Homeostasis

Question 1

What is homeostasis?

Answer 1

The maintenance of a constant internal environment in organisms

Ensuring that cells are in an environment that meets their needs despite external changes

Question 2

Why is homeostasis important?

Answer 2

Enzyme function - temperature and pH

Water potential- blood glucose level

Gives an organism a wider geographical range and a greater chance of finding food

Question 3

What is the control mechanism for homeostasis?

Answer 3

Set point the desired level. Monitored by the…

Receptor detects deviation. Informs the…

Controller coordinates information sending instructions to an appropriate…

Effector brings about change. Creates a…

Feedback loop informs the receptors of the changes

Question 4

How do animals gain heat?

Answer 4

Produce heat through respiration

Gain heat from the environment by conduction, convection and radiation

Question 5

How do animals lose heat?

Answer 5

Evaporation of water - sweat

Loss of heat to the environment though convection, conduction and radiation

Question 6

What is an endotherm?

Answer 6

Metabolic processes happen inside the body

‘Inside heat’

Endo = indo

Question 7

What are ectotherms?

Answer 7

Obtain most heat from outside their bodies

‘Outside heat’

Question 8

How do ectotherms regulate body temperature?

Answer 8

Expose themselves to the Sun

Take shelter to prevent over heating

Gain warmth from the ground

Generate metabolic heat

Colour variations - black absorbs more heat

Question 9

How do endotherms regulate body temperature?

Answer 9

Internal metabolic activities

34-44 degrees C

Question 10

Conserving heat in a cold environment

Answer 10

Small surface area to volume ratio

Smaller extremities

Vasoconstriction- diameter of the arterioles is made smaller
Shivering- produces metabolic heat
Hair raising- trapping a layer of air by the body
Decrease in sweating
Increased metabolic rate

Question 11

Losing heat in a warm environment

Answer 11

Large surface to volume ratio
Light coloured

Vasodilation- arterioles diameter increases
Increased sweating
Lower body hair
Behavioural mechanism- avoid heat by sheltering

Question 12

How is the hypothalamus used in controlling body temperature?

Answer 12

The stimulus is detected by receptors
These pass information to the hypothalamus
Causing the effector to produce a response

Question 13

What happens in the hypothalamus?

Answer 13

A thermoregulatory centre consisting of:

Heat gain centre activated by low temperature
Heat loss centre activated by high temperature

Question 14

Characteristics of hormones

Answer 14

Produced by glands
Carried in the blood plasma
Act on target cells
Effective in small quantities and have long lasting effects

Question 15

What is the second messenger model used for?

Answer 15

Used by two hormones, adrenaline and glucose to regulate blood glucose

Question 16

How does the second messenger model work?

Answer 16

A hormone is the first messenger and binds to a specific receptor on the cell membrane forming a hormone-receptor complex

Hormone-receptor complex activated an enzyme inside the cell - second messenger

Enzymes cause chemical changes produce a response. Adrenaline converts glycogen to glucose

Question 17

What is the pancreas used for?

Answer 17

Produces enzymes used in digestion and hormones used to regulate blood glucose

Question 18

Islets of Langerhans

Answer 18

Found in the pancreas and produce the hormones

Two types of cell:
a cells - larger and produce GLUCAGON
B cells - smaller and produce INSULIN

Question 19

Insulin and the B cells of the pancreas

Answer 19

Detect a rise in blood glucose level and respond by secreting insulin

Question 20

What changes does insulin cause?

Answer 20

Change the tertiary structure of the glucose transport protein allowing more more glucose in

Increases the number of carrier molecules in the cell membrane

Activation of enzymes that convert glucose to glycogen and fat

Question 21

How is blood glucose lowered?

Answer 21

Increase rate of glucose absorption into cells

Increasing respiratory rate of cells

Increasing the rate of conversion of glucose to glycogen

Increase the rate of conversion of glucose to fat

Question 22

Glucagon and the a cells of the pancreas

Answer 22

Detect a fall in blood glucose by secreting glucagon into the blood plasma

Only liver cells have receptors that bind to glucagon

Question 23

How do liver cells respond to glucagon?

Answer 23

Activate enzymes to convert glycogen to glucose

Increase gluconeogenesis (amino acids and glycerol into glucose)

Question 24

Cause of type I diabetes

Answer 24

The body is unable to produce insulin

Maybe as a result of an autoimmune response whereby the body’s immune system attacks it’s own cells

Question 25

Cause of type II diabetes

Answer 25

Due to the glycoprotein receptors on the body cells losing responsiveness to insulin

or an inadequate supply of insulin from the pancreas

Usually as a result of obesity and poor diet

Question 26

How can type I diabetes be controlled?

Answer 26

By injections of insulin frequently throughout the day

Manage carbohydrate intake and exercise

Question 27

How can type II diabetes be controlled?

Answer 27

Regulating intake of carbohydrates and matching the amount of exercise taken

Also helped by insulin injections or drugs that stimulate the production of insulin

Question 28

What is diabetes?

Answer 28

A chronic disease in which the person is unable to metabolise carbohydrate