Respiratory Physiology - Control of Respiration

Question 1

What are the 2 dual functions that respiration serves?

Answer 1

• Control of PO2, CO2, [H+]

- Modulation of breathing during swallowing, coughing, sneezing, speaking, etc.

Question 2

How does the dorsal respiratory group of the spinal cord regulate respiratory control?

Answer 2

Acts as a pacemaker which generates inspiratory “ramp” signal → low motor neurons > contraction of inspiratory muscles and inspiration

Question 3

How does the ventral respiratory group control respiration?

Answer 3

Inhibition of expiratory neurons in the VRG

Stimulation of inspiratory neurons

Question 4

DRG receives input from what nerves?

Answer 4

receives inputs through vagus and glossopharyngeal nn from chemo- and baroreceptors, and lung receptors

Question 5

What nuclei control breathing in the VRG?

Answer 5

nuclei ambiguous and retroambiguus

Question 6

Inspiratory activity of the DRG excites inspiratory cells and inhibits expiratory neurons found where?

Answer 6

VRG

Question 7

What does the bpneustic center do?

Answer 7

Activation (when both pneumatic center and vagi are blocked) causes apneusis- long and powerful inspiration and brief expiration

Controls the depth of inspiration (+ pneumotaxic center)

Question 8

What is the action of the pneumotaxic center?

Answer 8

volume limiting and rate controlling actions increase rate of respiration

Inhibitory effects on inspiration (like vagus) inhibitory effect on apneusitc center and prevention of apneusis

Question 9

How does RAS affect respiration?

Answer 9

Simulates ventilation
↓ activity (i.e., sleep) → ↓ ventilation & PA-CO2 increases by a few mmHg
May provide an important drive in individuals with decreased spontaneous respiratory center activity (drug overdose, morphine, barbiturates, alcohol)

Question 10

How do other higher brain centers affect respiration?

Answer 10

Hypothalamus (+ limbic system) – continual background excitatory drive to DRG and stimulation of breathing during fever, defence reactions, motivations, emotions
Limbic system – respiratory changes in emotions
Cerebellum – stimulation of respiration in exercise.

Question 11

Herin-breuer inflation reflex

Answer 11

Hering – Breuer inflation reflex
Overstretching of the airways and visceral pleura during lung inflation (when inspiratory volume increases to 1.5 L)  activation of stretch receptors in the smooth muscles of the trachea and bronchi → vagus

Off switch’ signal which terminates inspiration (duration and volume), shortens respiratory cycle (↑ RR) and causes reflex bronchodilation and increased HR

Question 12

What are factors that depress respiratory centers?

Answer 12

Overdose of narcotics, barbiturates, tranquilizers, anesthetics, and etc.

Brain edema

Increased PACO2 (And acidosis)

Hypoxia

Question 13

Where are the central chemoreceptors located? What connections do they make?

Answer 13

in the chemosensitive area of the medulla oblongata and have synaptic connections with neurons of the medullary respiratory center

Question 14

What do central chemoreceptors monitor?

Answer 14

Indirectly monitor blood Pco2 via associated changes in the Pco2 and pH of the brain ECF

Question 15

Most of the stimulation of central chemoreceptors results from changes to what?

Answer 15

PCo2 and H+ in ECF itself

Question 16

Where are the peripheral chemoreceptors located?

Answer 16

aortic (the arch of the aorta) and carotid (bifurcation of the common carotid arteries) bodies

Question 17

Peripheral chemoreceptors are primary sensitive to what chemical?

Answer 17

decreased PO2 in arterial blood also by hypercapnia via associated increase in blood H+ ins concentration and acidity

Question 18

Decreased O2 content the blood but not arterial blood Po2 leads to what?

Answer 18

lack of effect on peripheral chemoreceptors and ventilation