kidneys

Question 1

explain how the kidneys function

Answer 1

• the stimulus produces a change in variables
• the change is detected by variable
• the information is sent along afferent pathway to the control center
• information sent along the efferent pathway to the effector
• response of the effector feeds back to influence magnitude of stimulus and returns variable to homeostasis

Question 2

what is homeostasis and why is it important

Answer 2

• maintenance of a relatively constant environment for the cells within the body
• helps maintain optimum conditions for cellular reactions
• gives organisms independence from the external environment whilst still existing in it

Question 3

what is negative feedback

Answer 3

• whenever a factor moves away from the ideal/normal a set of processes moves it back towards normal

Question 4

what are hormones

Answer 4

• molecules that are released by endocrine glands directly into the blood that travel to a target organ to produce an effect

Question 5

what are endocrine glands

Answer 5

• a ductless gland that secretes hormones directly into the blood

Question 6

what are target cells/tissues

Answer 6

• cells that have receptors embedded in the plasma membrane that are complimentary in shape to a specific hormone molecule.
• only these cells will respond to that hormone

Question 7

what is an exocrine gland

Answer 7

• a gland that secretes hormones into a duct

Question 8

what is a duct

Answer 8

• a tube lined with epithelial cells and conveying a secretion

Question 9

what are the functions of the kidneys

Answer 9

• filter blood and remove nitrogenous metabolic waste
• homeostatic function of osmoregulation

Question 10

how is urea produced

Answer 10

• proteins are digested into amino acids
• the amino acids are transported to the liver
• the excess amino acids are deaminated and the amine groups are converted into urea

Question 11

how does a negative feedback loop work

Answer 11

• the set point is the norm at which the system operates
• the receptor detects the change
• then it sends a signal to a coordinator or controller - the coordinator communicated with one or more effectors
• the factors return to normal, monitored by the receptors
• the information is fed back to receptors

Question 12

explain the glucose threshold

Answer 12

• under normal circumstances the PCT reabsorbs all of the glucose
• if the concentration of glucose in the filtrate is too high, there may be too few transport molecules
• it can happen when the pancreas secretes too little insulin, or the response of the liver cells to insulin is reduced