Control of lung function Flashcards
What is the main function of medulla oblongata respiratory centres?
The control of ventilation arise from interactions of cranial regions, resulting in a rhythmic ventilation rate that provides the body with sufficient oxygen volume, whilst facilitating adequate carbon dioxide removal
Where are the respiratory centres located?
Medulla oblongata and pons
What are the four main respiratory centres?
Dorsal respiratory group
Ventral respiratory group
Apneustic centre
Pneumotaxic centre
What is the function of the dorsal respiratory group?
Involved in maintaining a constant breathing rhythm by stimulating the diaphgram and the intercostal muscles to contract
INSPIRATION
Which respiratory group is mainly focussed on inspiration ?
Dorsal respiratory group
What happens when the dorsal respiratory group activity decreases?
No longer stimulates diaphragm and intercostal to contract causing relaxation and expiration
What is the main expiratory centre?
The ventral respiratory group
Which centre causing forced expiration?
Ventral respiratory group
Which respiratory centre inhibits the apneustic centre?
Ventral respiratory group
Which respiratory centre stimulates the DRG?
Apneustic centre
What is the function of the apneustic centre?
Controls the depth of inspiration, for deep breathing
Double cluster of neuronal Bodies stimulates the neurones in the DRG
Which pontine respiratory centre inhibits the DRG?
Pneumotaxic centre
Which respiratory centre controls frequency and depth, & enables relaxation post inspiration?
Pneumotaxic centre
Which respiratory centre is classified as the inspiratory off switch?
Pneumotaxic centre
Which plexus of sympathetic and parasympathetic motor & visceral nerve fibres innervate the lung?
Pulmonary plexus
What is the pathway of nerve bundles taken during descent?
Nerve bundles descend parallel to the bronchial tissue & blood vessels
Which nerve contributes to parasympathetic motor fibres of the airways?
Vagus nerve
What is the effect of the vagus nerve on parasympathetic motor fibres on airways?
Regulates bronchoconstriction of airways. Autonomic excitatory cholinergic neves secrete acetylcholine into the bronchial smooth muscle & submucosal glands.
Bronchoconstriction & mucous production
Which hormone causes airway bronchodilation?
Noradrenaline
Vasoactive intestinal peptides, neural nitric oxide
Describe the pathway of sympathetic nerve fibreo the superior cervical ganglion?
Preganglionic neurones pass through the sympathetic chain of ganglia, synapsing with post ganglionic neurones the superior cervical ganglion
Which pulmonary ganglion contains postganglionic sympathetic cell bodies?
Superior cervical ganglion
Which nerves form the phrenic nerve?
C3, C4, C5
Which nerve innervates the diaphragm contraction?
Phrenic nerve
What is the primary muscle of respiration?
Diaphragm
What is the effect of diaphragmatic contraction?
Reduced intrathoracic pressure
Describe the endothelial arrangement of the blood brain barrier
Compact forming the blood barrier - continuous capillary structure with additional tight junctions
What type of capillary forms the blood barrier?
Continuous capillary
What type of junction supports the blood brain barrier?
Tight junctions
Describe the relationship with proton concentration and carbon dioxide:
Proton concentration is proportional to carbon dioxide proportion
Which enzyme is responsible for the activity of carbonic acid?
Carbonic anhydrase
Carbonic acid dissociates into which two ions?
Bicarbonate ions
Hydrogen ions
Can charged ions including hydrogen ion pass through the blood brain barrier?
No due to presence of tight junctions
Why can carbon dioxide pass through the blood brain barrier?
Neutral molecule, lipid soluble, therefore can diffuse through the blood brain barrier into the cerebrospinal fluid within the subarachnoid space
What does diffused carbon dioxide form within the CSF?
Carbonic acid β> Dissociates into hydrogen and bicarbonate ions
What does an increased hydrogen ion concentration reflect within CSF?
Reflective on the amount of diffused carbon dioxide
Which receptors detect hydrogen ion concentration within the medulla?
Central chemoreceptors
Which nucleus is innervated by the chemoreceptors within the medulla?
Dorsal respiratory nucleus (Conducts transmission to centres within the medulla and pontine respiratory group)
Where are irritant receptors located?
Embedded within and beneath the airway epithelium
What do irritant receptors detect?
Inhaled particles water
Irritants
What is the result from irritant receptor stimulation?
Leads to cough, forceful expiration (respiratory muscles contract forcefully, generate significant intrathoracic pressure), against closed glottis with sudden glottal opening and high velocity expulsion of air.
