Homeostatsis

Question 1

What is homeostasis?

Answer 1

Maintenance of internal conditions despite changing external conditions
–>dynamic equilibrium

Question 2

Describe negative feedback:

Answer 2

Change detected by sensory receptors

–> effectors reverse change and restore conditions back to base level

Question 3

Describe positive feedback:

Answer 3

Change is detected
–>effectors reinforce change and amplify response
e.g: childbirth + blood clotting

Question 4

What is thermoregulation?

Answer 4

Maintenance of constant core body temp to maintain optimum enzyme activity.

Question 5

Why do organisms constantly heat up/cool down?

Answer 5

Radiation

Convection –> warm air rises cool air sinks

Conduction –> collision of other molecules

Latent heat of evaporation

Exothermic chemical reactions

Question 6

What are exotherms?

Answer 6

Use surrounding to warm body

Core body temp relies on environment

Water animals = no thermoregulation = high SHC

Question 7

What are endotherms?

Answer 7

Rely on metabolic processes to warm up

Stable core body temp

Consume more food

Question 8

Behavioural responses of ectotherms:

Answer 8

Bask in sun

Press body on warm ground = heat increase by conduction

Seek shade through burrows + hiding inbetween rocks

Sit in mud/water

Orientate body so minimal SA exposed to sun

Question 9

Physiological responses of ectotherms:

Answer 9

Lizards in colder climates = darker
Dark colours absorb more radiation

Alter HR to increase/decrease metabolic rate

Question 10

Behavioural responses of endotherms:

Answer 10

Clothes
Huddling
hibernation
Migration

Question 11

Anatomical responses of endotherms:

Answer 11

Large SA:V
—> large ears + wrinkly skin

Pale fur/feathers to reflect radiation

Fat/blubber underneath skin

Question 12

How to endotherms cool down?

Answer 12

Vasodilation = arterioles near skin surface dilate

Increased sweating = sweat evaporates on skin surface = heat lost = cools blood below surface

Erector pili muscles on skin relax –> hair/feathers lie flat
–> avoid trapping insulating air

Question 13

How do endotherms warm up?

Answer 13

Vasoconstriction = arterioles near skin surface constrict = skin looks pale

Decreased sweating

Erector muscles contract –>pulls hair up

Shivering = involuntary contracting/relaxing of large muscles

Question 14

How does shivering cause body to warm up?

Answer 14

Metabolic heat from exothermic reactions warm up body

Question 15

What is the heat loss centre?

Answer 15

Activated when temp of blood flowing through hypothalamus increases

sends impulse to autonomic NS to effectors –> lower core temp

Question 16

What is the heat gain centre?

Answer 16

Activated when temp of blood flowing through hypothalamus decreases

sends impulse to autonomic NS to effectors in skin + muscle -> raise core temp