Module 4

Question 1

gas and liquid ting

Henry’s Law of Diffusion

Answer 1

‘When a liquid is in contact with a given gas, that gas will diffuse into solution in proportion to its partial pressure.’
- Gas becomes liquid

Question 2

what parts of the body does diffusion increase at

Diffusion during exercise?

Answer 2

O2 and CO2 diffusion increases to
- alveolar (lungs)
- capillary (blood)
- tissue (muscle)

Question 3

PO2 and PCO2diffusion relationship

Large Diffusion Gradient

Answer 3

PO2 muscle can approach 3-0 mmHg during intense exercise (100 arterial blood - 0 muscle = gradient of 100mmHg)

PCO2 muscle can approach 90mmHg (90 muscle - 40 alveolus = gradient of 50 mmHg)

Question 4

Transport of CO2

Answer 4

transported to lungs by venous blood

Question 5

what 3 ways does it leave

How does CO2 leave body?

Answer 5

1. dissolved in plasma (5%)
   - diffuses out of capillaries into alveoli to be exhaled
2. bount to HB (RBC) (carbamino-haemoglobin)
   - CO2 binds to AAs in globin part of HB
   - binds easily in muscle (high PCO2)
   - CO2 released by HB when PCO2 is low (lungs) –> alveoli –> exhalation
3. plasma bicarbonate (60-80%)
   - CO2 + water = carbonic acid (H2CO3) in muscles
   - H2CO3 –> CO2 and H2O –> exhalation

Question 6

Carbonic Anhydrase

Answer 6

• enzyme within RBC (zinc) that accelerates process

helps convert bicarbonate ions back to carbon dioxide for us to expel

Question 7

Carbon Dioxide Transport Equation

Answer 7

CO2 + H2O –carbonic anhydrase–> H2CO3 –> H + HCO3

Question 8

What happens during exercise overall???

Answer 8

When CO2 enters skeletal muscle tissue fluid, carbonic anhydrase catalyses formation of carbonic acid
Increased PCO2 (exercise) = decreased pH = oxyhaemoglobin dissociation
- More O2 liberation into tissues
Better contractions (synergist reaction)

Question 9

Ventilation at rest and exercise

Answer 9

Rest –> 12 breaths per minute x 0.5 L = 6L/min
Exercise –> 40+ breaths per minute x 2L = 80+L/min

Question 10

Where does respiratory control occur

Answer 10

In medulla
- neural circuits (info from brain, lungs, etc.)

Question 11

think about centres and receptors

Ventilation Process (neural factors)

Answer 11

respiratory centres
- afferent/sensory signals to brain centre, efferent/motor signals to effector/target organ

pulmonary stretch receptors
- in airway smooth muscle and responds to lung distension (smooth muscle)

joint and muscle receptors in limbs
- movement stimualtes increase in ventilation

baroreceptor reflexes
- fall in BP = increased ventilation

Question 12

Inspiratory centre activates

Answer 12

• diaphragm and external intercostals

Question 13

Expiratory centre activates

Answer 13

• intercostals and abdominal muscles

Question 14

think about central and peripheral

Ventilation Process (humoral factors)

Answer 14

blood transfer

central chemoreceptors
- medulla (stimulated by CSF)
- pH (increased H+ = increased VE)
- H+ increased by diffusion of CO2 across blood brain barrier
H2O + CO2 <-> H2CO3 <-> H+ + HCO3

peripheral chemoreceptors
- carotid bodies and aortic arch
- PCO2 (increased ventilation)
- pH (increased H+ = increased ventilation due to PCO2)
- arterial PO2 (increased ventilation if PO2 less than 60 mmHg)

Question 15

Break point of breath hold

Answer 15

increased in arterial PCO2 (50 mmHg)

Question 16

Hyperventilation

Answer 16

reduces alveolar and arterial PCO2 (e.g. breath hold)
- high PCO2 = stimulus to breathe

Question 17

Hypoxic Blackout

Answer 17

combo of low PO2 and PCO2 can lose consciousness

Question 18

how does body regulate this?

Respiratory Regulation

Answer 18

body monitors internal environment via central and peripheral chemoreceptors, stretch receptors in muscle and lungs

Question 19

think about neural process leading to proper breathing

Respiratory Regulation Process

Answer 19

• info goes to inspiratory centre
• motor signals stimulate inspiratory muscles (external intercostals and diaphragm) increasing thorax volume and lowering diaphragm
• stretch receptors sned messages to expiratory centre (expiration via expiratory muscles)
• decreased thorax volume and raising diaphragm to reduced volume and increased pressure (expiration)

Question 20

Hypernea

Answer 20

increased ventilation (at start of exercise before any chemical changes)

Question 21

Corticol Influence

Answer 21

Before Exercise
- neural outflow from motor cortex causing muscle contractions
- stimulate respiratory neurons + phrenic nerve increases ventilation

Question 22

Peripheral Influence

Answer 22

During Exercise
- proprioreceptive feedback from muscles, tendons and joints
- influence ventilation during exercise
- send signals to brain
- respiratory centre send signals of inspiration/expiratoin to increase TV/BR

Question 23

Phase 1

Answer 23

0-20s
- initial VE increase before chemical stimulation (corticol and peripheral)

Question 24

Phase 2

Answer 24

• VE rises exponentially to reach steady state due to neurogenic factors, temp changes and chemical status of blood/muscles

Question 25

Phase 3

Answer 25

• fine tuning steady state ventilation
• chemoreceptors give feedback to respiratory centre via ventilation needs

Question 26

what 3 ways is ventilation controlled

Ventilatory control during exercise (controlled by…)

Answer 26

1. feed-forward centralc ommand (motor cortex signalling muscles, tendons and joints for feedback)
2. peripheral sensory input from joint/muscle receptors
3. peripheral and central chemoreceptor activation by changes in H+ and PCO2

Question 27

Untrained VE Performance

Answer 27

60-85% max voluntary ventilation
- TV rarely exceeds 60% VC

TV = normal breathing

VC = greatest volume of breath expelled after taking longest breath

Question 28

Untrained Max Exercise

Answer 28

• alovelar PCO2 decreases and PO2 increases
• VE more adequate to maintain diffusion gradients for gas exchange

Question 29

what happens during this>

Trained Max Exercise

Answer 29

• drop in arterial O2 satuation (SaO2) as complete aeration of blood is not possible in pulmonary in pulmonary capillaries

UNKNOWN

• may be due to ventilation (perfusion mismatch), shunting of blood and capillary due to faster RBC transit time

During high-intensity exercise, the body’s rapid pace can lead to these issues where not all the blood passing through the lungs gets enough oxygen, resulting in a drop in arterial oxygen saturation (SaO2).