Respiratory Centers in the Brain Quiz

Study Notes

Apneustic Centre

The apneustic centre is responsible for generating impulses that excite the inspiratory area of the medulla.
The rhythm generated in the medulla can be modified by inputs from the pons.

Rhythm Generation in Medulla

The medulla generates a rhythm that can be modified by inputs from the pons.
The apneustic centre sends impulses to the inspiratory area of the medulla, which generates a rhythm.

Damage to Pneumotaxic Centre

Damage to the pneumotaxic centre in vagotomized animals leads to apneusis.
Vagotomy can cause apneusis, which is characterized by prolonged inspiration.

Reflex Modification of Breathing

Pulmonary stretch receptors, also known as mechanoreceptors, are found in the lungs.
When the lung expands, these receptors stimulate the Hering-Breuer reflex, which reduces the respiratory rate.
Increased firing of these receptors also increases the production of pulmonary surfactant.

Hering-Breuer Reflex

The Hering-Breuer reflex is a reflex triggered to prevent over-inflation of the lungs.
Pulmonary stretch receptors respond to excessive stretching of the lung during large inspirations.

Reflexes Originating from Body Movement

Impulses from moving limbs reflexly increase breathing.
These impulses probably contribute to the increased ventilation during exercise.

Factors That Increase Ventilation During Exercise

Reflexes originating from body movement
Increase in body temperature
Adrenaline release
Impulses from the cerebral cortex
Later, accumulation of CO2 and H+ generated by active muscles

Respiratory Structures in Brainstem

The medullary respiratory centre neurons are continuously active (spontaneous) and receive stimulation from peripheral and central receptors.
The brain concerned with voluntary respiratory movements and emotion influences the respiratory centre.

Rhythmic Ventilation (Inspiratory Off Switch)

Starting inspiration: medullary respiratory centre neurons are continuously active and receive stimulation from peripheral and central receptors.
Increasing inspiration: more and more neurons are activated.
Stopping inspiration: neurons receive input from pontine group and stretch receptors in lungs, leading to relaxation of respiratory muscles and expiration.

Higher Respiratory Centers Function

Modulate the activity of the more primitive controlling centers in the medulla and pons.
Allow the rate and depth of respiration to be controlled voluntarily.
Adapt to changes in environmental temperature (panting).

Chemical Control of Respiration

A negative feedback control system that senses blood gas tensions, especially carbon dioxide.
Chemoreceptors sense the values of the gas tensions.

Feedback to the Respiratory Center from Lungs

During inspiration, the lungs expand, and lung parenchyma is stretched.
Stretch receptors are activated and convey information to the brain via sensory branches of the vagus nerve.

Central and Peripheral Chemoreceptors

Central chemoreceptors respond to increased arterial PCO2 and act by way of CSF [H+].
Peripheral chemoreceptors respond to decreased arterial PO2, increased arterial PCO2, and increased H+ ion concentration.

Peripheral Chemoreceptors

Located in carotid bodies and aortic bodies.
Sense tension of oxygen and carbon dioxide; and [H+] in the blood.

Central Chemoreceptors

Situated near the surface of the medulla of the brainstem.
Respond to the [H+] of the cerebrospinal fluid (CSF).
CSF is separated from the blood by the blood-brain barrier, which is relatively impermeable to H and HCO3.

CO2 and H+ in Central Chemoreceptor

CO2 diffuses readily into the CSF, which contains less protein than blood and is less buffered.
CO2 + H2O → H2CO3 → H+ + HCO3.

Peripheral Chemoreceptor Pathways

Carotid bodies and aortic bodies are sensitive to PaO2, PaCO2, and pH.
Afferents in glossopharyngeal nerve and vagus.

Carbon Dioxide and Oxygen Effects

Indirect effects of CO2 through H+ in CNS.
Direct effects of CO2 on peripheral chemoreceptors.
Oxygen has a direct inhibitory effect on the respiratory center, and chronic hypoxemia can stimulate ventilation.

Hering-Breuer Reflex or Pulmonary Stretch Reflex

Includes pulmonary inflation reflex and pulmonary deflation reflex.
Receptors: Slowly adapting stretch receptors (SARs) in bronchial airways.
Afferent: vagus nerve.

Brainstem Transection

Normal pattern: apneustic breathing.
Increased inspiratory depth: apneustic breathing.
Gasping patterns: respiratory arrest.

Description

Test your knowledge about the respiratory centers in the brain including the apneustic centre, inspiratory area of the medulla, pneumotaxic center, and reflex modification of breathing. Explore the effects of damage to these centers and their role in regulating breathing rhythm.