Homeostasis

Question 1

Define Homeostasis.

Answer 1

Homeo=sameness

Stasis=standing still

Question 2

What factors must remain constant in the body?

Answer 2

Conc of O2, Co2, salt and electrolytes
Conc of nutrients and waste products
 pH
Temp
Volume and pressure

Question 3

Give an example of a negative feedback loop.

Answer 3

1) High blood glucose
2) Detected by insulin secreting cells
3) Pancreas secretes insulin so the liver converts glucose to glycogen
4) Glucose levels fall, insulin production stops

Question 4

Give an example of a positive feedback loop.

Answer 4

1) Tear in blood vessel
2) Clotting occurs as platelets adhere to site + release chemicals
3) Released chemicals attract more platelets
4) Clot grows until blocks the leak

Also see Ferguson reflex in birth causing oxytocin release.

Question 5

What should our core body temperature be?

Answer 5

37C (+/- 0.5)

It varies a little based on time of day, age, extreme fitness level and menstruation

Question 6

List some temperature control mechanisms

Answer 6

Shivering, sweating, vasoconstriction, vasodilation, piloerection, pilorelaxation, curling up, spreading out, removing layers

Question 7

List the fever temp range and some symptoms.

Answer 7

37.5-40C

Pale, sweaty, stomach cramps, limb cramps

Question 8

List the heat stroke range and some symptoms

Answer 8

40-46C

Flushed dry skin, hot to touch, bounding pulse

Question 9

List the heat exhaustion range and some symptoms

Answer 9

> 46C

Unconscious, fitting, confused, restless, headache, dizzy, uncomfortable

Question 10

List the mild hypothermia temp range and some symptoms

Answer 10

32-36.5C

Shivery, fatigued, slurring, confused, forgetful, stiff muscles

Question 11

List the severe hypothermia temp range and some symptoms

Answer 11

28-32C

No shivering, rigid muscles, slow+weak pulse, drowsy, poor response level

Question 12

What happens when we reach below 28C?

Answer 12

We have no vital signs at all.
We are unconscious, have dilated pupil and no detectable pulse.
We appear completely dead.

Question 13

What is the pH range of the body and which organs are responsible for maintaining them?

Answer 13

7.35-7.45pH

Maintained by lungs and kidneys

Question 14

What buffer systems does the body use?

Answer 14

Intracellular fluid-sodium phosphate and protein (as heamoglobin)
Extracellular Fluid-carbonic acid (to bicarbonate) and protein (as AAs and plasma protein)

Question 15

What happens if the body fluid level drops?

Answer 15

Cells first absorb water from the interstitial space, then each other, then the vital organs. It begins with the brain, then liver, kidneys and lastly heart. Leads to death.

Question 16

What happens if body fluid is too high?

Answer 16

High osmotic pressure leads to cell lysis and cells stop working. Pressure is put on the brain leading to seizures and death.

Question 17

What is the distribution of water in a human body?

Answer 17

60% of the body is water, of this 2/3 is intracellular fluid and 1/3 is extracellular fluid. Of the ECF 80% is interstitial fluid and 20% is plasma in the blood.

Question 18

Define isotonic.

Answer 18

Water potential is the same inside and outside the cell.

Question 19

Define hypertonic.

Answer 19

Solutes are higher outside the cell, so water moves out causing cell lysis.

Question 20

Define hypotonic.

Answer 20

Solutes are higher in the cell, so water moves in causing cell to burst.

Question 21

Define Osmality.

Answer 21

The conc of a solution as solute particles per Kg.
Can be measured of plasma or urine.
For ionising molecules every millimole gives 2 mosmoles.

Question 22

What is Oedema?

Answer 22

Fluid retention. Eg peripheral oedema is ankle swelling due to fluid.

Question 23

How does Oedema happen?

Answer 23

Hydrostatic pressure > osmotic pressure, water moves into the interstitial space from the blood.
Can be linked to heart failure, liver cirrhosis, or renal disease. Measured by a prescence of proteins in the interstitial space.