36 Questions
Which ancient physician observed the effects of spinal cord injuries on breathing?
Galen
What is the primary function of the pneumotaxic centre?
Inhibits the inspiratory phase
What is the effect of sectioning the spinal cord at the level of the pons?
Apneusis
Which nucleus is responsible for prolonging the inspiratory phase?
Apneustic centre
What is the role of the dorsal respiratory group?
Regulates the expiratory phase
What is the name of the ancient Greek city where Galen practiced medicine?
Pergamon
What is the term for normal, unlabored breathing?
Eupnea
Which of the following is NOT a part of the brain stem?
Cortex
What is the response to stimulation of nasal trigeminal nerve endings?
Sneeze reflex
Which part of the brain is responsible for the central pattern generator?
Medulla
What is the function of the pneumotaxic centre?
To regulate breathing rate
What is the main principle of chemical control of ventilation?
Ventilation must be matched to metabolism
What is the function of the dorsal respiratory group?
To stimulate inspiration
What type of receptors detect changes in lung volume and pressure?
Stretch receptors
What is the response to stimulation of pain receptors in the trigeminal region and larynx?
Apnoea or spasm
What is the function of the apneustic centre?
To inhibit breathing
What is the effect of combining hypoxia and hypercapnia?
The combined effect is greater than the sum of the individual effects.
What is the primary stimulus for respiration?
CO2 levels
Where are the central chemoreceptors located?
Ventrolateral surface of medulla
What is the relationship between CO2 and O2 levels in terms of respiration?
They have a synergistic effect.
What is the effect of high CO2 levels on respiration?
It increases respiration rate.
What is the location of the chemosensitive areas in relation to the cranial nerves?
Near the exit of cranial nerves IX and X
What is the effect of inflation on inspiration in the Hering-Breuer inflation reflex?
It inhibits inspiration
Which type of receptors are stimulated by increased alveolar wall fluid and oedema?
Juxtapulmonary receptors
What is the effect of stimulating irritant receptors in the trachea?
It leads to cough
What is the function of proprioceptive afferents in respiratory muscles?
To help cope with increased load
What is the effect of deflation on inspiration in the deflation reflex?
It stimulates inspiration
What is responsible for deep augmented breaths seen every 5-20 minutes at rest?
Proprioceptive afferents
What is the primary location of the peripheral chemoreceptors that respond to changes in PO2 and PCO2?
Carotid and aortic bodies
What is the effect of an increase in PCO2 or H+ on the peripheral chemoreceptors?
Increased discharge
What type of cells are rich in neurotransmitters and contact axons in the peripheral chemoreceptors?
Type 1 or glomus cells
What is the approximate percentage of response to PCO2 accounted for by the peripheral chemoreceptors?
20%
What is the term for the breathing pattern characterized by alternating periods of rapid breathing and apnea?
Cheyne-Stokes respiration
What is the primary stimulus for the peripheral chemoreceptors?
Partial pressure of oxygen in the blood
What is the term for the adaptation to chronic hypercapnia, resulting in a loss of CO2 drive?
Loss of CO2 drive
What is the location of the peripheral chemoreceptors that are very small but have a high blood flow?
Carotid body
Study Notes
Control of Ventilation
- Describe the source of the rhythm to breathe and the signals that affect this
- Neural control involves the brain stem, lung receptors, and other inputs
- Chemical control responds to changes in PCO2, PO2, and pH through central and peripheral chemoreceptors
Brain Stem
- The brain stem is essential for breathing, as observed by Galen, a Greek physician
- The cervical region sends information necessary for breathing
- The pneumotaxic center inhibits the inspiratory phase, while the apneustic center prolongs inspiration
Lung Receptors
- Juxtapulmonary "J" receptors are located in alveolar/bronchial walls, close to capillaries
- Stimulated by increased alveolar wall fluid, oedema, pulmonary congestion, microembolisms, and inflammatory mediators
- Causes apnoea or rapid shallow breathing, fall in heart rate and blood pressure, laryngeal constriction, and relaxation of skeletal muscles
- Irritant receptors are found throughout airways, stimulated by irritant gases, smoke, dust, inflammation, and rapid large inflations and deflations
- Proprioceptive afferents are located in respiratory muscles, stimulated by shortening and load of respiratory muscles
Chemoreceptors
- Central chemoreceptors are located in the ventrolateral surface of the medulla, near the exit of C IX and X
- Peripheral chemoreceptors are found in the carotid and aortic bodies, responding to changes in PO2, PCO2, and pH
- Carotid bodies are small but have high blood flow, comprising type 1 (glomus) and type 2 (sheath) cells
Response to Chemical Stimuli
- The CO2 response curve shows a synergistic relationship between PaO2 and PaCO2
- Acidosis and alkalosis affect the CO2 response curve
- Hypoxia stimulates breathing, with a synergistic effect when combined with hypercapnia
Breathing Disorders
- Loss of CO2 drive can lead to chronic hypercapnia and adaptation
- Cheyne-Stokes respiration is associated with heart failure, stroke, and altitude sickness
- Central sleep apnoea is characterized by an inability to breathe, often due to neuromuscular disorders
This quiz covers the neural and chemical control of ventilation, including the brain stem's role and the signals that affect breathing rhythm.
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