Physiology

Question 1

Immunoglobulins – what are they?

Answer 1

• Bind to antigens (toxins, proteins on pathogen surfaces)
• They’re basically antibodies
• Label for destruction by immune system
• Specificity determined by variable regions
• Diff types: IgG, IgM, IgA, etc

Question 2

Function of DNA polymerase

Answer 2

• Reads template strand from 3’ to 5’ (daughter strand from 5’ to 3’)

Question 3

DNA replication

Answer 3

• Topoisomerase unwinds DNA slightly
• DNA helicase can break hydrogen bonds and separate strands
• Single strand binding protein coat single DNA strands to prevent re-annealing
• DNA primase synthesises short RNA primer to get DNA polymerase started
• DNA polymerase reads 3’ to 5’ strand to create daughter cell 5’ to 3’
• On the 5’ to 3’ strand, synthesis can’t occur the same way:
o DNA primase adds RNA primers, allow nucleotides to be added in fragments by DNA polymerase (OKAZAKI FRAGMENTS)
o DNA polymerase can then add these together into a continuous strand

Question 4

Autocrine communication

Answer 4

• Chemical released from cell to extracellular fluid – goes back to same cell

Question 5

Paracrine communication

Answer 5

• Chemical messengers between cells
• Local communication
• E.g Acetylcholine

Question 6

Endocrine communication

Answer 6

• Produce and secrete hormones
• Into BLOOD
• Hypothalamus => dopamine
• Anterior Pituitary => FSH, LH, TSH
• Posterior pituitary => oxytocin, ADH/vasopressin

Question 7

Exocrine communication

Answer 7

• Secretion into ducts then organ

Question 8

Positive Feedback Loop

Answer 8

• Signal amplification

* E.g. clotting cascade, oxytocin during childbirth

Question 9

Negative Feedback Loop

Answer 9

• Main way endocrine hormones controlled

* E.g. blood sugar, temperature, blood pressure, thyroid regulation

Question 10

Thyroxin regulation

Answer 10

• Thyroxin sensed by pituitary – if too much thyroxine => pituitary stops producing TSH

Question 11

Primary hypothyroidism

Answer 11

• Thyroid producing too little thyroxine
• Not enough to induce negative feedback in pituitary
• Pituitary continues producing TSH
• Blood test: high TSH, low T4

Question 12

Secondary hypothyroidism

Answer 12

• Pituitary not producing enough TSH
• Thyroid not stimulated to produce thyroxin
• Blood test: low TSH, low thyroxin

Question 13

Water distribution in the body

Answer 13

60% of 70kg man is water - 42L
•	Intracellular fluid 40% 28L
•	Extracellular fluid 20% 14L
o	Intravascular 3L (plasma)
o	Interstitial 11L (around cells)

Question 14

Water regulating hormones

Answer 14

• ADH
• Aldosterone
• Atrial natriuretic peptide

Question 15

Osmolality vs. Osmolarity

Answer 15

• Osmolality - No. of dissolved particles per kg

* Osmolarity – no. of dissolved particles per Litre

Question 16

Water lost from ECF (water deprivation or increase in solute) results in…

Answer 16

• Increase in osmolality in ECF
• Change detected by osmoreceptors in hypothalamus
• Stimulate thirst centres in hypothalamus - elderly get reduction
• Released ADH (anti-diuretic hormone) from posterior pituitary
• ADH increases water reabsorption in collecting ducts in kidney to dilute solute

Question 17

Renin-Angiotensin-Aldosterone System

Answer 17

leads to reduction in renal perfusion, increase in BP
Stimulates release of renin (enzyme) from kidneys
Renin catalyses angiotensinogen (liver) into angiotensin I
ACE hormone produced mostly by lungs converts Angiotensin I to II
- Stimulates Na+ and water retention, K+ loss
- Indirectly stimulate release of ADH
- Arteriolar vasoconstriction - increase blood pressure
Negative feedback mechanism => renin secretion decreases

Question 18

Types of Oedema

Answer 18

• Inflammatory
§ Large albumin able to move out of cell => lose oncotic pressure and water not drawn back into venous end
• Venous
§ Congestive cardiac failure - increased pressure at venous end
§ Water being pushed out - hydrostatic > oncotic
• Lymphatic
§ Disease of lymph node or removal - impaired water reabsorption into lymphatics
•Hypoalbuminaemic
§ Albumin low bc of sever malnutrition
§ Sever diarrhoea - protein losing enteropathy?
§ Liver problems which makes protein
§ Lose oncotic pressure so water not reabsorbed - moves into interstitial space

Question 19

Difference between transudate and exudate pleural effusion

Answer 19

Pleural effusions - diff fluids enter pleural cavity
Transudate
• Change hydrostatic pressure (e.g. congestive heart failure)
• Protein conc is lower than norm, intravascular fluid moves out of vessel
• Venous effusion, fluid leaks to pleural space

Exudate
• Inflammatory e.g. Pneumonia, lupus
• Vessels dilate, endothelial cells more spaced out so fluid and protein in the effusion
Test?
• Light’s criteria, look for presence of protein, cholesterol, glycerol (large protein) know its exudate

Question 20

Dietary energy sources

Answer 20

Carbohydrates - 4kcal/g
Proteins - 4kcal/g
Alcohol - 7kcal/g
Lipid - 9kcal/g

Question 21

Methods of generating ATP

Answer 21

glycolysis
Kreb's cycle
Oxidative phosphorylation 
Substrate level phosphorylation 
Electron Transport chain
Beta oxidation