Control of Lung Function Flashcards
What are the four centers in the brain that control lung function called?
- Dorsal Respiratory Group
- Ventral Respiratory Group
- Apneustic Center
- Pneumotaxic Center
What is the Dorsal Respiratory group responsible for?
Main controller of inspiration
Which group in the medulla sets the rate for inspiration?
The dorsal respiratory group
Which group in the medulla is the expiratory center?
The ventral respiratory group
What does the ventral respiratory group Inhibit?
The dorsal and apenustic
What does the apneustic center do?
Stimulates the dorsal respiratory group
What is the pneumotaxic center known as?
The inspiratory off switch
What does the pneumotaxic center do?
Regulates depth and frequency of breathing
What does the pneumotaxic center inhibit?
The dorsal respiratory group
Why is the pneumotaxic center especially important?
Prevents pulmonary damage and over inflation of the lungs
Which two centers make up the pontine respiratory group?
The apnuestic center and the pneumotaxic center
Which muscles does the dorsal respiratory group innervate?
The external intercostals
Which muscles are involved with expiration?
Internal intercostals
Which muscles are involved with inspiration?
External Intercostals
Aside from the external intercostals, what else is involved with inspiration?
- The diaphragm
- It moves down during inspiration to reduce pressure in the lungs, which allows the flow of air into the lungs
Aside from the internal intercostals, what else in involved with inspiration?
Accessory respiratory muscles
Which anatomical structure(s) create the primary drive to breathe?
Specialised medullary/pontine nuclei
What inhibits the apneustic center?
Pulmonary afferents
What type of gap junctions do normal capillaries have?
H2O-filled gap junctions
What type of junctions are found in the Blood Brain Barrier?
Tight junctions
Why can charged or large molecules not pass through the blood brain barrier?
Due to the presence of tight junctions
Why can Carbon Dioxide pass the Blood Brain Barrier?
CO2 is highly lipid soluble and therefore can pass the blood brain barrier
Why are the tight junctions found in the brain?
Certain nervous cells like astrocytes pack the H2O filled junctions which make them tight junctions
What does CO2 and H2O do to affect our drive to breathe?
- CO2 can cross into the CSF where it reacts with H2O to form carbonic acid, which dissociates into H+ and bicarbonate
- H+ interacts with afferent fibres in the medulla which send signals to the dorsal respiratory group to determine rate and rhythm of breathing
Levels of oxygen are sensed by what on the surface on the medulla oblongata?
Central Chemoreceptors
Where are central chemoreceptors found?
In the medulla oblongata
What do central chemoreceptors respond to?
Hydrogen ion concentration from the dissociation of CO2 within the surrounding tissue and the CSF, NOT BLOOD
Why do central chemoreceptors not response to changes in the blood?
The diffusion of the ions such as H+ and HCO3- from the blood is poor due to the tight junctions between the cells which forms the blood brain barrier
Where are peripheral receptors located?
Around the aortic arch and the carotid sinus (Aortic and Carotid Bodies)
Afferent neurones from the peripheral chemoreceptors are via which two nerves?
Glossopharyngeal and the Vagus nerve
What enzyme is responsible for converting H2O and CO2 into H2CO3 and then H+ and HCO3-?
Carbonic anhyrase
What happens when central chemoreceptors found in the medulla detect a reduced blood pH?
They cause the respiratory centers to increase the rate and depth of breathing
How does the partial pressure of Carbon Dioxide change going from Rest into Exercise?
Does not change
Why does the transition from rest to exercise not impact the partial pressure of CO2?
The overall affect is no change
What are irritant receptors?
Afferent receptors found within and beneath the airway epithelium
What does activation of irritant receptors lead to?
Cough
What does a cough involve?
- Forceful expiration against a closed glottis
- Sudden glottal opening and high velocity expulsion of air
What does excessive inflation of the lungs activate?
Pulmonary Stretch Receptors
What does activation of the stretch receptors do?
Inhibits inspiration and stimulates expiration
When stretch receptors are activated, which centers are activated and which are inhibited?
- Apneustic and dorsal are inhibited
- Ventral is stimulated
What are J receptors sensitive to?
Pulmonary capillary engorgement (high pressure) and oedema
What does stimulation of the J receptors lead to?
Increased breathing frequency as oedema and engorgement affect the lungs’ ability to ventilate
What is Volitional Apnoea?
Cessation of breathing which decreases arterial oxygen and increases CO2
What stimulates the medulla to breathe in?
Accumulation of H+ beyond the blood brain barrier when holding breath
Describe the emotional change to ventilation
- Special senses and higher brain centres (e.g. limbic system) elicit an emotional response
- This can affect the respiratory control centre
How are nerves distributed so that exercise can affect breathing?
- A branch of the efferents that go from the primary motor cortex to gross skeletal musculature also innervate the medulla
- This tells the brain to start breathing during exercise
- Proprioceptive afferents from muscle spindles and golgi tendon organs innervate the medulla on the way to the brain
What is meant by chloride shift?
Where one chloride ion is exchanged into red blood cell for one bicarbonate ion out the red blood cell
What is an acid
A proton donor
A greater H+ concentration refers to what in terms of pH?
A low pH
Why must the acidity of the blood be tightly regulated?
marked changes will alter the 3D structure of proteins (enzymes, hormones, protein channels)
What transporter is involved in chloride shift?
AE1 Transporter
Whatis the ability of the blood to react to changes in H+ ion conc known as?
buffering capacity
What is meant by alkaemia?
A higher than normal pH of blood
What is meant by acidaemia?
A lower than normal pH of blood
What is alkalosis?
Circumstances that will decrease [H+] and increase pH
What is acidosis?
Describes circumstances that will increase [H+] and decrease pH
What stimulates a rapid compensatory response to affect pH?
Changes in ventilation
What stimulates a slow compensatory response to affect pH?
Changes in HCO3- and H+ retention/secretion in the kidneys
What is needed to correct an acidaemia?
Alkalosis
What are baroreceptors?
Receptors which are sensitive to changes in blood pressure
What receptors are involved in the control of alveolar ventilation during exercise?
Central chemoreceptors
What triggers the change in ventilation due to emotional change?
The respiratory control center
Efferents from primary motor cortex to
gross skeletal musculature partly
innervate what?
the medulla
What innervates the medulla on the way to the brain during exercise?
Proprioceptive afferents from the muscle spindles and golgi tendon organs
What effect does cycling someones legs have and what does this show?
- Increases ventilation
- Shows that the afferent nerves from muscles and tendons also innervate the medulla on the way to the brain
- As the shortening and lengthening of the muscle fibres is enough to create an increase in ventilation
What effect does immersion in cold water have on ventilation?
Results in an inspiratory gasp and hyperventilation
What pH range is the blood pH tightly regulated between?
7.35 and 7.45
What do peripheral chemoreceptors do?
They respond to changes in blood molecule concentrations (like oxygen and carbon dioxide) and help maintain cardiorespiratory homeostasis
Why does the partial pressure of carbon dioxide and oxygen not change during normal exercise?
use of oxygen increases and prouction of CO2 increases, however this is compensated for by corresponding increases in ventilation such that blood gas levels remain in normal limits
In what circumstance might the partial pressure of oxygen or carbon dioxide change?
During strenuous exercise, when the production of lactic acid results in an acideamia
