Control of Breathing Flashcards
What are the respiratory muscles and what do we use them for?
Diaphram and intercostal muscles, used for:
- appropriate gas exchange
- defence of lung and airways
- other functions (non-metabolic)
What are the two separable controllers in the brain?
- Automatic bulbopontine controller (Brainstem)
- Behavioural Suprapontine control (widely distributed)
(slide 5)
What are the 2 chemoreceptors?
- peripheral
- central
Where are the peripheral chemoreceptors located?
- carotid bodies
stimulated by acidosis, hypercapnia and Hypoxaemia. - aortic arch
stimulated by hypercapnia and hypoxia
Where are the central chemoreceptors located?
- located on the surface of the medulla (brain)
respond to ↑PaCO2
not arterial pH, not arterial PO2
What are the different types of mechanoreceptor inputs from the lungs?
- slowly adapting pulmonary stretch receptors
- rapidly adapting pulmonary stretch receptors
- J receptors (bronchial C fiber receptors)
- irritant receptors
(slide 7)
What are slowly adapting pulmonary stretch receptors?
(inflation reflex or Hering-Breuer reflex) a protective reflex that prevents overinflation of the lungs
What are rapidly adapting pulmonary stretch receptors?
Mechanoreceptors that respond to changes in lung volume and play a role in regulating breathing patterns.
What are J receptors?
(bronchial C fiber receptors)
- small-diameter non-myelinated fibers
- that respond to tissue damage or oedema
What are irritant receptors?
- small-diameter myelinated fibers
- that respond to inhaled irritants and initiate cough & sneeze reflexes
What are the mechanoreceptor inputs from the chest wall?
- joint receptors
- Golgi tendon organs
- muscle spindles
What are the different sensory inputs from the respiratory system and chest wall?
- nose - trigeminal nerve (V)
- pharynx - glossopharyngeal nerve (IX) & vagus nerve (X)
- larynx - vagus nerve (X)
- lungs - vagus nerve (X)
- chest wall - spinal nerves
What is the common neural output to the pump muscles involved in breathing?
- diaphragm - phrenic nerve & cervical plexus (C3-C5)
- intercostal muscles innervated by T1-T12 spinal nerves
- abdominal muscles innervated by T6-L1 spinal nerves
What happens if there is a lesion (abnormal tissue) at C2 in the spinal cord?
Can lead to complete dependence on artificial ventilation, as it affects the phrenic nerve
What happens if there is a lesion at C7 in the spinal cord?
The person may only be able to breathe in with the diaphragm and not exhale effectively.
What happens if there is a lesion at T5 in the spinal cord?
The person may not be able to actively exhale and have difficulty with forced expiration during breathing
What are the respiratory centers in the medulla oblongata and pons?
- Dorsal Respiratory Group (DRG)
- Ventral Respiratory Group (VRG)
- Pontine Centers
What is the function of the Dorsal Respiratory Group?
The Dorsal Respiratory Group innervates the inspiratory muscles and is responsible for generating the basic rhythm of breathing.
What is the function of the Ventral Respiratory Group?
The Ventral Respiratory Group innervates the accessory muscles of both inhalation and exhalation and is only active during forced breathing.
What are the Pontine Centers in the respiratory system?
- located in the pons
- responsible for smooth and modifying the pattern of respiration
What are the 2 Pontine Centres?
- Apneustic Centre – stimulates the DRG
- Pneumotaxic Centre – inhibits apneustic
What sensory information modifies the activity of respiratory centers?
Modified by sensory information from various receptors such as chemoreceptors, baroreceptors, lung stretch receptors, and other sensory receptors.
What is the activity of the respiratory centers during quiet breathing?
generate an automatic rhythm of inhalation and exhalation that repeats even during sleep
What are the factors that can modify respiratory center activity during breathing?
Can be modified by circumstances and demand such as
- exercise metabolic needs
- sensory receptor feedback
or by influences from higher brain areas such as
- voluntary interference
- psychological modulation
- behavioral modulation
When does the respiratory centre activate during forced breathing?
Kicks in when you need to breathe heavily
- Heavy exercise
- Lung disease (e.g. during asthma)
- Engages accessory muscles
What is the automatic reflex for ventilatory response to increased CO2 and reduced O2?
increase rate & depth of breathing
What is meant by ‘behavioral’ higher center control of respiration?
Refers to voluntary, willful control of breathing that competes for control of respiratory muscles.
What is the precision of breathing control in behavioral higher center control?
Very high, allowing for fine-tuning of breathing patterns. For example, the ability to sing, play musical instruments
Can behavioral higher center control of respiration be learned subconsciously?
Yes
What are the sources of volitional drive?
- motor homunculus
- voluntary breathing
What are the other influences of ‘Behavioral’ higher centre control on breathing?
- Emotional drives: Involuntary psychological influences such as anxiety, sobbing etc.
- Tonic wakefulness drives: Can be excitatory or inhibitory from various parts of the higher brain.
- ‘Learned’ responses: Ventilatory response to exercise
What type of respiratory control is sleep?
Reflex/automatic control
