The respiratory system pt.1

Question 1

What are the functions of the respiratory system?

Answer 1

1. Pulmonary ventilation, breathing of air in and out of lungs (inspiration and expiration)
2. Gaseous exchange:
   - External respiration, exchange O2 and CO2 between the lungs and blood
   - Internal respiration, exchange of O2 and CO2 between blood and muscles tissues (cells)

Question 2

How are O2 and CO2 transported in the body?

Answer 2

1. 97% of O2 is transported by haemoglobin, 3% with plasma

2. 70% of CO2 is dissolved in water and carried as carbonic acid, 23% within haemoglobin, 7% dissolved in blood plasma.

Question 3

What is breathing rate, resting and maximal values for trained and untrained?

Answer 3

Breathing rate is the number of inspiration or expirations per minute:

• Average untrained at rest is 12-15 breaths/min
• Average trained at rest is 11-12 breaths/min
• Average untrained maximal is 40-50 breaths/min
• Average trained maximal is 50-60 breaths/min

Question 4

What is tidal volume, resting and maximal values for trained and untrained?

Answer 4

Tidal volume is the volume of air inspired or expired per breath:

• Average untrained at rest is 500ml
• Average trained at rest is 500ml
• Average untrained maximal is 2.5-3 litres
• Average trained maximal is 3-3.5 litres

Question 5

What is minute ventilation, resting and maximal values for trained and untrained?

Answer 5

Minute ventilation is the volume of air inspired or expired per minute (TV x f = VE):

• Average untrained at rest is 6-7.5 l/min
• Average trained at rest is 5.5-6 l/min
• Average untrained at maximal is 100-150 l/min
• Average trained at maximal is 160-210 l/min

Question 6

How does breathing rate, tidal volume and minute ventilation respond to exercise?

Answer 6

1. Breathing rate increases in proportion to exercise intensity up to a maximum of 50-60 breaths/minute
2. Tidal volume increases initially in proportion to exercise intensity at sub-maximal intensities up to approximately 4 litres
3. Minute ventilation increases in line with exercise intensity. During sustained sub-maximal intensity exercise, minute ventilation can plateau as we reach a comfortable steady state.

Question 7

What are the mechanics of breathing at rest?

Answer 7

1. Inspiration (active process):
   - External intercostal muscles between the ribs contract, pulling the chest walls up and out
   - The diaphragm muscle below the lungs contracts and flattens, increasing the size of the chest
2. Expiration (passive process):
   - External intercostal muscles between the ribs relax so that the chest walls move in and down
   - The diaphragm muscle below the lungs relaxes and bulges up, reducing size of the chest.

Question 8

What is respiratory regulation?

Answer 8

1. Respiratory regulation is when breathing rate and depth is continually adjusted to maintain appropriate levels of 02 and CO2
2. The respiratory control centre (RCC) located in the medulla oblongata is responsible for respiratory regulation
3. There are 2 centres within the RCC, the inspiratory centre (IC) and the expiratory centre (EC):
   - IC stimulates inspiratory muscles to contract at rest and during exercise
   - EC is inactive at rest, but will stimulate additional expiratory muscles to contract during exercise.

Question 9

What is respiratory regulation at rest?

Answer 9

1. At rest, the IC is responsible for the rhythmic cycle of breathing.
2. Nerve impulses are generated and stimulate inspiratory muscles, causing them to contract, via the:
   - Intercostal nerve to the external intercostal
   - Phrenic nerve to the diaphragm