3.7 homeostasis

Question 1

Homeostasis?

Answer 1

maintaining a constant internal environment

Question 2

Negative feedback?

Answer 2

a change in a system produces a second change reverses the first change, back to a set point

Question 3

Negative feed back mechanism?

Answer 3

Receptor detects level of a factor and deviation from set point
Detects change and sends instructiions to a co-ordinator which communicates with an effector i.e muscle or gland
Effector makes corrective response, retuning factor to set point

Question 4

Examples of negative feedback

Answer 4

Glucose concentration in plasma, if above set point, insulin is secreted from pancreas, converting to glycogen, and increasing the rate of glucose respiration
If below set point glucagon secreted which converts glycogen to glucose
If body temp below set point, increased respiration generates more heat and blood vessels constrict to retain heat

Question 5

Positive feedback?

Answer 5

an effector increases a change further away from the set point

Question 6

Examples of positive feedback

Answer 6

Oxytocin stimulates uterus contractions at end of pregnancy
Aggregation of platelets - at first stage of clot formation - secrete signalling molecules to attract more molecules

Question 7

4 places of excretion

Answer 7

Lungs - (Carbon dioxide, water in expired air)
Kidneys - (urea, uric acid, creatinine in urine)
Skin(urea) in sweat
Liver( bile pigments) in faeces

Question 8

How is water removed from the body?

Answer 8

secreted in tears and saliva
egested in faeces
Metabolic waste product of respiration in expired air

Question 9

2 functions of kidney and definitions

Answer 9

Excretion - removal of nitrogenous metabolic waste made by the body
Osmoregulation - control of the water potential of the body fluids ( plasma, tissue, fluid, lymph) by regulating water content, and therefore the solute potential

Question 10

Production of Urea

Answer 10

Proteins hydrolysed to amino acids
Excess amino acids deaminated in the liver and the ammonia group is converted to urea
Amino acids > Alpha Keto Acid + Ammonia >Urea

Question 11

Kidney coated in?

Answer 11

Tough renal capsule

Question 12

Structure of Kidney?

Answer 12

Blood from renal artery filtered in the cortex from the glomerulus into Bowman’s Capsule
Medulla contains loop of Henle