Control Of Breathing Flashcards
Dorsal Respiratory Group
Contain inspiratory neurons
Demonstrate rhythmic activity and stimulate inspiratory muscles
DRG = receive afferent input from lung receptors via vagus nerve
Central Respiratory Group
Contains neurons with a degree of spontaneous rhythmic electrical pacemaker activity
Contains neurons that stimulate respiratory muscles to initiate:
Inspiration = inspiratory neurons
Expiration = expiratory neurons
Receive input from DRG and central chemoreceptors
Pre-Botzinger complex
Upper end of VRG
What is Pre-Botzinger complex?
Network of neurons display pacemaker activity
Self induced AP
What does VRG and DRG form?
Central Respiratory rhythm generator
What happens during normal quiet breathing?
Respiratory rhythm generator stimulates inspiratory neurons causing contraction of respiratory muscles
What is expiration mostly?
Passive elastic recoil
What does mutual inhibition of inspiratory and expiratory neurons result in?
Alternat stimulation of inspiratory and exploratory mucked
Where does 2 regions of pons receive input from?
Cerebrum
Hypothalamus
Feed them into the Medullary respiratory centre
What does sectioning of pons not alter but affect?
Alter: basic rhythmicity
Affects: breath duration
When is Hering-Breuer Reflex?
Triggered when Tidal volume is large
E.g. during exercise
Prevents over Inflation of lungs
What is Reflex if Hering-Breuer Reflex?
Tidal volume > 1 Litre
Pulmonary stretch receptors activated
AP travel via afferent nerves to primary RCC
What is the effect of Hering-Breuer Reflex?
Inhibit inspiratory neurons
Stops inspiration, prevent over-inflation if lungs
Why may PH change?
Extreme physiological situations
What is Acidosis?
Proton accumulation
Acidosis
Occurs after hard physical exercise producing lactic acid in the muscle
Lowers PH
What are examples of metabolic acidosis?
Pathogen-physiological situations such as bicarbonate, HCO3-, loss in renal disease or in gut due to diarrhoea or diabetes
What is hypoxia?
Deficiency in the amount of oxygen reaching the tissues
What is hypercapnia?
Abnormally elevated carbon dioxide levels in the blood
Small changes in PCO2
Marked changes in ventilation
Increase in [H+]
Increase ventilation
Pneumotaxic centre
Inhibit inspiration
Allow transition from inspiration to expiration
Apneustic centre
Prolonged inspiration
It sends signal to VRG and DRG and trigger inspiration
Central chemoreceptors
Sense any changes in PH of cerebrospinal fluid and interstitial fluid within CNS
Respond to PH through changes in partial pressure of CO2
Dorsal Respiratory Group
Receive stretch receptor signals
Send signal down to go an trigger inspiration via intercostal muscle and diaphragm
Contains nucleus tractus solitarus
Ventral Respiratory Group
Consist of expiratory and inspiratory neurons
Consist of pre-botzinger complex
Pre-Botzinger complex
Pacemaker neurons
Contr breathing
Responding to hypoxia
Hering-Breuer reflex
Initiated by lung expansion
Excites stretch receptors in the airways
Send signal to Medulla by the vagus nerve
Shortens inspiratory times as tidal volume increases
Accelerating the frequency of breathing
Prevents overinflation of lungs
What 2 regions does pons receive input from?
Cerebrum
Hypothalamus
What does hypothalamus mediate?
Response to changes in temperature
What does limbic system mediate?
Response to changes in emotional state
The Hering-Breuer inflation reflex
Inspiration stretches airways
Activates stretch receptors in bronchial smooth muscle
Vagus nerve sends impulses to DRG
Inspiratory neurons of DRG are inhibited
Inhibits further inspiration, giving expiration time to occur
Where are central chemoreceptors located
Ventrolateral surface of Medulla
Near the entry of vagus and glosso-pharyngeal nerves
What is central chemoreceptors bathed in?
Cerebrospinal fluid
What are examples of peripheral chemoreceptors
X vagus nerve
IX glossopharnygeal nerve
Where are peripheral chemoreceptors located in?
Aortic and carotid bodies
What does Glomus cells respond to?
Decrease PO2
Increase PCO2 and [H+]
Main oxygen sensing cells in respiration
What is protective involuntary factors of ventilation
Coughing/sneezing
Inhaling noxious agents - cessation of ventilation
Pain stimulates RCC
Emotional:
Laughing, crying, sighing
Limbic system and RCC
Other:
swallowing
Hiccups - involuntary spasmodic contractions of diaphragm
What is voluntary factor of ventilation?
Hyperventilate, breath holding
Brief period of time
Chemical changes ultimately override voluntary input
Other: speaking, singing, whistling
