5.1.1 Communication and homeostasis

Question 1

how does the body respond to a change?

Answer 1

through the endocrine system or through the nervous system

Question 2

what is the type of signal in the endocrine system?

Answer 2

hormonal (chemical)

Question 3

how is the signal transmitted in the endocrine system?

Answer 3

in the blood

Question 4

what is the speed of transmssion in the endocrine system?

Answer 4

slow

Question 5

what is the nature of the response in the endocrine system?

Answer 5

long term

Question 6

what is the type of signal in the nervous system?

Answer 6

electrical impulses

Question 7

how is the signal transmitted in the nervous system?

Answer 7

along neurones

Question 8

what is the speed of transmission in the nervous system?

Answer 8

fast

Question 9

what is the nature of response in the nervous system?

Answer 9

short term

Question 10

why do cells in the body need to coordinate?

Answer 10

-multicellular organisms must coordinate their functions to operate effectively
-very few body cells can work in isolation

Question 11

define homeostasis

Answer 11

the maintenance of a stable equilibrium in the conditions inside the body

Question 12

what is the role of cell signalling in homeostasis?

Answer 12

-the nervous and endocrine systems are coordinated by cell signalling
-one cell releases a chemical which then has an effect on another cell

Question 13

how does cell signalling work in homeostasis?

Answer 13

1. signal initiation
2. signal response

Question 14

describe signal initiation

Answer 14

-sensory receptors detect changes in the bodies internal and external environments
-information from the receptors is transmitted to the brain via sensory neurons

Question 15

describe signal response

Answer 15

-impulses are sent along motor neurones to effectors which bring about changes to restore equilibrium
-effectors are the muscles or glands that respond to the stimulus

Question 16

plants don’t have nerves so how do they respond?

Answer 16

-they use plant hormones to achieve a response
-plant stems grow towards a light source to maximise their rate of photosynthesis, this is due to plant hormone (auxins)

Question 17

define negative feedback

Answer 17

the reversing of a change in the internal environment

Question 18

define positive feedback

Answer 18

where a change in the internal environment is detected and then reinforced by effectors

Question 19

what is an example of positive feedback?

Answer 19

role of oxytocin in childbirth

Question 20

how do the target cells recognise the signal in the nervous system?

Answer 20

binding sites for neurotransmitters

Question 21

how do the target cells recognise the signal in the hormonal system?

Answer 21

target receptors

Question 22

what is an ectotherm?

Answer 22

animals that use their surroundings to warm their bodies so their temperature is heavily dependent on the environment

Question 23

what is an endotherm?

Answer 23

animals that rely on their metabolic processes to warm their bodies and maintain their core temperature

Question 24

how are changes in temperature detected?

Answer 24

by receptors

Question 25

what are the two different types of receptors that detect changes in temperature?

Answer 25

-peripheral receptors -temperature receptors

Question 26

what are peripheral receptors?

Answer 26

they are in the skin and detect changes in the surface temperature

Question 27

what are temperature receptors?

Answer 27

they are in the hypothalamus and detect the temperature of the blood deep in the body and help to maintain a core body temperature of 37°C

Question 28

what are the two control centres within the hypothalamus?

Answer 28

-heat loss centre -heat gain centre

Question 29

describe the hypothalamus coordination when the normal body temperature increases

Answer 29

-heat loss centre in hypothalamus is signalled due to warm receptors in skin -the autonomatic nerves are then signalled -which signals to effectors in skin and muscles -which cause a response that returns to normal blood temperature

Question 30

describe the hypothalamus coordination when the normal body temperature decreases

Answer 30

-heat gain centre in hypothalamus is signalled due to cold receptors in skin -the autonomatic nerves are then signalled -which signals to effectors in skin and muscles -which cause a response that returns to normal blood temperature

Question 31

what are the behavioural responses that endotherms use to maintain their body temperature?

Answer 31

-basking in the sun -pressing themselves to warm surfaces -wallowing in water and mud to cool down -digging burrows to keep warm or cool -hibernation in winter

Question 32

what are the different physiological responses endotherms have to cool down?