Coughing is a productiee reflex, with the production of sputum
Hyperinflation of lungs results in the activation of which receptors?
Stretch receptors
Activation of stretch receptor inhibits which respiratory centres?
Dorsal respiratory group
Apneustic centre
Activation of stretch receptors within the lung activates which respiratory centres?
Pneumotaxic centre
Ventral respiratory group
What is inhibited and stimulated in terms of inspiration and expiration during stretch receptor afferent transmission?
Inspiration inhibited
Expiration stimulated
What are J-receptors sensitive to?
Oedema
Pulmonary capillary engorgement
Activation of J-receptors results in what?
Increased breathing frequency
Which pulmonary fibres adjacent to capillary cells of the alveoli detect the accumulation of fluid within the interstitial space?
Pulmonary C-fibres
What is pulmonary vessel engorgement?
Congestion of blood exceeding capacity
What happens during the struggle phase of volitional apnoea?
Respiratory muscles contract autonomically, carbon dioxide is unloaded from the lungs (hyperventilation) removes central stimulus
Why is volitional apnoea dangerous in terms of breathing thresholds?
The risk of oxygen threshold, blackout occurs before the carbon dioxide threshold for breathing
What are acids?
Proton donors
What is a proton?
Valency of +1 has no electrons or neutrons
What is the relationship between pH and Hydrogen ion concentration?
pH = -Log10[H+]
A greater concentration of hydrogen ions logarithmic ally causes a lower pH
What is the importance of acid-base balance in terms of proteins?
The acidity of blood is regulated to ensure that the tertiary structure of proteins are not stereochemically altered (Enzymes, hormones, protein channels).
What is a base?
Anionic (negatively charged ions), molecule is capable of reversibly binding protons, reducing the available dissociated hydrogen ions present within the plasma
What is the acid base relationship of carbonic acid?
π―ππΆ+πͺπΆπβπππππβπ+ +ππππβ (Reversed reaction at pulmonary capillaries)
Which enzyme is responsible for the formation of carbonic acid?
Carbonic anhydrase
What does carbonic acid dissociate into?
Hydrogen ions
bicarbonate ions
In order to maintain acid-base balance what is the fate of bicarbonate ions within erythrocytes?
Exchanged for chloride ions through the AE1 transporter, maintains resting potential
What do hydrogen ions form within RBCs?
Protonate haemoglobin molecules forming haemoglobin acid
What % of carbon dioxide is transported as bicarbonate ions?
70%
The direct binding of carbon dioxide haemoglobin forms what molecule?
Carbaminohaemoglobin
How is acidotic environments balanced?
Capacity to accommodate acid. pH detriment experienced was negligible, acidotic, capacity of different proteins had bicarbonate release into blood to reversibly neglect effect on proton concentration (neutralisation).
What is alkalaemia?
Refers to elevated blood pH in respect to standard
What is acidaemia?
Refers to lower than standard blood pH
What is alkalosis?
Describes circumstances that will decrease hydrogen ion concentration and increase pH
What is acidosis?
Describes circumstances that will increase [H+] and decrease pH.
Where are peripheral chemoreceptors located?
Within aortic arch and carotid sinus
What are peripheral receptor sensitive to?
Concentration of hydrogen ions and carbon dioxide
Stimulation of peripheral chemoreceptors results in transmission to which structure?
Medulla oblongata & pons
How would acidosis affect ventilation?
Increased ventilation to expel carbon dioxide from circulation faster, removal from carbon dioxide reduced hydrogen ion concentration therefore increasing pH
How does oxygenation influence respiratory rate?
Detected by peripheral chemoreceptors low blood oxygenation will stimulate increase in respiratory activity (Sense dissolved oxygen molecules not oxyhaemogloibin ) reduced partial pressure will increase oxygen dissociation
Which cranial system exerts an influence on breathing rate by interacting with respiratory centres?
Limbic system
How does increased basal temperature influence respiratory rate?
Increases respiratory rate
What are the two main proprioreceptors in muscle?=
Muscle spindles
Golgi tendon organs
What is inspiratory gasp?
Exposure to sudden temperature decline results in an inspiratory gasp directed by the apneustic centre (Water aspiration may occur ο drowning).
Systemic cold water leads to hyperventilation (Respiratory demand increases through shivering as basal metabolic rate increases) Thermoreceptors in skin detect temperature change <10β
