5.1 communication and homeostasis

Question 1

what internal conditions need to be maintained?

Answer 1

• temperature
• pH
• water levels

Question 2

possible response to build up of CO2 in body

Answer 2

breathe more

Question 3

features of a good communication system

Answer 3

1. cover whole body
2. enable cells to communicate with each other
3. enable specific communcation
4. enable rapid communcation
5. enable both short and long term responses

Question 4

2 methods of communcation in cell signalling

Answer 4

1. neuronal
2. hormonal

Question 5

NEED for communcation systems in multicellular organisms

Answer 5

• respond to changes in internal and external environment
• to make sure conditions eg for enzymes okay
• to coordinate the activities of different organs

Question 6

some things controlled by homeostasis

Answer 6

1. blood glucose
2. body temperature
3. blood wp

Question 7

homeostasis pathway

Answer 7

stimulus
receptor
communcation pathway (Cell signalling; neuronal or hormonal)
effector
response

Question 8

stimulus

Answer 8

change in environment

Question 9

sensory receptors

Answer 9

cells/ sensory nerve endings that detect a stimulus and respond

Question 10

negative feedback

Answer 10

the mechanism that reverses a change, bringin levels back to the optimum

Question 11

positive feedback

Answer 11

a mechaism that increases a change, taking levels further from the optimum

Question 12

describe positive feedback with cervix

Answer 12

1. cervix stretches, oxytocin released from POSTERIOR PITUITARY
2. oxytocin increases uterus contractions, so cervix dilates more, more oxytocin secreted
3. baby birthed, oxytocin inhibited

Question 13

ectotherm

Answer 13

organism that relies on external sources of heat to maintain body temp

Question 14

endotherm

Answer 14

organism that uses heat from metabolic reactions to maintain body temp

Question 15

why is core temperature more important than peripheral

Answer 15

core is where all the vital organs are

Question 16

main responses of ectotherms

Answer 16

BEHVARIOUAL

Question 17

What might ectotherms do in the cold:

Answer 17

• move to a sunny area
• lie on a warm surface
• increase SA exposed to sun

Question 18

what might ectotherms do in the hot:

Answer 18

• move out of sun
• move underground
• reduce body SA exposed to sun

Question 19

why might an insect breath more and deeper when its HOT

Answer 19

• ectotherm
• more water evaporates from tracheal system , cooling the body

Question 20

advantages of ectothermy

Answer 20

1. less food used for respiration
2. so more food can be used for growth
3. need less food
4. can survive for longer without food

Question 21

disadvantages of ecothermy

Answer 21

• less active when cold -> more susceptible to predators

Question 22

endotherms respiration when cold

Answer 22

• respiration exothermic
• more heat energy released

Question 22

IF TOO HOT (endotherms:)

Answer 22

1. sweat glands secrete fluid -> high latent heat of vaporisation -> little released, lots of energy lost
2. erector muscles relax, hairs (and feathers) lie flat, less heat trapped and so less insulation
3. vasoconstriction, reduces vol blood flowing close to surface of skin, less heat lost by radioation
4. LESS SHIVERING (exothermic respiration)

Question 23

advantages endothermy

Answer 23

1. fairly constant body temp despite cold
2. active even when cold, can take advantage of ectotherm prey
3. can live in colder parts of planet

Question 24

disadvantages endothermy

Answer 24

1. more food
2. less food used for growth as more for this

Question 25

who detects temperature in mammals

Answer 25

• thermoreceptors in hypothalamus, detecting BLOOD TEMPERATURE

Question 26

importance of peripheral temperature receptors

Answer 26

• in skin , eg in extremities of the body
• forewarning to hypothalamus
• and can initiate behavioural mechanisms eg move into shade if too hot