Section 6: Coordination and Response

Question 1

what is a stimulus?

Answer 1

a change to the internal or external environment

Question 2

what are receptors?

Answer 2

receptors detect stimuli

Question 3

what do receptors in the sense organs detect?

Answer 3

external stimuli

Question 4

what do effectors do?

Answer 4

they bring about a response to stimuli

Question 5

how do muscle cells (effectors) respond to stimuli?

Answer 5

they contract

Question 6

how do glands (effectors) respond to stimuli?

Answer 6

they secrete hormones

Question 7

how do receptors communicate with effectors?

Answer 7

via the nervous system the hormonal system or both

Question 8

what are the three types of neurones?

Answer 8

sensory neurones, relay neurones, motor neurones

Question 9

what does the central nervous system (the CNS) consist of?

Answer 9

the brain and the spinal cord

Question 10

what happens when receptors in a sense organ detect a stimulus?

Answer 10

they send electrical impulses along sensory neurones to the CNS

Question 11

how does the CNS react to receiving electrical impulses along sensory neurones in the sense organs when a stimulus has been detected?

Answer 11

the CNS sends electrical impulses to an effector along a motor neurone - the effector then reacts accordingly

Question 12

what do coordinated responses always require?

Answer 12

a stimulus, a receptor and an effector

Question 13

why are the responses coordinated by the nervous system so quick?

Answer 13

because neurones transmit information using high speed electrical impulses

Question 14

why are reflexes useful?

Answer 14

they help to prevent injury

Question 15

what is the route from receptor to effector known as?

Answer 15

the reflex arc

Question 16

what is the flow chart for a reflex arc?

Answer 16

stimulus –> receptor –> sensory neurone –> relay neurone –> motor neurone –> effector –> response

Question 17

what is the role of the conjunctiva in the eye?

Answer 17

lubricates and protects the surface of the eye

Question 18

what does the cornea do? how does it receive oxygen?

Answer 18

refracts light into the eye. Transparent and has no blood vessels to supply it with oxygen so oxygen diffuses in from the outer surface

Question 19

what is the role of the iris?

Answer 19

controls the diameter of the pupil, and therefore how much light enters the eye

Question 20

what does the lens do?

Answer 20

focuses the light onto the retina (the light sensitive part- covered in light-sensitive receptors called rods and cones)

Question 21

when are rods useful?

Answer 21

rods are more sensitive in dim light but can’t see colour

Question 22

what are cones useful for?

Answer 22

sensitive to colours but aren’t good in dim light

Question 23

where are cones found in the eye?

Answer 23

all over the retina but mainly at the fovea

Question 24

what is the role of the optic nerve in the eye?

Answer 24

carries impulses from the light receptors in the eye to the brain

Question 25

hormone INSULIN:

• role?
• secreted from…?
• effects?

Answer 25

• helps control blood sugar level
• secreted from the pancreas
• stimulates the liver to turn glucose to glycogen for storage

Question 26

hormone: TESTOSTERONE:
- role?
- source?
- effects?

Answer 26

• main male sex hormone
• testes
• promotes male secondary sexual characteristics

Question 27

hormone: PROGESTERONE
- role?
- source?
- effects?

Answer 27

• supports pregnancy
• ovaries
• maintains the uterus lining

Question 28

hormone: OESTROGEN:
- role?
- source?
- effects?

Answer 28

• main female sex hormone
• ovaries
• controls the menstrual cycle and promotes secondary sexual characteristics

Question 29

what are three differences between nervous and hormonal responses?

Answer 29

nerves: very fast message, act for a very short time, act on a very precise area
hormones: slower message, act for a long time, act in a more general way

Question 30

what is homeostasis?

Answer 30

the maintenance of a constant internal environment

Question 31

what is the optimum temperature for the body’s enzymes?

Answer 31

about 37 degrees

Question 32

why can organisms with bigger surface area to volume ratios gain or lose heat faster?

Answer 32

because there is more area for the heat to transfer across

Question 33

why do animals living in cold conditions have a compact shape?

Answer 33

to keep there surface area to a minimum, reducing heat loss

Question 34

what are plant’s growth hormones called?

Answer 34

auxins

Question 35

where are auxins found in the plant?

Answer 35

in the tips of shoots and roots

Question 36

what are three ways plants respond to changes in their environment?

Answer 36

• they sense the direction of light and grow towards it to maximise light absorption for photosynthesis (PHOTOSYTHESIS)
• they can sense gravity, so their roots and shorts grow in the right direction (GEOTROPISM)
• climbing plants have a sense of touch so they can find things to climb and reach the sunlight

Question 37

how does positive phototropism occur in plants?

Answer 37

when a shoot tip is exposed to light it accumulates more auxin on the side that’s in the shade than the side that’s in the light. This makes the cells grow faster on the shaded side so the shoot bends towards the light

Question 38

how does negative geotropism occur in plant’s shoots?

Answer 38

when a shoot is growing sideways gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side. This causes the lower side to grow faster, bending the shoot upwards

Question 39

how are roots positively geotropic?

Answer 39

a root growing sideways will also have more auxin on its lower side - but