5: Homeostasis

Question 1

Why do ph and temperature need to be maintained?

Answer 1

Ph - enzymes have optimum ph, denaturation

Temp - too slow, or denatured

Question 2

Why does blood glucose need to be controlled?

Answer 2

High enough to provide enough cells with glucose for respiration, brain cells particularly susceptible as they can only respire glucose
Not too high to affect eater potential and shrink cells

Question 3

5 ways ectotherms control body temperature

Answer 3

Exposing themselves to the sun
Taking shelter
Gaining warmth from the ground
Generating metabolic heat
Colour variations

Question 4

What is a body temperature of 37 a compromise between?

Answer 4

Being warm enough so enzymes work rapidly

The amount of energy needed to maintain this temperature

Question 5

6 ways endotherms gain heat

Answer 5

Vasoconstriction
Shivering
Raising of hairs
Increased metabolic rate
Deceased sweating
Behavioural mechanisms

Question 6

4 ways in which endotherms lose heat

Answer 6

Vasodilation
Increased sweating
Lowering of body hair
Behavioural mechanisms

Question 7

Describe the second messenger model

Answer 7

The hormone is the first messenger. Binds to receptor to form hormone receptor complex
This activates enzymes inside the cells that produces a second messenger
This causes a series of chemical changes that produce the required response

Question 8

Which cells produce hormones in the pancreas? What are the two types?

Answer 8

Islets of langerhans
Alpha = glucagon
Beta = insulin

Question 9

What is the normal blood glucose level?

Answer 9

90mg per 100cm^3 of blood

Question 10

What three sources does glucose come from?

Answer 10

Directly from the diet
From the breakdown of glycogen (glycogenolysis)
From gluconeogenesis

Question 11

How does insulin reduce blood glucose?

Answer 11

Binds to receptors 
Increases no. of glucose transporters
Opens glucose channels 
Activates enzymes that converted glucose to glycogen and fat
Increases respiratory rate of cells

Question 12

How does glucagon increase blood glucose

Answer 12

Only liver cells have glucagon receptors
They activate an enzyme that converts glycogen to glucose
Increase conversion of amino acids and glycerol into glucose, gluconeogenesis

Question 13

What does adrenaline do and how?

Answer 13

Increases blood glucose
Activates enzyme that causes the breakdown of glycogen in the liver
Inactivates an enzyme that synthesises glycogen from glucose

Question 14

Define homeostasis

Answer 14

The maintenance of a constant internal environment

Question 15

Explain two advantages of endothermy over ectothermy

Answer 15

Enzymes always at optimum temperature, metabolic reactions are quicker
More independent of external environment, better able to survive in different environments

Question 16

What is the cause of Type 1 diabetes?
Describe and explain the symptoms
How is it treated?
How to avoid sudden rise in glucose

Answer 16

• the beta cells in the islets of langerhans don’t produce any insulin
• after eating, the blood glucose level rises and stays high (hyperglycaemia), this can result in death. Kidneys can’t absorb all this glucose, so some of its excreted in the urine
• eating regularly and controlling simple carbohydrate intake

Question 17

Who is likely to develop Type 2 diabetes?
What is the cause of Type 2 diabetes?
How can it be treated?

Answer 17

• Usually acquired later in life and its often linked with obesity
• beta cells don’t produce enough insulin or when body cells become insensitive to insulin. receptors don’t work properly
• controlling simple carbohydrate intake and losing weight. glucose lowering tablets can be taken

Question 18

How does a swimmer respond to jumping into cold water

Answer 18

Thermoreceptors on skin detect decrease in external temperature
Send signals via sensory neurones to heat gain centre of hypothalamus
Hypothalamus sends siganls down motor neurones to erector pili muscles, to raise body hair
And to sphincter muscles on arterioles to reduce blood flow to surface

Question 19

Why do glucose levels fluctuate?

Answer 19

We do not eat continuouly

Glucose is used up at different rates depending on metabolic activity