Physiology

Question 1

Describe Fick’s Law

Answer 1

Fick’s law states that the rate of diffusion of a gas through a tissue sheet is proportional to the area of the sheet and the partial pressure difference across it, and inversely proportional to the thickness of the sheet.

Question 2

Under which circumstances is oxygen transfer diffusion limited?

Answer 2

Diffusion limitation of O2 may occur during intense exercise, thickening of the blood-gas barrier and alveolar hypoxia (high altitude).

Question 3

How to you convert mmHg to kPa

Answer 3

Divide the figure by approx 7.5

Question 4

Right atrial pressure

Answer 4

4-12 mmHg

Question 5

Right ventricular pressure

Answer 5

28/4 mmHg ( 15-30 / 0-8) mmHg

Question 6

Pulmonary artery pressure

Answer 6

25/12 mmHg

Question 7

Left atrial pressure

Answer 7

Mean of 8 mmHg

Question 8

Left ventricular pressure

Answer 8

125/8 mmHg (90 - 140 / 4 - 12) mmHg

Question 9

The Pasteur Point

Answer 9

The Pasteur Point is the oxygen concentration below which oxidative phosphorylation cannot occur in the mitochondria. It is considered to be around 1 mmHG (0.13 kPa).

Question 10

Hüffner’s constant

Answer 10

It describes the volume of O2 (in ml) that can combine with each 1g of Hb. IN Vitro 1.30, in vivo 1.34.

Question 11

Typical oxygen consumption at rest

Answer 11

250 - 500 ml/min

Question 12

Critical DO2 (Oxygen delivery)

Answer 12

The degree of oxygen delivery below which supply is inadequate to meet oxygen demand. (Typically 4-8ml/kg/min)

Question 13

Oxygen extraction ratio

Answer 13

The Fraction of delivered oxygen that is taken up by the tissues. Typically 0.2-0.2. Varies between organs. I.e. heart is particularly sensitive to ischaemia due to an O2ER of 0.6.

Question 14

Hypoxia

Answer 14

Insufficient supply of oxygen to the tissues to maintain normal cellular function.

Question 15

Hypoxaemic hypoxia

Answer 15

Insufficient tissue oxygenation arising from an abnormal reduction in the partial pressure of oxygen in the arterial blood.

Question 16

Anaemic hypoxia

Answer 16

Insufficient tissue oxygenation arising from a failure of the oxygen-carrying capacity of blood in the face of a normal partial pressure of oxygen.

Question 17

Ischaemic hypoxia

Answer 17

Insufficient tissue oxygenation arising from a failure of perfusion.

Question 18

Histotoxic hypoxia

Answer 18

Insufficient tissue oxygenation in the face of normal oxygen delivery due to the failure of oxidative phosphorylation.

Question 19

Location of GLUT1 Receptors

Answer 19

Universally distributed

Question 20

Location of GLUT2 Receptors

Answer 20

Present in Gut, Liver and Pancreatic Islets

Question 21

Location of GLUT3 Receptors

Answer 21

Present in CNS & Brain (Insulin independent)

Question 22

Location of GLUT4 Receptors

Answer 22

Present in insulin-responsive tissues such as skeletal muscle, adipose tissue, heart

Question 23

Insulin

Answer 23

Is composed of two polypeptide chains (A and B) linked by disulphide bridges. The A chain contains 21 amino acids, the B chain contains 30 amino acids.

One physiological action of insulin is to increase the permeability of cell membranes to potassium, magnesium and phosphate ions. This forms the basis of treating life threatening hyperkalaemia with a glucose/insulin infusion.

During fasting, serum insulin and glucose levels fall whilst lipolysis increases.

Question 24

Acetazolamide

Answer 24

Is a Zinc containing enzyme that inhibits carbonic anhydrase. It is found in: Erythrocytes, the nephron, Pulmonary endothelium, gut, pancreas, cardiac and skeletal muscle.
There are 7 isoenzymes known.
Isoenzyme IV is found in the brush border of the proximal convoluted tubule.
Isoenzyme II is found in luminal cells.

Question 25

What Lung Volumes can be measured with a Spirometer?

Answer 25

Most lung volumes except TLC, FRC and RV.

Question 26

How can you measure FRC

Answer 26

Helium dilution or body plethysmography

Question 27

What does STOP-BANG stand for?

Answer 27

S - Snoring
T - Tiredness
O - Observed Apnoea
P - Hypertension
B - BMI >35
A - Age >49
N - Neck Circumference 41 or greater in women, 43 or greater in men
G - Gender: Male

Question 28

Tell me about Calcitonin

Answer 28

Calcitonin is a polypeptide hormone released from the C cells of the thyroid in response to hypercalcaemia (not hypocalcaemia).

Its hypocalcaemic effects are mediated by preventing bone resorption by osteoclasts.

It is secreted in excess in patients with medullary carcinoma of the thyroid.

Question 29

Causes of Increased PVR

Answer 29

Vasoconstrictor drugs
5-HT
Histamine
Maximal Expiration
Hypoxia
Hypercapnia
Acidosis

Question 30

Causes of decreased PVR

Answer 30

Anaemia
Prostacycline
Acetylcholine
Vasodilator drugs
Hyperoxia
Hypocapnia
Alkalosis