Control of Ventilation

Question 1

Two ways of breathing

Answer 1

• Autonomic control maintains breathing pattern that allows gas exchange to occur
  > Occurs in the Medulla: neuronal, chemical and reflexes
• Voluntary control adjust breathing pattern during eating, speaking, and holding your breath
  > Occurs in the Cortex and thalamus

Question 2

Another word for autonomic control of ventilation and what is its purpose?

Answer 2

Neuronal control- purpose is to provide smooth, rhythmic breathing pattern&raquo_space; decrease V02 and decrease WOB
- Originates in the medulla oblongata

Question 3

What are the two branches of the medulla

Answer 3

Dorsal respiratory group and ventral respiratory group

Question 4

What is the purpose of the Dorsal respiratory group

Answer 4

• Located in the medulla
• Primarily inspiratory neurons that establish:
  > Depth of inspiration
  > Breath rate (12-15 b/min)
  > Rhythm (1-2 seconds Ti and then stop)
• Send impulses to cause inspiration
  > Phrenic and intercostal nerves
• Receive impulses&raquo_space; alteration of breathing pattern

Question 5

What is the purpose of the Ventral respiratory group

Answer 5

• Located in the medulla
• VRG consists of:
  1. Inspiratory neurons: Help with vocal cord abduction and help DRG
  2. Expiratory neurons: Active during laboured breathing or exercise (force exhalation to occur when high RR).
  Inactive during passive breathing. (Inhibit DRG and VRG inspiration)

Question 6

What are pons made up of and what do they control in reference to breathing?

Answer 6

1. Apneustic center
2. Pneuomtaxic center
   - Does not control breathing but can alter rhythm. Modifies output of the medullary centers

Question 7

Lower part of pons is called

Answer 7

Apneustic center

- Prolonged gasping inspiration, only happens if the vagal nerve is not intact

Question 8

What is the inhibitory center

Answer 8

Pneumotoxic center

• Inhibits both the apneustic center and the DRG inspiratory center&raquo_space; Slowing or stopping inspiration&raquo_space; affects RR
• Prevents hyperventilation of the alveoli

Question 9

How do chemoreceptors affect breathing

Answer 9

Chemoreceptors are specialized nerve structures that respond to hypercapnia (CO2) and/or hypoxia (O2) and acidemia (H+)

Chemoreceptors send impulses to the medulla via the afferent nerves&raquo_space; produce change in ventilation to “correct” hypercapnia, hypoxia, and acidemia

2 types of chemoreceptors are central and peripheral

Question 10

Where are Central chemoreceptors found and what chemical changes to that cause and how do they affect breathing?

Answer 10

Found in the medulla
- Respond directly to [H+} which is related to CO2
- Acute increase in CO2 results in an increase in [H+] in CSF (cerebral spinal fluid)
> Increase [H+] = Acidosis of CSF&raquo_space; increase ventilation
- Acute decrease in CO2 results in decrease in [H+] in CSF
> decrease [H+] = Alkalosis of CSF&raquo_space; decrease ventilation

Central chemoreceptors do not respond to O2

Question 11

What happens in the body when there is chronic changes in CO2 (patient’s with COPD)

Answer 11

Body normalizes and accepts increased CO2 levels
Does this by:
- Increased PaCO2 (over days)
- Increase [HCO3-] in blood (retained by kidneys)
- HCO3- diffuses across blood brain barrier into the CSF (combines with H+)
- Normal pH of CSF
- Decreased venitlation

Question 12

Peripheral chemoreceptors: what do they respond to and what affect does this have on ventilation

Answer 12

• Consists of Aortic bodies and Carotid bodies
• Responds directly to [H+] or increased PaCO2&raquo_space; increased firing of nerve impulses to the control chemoreceptors&raquo_space; increase ventilation
• Carotid bodies and Aortic bodies respond to hypoxemia
• PaO2 > increased sensitivity to [H+]&raquo_space; causing hyperventilation

Question 13

What route do the aortic bodies and carotid bodies send impulses to the medulla

Answer 13

Aortic bodies send impulses to the medulla via the vagus nerve.
Carotid bodies send impulses to the medulla via the glossopharyngeal nerve.

