5.1 Communication And Homeostasis

Question 1

Why do we need a communication system

Answer 1

• multicellular organisms need to maintains a suitable temp + ph = so cells need to communicate w eachother to respond to changes in internal + external environment + coordinate activities of diff organs

Question 2

Neuronal system

Answer 2

Faster, short lasting

Question 3

Hormonal system

Answer 3

Slower, longer lasting

Question 4

Stimulus

Answer 4

Change in environment

Question 5

How do the internal environment change

Answer 5

New toxins and build up of waste products

Question 6

Good communication system

Answer 6

• cover the whole body
• Enable cells to communicate w eachother
• Specific + fast communication
• Both short term + long term responses

Question 7

Homeostasis

Answer 7

maintaining a constant internal environment, despite changes in the external or internal environment

Question 8

What does homeostasis allow?

Answer 8

Allows us to maintain our blood temp, glucose levels etc in a narrow range

Question 9

How does homeostasis work

Answer 9

Stimulus—> detected by sensory receptors—> sent to communication pathway (neuronal or hormonal)—> goes to effector—> response

Question 10

Negative feedback

Answer 10

• reverse the change and bring back the condition to optimum

Question 11

Negative feedback example

Answer 11

Question 12

Positive feedback

Answer 12

Initial change occurs and body increases the change

Question 13

Example of positive feedback

Answer 13

if body temp rises the body will increase the temp further

Question 14

Example of usually negative feedback but sometimes positive

Answer 14

cervix dilating during labour in response to the hormone oxytocin, the more oxytocin the more the cervix dilates which allows the baby to come out.

Question 15

Ectotherms

Answer 15

organisms that rely on external sources of heat to maintain body temperature

Question 16

What do ectotherms do if they’re too cold

Answer 16

may move into sunny area, lie on warm surface, expose a large SA of skin towards the sun

Question 17

What do ectotherms do when they’re too hot

Answer 17

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

Question 18

Examples of ectotherms

Answer 18

Snakes, locust, lizards

Question 19

Advantages of ectotherm temp control

Answer 19

less food used for respiration so don’t need much food, more energy in body used towards growth, can survive a long period without food

Question 20

Disadvantage of temp control in ectotherms

Answer 20

less active when temp is colder = more at risk of predators, can’t live anywhere in the world they’d have to live where the temperature suits them

Question 21

Endotherms

Answer 21

use internally generated heat (generated from respiration) to maintain steady body temperature regardless
of environment.

Question 22

Endotherms when hot

Answer 22

• liver = sweat glands secrete sweat bc heat energy is used to evaporate sweat
• hairs would be flat
• vasodilation = arteries dilate so more blood flows = more heat energy released by skin
• gas exchange increases so heat from lungs can come out

Question 23

Endotherms when it’s cold

Answer 23

• exothermic reactions that release heat to keep warm
• Vasoconstriction = arteries contract so less blood flows near surface of skin = less heat energy released by skin
• muscles contract less so less heat released
• skin = less sweat secreted
• hairs and feathers stand up to trap heat
• gas exchange system: less panting + gas exchange so less heat is lost

Question 24

Advantage of temp control in endotherms

Answer 24

• can maintain a stable body temp despite the external temperature
• can remain active even when the temperatures are low = less prone to being attacked by predators
• can live in colder parts of the world

Question 25

Disadvantages of temp control in endotherms

Answer 25

• most of our energy is used to keep our body warm so we need more food
• less energy used towards growth compared to an ectotherm
• we can overheat in hot weathers

Question 26

Thermoregulatory centre

Answer 26

Detects core temp

Question 27

Peripheral receptors

Answer 27

monitor the temperature on the outside and any changes would be sent to the thermoregulatory centre in the hypothalamus

Question 28

What are the two types of response used by endotherms to regulate body temperature?

Answer 28

Physiological and behavioural

Question 29

ii

Answer 29

Question 30

Answer 30

Question 31

Answer 31

Question 32

Answer 32