3.7 Homeostasis and the kidney

Question 1

What is homeostasis?

Answer 1

The maintenance of a constant internal environment

Question 2

What is the internal environment?

Answer 2

Includes tissue fluids that bathe cells, supplying nutrients and removing wastes and maintaining glucose concentration, pH, core temperature and solute potential.

Question 3

How can the body be protected by changes in the external environment?

Answer 3

by keeping the body fluids at a constant and optimum level protects cells from changes in the external environments.

Question 4

What do I mean when I say the body is kept at a dynamic equilibrium?

Answer 4

constant changes occur but a set point is resumed. Homeostasis is the ability to return to that set point.

Question 5

What controls homeostatic responses and how?

Answer 5

The endocrine system controls homeostatic responses, with hormones operating by negative feedback.

Question 6

What is negative feedback?

Answer 6

A change in the system produces a second change, which reverses the first change.

Question 7

What are the stages in which negative feedback occurs?

Answer 7

1. Set point (normal state)
   2.Input (change to normal state)
   3.Receptor (measures the change)
   4.Co-ordinator (stores info and used to co-ordinate the effector)
   5.Effectors (bring about changes to the system that reverse effect of the input)
   6.Output (corrective procedures)
   7.Set point (back to normal)

Question 8

what are examples of effectors?

Answer 8

muscles and glands

Question 9

Give 2 examples of negative feedback:

Answer 9

• If glucose concentration in the plasma increases above a set point, insulin is secreted, reducing the glucose concentration by converting it to glycogen and increasing the rate at which is is respired. If the level falls below the set point, glucagon is secreted, which results in glycogen being converted to glucose.
• If the body’s core temperature falls below the set point, increased respiration generates heat, and constriction of superficial blood vessels allows the body to retain it. if the temp rises above the set point, superficial blood vessels dilate, and heat radiates from the body, reducing its temperature.

Question 10

What is positive feedback?

Answer 10

where an effector increases a change i.e movement away from norm causes a further movement away from the norm.

Question 11

Give two examples of postitive feedback:

Answer 11

• Oxytocin stimulates the contraction of the uterus at the end of a pregnancy. The contractions stimulate the production of more oxytocin, which increases the contractions.
• When skin is cut, the platelets cut cause a clot, they also send out signalling molecules that attract more platelets forming more clots.

Question 12

What is excretion?

Answer 12

removal of wastes made by the body

Question 13

what is excreted in the urine?

Answer 13

Urea - amino acid breakdown
Creatinine - muscle tissue breakdown
Uric acid - Nucleic acid breakdown

Question 14

What is excreted in expired air?

Answer 14

• CO2
• Water
  this happens in respiration

Question 15

what is excreted through the skin?

Answer 15

Sweat containing urea

Question 16

What is excreted in faeces?

Answer 16

Bile pigments due to haemoglobin breakdown

Question 17

what are the kidneys two main functions?

Answer 17

• Excretion - the removal of nitrogenous metabolic waste from the body
• Osmoregulation - the control of the water potential of the body’s fluids (plasma, tissue fluid, lymph) by regulating the water content, and thus the solute concentration.

Question 18

what is osmoregulation?

Answer 18

The control of the body’s fluids by the regulation of the water content of the body.

Question 19

What is deamination:

Answer 19

The removal of an amine group from a molecule. Excess amino acids are deaminated in the liver, and the amine group is converted to urea.

Question 20

What is the structure of the kidney?

Answer 20

a tough renal capsule covers each kidney. Each kidney receives blood from a renal artery and returns blood to the general circulation in a renal vein. The blood from the renal artery is filtered in the outer layer, the cortex, at the bowmans or renal capsules. The medulla contains the loop of Henle and the collecting ducts that carry urine to the pelvis. The pelvis empties urine into the ureter and a ureter from each kidney carries urine to the bladder.

Question 21

What are the tube like structures called that you see when observing a kidney under a microscope?

Answer 21

Nephrons, there are many to increase SF for exchange

Question 23

Describe the image of this kidney cortex.

Answer 23