrower than the area of the red blood cell (RBC):

This causes the RBC to become distorted:

• increasing the surface area
• forces them to flow through in single file

Question 15

Internal Respiration

Definition?
Why it occurs?
What happens to oxygen?
What happens to carbon dioxide?

Answer 15

• Gaseous exchange at the tissues/muscles
• it occurs due to a partial pressure gradient between the capillaries and that of the muscle tissue
• O2 must move along the concentration gradient and O2 will continue to travel across in the muscles until equilibrium is reached
• Partial pressure of carbon dioxide (PCO2) is higher in the tissues than in the capillaries and therefore, CO2 moves out of the muscles and into the blood stream

Question 16

Internal Respiration - Factors affecting the effectiveness at the muscles/ tissues (4)

Answer 16

• Diffusion gradient along O2 travels from the blood to the muscles is relatively large
• Myoglobin has a higher affinity for O2 than haemoglobin, therefore, attracting O2 to it
• Extensive network of capillaries surrounding the tissues provides a large surface area
• Capillary walls are one cell thick which means the diffusion distance is very short

Question 17

The oxy-haemoglobin dissociation curve

What does it show?
What shape is the graph and why?
What about the ends and the middle?

At respiring muscles what is the pO2 like?
Why?
What is the pO2 like and saturation of Hb?

Answer 17

• This shows how saturated with oxygen the haemoglobin is; at any given pO2.
• The graph is S-shaped because when haemoglobin combines with the first oxygen molecule it changes shape, so that it is easier for other molecules of oxygen to join.
• This means it has a steep part in the middle where it is easier for the oxygen to combine and shallow parts where it’s harder.
• At respiring muscles there is a very low pO2 which means the saturation of haemoglobin is also low
• Because a large proportion has been released to the muscles for energy production
• At the arteries/lungs where there is a high pO2 we find that saturation of haemoglobin is almost 100%

Question 18

Exercise and the Bohr Shift

Why does it happen and what happens the curve?

Answer 18

During exercise muscles require more oxygen which means that oxygen will disassociate from haemoglobin more readily so the curve shifts to the right

Question 19

Factors which affect Haemoglobin saturation (3 factors and description points)

Answer 19

• Blood temperature

     - increased blood temperature
     - reduces haemoglobin affinity for O2
     - hence more O2 is delivered to warmed-up tissue

• Blood pH

     - lowering of blood pH (making blood more acidic)
     - caused by presence of H+ ions from lactic acid or carbonic acid
     - reduces affinity of Hb for O2
     - and more O2 is delivered to acidic sites which are working harder

• Carbon dioxide concentration

     - the higher CO2 concentration in tissue
     - the less the affinity of Hb for O2
     - so the harder the tissue is working, the more O2 is released

Question 20

Oxy-haemoglobin vs myoglobin saturation

Difference between their curves?

What does this mean? (2 things)

Answer 20

As myoglobin has a much higher affinity for oxygen the curve lies further to the left.

This means that:

• Even at very low partial pressure of oxygen (pO2) myoglobin remains relatively saturated.
• Even if the percentage of haemoglobin saturation is low, myoglobin still has oxygen to supply to the working muscles.

Question 21

Respiratory Control Centre

When we breathe it happens ______________and is under the influence of the respiratory control centre (RCC) located in the ___________ _____________.

What two centres are involved?

Answer 21

When we breathe it happens automatically and is under the influence of the respiratory control centre (RCC) this is located in the part of the brain known as the medulla oblongata. The RCC has two areas, both of which are under involuntary nervous control:

Inspiratory Control Centre:

• Uses two nerves:

   - Phrenic nerve - makes the diaphragm contract
   - Intercoastal nerve - makes the external intercostals contract

• Results in increased breathing frequency

Causes:

     - TC volume to increase and TC pressure to decrease
     - 500ml of air to be inspired
     - Breathing rate to be 12-15 breaths a minute

Expiratory Control Centre:

• Is inactive at rest, but will stimulate additional expiratory muscles to contract during exercise.
• Results in increased depth of breathing

Question 22

Respiratory Control Centre when exercising

During exercise the breathing frequency and depth of breathing must be __________to meet the ________for oxygen and the removal of ________ ________. In order for this to happen _________information is relayed to the ____ where a response occurs from both the __and the __.

Information is picked up from ___________ __________: (4)

This information is passed onto the IC which ____________the stimulation of the ___________ and ___________intercostals to contract with _____ _______. It will also recruit more muscles to assist in the process these are sternocleidomastoid and ___________ _____which will contract and will generate _____ ______ which in turn ___________ the depth of inspiration.

Baroreceptors inform the EC of the extent to which the lungs are ___________; if they are excessively ____________the EC will stimulate extra expiratory muscles; __________ intercostals and ______ __________ to contract. This results in forced expiration, which _________the time for inspiration.

As intensity increases the IC and EC will ________the depth and frequency of breathing even more. Breathing rate will ________and depth of breathing will __________to maximise efficiency.

Answer 22

During exercise the breathing rate and depth of breathing must be increased to meet the demands for oxygen and the removal of carbon dioxide. In order for this to happen sensory information is relayed to the RCC (respiratory control centre) where a response occurs from both the IC (inspiratory centre) and the EC (expiratory centre).

Information is picked up from several receptors:

• Thermoreceptors informs about an increase in blood temperature
• Proprioreceptors informs about motor activity in the muscles and joints
• Baroreceptors (aka stretch receptors) found in the lung tissue and bronchioles inform about the state of lung inflation
• Chemoreceptors located in the carotid artery and aorta informs about the increase in blood acidity, increase in CO2 concentration and decrease in O2 concentration.

This information is passed onto the IC which increases the stimulation of the diaphragm and external intercostals to contract with more force. It will also recruit more muscles to assist in the process these are sternocleidomastoid and pectoralis minor which will contract and will generate more force which in turn increases the depth of inspiration.

Baroreceptors inform the EC of the extent to which the lungs are inflating; if they are excessively stretched the EC will stimulate extra expiratory muscles; internal intercostals and rectus abdominis to contract. This results in forced expiration, which reduces the time for inspiration.

As intensity increases the IC and EC will control the depth and frequency of breathing even more. Breathing rate will increase and depth of breathing will decrease to maximise efficiency.

Question 23

Gaseous Exchange

External site vs Internal Site (at rest and at exercise for each)

Answer 23

External site

At rest:

• pO2 is high in alveoli but low in capillaries (blood)
• Causes a diffusion gradient in which oxygen will diffuse from alveoli to blood in capillaries
• pCO2 is high in the blood and low in the alveoli
• Causes a diffusion gradient to form in which CO2 diffuses from blood into alveoli

At exercise:

• pO2 increases in the alveoli and decreases in the blood
• So an even steeper diffusion gradient is created and even more O2 diffuses into the blood
• pCO2 decreases in the alveoli and increases in the blood
• So an even steeper diffusion gradient is created
• And even more CO2 diffuses into the alveoli

Internal site

At rest:

• pO2 is high in the capillaries but low in the muscles
• creates a small diffusion gradient so oxygen will diffuse from the capillaries into the muscles (myoglobin)
• pCO2 is high in the muscles and low in the capillaries
• creates a small diffusion gradient so CO2 will diffuse from the muscles into the capillaries

At exercise:

• pO2 increases at the capillaries but decreases in the muscles
• creates a steeper diffusion gradient so even more O2 moves from capillaries to working muscles (myoglobin) and it is used for Aerobic Respiration
• pCO2 increases in the muscles and decreases at the capillaries
• creates a steeper concentration gradient so more CO2 moves out of the muscles into the capillaries