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Respiratory physiology > Control of Respiration > Flashcards

Control of Respiration Flashcards

1
Q

somatic motor neurones - cell bodies location and function

A

located in gray matter of thoracolumbar region spinal cord

stimulate the respiratory muscles

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2
Q

motor neurones of phrenic nerves - cell bodies location and function

A

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

stimulate the diaphragm

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3
Q

Where is the respiratory rhythm generated?

A

In the medulla oblongata

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4
Q

Dorsal respiratory group neurone functions

A

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

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5
Q

Ventral respiratory group nerve functions

A

Excite muscles during forceful expiration

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6
Q

Breathing rhythm is generated by

A

Pre-Botringer Complex

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7
Q

What activity does the Pre-Botringer Complex display

A

Pacemaker activity - spontaneous, cyclic changes in the membrane potential

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8
Q

How is rhythm modified

A

Inputs from pons

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9
Q

Apneustic centre

A

Promotes inspiration by stimulating the inspiratory area of the medulla

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10
Q

Pneumotaxic centre

A

Antagonises apneustic centre and inhibits inspiration

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11
Q

Chemoreceptors sense the values of the

A

Gas tensions

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12
Q

Central chemoreceptors are found

A

In the medulla oblongata

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13
Q

Peripheral chemoreceptors are made up of

A

Aortic and carotid bodies

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14
Q

Carotid bodies are located

A

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

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15
Q

Peripheral chemoreceptors sense

A

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

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16
Q

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

A

medulla in the vagus nerve (X)

17
Q

Carotid bodies stimulate sensory fibres in the … nerve

A

Glossopharyngeal nerve (IX)

18
Q

Inadequate ventilation (hypoventilation) causes

A

PCO2 to rise and pH to fall

19
Q

Hyperventilation causes

A

PCO2 to fall and pH to rise

20
Q

Why does pH fall in hypoventilation

A

Due to hydrogen ions:

CO2 + H2O = H2CO3 = H + HCO3

21
Q

Why does oxygen content of blood only decrease slowly

A

Due to reservoir of oxygen attached to haemoglobin

22
Q

Why does pH rise in hyperventilation

A

Due to the excessive elimination of carbonic acid.

23
Q

How is a constant PCO2 maintained

A

Ventilation is adjusted

24
Q

Average normal arterial PCO2

A

40mmHg

25
Q

Hypercapnia is caused by

A

Hypoventilation - increased PCO2

26
Q

Hypocapnia is caused by

A

Hyperventilation - decreased PCO2

27
Q

How do central chemoreceptors increase ventilation

A

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

28
Q

Do peripheral or central chemoreceptors increase ventilation faster

A

Peripheral - central may take several minutes

29
Q

Hypoxic drive of respiration

A

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

30
Q

Hypoxia at high altitudes is caused by

A

Decreased partial pressure of inspired oxygen

31
Q

Acute response of hypoxia

A

Hyperventilation and increased cardiac output

32
Q

Chronic adaptions to high altitude hypoxia

A

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

33
Q

Hydrogen ion drive of respiration

A

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

34
Q

How do the peripheral chemoreceptors help adjust for acidosis

A

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

35
Q

Pulmonary stretch receptors

A

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

Respiratory physiology (2 decks)

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