Physiology Flashcards
What is Partial pressure of O2 in Arterial Blood
13.3 kPa
What is Partial Pressure of O2 in venous blood
5.3kPa
What region in the body has the lowest pO2?
Mitochondria
What type of Haemoglobin is very common in foetus’ but not adults?
Y haemoglobin
What is Thalassaemia?
An inherited defect in globin chain synthesis
What causes Sickle Cell disease
A mutation in B Globin causing Glutamine to become Valine
What does a rightwards Oxyhameoglobin curve shift cause?
Reduced affinity for O2
What does a leftwards Oxyhameoglobin curve shift cause?
Increase O2 affinity
How is methameoglobin produced?
O2 oxidising the Haem from Fe2+ to Fe3+
What is the problem with too much methaemoglobin?
It cannot bind to O2 so causes hypoxia
At what percentage of methameoglobin is methamoglobinaemia diagnosed?
Over 5%
What percent of alveolar gas is turned over in the lungs each breath?
About 15%
What is Vital Capacity
Total volume of gas inhaled or exhaled im 1 breath
What is Residual Volume?
Total volume of gas left in lungs after maximal expiration
What part of the lungs have better Perfusion?
The base of the lungs
Why is there greater ventilation at the base of the lung?
Fluid in the pleural cavity increases intrapleural pressure at the base compacting alveoli, this means a greater volume increase from inspiration
What is a VQ mismatch?
When venous blood passes through poorly ventilated areas it will not fully oxygenate
What Ph should blood be at?
7.35-7.45
What is it called if Ph<7.35
Acidemia
What is it called if Ph>7.45
Alkalaemia
What happens if Ph is too high in the blood?
The increased H+ will denature enzymes
What will adding H+ to a buffer do to an equilibrium?
Shift equilibrium to the left
What is a carbamino compund?
When CO2 combines wih amino acids/proteins
What is Respiratory Acidosis
Increased PaCO2
What is Respiratory Alkalosis
Decreased PaCO2
What is Metabolic Acidosis
Non-respiratory increase in Acid
What is Metabolic Alkalosis
Non-respiratory decrease in Acid
What is minute ventilation?
Tidal volume x Respiratory rate
What is a dead space in ventilation?
Areas that are not involved in gas exchange
How do you calculate Alveolar Ventilation?
(Tidal Volume - Dead Space) x Resp. Rate
What are the peripheral chemoreceptors in ventilation called?
Carotid bodies
How is ventilation controlled centrally
Chemoreceptors on ventral surfaces of medulla
What range should PaCO2 be?
4.5kPa - 6.0kPa
What is a Pulmonary Stretch receptor
Smooth muscle in airway which is stimulated by lung inflation
What nerve stimulates the diaphragm?
Phrenic nerve
What is alveolar pressure?
The sum of pressure acting on the outside of the alveolus and pressure generated by elastic recoil
How is pleural pressure determined?
Passing a balloon into the oesophagus
Why does resistance increase with effort?
Small airways are compressed by external pressure
What is the purpose of surfactant
Lowers surface tension to make expansion easier
What is a restrictive lung disease?
Decrease of lung compliance restricitng inflation, it increases expiratory drive
What is an obstructive lung disease
Impaires airflow possibly due to airway narrowing
What is emphysema?
Enlargement of air spaces distal to terminal bronchioles resulting in loss of alveolar walls and elastic recoil
What is bronchitis?
Chronic overproduction of mucus in the bronchial tree
The heart can depolarise itself, what is the term used to describe this?
Automaticity
What do nodal cells do?
Set rhythm/ pace of the heart
What cells are used to produce force within the heart?
Contractile cells
Where is the SA node found?
Superior part of the Right Atrium beneath the SVC
What beat does the SA node usually set? What is it known as?
60-80 bpm, called sinus rhythm
How does the SA node give Innervation to the AV node?
Intermodal pathways
Why is there a delay in the AV node firing to the bundle of HIS
To give the atria a chance to contract before the ventricles do
What does the Bundle of HIS split into?
Right and Left bundle branches
What do the Right and Left bundle branches break into?
Purkinje fibres
Give an example of a vasoconstrictor released by the endothelium
Endothelin
Give 2 examples of a vasodilator produce by endothelium
Nitric oxide and Prostacyclin
What happens when there is low O2 detected in vessels near the lung and why?
Vasoconstriction to improve VQ matching
What is autoregulation
The ability of an organ to maintain constant blood flow despite alterations in perfusion pressure
