Control of Respiration – Dr. Lee Siew Keah

These flashcards cover the neural and chemical regulation of respiration, including the roles of medullary and pontine centers, chemical factors (CO2, O2, pH), reflexes, and higher brain influences, as discussed in Dr. Lee Siew Keah’s lecture.

What three major components participate in the control of respiration?

Higher brain centers, chemoreceptors, and other reflexes.

Which part of the brain control the breathing?

Medulla & pons

Where are the neural respiratory centers located?

In neurons of the reticular formation of the medulla and pons.

Name the two medullary respiratory centers.

The ventral respiratory group (VRG) and the dorsal respiratory group (DRG).

What is the primary function of the ventral respiratory group (VRG)?

It acts as the rhythm-generating and integrative center that sets eupnea (about 12–15 breaths per minute).

How does the VRG initiate inspiration?

Its inspiratory neurons excite the diaphragm via the phrenic nerve and the external intercostals via intercostal nerves.

What is the role of VRG expiratory neurons?

They inhibit inspiratory neurons to terminate inspiration.

What is the main role of the dorsal respiratory group (DRG)?

It integrates input from peripheral stretch and chemoreceptors and relays the information to the VRG.

Which brain center smooths the transition between inspiration and expiration?

The pontine respiratory centers.

During which activities do pontine centers fine-tune breathing rhythms?

Vocalization, sleep, and exercise.

What breathing pattern indicates a pontine or upper-medulla lesion?

Apneustic breathing—prolonged inspiratory phase followed by apnea.

Medullary inspiratory neurons are very sensitive to inhibition by which drugs?

Barbiturates and morphine.

Which chemical factor is the most potent regulator of breathing?

Arterial partial pressure of carbon dioxide (PCO2).

Describe how hypercapnia stimulates ventilation.

Elevated PCO2 forms carbonic acid in the brain, lowering pH; central chemoreceptors sense the rise in H+ and trigger increased rate and depth of breathing.

What effect does hyperventilation have on blood CO2 levels?

It decreases blood CO2, producing hypocapnia.

Which two symptoms can hypocapnia cause due to cerebral vasoconstriction?

Dizziness and fainting.

What term describes breathing cessation caused by abnormally low PCO2?

Apnea.

At roughly what arterial PO2 (in mm Hg) does ventilation markedly increase?

When PO2 falls to about 60 mm Hg.

Which receptors sense a fall in arterial PO2?

Peripheral chemoreceptors in the aortic and carotid bodies.

How can a fall in arterial pH influence breathing even if CO2 and O2 are normal?

It stimulates peripheral chemoreceptors to increase respiratory rate and depth to raise pH.

Which buffer system resists shifts in blood pH related to CO2 changes?

The carbonic acid–bicarbonate buffer system.

Give two hypothalamic factors that modify breathing.

Pain, strong emotions, or changes in body temperature (any two).

What voluntary control can the cerebral cortex exert over respiration?

Short-term breath-holding or purposeful alteration of breathing patterns.

Which reflex terminates inspiration during extreme lung inflation?

The inflation (Hering–Breuer) reflex.

Which pulmonary reflex is triggered by dust, fumes, or pollutants?

The pulmonary irritant reflex, leading to bronchoconstriction, sneezing, or coughing.

How does the respiratory system respond to metabolic acidosis (low pH) to restore pH balance?

It increases the rate and depth of breathing to expel more CO2, thereby raising pH.

Define eupnea.

Normal quiet breathing at about 12–15 breaths per minute in healthy adults.