Question 14

Explain the abnormal breathing pattern Cheyne- stokes: Symptoms and Cause

Answer 14

Cheyne-stokes: Combination of hyperpnea and apnea
May be caused by:
- Congestive heart failure or other cardiac pathology
- Brainstem damage

Question 15

What is Biot’s Breathing: Symptoms and Causes

Answer 15

• Breathing with irregular periods of apnea imposed with runs of breathing
• Breathing consists of 4-6 consistant Vt
  Causes: Increased cranial pressure/ Tumor/ Cerebral infarcts

Question 16

What is Apneustic breathing

Answer 16

• Breathing with prolonged gasping inspiration with occasional expirations
• Caused by damage to the pons of the vagus nerve

Question 17

What is Kussmaul’s breathing

Answer 17

It is an example of hypernea. It is associated with metabolic acidosis. Compensatory attempt o remove CO2

Question 18

Central Reflex Hypernea: What is the breathing pattern and what is the cause, and what affect does it have?

Answer 18

• Deep rapid breaths
• Caused by severe head injuries or strokes involving the midbrain
• It is a central reflex response to increase intracranial pressure
• Causes decrease PaCO2 in cranial arteries and causes vasoconstriction in areas of brain damage

Question 19

What is Central Refelx Hypopnea

Answer 19

• Respiratory centers in the medulla do not respond to CO2 like they should
• Associated with head injuries, brain hypoxia, and CNS depressant drugs
• Eg is acute cerebral edema (has caused ischemia [inadequate blood supply]&raquo_space; neuron destruction or inactivation)

Question 20

What is the sensory or reflex control of breathing?

Answer 20

There are sensory receptors that send impulses back to the medulla and the medulla responds by alternating the breathing pattern

Question 21

What do stretch receptors do?

Answer 21

• Found in smooth muscle

- Respond to stretch (stretched too much, or too little)

Question 22

What is the Hering-Breuer Inflation Reflex?

Answer 22

• It is a sensory receptor which stimulates inspiration to end and prevents over distension
• Not present in normal breathing but present during exercise and in new borns

Question 23

What is Hering-Breuer Deflation Reflex?

Answer 23

• Sudden collapse of the lungs causes increased RR and inspiratory effort
• Probably responsible for hypernea which occurs with pneumothorax

Question 24

What is Heads Paradoxical Reflex

Answer 24

• Opposite to the Hering-breuer inflation reflex
• Stimulates a deeper breath on top of normal breath (exercise or yawns)
• Example is new borns gasping for breath

Question 25

What are Irritant receptors: where are they found/ what do they respond to

Answer 25

• Found in airway epithelia
• Protective mechanism that is not active during normal breathing
• Respond rapidly to irritation via that vagal reflex
• Irritants include: noxious gases, liquids, mechanical stimulation and histamine
• Stimulation results in: sneezing, coughing, tachypnea (rapid breathing), bradycardia (abnormally slow heart rate), laryngospasm and bronchospasm

Question 26

What do J receptors do?

Answer 26

• Part of NANC system
• Located in lung parenchyma next to the pulmonary capillaries
• React to stimuli such as increases PAP, alveolar inflammatory processes, and edma
• Causes rapid shallow breathing&raquo_space; SOB

Question 27

Peripheral Proprioceptors

Answer 27

• Located in joints, tendons, and pain receptors in muscle and skin
• Stimulation of these receptors sends impulse to medulla to breath (if you splash cold water on someones skin)
• Proprioceptors in joints and tendons increase RR during exercise
• Sudden pain = apnea
• Prolonged pain = tachypnea