Respiratory system

Question 1

Mechanics of inspiration

Answer 1

Contracting at rest:
- Diaphragm
- External intercostals

Contracting during exercise:
- Diaphragm
- External intercostals
- Pectoralis minor
- Sternocleidomastoid

Effects:
- Volume inside thoracic cavity increases
- Volume inside lungs increases
- Thoracic cavity pressure inside the chest decreases
- Ribs move up and out
- Air is sucked into the lungs from high pressure to low pressure

Question 2

Mechanics of expiration

Answer 2

Relaxing at rest:
- External intercostals
- Diaphragm
- Both passively relax

Contracting during exercise:
- Internal intercostals
- Rectus abdominis

Effects
- Volume inside thoracic cavity decreases
- Volume inside lungs decreases
- Thoracic cavity pressure inside the chest increases
- Ribs move down and in
- Air is forced out of the lungs from high pressure to low pressure

Question 3

Intercostal nerve

Answer 3

The nerve that stimulates the external intercostal muscles to contract

Question 4

Phrenic nerve

Answer 4

The nerve that stimulates the diaphragm to contract (flatten)

Question 5

RCC

Answer 5

• Respiratory control centre
• RCC is found in the medulla
• RCC is controlled by the autonomic nervous system which works automatically, without requiring our conscious effort.

Question 6

Chemoreceptors

Answer 6

Detect chemical changes in the body

Question 7

Proprioceptors

Answer 7

Detect changes in muscle activity

Question 8

Baroreceptors

Answer 8

Detect changes in blood pressure

Question 9

Thermoreceptors

Answer 9

Detect changes in blood temperature

Question 10

Breathing rate (f) response to exercise

Answer 10

The number of inspirations or expirations per minute

As the intensity increases, breathing rate increases. Keep increasing until maximum capacity is reached, approximately 50-60 breaths/minute. If the oxygen supply meets the muscles’ demand, breathing rate will plateau. This can happen during steady state, sub-maximal exercise.

Question 11

Tidal volume (mL)

Answer 11

The volume of air inspired or expired in one breath.

Tidal volume will increase as exercise intensity increases, up to a volume of approximately 3000mL. Eventually tidal volume will plateau because breathing rate will be so fast that there is not enough time and it takes too much muscular effort for breaths to become deeper.

Question 12

Minute ventilation (L/min)

Answer 12

The volume of air inspired or expired per minute

VE = TV * f

Light intensity
There is an anticipatory rise in VE before exercise starts due to release of adrenaline. There is a rapid increase in VE as exercise starts to increase oxygen delivery and waste removal as exercise intensity builds. A plateau is eventually reached as oxygen supply meets demand of the exercise intensity. During a recovery, there is a rapid decrease in VE and then slowly more gradual as demand for oxygen is drastically reduced.

Heavy intensity
The anticipatory rise in VE before exercise starts is due to the rapid release of adrenaline. The rapid increase in VE as exercise starts, is to increase oxygen delivery and waste removal as exercise intensity builds. No plateau is reached as the respiratory system keeps trying to meet oxygen demands of the exercise intensity. Since the TV plateaus, any further increase in VE must be from an increased breathing rate. During recovery, a rapid decrease in VE and then slowly more gradual as demand for oxygen is drastically reduced.

Question 13

The Bohr Shift

Answer 13

The Bohr effect refers to shifts to the oxyhaemoglobin dissociation curve. An increase in partial pressure of carbon dioxide will shift the S-curve to the right, whereas a decrease in partial pressure of carbon dioxide shifts the curve to the left.

The Bohr shift describes the movement of the oxyhaemoglobin dissociation curve to the right. It is the result of increased blood acidity/ lower pH due to higher CO2 and lactic acid and increased blood temperature. These conditions mean that at any given partial pressure for oxygen at an exercising muscle, the % saturation of oxyhaemoglobin is much lower. O2 dissociates more readily from haemoglobin, so haemoglobin affinity for O2 is reduced. This enhances the unloading of oxygen into muscles to meet their demand for oxygen to produce energy aerobically during exercise.

