Homeostasis

Question 1

Define homeostasis.

Answer 1

The tendency towards a relatively stable equilibrium between interdependent elements

Especially as maintained by physiological processes

Question 2

What is negative feedback?

Answer 2

Output reduces the original effect of the stimulus

Question 3

What is positive feedback?

Answer 3

Output increases the original stimulus

Question 4

Give 3 methods of cell communication.

Answer 4

Autocrine
Paracrine
Endocrine

Question 5

What does Autocrine mean?

Answer 5

A cell-produced substance that has an effect on the cell that secretes it

Question 6

What does paracrine mean?

Answer 6

A hormone which has effect only in the vicinity of the gland secreting it

Question 7

What does endocrine mean?

Answer 7

Glands which secrete hormones or other products directly into the blood

Question 8

What ways can water enter the body?

Answer 8

Drinks, food, IV

Question 9

What ways can water leave the body?

Answer 9

Kidneys - excretion
GI - faeces, vomit
Blood loss from wounds, internal bleeding
Sweating
Breathing

Question 10

What does ‘insensible loss’ mean?

Answer 10

Water loss that can’t be measured! For example sweat, breathing

Question 11

Name the 2 fluid compartments water is found in in the body. % in each?

Answer 11

Intracellular fluid - 67%

Extracellular fluid - 33%

Question 12

There are 2 types of extracellular fluid - describe them and give values.

Answer 12

Interstitial (75-80%) - solution surrounding cells

Intervascular (20-25%) - blood plasma

Question 13

What hormones influence the balance of water in the body?

Answer 13

ADH - anti diuretic hormone (also known as vasopressin)

Aldosterone

ANP - atrial natriuretic peptide

Question 14

Briefly describe the function of ADH. Also where is it released?

Answer 14

Retain water in the body by increasing water reabsorption in the collecting ducts of the nephron

Also constricts blood vessels

Stored and released from posterior pituitary

Question 15

How does ADH increase reabsorption of water in the collecting duct of the tubule?

Answer 15

Induces translocation of aquaporin water channels in the plasma membrane of the collecting duct. (This also occurs in the DCT)

Question 16

Briefly describe the function of aldosterone. Also where is it released?

Answer 16

From adrenal cortex of adrenal gland.

Causes retention of sodium, secretion of potassium, water retention and an increase in BP and blood volume

Activates Na+/K+ pumps in membranes of DCT and collecting ducts of nephrons

Question 17

Briefly describe the function of ANP. Also where is it released?

Answer 17

Secreted by atrial heart muscle cells

Acts to reduce water, sodium and adipose loads in the bloodstream - thus reducing blood volume and BP

Also a vasodilator

Question 18

Define osmotic pressure.

Answer 18

Pressure that would need to be applied to a solvent to prevent it passing into a given solution by osmosis

Used to express concentration

Question 19

Define oncotic pressure.

Answer 19

A form of osmotic pressure exerted by proteins (notably albumin)

Tends to pull fluid into circulatory system

Question 20

What is oedema?

Answer 20

Excess fluid in the interstitium (fluid that surrounds tissue cells)

Question 21

Name 4 types of oedema.

Answer 21

Inflammatory
Venous
Lymphatic
Hypoalbuminaemic

Question 22

What causes inflammatory oedema?

Answer 22

Vascular permeability

Fluid and cells leave the vessels, protein follows. More fluid is in the interstitium.

Question 23

What is interstitial fluid?

Answer 23

A solution that bathes and surrounds the tissue cells of multicellular animals.

Question 24

What causes venous oedema?

Answer 24

High pressure in the circulatory system forces fluid out into interstitium

Question 25

What causes lymphatic oedema?

Answer 25

Impaired lymphatic drainage

Question 26

What causes hypoalbuminaemic oedema?

Answer 26

Low albumin reduces oncotic pressure.

Oncotic pressure is lower than hydrostatic pressure

Water is not reabsorbed

Question 27

1) What is hypernatraemia? 2) What causes it?

3) What does it do to the body?

Answer 27

1) High sodium levels!

2) Renal failure
Cushing’s syndrome
Conn’s syndrome

3) Increased blood volume
Oedema

Question 28

1) What is hyponatraemia?
2) What causes it?
3) What does it do to the body?

Answer 28

1) Low sodium

2) Addison’s disease
Excess diuretic therapy
Heat exhaustion

3) Reduced blood volume
Hypotension

Question 29

1) What is hyperkalaemia?
2) What causes it?
3) What does it do to the body?

Answer 29

1) High potassium

2) Renal failure
Acidosis
Extensive tissue necrosis

3) Risk of cardiac arrest

Question 30

1) What is hypokalaemia?
2) What causes it?
3) What does it do to the body?

Answer 30

1) Low potassium

2) Vomiting/diarrhoea
Alkalosis
Cushing’s
Conn’s

3) Weakness
Cardiac dysrhythmia
metabolic alkalosis

Question 31

1) What is hypercalcaemia?
2) What causes it?
3) What does it do to the body?

Answer 31

1) High calcium

2) Primary Hyperparathyroidism
Too much vitamin D
Skeletal metastases

3) Metastatic calcification
Renal calculi (kidney stones)

Question 32

1) What is hypocalcaemia?
2) What causes it?
3) What does it do to the body?

Answer 32

1) Low calcium

2) Renal disease
Parathyroidectomy
Intestinal malabsorption
Resp. alkalosis

3) Tetany - involuntary muscle contractions (like a seizure)