Control of Respiration

Question 1

somatic motor neurones - cell bodies location and function

Answer 1

located in gray matter of thoracolumbar region spinal cord

stimulate the respiratory muscles

Question 2

motor neurones of phrenic nerves - cell bodies location and function

Answer 2

located in the cervical level of the spinal cord - C3,4 ,5

stimulate the diaphragm

Question 3

Where is the respiratory rhythm generated?

Answer 3

In the medulla oblongata

Question 4

Dorsal respiratory group neurone functions

Answer 4

Stimulate the spinal motorneurones of the phrenic nerve to the diaphragm - causing inspiration

Question 5

Ventral respiratory group nerve functions

Answer 5

Excite muscles during forceful expiration

Question 6

Breathing rhythm is generated by

Answer 6

Pre-Botringer Complex

Question 7

What activity does the Pre-Botringer Complex display

Answer 7

Pacemaker activity - spontaneous, cyclic changes in the membrane potential

Question 8

How is rhythm modified

Answer 8

Inputs from pons

Question 9

Apneustic centre

Answer 9

Promotes inspiration by stimulating the inspiratory area of the medulla

Question 10

Pneumotaxic centre

Answer 10

Antagonises apneustic centre and inhibits inspiration

Question 11

Chemoreceptors sense the values of the

Answer 11

Gas tensions

Question 12

Central chemoreceptors are found

Answer 12

In the medulla oblongata

Question 13

Peripheral chemoreceptors are made up of

Answer 13

Aortic and carotid bodies

Question 14

Carotid bodies are located

Answer 14

In each common carotid artery where it branches into the external and internal

Question 15

Peripheral chemoreceptors sense

Answer 15

Tensions of oxygen and carbon dioxide, and H ion concentration in the blood

Question 16

Aortic bodies send sensory information to the …. in the …nerve

Answer 16

medulla in the vagus nerve (X)

Question 17

Carotid bodies stimulate sensory fibres in the … nerve

Answer 17

Glossopharyngeal nerve (IX)

Question 18

Inadequate ventilation (hypoventilation) causes

Answer 18

PCO2 to rise and pH to fall

Question 19

Hyperventilation causes

Answer 19

PCO2 to fall and pH to rise

Question 20

Why does pH fall in hypoventilation

Answer 20

Due to hydrogen ions:

CO2 + H2O = H2CO3 = H + HCO3

Question 21

Why does oxygen content of blood only decrease slowly

Answer 21

Due to reservoir of oxygen attached to haemoglobin

Question 22

Why does pH rise in hyperventilation

Answer 22

Due to the excessive elimination of carbonic acid.

Question 23

How is a constant PCO2 maintained

Answer 23

Ventilation is adjusted

Question 24

Average normal arterial PCO2

Answer 24

40mmHg

Question 25

Hypercapnia is caused by

Answer 25

Hypoventilation - increased PCO2

Question 26

Hypocapnia is caused by

Answer 26

Hyperventilation - decreased PCO2

Question 27

How do central chemoreceptors increase ventilation

Answer 27

An increase in arterial PCO2 causes a rise in H ion concentration of blood as a result of increased carbonic acid. H ions cant cross the blood-brain barrier. CO2 diffuses across BB barrier and lowers the pH of CSF. Increased ventilation

Question 28

Do peripheral or central chemoreceptors increase ventilation faster

Answer 28

Peripheral - central may take several minutes

Question 29

Hypoxic drive of respiration

Answer 29

Via the peripheral chemoreceptors Stimulated only when arterial PO2 falls to low levels Important in patients with CO2 retention (e.g. COPD) or at high altitudes

Question 30

Hypoxia at high altitudes is caused by

Answer 30

Decreased partial pressure of inspired oxygen

Question 31

Acute response of hypoxia

Answer 31

Hyperventilation and increased cardiac output

Question 32

Chronic adaptions to high altitude hypoxia

Answer 32

Inc RBC production - polycythaemia Inc 2,3 DPG production within RBC - oxygen offloaded more easily into tissues Inc number of capillaries Inc number of mitochondria Kidneys conserve acid - decrease arterial pH

Question 33

Hydrogen ion drive of respiration

Answer 33

Peripheral chemoreceptors stimulation by H ion causes hyperventilation and increase elimination of CO2 from the body - CO2 can generate H ion so its increased elimination can help reduce the load of hydrogen ion in the body. Important in acid base balance

Question 34

How do the peripheral chemoreceptors help adjust for acidosis

Answer 34

By the addition of non-carbonic acid H ions to the blood (e.g. lactic acid during exercise)

Question 35

Pulmonary stretch receptors

Answer 35

Activated during inspiration , afferent discharge inhibits inspiration - Hering-Breuer reflex.