B3.3 Homeostasis

Question 1

Define homeostasis

Answer 1

Maintaining a constant internal environment despite external change

Question 2

State 3 conditions which need to be controlled within the body

Answer 2

• Temperature
• Water levels
• Blood glucose concentration

Question 3

Why does the temperature need to be controlled?

Answer 3

To provide a suitable environment for enzymes so that they can work fastest at their optimum temperature

Question 4

Give 2 processes involving the skin that cool the body down

Answer 4

Sweating - Cools the body by evaporation

Vasodilation - Allows blood to flow closer to the surface of the skin where it can cool

Question 5

Describe the process of vasodilation

Answer 5

• The body detects a rise in temperature
• Blood vessels supplying the capillaries at the skin surface dilate
  (the muscles in the vessels relax)
• More blood flows closer to the skin where it can cool

Question 6

Give 3 processes that work to keep the body warm

Answer 6

• Vasoconstriction
• Shivering
• Erection of hairs on the skin

Question 7

Describe the process of vasoconstriction

Answer 7

• The body detects a drop in temperature
• Blood vessels supplying the capillaries at the skin surface constrict (the muscles in the vessels contract)
• Less blood flows closer to the skin surface so less heat is lost to the surroundings

Question 8

State 2 effects caused by insulin secretion

Answer 8

• More glucose is taken up by cells
• Glucose is converted to glycogen for storage
  (Both of these cause a decrease in blood glucose levels)

Question 9

What does the secretion of glucagon cause?

Higher

Answer 9

Glucagon secretions cause glycogen to be broken down into glucose to raise the blood glucose concentration

Question 10

What is the difference between type 1 and type 2 diabetes?

Answer 10

Type 1 diabetes is where the body doesn’t produce enough insulin
Type 2 diabetes is where the body no longer responds to insulin

Question 11

How can type 1 diabetes be treated?

Answer 11

Insulin injections

Question 12

How can type 2 diabetes be treated?

Answer 12

Type 2 diabetes can be treated by eating healthily and exercising regularly

Question 13

What happens if an animal cell is placed in a solution of lower water potential?

Answer 13

The cell will shrink (crenate)

Question 14

What happens if an animal cell is placed in a solution of higher water potential?

Answer 14

Water will move into the cell and it will burst (lysis)

Question 15

What happens if an animal cell is placed in a solution of equal water potential?

Answer 15

There will be no net movement of water in or out of the cell

Question 16

What is the function of the kidneys?

Answer 16

• To regulate the volume and concentration of urine

- To remove waste and regulate body water content

Question 17

Describe the general structure of a kidney

Answer 17

• Contains a cortex and medulla
• Renal artery carries blood to the kidney
• Renal vein carries blood away from the kidney
• Each kidney contains many nephrons
• Ureter carries fluid from the kidneys to the bladder

Question 18

What does ADH do? (Higher)

Answer 18

• When ADH is secreted into the bloodstream it increases the permeability of the kidney tubules
• This increases the reabsorption of water

Question 19

Describe the negative feedback loop when dehydration is detected (Higher)

Answer 19

• Thirst signals activated

- More ADH released (water retained by kidneys)

Question 20

Describe the negative feedback loop when overhydration is detected (Higher)

Answer 20

• Less ADH is released
• Dilute urine is produced
• Salts are retained