Question 14

Oxyhaemoglobin association

Answer 14

When oxygen combines with haemoglobin it is called association. When oxygen associates with haemoglobin, it creates oxyhaemoglobin. When a haemoglobin molecule is saturated with oxygen it is carrying the maximum amount of oxygen that can be associated to it: 1 * Hb can carry 4 * O2
The amount of oxygen that will associate with haemoglobin depends on the partial pressure of oxygen. In places where there is a higher partial pressure of oxygen (e.g in the alveoli), there will be more association of oxygen to form oxyhaemoglobin.

Question 15

Oxyhaemoglobin dissociation

Answer 15

However, in places where the partial pressure of oxygen is low (e.g the muscles), haemoglobin starts to give up its oxygen instead. When oxygen detaches from haemoglobin for gaseous exchange at the muscles, it is called dissociation. Dissociation of oxyhaemoglobin depends on the partial pressure of oxygen. Oxyhaemoglobin dissociation is more likely to occur if the partial pressure of oxygen in a muscle is low, because a pressure gradient will exist. This means oxygen will dissociate from haemoglobin and move into the muscle where partial pressure of oxygen is low.

Question 16

Affinity of haemoglobin for oxygen

Answer 16

Affinity of haemoglobin for oxygen refers to if haemoglobin gives up oxygen more readily. If the affinity of haemoglobin for oxygen is reduced then more oxygen is free to diffuse into the muscle. This means that more oxygen is free to diffuse into the muscle. This increases the capacity for aerobic energy production.

Question 17

Oxygen transport in the blood

Answer 17

97% is carried bound to haemoglobin in the red blood cells as oxyhaemoglobin and 3% is carried dissolved in the blood plasma

Question 18

Haemoglobin

Answer 18

Haemoglobin is an iron rich globular protein found in red blood cells. It can chemically bind with 4 oxygen molecules. When oxygen associates with haemoglobin it forms oxyhaemoglobin.

Question 19

Myoglobin

Answer 19

• Myoglobin has a higher affinity for oxygen than haemoglobin
• Myoglobin is found in muscle fibres
• Myoglobin stores and transport oxygen in the muscles
• Myoglobin passes oxygen to the mitochondria in muscle cells where energy is produced

Question 20

Transport of carbon dioxide in the blood

Answer 20

• 23% of carbon dioxide binds with haemoglobin to form carbaminohaemoglobin
• 7% is carried as carbon dioxide molecules simply dissolved in blood plasma
• 70% is bound with water in the blood plasma to form carbonic acid (CO2 + H20)

Question 21

Pulmonary ventilation

Answer 21

To allow air to pass in and out of the body

Question 22

Structure of the alveoli

Answer 22

• Large surface area
• Moist surface area (lined with fluid)
• Elastic
• Alveoli walls are one cell thick
• Capillary walls are one cell thick
• Large capillary network/ blood supply

Question 23

Structure of the respiratory system related to function

Answer 23

• Pharynx, larynx and trachea have a mucous lined membrane and are ciliated - moisten, warm and filter the air before it flows into the lungs
• Large surface area of alveoli means that there is more area across which gases can be diffused from; high efficiency
• Fluid lined surface of alveoli: gases dissolve in the moisture, which helps them to pass across the gas exchange surface .
• Elastic: allows expansion and contraction of the thoracic cavity, which changes the pressure in the thoracic cavity and draws air in/ forces air out of lungs
• Alveoli and capillary walls are one cell thick so there is a short diffusion distance and low resistance for gas diffusion
• Large capillary network/ blood supply ensures that there’s an efficient exchange of oxygen from the lungs to the blood, and carbon dioxide from the blood to the lungs.

Question 24

Respiratory respiration at rest

Answer 24

The inspiratory centre is responsible for controlling the rhythm of breathing at rest. Nerve impulses are generated in the inspiratory centre and sent out into the inspiratory muscles. The nerve impulses are delivered to the inspiratory muscles by specific nerves. When the inspiratory muscles are innervated to contract , the thoracic cavity volume increases. This decreases the pressure inside the lungs and allows air to be inspired down a pressure gradient. About 500 mL of air is inspired on average at rest. After about 2 seconds, stimulation of the inspiratory muscles stops and they can relax. This creates a passive expiration.

Question 25

Tidal volume response to exercise

Answer 25

Tidal volume will increase as exercise intensity increases, up to a volume of approximately 3000mL. Eventually tidal volume will plateau because breathing rate will be so fast that there is not enough time and it takes too much muscular effort for breaths to become deeper.