Respiratory Centers in the Brain Quiz

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.