6.16: Control of lung function Flashcards
5 regions of the cardiovascular centre of the medulla
The dorsal respiratory group is responsible for
Controlling inspiration
Set the rate of inspiration
The ventral respiratory group is responsible for
Expiratory centre
Inactive during quiet breathing
Inhibit apneustic centre
Function of the apneustic centre
Stimulates activity in DRG
Inhibited by pulmonary afferents
Function of the pneumotaxic centre
Inspiratory off switch
Regulates depth and frequency
Two types of respiratory groups
Dorsal -inspire
Ventral - expire
Role between dorsal and ventral groups
Inhibit one another
What nerve is the main cause for breathing Innervation and it’s origins
Phrenic nerve
C3/4/5
Where is the dorsal respiratory group located?
Dorsomedial medulla in the ventrolateral nucleus of the solitary tract
Where is the apneustic centre located?
Lower part of the pons
Where is the pneumotaxic centre located?
Upper part of the pons
What effect does the pneumotaxic centre have on the dorsal respiratory group?
Inhibitory
What effect does the apneustic centre have on the dorsal respitatory group?
Stimulatory
What effect does the dorsal respiratory group have on the ventral respiratory group?
Inhibitory
What effect does the ventral respiratory group have on the DRG and AC?
Inhibitory
Do action potentials at a low frequency stimulate the AC or the PC?
AC
When the action potentials fire at a higher frequency, are the AC or PC stimulated?
PC
What effect does the PC have on the action potentials and what is this effect followed by?
Causes a cessation (stop)
Follwed by a period of latency before the AC then stimulates the DRG again to increase the action potential frequency
What motor and sensory innnervation does the phrenic nerve provide?
Motor Innervation to the diaphragm
Sensation to the central tendon aspect of the diaphragm
What action do the external intercostal muscles contribute to?
Inspiration
What action do the internal intercostal muscles contribute to?
Expiration
If there are gaps in the capillaries of normal circulation, then why are they described as ‘continuous’?
These gaps between capillary endothelial cells are filled with H2O
What is the blood brain barrier and why is it important?
The purpose of the blood-brain barrier is to protect against circulating toxins or pathogens that could cause brain infections, while at the same time allowing vital nutrients to reach the brain
Why is the blood brain barrier considered to have continuous capillaries?
Tight junctions between capillary endothelial cells formed by nervous cells to prevent unnecessary leakage of molecules
Is dissolved carbon dioxide able to pass through the lipid bilayer and therefore the blood brain barrier (BBB)?
Yes
How does this CO2 that is now in the CSF as it crossed the BBB from the capillaries, initiate activation of the DRG?
CO2 reacts with water to form a carbonate ion (HCO3-) and a proton
Protons enter the medulla and interact with the afferent fibres in medulla
These take signal straight to dorsal respiratory group to be able to determine what type of rate and rhythm should be created
Where are irritant receptors found?
Embedded within and beneath airway epithelium (larynx, trachea, bronchi, and intrapulmonary airways)
What is the role of the irritant receptor?
Detects foreign mattter
Leads to cough which involves forceful expiration against a closed glottis with sudden glottal opening and high velocity expulsion of air
Where are pulmonary stretch receptors found?
Past the secondary bronchi
How are stretch receptors activated?
Excessive inflation of lungs
What do the stretch receptors do once they are activated?
Send afferent signals to respiratory centres and stimulate pneumotaxic VRG
Inhibit inspiration and stimulate expiration
Where are J-receptors found
Alveolar walls in close proximity to the capillaries
What is the role of a J-receptor?
Because of their location they respond readily to chemicals in pulmonary circulation, distension of pulmonary capillary walls and accumulation of interstitial fluid
Increases breathing frequency as a response to these factors send action potentials via vagus nerve leading to bronchoconstriction and increased respiratory rate
What happens when you reach the CO2 threshold for breathing?
Accumulation of H+ beyond the blood brain barrier activates the DRG - the struggle phase
What happens when you reach the O2 threshold for blackout?
You blackout
What happens to the 3D structure of proteins if the level of acidity of the blood is not tightly regulated enough?
It is altered -> denatured
Is a base anionic or cationic?
Anionic, also a molecule that reversibly binds to protons
Why does an acid have a low pH compared to a base?
It dissociates with H+, which creates a decreased pH as the higher the concentration of H+, the lower the pH
Whereas a base binds to the H+ and would decrease the concentration
What is the formula for calculating pH
-log10[H+]
What is the difference between alkalaemia and alkalosis?
Alkalaemia refers to a higher-than-normal blood pH, whereas alkalosis describes the circumstances that will decrease [H+] and increase pH
What is meant by a ventilatory disturbance and how is this corrected?
Minor change in breathing that changes the pH which is then corrected by the kidneys which are slow responses
What is meant by a metabolic disturbance and how is this corrected?
Any non-lung cause of a change in the pH that is subsequently corrected for by the lungs which are fast responses
What type of reaction is required to correct acidosis?
Alkolitic response
Where are the peripheral chemoreceptors found?
Bifurcation of carotid arteries in region called carotic bodies in the carotid sinus and aortic bodies in the aortic arch
They are found very close to the baroreceptors
What is the role of the peripheral chemoreceptors?
To stimulate breathing in response to hypoxia
Which part of the brain is responsible for the emotional responses?
Limbic system - composed of the hypothalamus, amygdala, thalamus, hippocampus
How can the movement of a muscle lead to an increase in breathing?
Efferents from pirmary motor cortex to gross skeletal musculature partly innervates medulla by sending volitional instructions to it as it will inevitably be necessary
Proprioceptive afferents from muscle spindles and golgi tendon organs also innervate medulla on way to brain
Demonstrated by cycling someone’s legs
What is the cold shock ventilator response?
Immersion in cold water (<10 degrees Celsius) causes a large and fast fall in skin temperature, detected by the superficial sensory nerve endings in the skin which evokes muscle spasms and hyperventilation
Which the respiratory center coordinates a response to prevent pulmonary damage seondary to over‐inflation?
Pneumotaxic centre
Which receptors are most likely to identify the inhalation of smoke in a house fire?
Irritant receptors
Which anatomical structure(s) create the primary drive to breathe?
Specialised medullary/pontine nucleii
How many respiratory nuclei are found in the medulla oblongata
Four
What center and group control inspiration
Dorsal respiratory group
Apneustic center
What group and centre is responsible for expiration
Ventral respiratory group
Pneumotaxic center
What kind of pattern does a respiratory pacemaker display
Ramp potential
6 stimuli of inspiration
Central H+ concentration
Juxtacapillary oedema
Motor control
Limbic system
Peripheral O2 concentration
Peripheral proprioceptors and skin thermoreceptors
3 stimuli of Expiration
Airway stretch receptors
Limbic system
Motor control
What receptors stimulate coughing
Airway irritant receptors
What is blood pH tightly regulated between
7.35-7.45
Words ending in -osis refer to
Conditions precipitating a changing pH
Words ending in -aemia refer to
Blood conditions at a snapshot in time
Relationship between pH and proton concentration
Inversely and logarithmically proportional
What is bloods ability to buffer acid like
Rapid and enormous
Two types of pH disturbances
Respiratory
Metabolic
Relationship between compensatory responses and the original aetiology
Response Usually opposite of original