Answer 32

-vasodilation -increased sweating -reducing the insulating effect of hair and feathers

Question 33

how does vasodilation allow endotherms to cool down?

Answer 33

-the arterioles near the surface of the skin dilate when the temperature rises -this forces blood through the capillary networks close to the surface of the skin, the skin flushes and cools as a result of increased radiation -if the skin is pressed against cool surfaces, then the cooling results from conduction

Question 34

how does increased sweating allow endotherms to cool down?

Answer 34

-as sweat evaporates from surface of the skin, heat is lost, cooling the blood below the surface -in some animals, the sweat glands are restricted to the less hairy areas of the body, these animals often open their mouths and pant when they get hot, again losing heat as water evaporates

Question 35

how does reducing the insulating effect of hair or feathers allow endotherms to cool down?

Answer 35

as the body temperature begins to increase, the erector pili muscles in the skin relax- as a result, the hair or feathers of the animal lie flat to the skin, this avoids trapping an insulating layer of air

Question 36

what are the different physiological responses that endotherms have to warm up?

Answer 36

-vasoconstriction -decreased sweating -raising the body hair or feathers -shivering

Question 37

how does vasoconstriction allow endotherms to warm up?

Answer 37

-the arteries near the surface of the skin constrict so very little blood flows through the capillary networks close to the surface of the skin -the skin looks pale and very little radiation takes place as the warm blood is kept well below the surface

Question 38

how does decreased sweating allow endotherms to warm up?

Answer 38

as the core temperature falls, rates of sweating decrease and sweat production will stop entirely, this greatly reduces cooling by the evaporation of water from the surface of the skin

Question 39

how does raising the body hair or feathers of endotherms allow them to warm up?

Answer 39

-as the body temperature falls, the erector pili muscles in the skin contract, pulling the hair or feathers of the animal erect -this traps an insulating layer of air and so reduces cooling through the skin

Question 40

how does shivering allow endotherms to warm up?

Answer 40

-as the core temperature falls the body may begin to shiver -this is the rapid, involuntary contracting and relaxing of the large voluntary muscles in the body -the metabolic heat from the exothermic reactions warm up the body instead of moving it

Question 41

what are some anatomical adaptions that endotherms have to cool them down?

Answer 41

-relatively large SA:V ratio to maximise cooling e.g. large ears -pale fur or feathers to reflect radiation

Question 42

what are some anatomical adaptions that endotherms have to warm them up?

Answer 42

-minimising SA:V ratio to reduce cooling e.g. small ears -thick layers of insulating fat underneath the skin e.g. blubber in whales

Question 43

what are ectotherms?

Answer 43

animals that use their surroundings to warm their bodies

Question 44

why do water dwelling ectotherms not need to thermoregulate?

Answer 44

water has a high specific heat capacity so requires a lot of energy to change temperature so this enables to temperature of the water to stay constant

Question 45

what are the behavioural responses ectotherms have to warm up?

Answer 45

-basking in the sun -conduction, press their bodies against warm ground -exothermic metabolic reactions, vibration of muscles/wings -huddling

Question 46

what are the behavioural responses ectotherms have to cool down?

Answer 46

-shelter from the sun -press bodies against cool earth or stone -wallow in water or mud

Question 47

what are the physiological adaptations of ectotherms?

Answer 47

-dark colours to absorb radiation -alteration of heart rate to increase or decrease metabolic rate -contraction of muscle to cause vibrations (cellular metabolism increases temperature)

Question 48

what are the advantages of ectotherms?

Answer 48

-rate of respiration is slower -less food is needed per day -more energy from food is used for growth -can survive for longer without eating

Question 49

what are the disadvantages of ectotherms?

Answer 49

-less active in cold temperatures due to lower core body temperatures -must have sufficient energy stores to survive cold weather -may need to be inactive and hibernate in cold weather -puts them at risk of predation

Question 50

what are the advantages of endotherms?

Answer 50

-can be active at all times of day/year -core body temperature is kept constant -can live in colder habitats

Question 51

what are the disadvantages of endotherms?

Answer 51

-huge proportion of energy intake is used on temperature regulation -may need to hibernate if food is scarce -less energy from food is used for growth -more food must be eaten in a day