13. Respiratory System 3

Question 1

The bicarbonate buffer system is not powerful in the sense that the pK’ is more than a unit away from the blood pH and in terms of the fact that the weak acid and base concentrations are low and yet it is more important than all the other buffers in the body combined. Why? (3)

Answer 1

1. The pH of blood is more than one pH unit away from the pK’
2. The concentrations of the weak acid and base are low
3. Important because can shift pCO2 via respiration and HCO-3 via renal excretion

Question 2

What causes respiratory acidosis and how does the kidney attempt to correct it? (3)

Answer 2

1. Result of an increase in pCO2
2. Causes impaired respiration or gas exchange
3. Kidney attempts to correct the pH by increasing H+ excretion and increasing re-absorption of bicarbonate (HCO3)

Question 3

What causes respiratory alkalosis and how does the kidney attempt to correct it? (3)

Answer 3

1. Result of a decrease in pCO2
2. Causes ammonia toxicity
3. Kidney attempts to correct the pH by decreasing H+ excretion and decreasing re-
   absorption of bicarbonate.

Question 4

What kind of events can lead to metabolic acidosis and what is the respiratory response? (6)

Answer 4

1. Excess H+ or loss of HCO-3
   - Ketosis
   - Grain overload
   - Diarrhea
   - Excess K+
2. Correct by increasing respiration rate to decrease pCO2

Question 5

What kind of events can lead ot metabolic alkalosis and what is the respiratory response? (4)

Answer 5

1. Excess base or loss of H+
   - Vomiting
   - K+ deficiency
2. Correct by decreasing respiration rate to
   increase pCO2

Question 6

Explain this graph (4)

Answer 6

1. Pco2 isobar (blue)
2. any combination of bicarbonate [ ]and pH that can exist when Pco2 is normal (40 mm Hg)
3. Normal Buffer Line (green)
4. A balance between metabolic acids and bases in the body

Question 7

Answer 7

Question 8

Answer 8

Question 9

Answer 9

Question 10

What is the name given to each of the following respiratory states? - States of breathing
a. Normal quiet breathing
b.Transient cessation of breathing
C. Increased frequency and/or depth of breathing
d. Rapid shallow type of respiration
e. Increased ventilation of lungs
f. Decreased ventilation of lungs

Answer 10

a. Normal quiet breathing - Eupnea
b.Transient cessation of breathing - Apnea
C. Increased frequency and/or depth of breathing - Hyperpnea
d. Rapid shallow type of respiration - Polypnea
e. Increased ventilation of lungs - hyperventilation
f. Decreased ventilation of lungs - hypoventilation

Question 11

What do each of the following terms mean in regards to the state of the oxygen and/or carbon dioxide levels in tissues? - States of breathing
a. Anoxia
b. Hypoxia
c. Cyanosis
d. Hypercapnia

Answer 11

a. Anoxia – no O2 in tissues
b. Hypoxia – low O2 in tissues
c. Cyanosis – tissue appears blue due to low
O2
d. Hypercapnia – high CO2 in tissues

Question 12

Where is the respiratory centre located? (1)

Answer 12

Located in the brain stem (pons and medulla)

Question 13

What input does the respiratory centre get? (7) - Regulation of respiration

Answer 13

1. Has a chemosensitive area (sensitive to H+ and CO2)
2. Vagus and glossopharyngeal nerves send signals to the respiratory center from both chemical and physical receptors in the body
3. Is the central pattern generator
4. Basic respiratory rhythm
   - Inspiration 2 sec (ramp)
   - Expiration 3 sec
5. Inspiratory neurons are firing during quite respiration but not expiratory neurons

Question 14

What is the Hering-Breuer reflex? (3) - Physical control of respiration

Answer 14

1. Stretch receptors located in the walls of the bronchi and bronchioles throughout the lungs
2. Send inhibitory signals to the respiratory center via the vagus nerve to limit the duration of inspiration
3. Prevents excess inflation of the lungs

Question 15

What is the role of tactile receptors on the skin? (2) - Physical control of respiration

Answer 15

1. Excites the respiratory center and deeper than normal inspiration may occur
2. Used in newborn animals – rub the skin with a rough cloth to stimulate breathing cycle

Question 16

Tactile receptors in the upper respiratory tract cause what events and why? (4) - Physical control of respiration

Answer 16

1. Inhibition of respiration during swallowing
2. If mucous membranes of the larynx are irritated it will end inspiration effort and causes a powerful expiratory effort (cough)
3. If mucous membranes of the nose are irritated it causes sneezing
4. All function to protect the delicate respiratory passages and depths of the lungs from harmful substances (dirt, irritating gases, food particles)

Question 17

How does blood pressure affect respiration (3) - Physical control of respiration

Answer 17

1. In the carotid and aortic bodies
2. Send inhibitory signals to the respiratory centre
3. If blood pressure drops, there is a reduction in the signals sent so that the respiration rate increases – this aids in the return of blood to the heart

Question 18

Why do we see increases in respiration rate from exercise? (4) - Physical control of respiration

Answer 18

1. Increased consumption of O2 and increased production of CO2
2. Ventilation rate increases – but it increases
   before there are changes in blood gases

CAUSED BY:
3. Collateral neurons to the respiratory center
4. Propioceptors in joints and muscles

Question 19

Describe the direct effect of [H+] and Pco2 on respiration rate (5) - Humoral control of respiration

Answer 19

1. Chemosensitive area of medulla extremely sensitive to H+
2. However, H+ diffuses poorly through the blood-brain barrier therefore [H+] of blood has a minimal effect
3. CO2 easily diffuses across the blood- brain barrier and once across undergoes hydration
4. CO2 + H2O ↔H2CO3↔ H+ + HCO-3 so the H+ reaches the chemosensitive area and has an effect
5. Therefore see a greater respiratory response to blood Pco2 than to blood [H+]

Question 20

What is the effect of blood Pco2 on respiration (6) - Humoral control of respiration

Answer 20

1. Reaches peak within a minute of increase in Pco2
2. Thereafter effect declines
   - Within a few days is a 5th to an 8th of initial response
   - Due to movement of bicarbonate ions into cerebrospinal fluid
3. Therefore Pco2 has a potent acute effect but only a weak chronic effect
4. Effect of blood [H+] actually increase with time

Question 21

Discuss the indirect effect of H+, Pco2 and Po2 on the respiratory center (7) - Humoral control of respiration

Answer 21

1. Peripheral chemoreceptors
2. Carotid and aortic bodies detect Pco2 and [H+]
3. Sends signals to the respiratory center via the glossopharangeal nerve (carotid bodies) and the vagus nerve (aortic arch)
4. Responsible for ~ 30% of the response to
   carbon dioxide
5. Carotid and aortic bodies detect Po2
6. only place where oxygen is sensed – responds to Po2 not total oxygen
7. Impulses are excitatory – see increases in impulses with Po2 in range of 30-60 mm Hg

Question 22

What is the primary chemical factor regulating ventilation, and how do changes in this affect the process?

Answer 22

Po2
1. Pco2 is the leading chemical factor in the normal regulation of ventilation
2. Don’t want the Pco2 to fall or rise due to effects on pH
3. The low Pco2 and low [H+] have a braking effect on increased respiration due to low Po2

Question 23

When does oxygen play a major role in
regulation of respiration?

Answer 23

1. Pneumonia, emphysema and other lung
   ailments in which gases are not readily
   exchanged
2. High altitudes