Respiratory L5.1 Flashcards
Basic elements of the respiratory control system
- What is the choroid pleuxs?
Describe formation of CSF
Function of CSF
Describe the circulation of CSF
- Found in brain ventricels
Consists of capllaires, allow water + small ions to pass out. Forms CSF - Formed by fluid passing out capillaries of choroid plexus. Consists of water, small ions
- CSF fill sventricles of brain, surrounds brain + spincal cord
Cushion, protects from truama
Aids with nutrient circulation + waste product removal - CSF circulates through ventricels, then subarachid space, then reabsorbed into blood
1) What are central chemoreceptors? Location. Function
- Mechanism of action
1) Located at ventral surface of MEDULLA OBLONGATA in BRAINSTEM
Highly senstitive to pH of CSF that bathes them
- Carbon dioxide (CO₂) diffuses freely across the blood-brain barrier and enters the CSF
n the CSF, CO₂ reacts with water (H₂O) to form carbonic acid (H₂CO₃) via the enzyme carbonic anhydrase.
Carbonic acid quickly dissociates into protons (H⁺) and bicarbonate ions (HCO₃⁻).
This dissociation increases the concentration of protons (H⁺), thereby lowering the pH of the CSF (making it more acidic)
The central chemoreceptors detect changes in CSF pH.
When the pH drops (indicating a rise in CO₂ and an increase in acidity), the central chemoreceptors signal the respiratory centers in the medulla to increase the breathing rate to expel more CO₂ and restore pH balance.
1) What is the normal pH of CSF?
2) Why are there no proteins in CSF?
3) Why is pH buffering capacity of CSF lower than blood?
4) Why are central chemoreceptors very sensitive to changes in pH?
1) The normal pH of CSF is 7.32, which is slightly lower than the normal blood pH (~7.4).
2) No plasma proteins filtered though choroid plexus into CSF. Therefore, pH buffering capacity of CSF is lower than blood. Therefore, the change in CSF pH for a given change in PC02 is greater than blood. CSF pH more sensitive to fluctations in CO2 levels, and therefore, central chemoreceptors are more responisve to changes in CO2.
What is the main chemical drive to ventilation?
Hypoxia Alone:
Interaction Between Hypoxia and Hypercapnia:
1) What are the lung based respiratory receptors?
a) location
b) function
c) response to lung inflation
d) role
What are proprioceptors ?
1) Pulmonary stretch receptors
- smooth muscle of airways
-discharge in response to stretching (lung distension)
-activity is sustained with lung inflation, little adaptation (continue firing as long as lungs are inflated)
2) Irritant Receptors
-airway epithelial cells
-stimulated by irritants (noxious gas, cold air, inhaled dust, cigarette smoke)
-stimulation triggers reflex like coughing + bronchoconstriction
3) J receptors
-alveolar airways close to pulmonary capillaries
-respond to pulmonay edema, pulmonary emboli, pneumonia, baraotruma, congestvie heart faiulre
-stimulation causes rapid, shallow breathig, lead to dyspnea (shortness of breath)
Proprioceptors
- Found in joints + muscles (leg muscles!)
- Provide feedback during physical activity, increase resp rate, meet bodys o2 demands for exercsie
Where are the sensors for hypoxia?
They are in
the Peripheral Chemoreceptors
State 2 locations of peripheral chemoreceptros
Role of peripheral chemoreceptors
Role of peripheral chemoreceptors in hypoxia
- Carotid bodies
(located at bifurcation of carotid arteries)(where common carotid arteries split into internal and external carotid arteries)
Aortic bodies - aortic arch - Detect changes in oxygen levels. Aortic bodies less sensitive than carotid bodies.
- Peripheral chemoreceptors respond to low PO₂ (hypoxia), particularly when the partial pressure of oxygen falls below 8 kPa (60 mmHg).
When activated, they send signals to the respiratory centers in the brainstem, triggering an increase in ventilation to raise oxygen levels in the blo
What are afferent nerves from carotid bodies?
What are afferent nerves from aortic bodies?
Glossopharyngeal Nerve (Cranial Nerve IX):
Vagus Nerve (Cranial Nerve X):
What are the two cell types present ?
- Glomus Type I (Chief) cells: derived from neuroectoderm. primary chemosensory cells that respond to changes in oxygen, carbon dioxide, and pH.
When PO₂ decreases (hypoxia), the type I cells release neurotransmitters (e.g., dopamine, acetylcholine) that stimulate the sensory endings of the glossopharyngeal and vagus nerves.
: These afferent signals are sent to the medullary respiratory centers in the brainstem, which adjust ventilation to maintain normal blood gas levels.
GLOMUS TYPE II CELLS - SUSTENTACUALR CELL
How do type 1 (glomus) cells detect hypoxia??
- Decrease in PO2 detected. / decrease arterieal p
- Inhibition of Potassium (K⁺) Channels: normally, K+ leaks out potassium channels, generating -ve membranepotential. During hypoxia, K+ channels close. No K+ leaks out. Leads to membrane depolarisation
- Depolarisation = inward leak of Na+, further depolarisaition
- Ca2+ voltage gated channels open
- Influx of calcium = reelease aceytlcholine from glomus cells
- Activates afferent nerves. action potentials travel up the glossopharyngeal nerve (CN IX). to the medullary respiratory centers in the brainstem, triggering an increase in ventilation.
1) What is autorythmic respiration?
1) Respiration controlled by autorythmic neurones located in pons + medulla of brainstem
Respiratory centres. MAIN ONE = medulla: initiates inspiration by projecting signals down reticulospinal tract to active diaphragm
What does the reticulospinal tract innervate?
Phrenic nerves - controls diaphragm
Intercostal nerves - intercostal muscles
1) What is the role of the nucleus of solitary tract?
1) Located at Dorsal surface of medulla
Recieves input from pH detectors, central + peripheral chemoreecptors, pulmonary stretch, irritant, J receptors.
Projects to dorsal respiratory group: contains cells that fire during inspiration. Signals either stimulate / inhbit inspiration
What is autorythmic respiration in simple terms?
brain’s ability to automatically generate the rhythm of breathing without conscious effort. It ensures that you keep breathing, even when you’re not thinking about it, like when you’re asleep or focused on something else
Which respiratory centre is mainly activated during forced expiration?
Ventral respiratory centre
In ventral medulla
Becomes more active during forced expiration.
axons
project down the
reticulospinal tract
and activate the
internal
intercostals.
Expiration usually passive.
Forced expiration involves activity of internal intercostal muscles.
What is the role of the pontine respiratory centre
Medullary resp centre - autorryhmic control of breathing.
2 key regions in pontine resp cenre modulate this:
- Apneustic centre
- Pneumotaxic centre
How does the cerebral cortex coordinate with pneumotaxic and apneustic centers?
Influences breathing
through pneumotaxic + apneustic centres
volunary control of breathing
for talking, singing, holding breath
Only for short periods of time. Cerbral cortex influence cannot completely override the medullary centers.
For example, while you can hold your breath, eventually the automatic breathing control from the medulla will take over, forcing you to breathe.
Autoryhtmic Control Flow Chart
Henderson – Hasselbalch equation
How does the brainstem resp groip mantain acid base balance?
Through automatic control of ventilation
What are the 3 main buffers in the blood which control acid and base shifts?
- Protein
- Haemoglobin
- Carbonic acid bicarbonate system
Compare hypoventilation and hyperventilation in terms of CO2 production
Compare and contrast metabolic acidosis and metabolic alkalosis
