HOMOESTASIS

Question 1

why do cells need to communicate with each other?

Answer 1

coordinate activities and maintain constant conditions.
all cells rely upon one another

Question 2

what are the conditions required for enzyme to work efficiently?

Answer 2

suitable pH
suitable temperature
aqueous solution

Question 3

explain external changes

Answer 3

external changes act as a stimulus for the organism (may be stressful), to which they MUST respond with a CHANGE OF BEHAVIOUR or PHYSICAL CHANGE

Question 4

Wha are the changes through which an organism may respond to external changes?

Answer 4

behavioural or physical

Question 5

types of changes

Answer 5

slow and quick

Question 6

explain internal changes

Answer 6

an example of internal change is the ACCUMULATION OF WASTE PRODUCTS (stimuli), the removal of these products is the response.
this will allow the survival of the cell.

Question 7

how is the internal environment maintained?

Answer 7

blood and a good communication system

Question 8

a good communication system will:

Answer 8

cover the whole body
allow rapid communication
enable communication between cells
enable specific communication
short-term and long-term response

Question 9

what are the communication systems used for cell signalling?

Answer 9

neuronal system - communication between neurons through signal transmission

hormonal system - communication by release of hormones

Question 10

define HOMOESTASIS

Answer 10

maintaing a constant internal environment despite external or internal changes

Question 11

what is controlled by homoestasis?

Answer 11

body temperature
glucose concentration
salt concentration
water potential
blood pressure
CO2 concentration

Question 12

Homoestasis process

Answer 12

stimulus {temp change} –> receptor –> communication pathway (cell signalling) {infos processing} –> effector {muscles} –> response {moving away}

Question 13

what is a feedback?

Answer 13

the body response to change

Question 14

types of feedback?

Answer 14

negative or positive

Question 15

explain what is NEGATIVE FEEDBACK:

Answer 15

this mechanism reverse the change, so it returns to the optimum conditions

Question 16

describe negative feedback :

Answer 16

optimum condition > change away from opt.condition > detected by receptor > communication system > effector REACTS TO REVERSE THE CHANGE > return to opt. condition >opt. condition

Question 17

are body condition ALWAYS constant?

Answer 17

No, the conditions always fluctuate around the optimum condition, as long as the variaions are not too great, NF is not activated.

Question 18

explain what is POSITIVE FEEDBACK:

Answer 18

opposite of Negative feedback, INCREASES the change
can be harmful but also beneficial (dilation of cervix)

Question 19

describe positive feedback

Answer 19

opt. condition > change away from opt. > detected by receptors > cell signalling informs effectors > INCREASE OF THE CHANGE.

Question 20

What is an example of beneficial positive feedback?

Answer 20

cervix contraction:
1. baby pushes their head against cervix
2.nerve impulse carries information to the brain
3. brain stimulates pituitary gland to release oxytosin
4. oxitosin carried in the blood,targets cervix
5. causes more dilatation of cervix

Question 21

ECTOTHERMS

Answer 21

not able to control their body temperature, relies on external temperature

Question 22

ENDOTHERMS

Answer 22

able to control their body temperature through mechanisms

Question 23

how do ectotherms increase their body temperature?

Answer 23

move into sunny areas
lie on warm surfaces
expose their large surface are to the sun

Question 24

how do ectotherms decrease their body temperature?

Answer 24

move out of the sun
move underground
reduce body surface exposed to sun

Question 25

advantages of ectotherms :

Answer 25

less energy is used in respiration to keep thei body temp warm.

need to find less food

can survive without food for long periods

Question 26

disadvantages of ectotherms:

Answer 26

less active in cooler temperature, risk form predators.

Question 27

ENDOTHERMS physiological mechanism when body is too hot:

Answer 27

skin : sweat gland secretes fluid on the skin, as it evaporates,uses heat from blood as latent heat

Hair lie flat to reduce insulation

vasodilation, directs blood to skin surface

panting

Liver- less respiration takes place, less heat released

fewer muscular contraction ,less heat released

dilation to direct blood on skin surface to llow heat loss.

Question 28

ENDOTHERMS physiological mechanism when body is too cold:

Answer 28

less sweating

hairs stand erect to insulate the skin

vasoconstriction - blood diverted form skin surface

less panting, less heat lost

liver - increased repiration to produce more heat

-more muscle contraction (shivering)

-constriction to limit blood flow at extremities

Question 29

ENDOTHERMS behavioural mechanism when body is too hot:

Answer 29

hide away from sun

reduce surface area exposed to sun

inactive and spread limps to allow greater heat loss

wet skin.

Question 30

ENDOTHERMS behavioural mechanism when body is too cold:

Answer 30

lie in the sun

orientate body toward the sun

move more to generate heat

remain dry

Question 31

endotherms advantages

Answer 31

can maintain a constant body temp despite external temp.

can remain active , prey

leave in colder part of the world

Question 32

endotherms disadvantages

Answer 32

most of the energy used to maintain body temp

need more food

nutrients used less for growth

may overheat in hot weather.

Question 33

what is structure that detects body temperature changes?

Answer 33

hypothalamus