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Year 1 - Semester 2 > Resp > Flashcards

Flashcards in Resp Deck (124)
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What is the pathway of airway

Nasal or oral cavities >pharynx>trachea>primary bronchi>secondary>tertiary>bronchioles>alveoli


What is Vt

Tidal volume - volume of gas breathed in or out in one breath (usually 0.4-0.8L at rest)


What is fR

Respiratory frequency - breaths per min (usually 12-15 at rest)


What is Ve

Minute ventilation - usually 5-8L/min

Tidal volume x frequency


What are the capacities of the lungs

Tidal volume - normal breathing

Inspiratory reserve volume - Max you can breathe in on top of your normal inhalation

Inspiratory capacity is tidal volume + inspiratory reserve volume - Max you can breathe in after a normal exhalation

Vital capacity is the inspiratory capacity + expiratory reserve volume - max someone can exhale after a max inhalation

Functional residual capacity is the residual volume + expiratory reserve volume - amount left in the lungs after a normal exhalation

Residual - air left in lungs after max exhalation


What happens in inspiration

Diaphragm and external intercostals contract, expanding the rib cage and decreasing pleural pressure allowing air to flow in down the pressure gradient


What happens in expiration

During normal breathing, the natural elastic recoil of lung tissue causes lungs to decrease in size

During forced breathing, internal/innermost intercostals and abdominal muscles contract, which pushed the diaphragm up and compresses the ribs, reducing the size of the thoracic cavity


Describe the dorsal respiratory groups

In the medulla oblongata

Composed of mainly inspiratory neurones

Controls generation of basic rhythms


Describe the ventral respiratory groups

In the medulla oblongata
Contain inspiratory and expiratory neurones

Primarily active during exercise and stress


Describe the pontine respiratory groups

In the pons

Contains inspiratory and expiratory neurones

Pneumotaxic center (PNC) involved in inhibiting neurones from the medulla. Sectioning the upper pons results in slow, gasping breaths


Describe the generation of breathing rhythm

Discharge from inspiratory neurones activates resp muscles via spinal motor nerves
Expiratory neurones fire and inhibit the inspiratory neurones and passive expiration occurs

If forceful expiration is needed, expiratory neurone activity also activates expiratory muscles


What can respiratory rhythms be affected by

Lung receptors and chemoreceptors


What are the types of lung receptors

Rapidly adapting (irritant) receptors
These are sub epithelial mechanoreceptors in the trachea and bronchi simulated by irritants or mechanical factors, such as smoke, dust and chemicals such as histamine. They cause coughing, mucus production and bronchoconstriction. Afferent fibres are myelinated

Slowly adapting (stretch) receptors
These are mechanoreceptors located close to airway smooth muscle which are stimulated by stretching of airway walls. This helps prevent over-inflation by initiating expiratory rhythms. This has an important role in the hering-brueemr reflex (prolonged inspiration causes prolonged expiration). Also myelinated afferent fibres

C fibres - unmyelinated nerve endings stimulated by oedema and various inflammatory mediators. Cause rapid, shallow breathing and dyspnoea


How do chemoreceptors work

CO2 crosses the blood brain barrier and reacts with H2O to form H2CO3 which is then converted to HCO3 and H

This hydrogen ion is detected by the medulla and the response is generally slow

Located in the corotid sinus (IX glossopharyngeal nerve)
And aortic arch (X vagus nerve)
Both respond rapidly to pO2 but those in carotid are more responsive


What does hypercapnia cause

Linear increase in minute ventilation

Response to hypercapnia is increased by hypoxia and decreased by hyperoxia

Interaction mediated by peripheral chemoreceptors


What does hypocapnia cause

Little change in ventilation


What does hypoxia cause

Curvilinear increase in ventilation
Little change until pO2 drops below about 8kPa

Mediated by peripheral chemoreceptors
Almost exclusively by carotid body

Increased by hypercapnia


What does hyperoxia cause

Small decrease in ventilation


What can happen in COPD

Chronic elevation of CO2

Desensitisation of central chemoreceptors

Giving high flow oxygen can depress breathing


What happens to breathing during sleep

Patients often develop resp failure in their sleep


What happens in obstructive sleep apnoea

Upper airways narrowed
Allowed upper airway to collapse during sleep
Can cause extreme tiredness


What drugs affect respiration

Depress - opioids, almost all anaesthetics, sedatives e.g. benzodiazepines, ethanol

Stimulate - doxapram, beta agonists


Daltons law

Each gas exerts a pressure in a mixture


Henry's law

Concentration of a gas dissolved in a liquid is proportional to it's partial pressure


What is important about different gases with the same partial pressures?

Will have different concentrations in solution due to different solubility constants


Which factors affect O2 affinity for haemoglobin

O2 binding - cooperativity

H+ - Bohr effect - increasing h+ decreases oxygen affinity

[CO2] - Haldane effect - increasing co2 decreases oxygen affinity

Temperature - increasing temperature decreases oxygen affinity

Carbon monoxide - binds with affinity 200x greater than oxygen. Also affects other oxygen binding sites - oxygen poorly released

2,3 biphosphoglycerate - lowers O2 affinity


What happen if the iron in haemoglobin is oxidised

Becomes methaemoglobin which does not bind oxygen
ferrous --> ferric
metHb reductase reduces it back to Hb


What is special about foetal haemoglobin

It has a higher affinity for oxygen so can take oxygen from maternal blood


What are the three ways CO2 is transported

60% is mediated by HCO3 - from carbonic acid which is formed from CO2 and H2O by carbonic anhydrase

(Further ionisation to CO3 is negligible as the pKa is too high)

30% is carried by carbamino groups - mostly haemoglobin

10% is dissolved in blood


How to measure Hb saturation

Absorption spectrometry as oxygenated is red and deoxygenated is blue