Homeostasis, Bodily Fluids and Oedema

Question 1

Define homeostasis

Answer 1

Homeo = sameness
Stasis = standing still
The process whereby cells, tissues and organs maintain the status quo of the body.

Question 2

What is negative feedback? Give an example.

Answer 2

When the internal environment of the body is not in balance, a negative feedback loop works to put the body back into its original position; it’s status quo.
An example is when you have eaten a lot of food, insulin is released from the pancreas in order to combat an increased glucose level in your blood. Cells take up glucose with the help of insulin and the blood glucose decrease and therefore the insulin secretion stops.

Question 3

What is positive feedback? Give an example.

Answer 3

When the output instead enhances the original stimulus. In this case the increased glucose level would lead to an even more increased level. But this doesn’t happen…
Regulation of blood clotting is a better example.
There is a tear in tissue, clotting occurs as platelets adhere to the site and release chemicals. These chemicals attract even more platelets and so it goes on until the clot is done.

Question 4

What is the core temperature of the body?

Answer 4

36.5 to 37.5 celsius

Question 5

What degrees are mild hypothermia?

Answer 5

36.5 to 32 degrees celsius

Question 6

What degrees are severe hypothermia?

Answer 6

32 to 28 degrees celsius

Question 7

What degrees are a fever?

Answer 7

37.6 to 40ish

Question 8

What degrees are a heat stroke?

Answer 8

40 is to 46

Question 9

What degrees are heat exhaustion?

Answer 9

46 above

Question 10

What is the normal pH range in blood?

Answer 10

7.35 to 7.45 pH

Question 11

What are the limits of human tissue survival in terms of pH?

Answer 11

6.8 to 7.8 pH

Question 12

Describe how much water there is in a standard male and explain where the water is.

Answer 12

70kg male
60% water = 42 kg
2/3 is in ICF = 28 kg
1/3 is in ECF = 14 kg
in ECF 80% is in the interstitial fluid = 11.2 kg
20% is in plasma = 2.8 kg

Question 13

What is hypertonicity?

Answer 13

Less water inside a cell. cell shrinks

Question 14

What is hypotonicity?

Answer 14

More water inside a cell. cell swells

Question 15

Define osmolality.

Answer 15

The concentration of a solution expressed as the total number of solute particles per kilogram.
It is calculated considering the mass of the solution.

Question 16

How does osmolality differ to osmolarity?

Answer 16

Osmolality uses the mass of the solution, osmolarity uses the volume of the solution.

Question 17

Why is this difference important and how does it favour osmolality?

Answer 17

Because osmolality does not depend on temperature and pressure since it doesn’t calculate volume.

Question 18

What is the total osmolality of a patient with the given plasma concentrations:
Sodium = 140 mmol/L
Potassium = 5 mmol/L
Glucose = 5 mmol/L
Urea = 5 mmol/L

Answer 18

Na+ is an ion so it is counted ‘twice’ 280 mmol
Potassium is an ion so it counted ‘twice’ 10 mmol
5 mmol
5 mmol
=
300 mOsm/kg

Question 19

What is oedema?

Answer 19

Fluid retention which causes swelling. Peripheral oedema is swelling of limbs

Question 20

What causes oedema?

Answer 20

When the hydrostatic pressure is larger than the osmotic pressure.
Also a low plasma oncotic pressure can explain oedema.
Also if plasma proteins are found in the interstitial space.
If the lympathics are blocked or damaged this can also cause oedema.