response to stimuli

Question 1

what is a stimulus

Answer 1

a detectable change in the internal or external environment that leads to a response in the organism

Question 2

what are stimuli detected by

Answer 2

receptors which are specific to one type of stimulus

Question 3

role of an effector

Answer 3

produces a response

Question 4

the nervous system sequence of event

Answer 4

stimulus - receptor - coordinator - effector - response

Question 5

what is a taxes

Answer 5

a simple response whose direction is determined by the direction if the stimulus

Question 6

what is a positive taxes

Answer 6

movement towards a stimulus

Question 7

what is a negative stimulus

Answer 7

movement away form a stimulus

Question 8

what is positive phototaxis

Answer 8

movement towards light (single celled algae)

Question 9

what is negative phototaxis

Answer 9

movement away form light (earthworms)

Question 10

what is positive chemotaxis

Answer 10

movement towards high concentrations of glucose

Question 11

what is kineses

Answer 11

an organism changes the speed at which it moves and the rate at which it changes direction

Question 12

kineses in woodlice

Answer 12

when they enter a dry ares their movement becomes more rapid and they change direction often, increasing the chance of moving back into the damp area, once in the damp ares their movement slops and change direction less

Question 13

what is a tropism

Answer 13

the growth of a part of a plant in response to a directional stimulus

Question 14

example of positive photothropism

Answer 14

plant shoots grow towards light

Question 15

example of negative phototropism

Answer 15

plant roots grow away form light

Question 16

example of positive gravitropism

Answer 16

plant roots grow towards gravity

Question 17

example of negative gravitropism

Answer 17

plant shoot grow away form gravity

Question 18

example of a plant growth factor

Answer 18

indoleacetic acid (IAA)
belongs to the group of auxins
controls plant elongation

Question 19

process of phototropism in flowering plants

Answer 19

1. cells in the tip of the shoot produce IAA which is transported down the shoot
2. light causes the movement of IAA from the light side to the shaded side of the shoot
3. a greater conc of IAA builds up on the shaded side
4. the cells on the shades side elongates more causing the shoot tip to bend towards the light

Question 20

effect of IAA in root cells

Answer 20

inhibits cell elongation

Question 21

IAA in roots

Answer 21

more IAA in light light so more cell elongation so more bending away form the light

Question 22

process of gravitropism in flowering plants roots

Answer 22

1. cells in the tip of the root produces IAA which is transported along the root
2. a greater conc of IAA builds up on the lower side as gravity influences the movement of IAA form the upper to the lower side
3. lower side elongates more causeing the root to bend towards the force of gravity

Question 23

process of gravitropism in flowering plants shoots

Answer 23

the greater conc of IAA on the lower side increases cell elongation causing it to grow upwards away form the force of gravity

Question 24

what are the divisions of the nervous system

Answer 24

1. central nervous system (CNS) made up of the brain and spinal cord
2. peripheral nervous system (PNS)

Question 25

what is the peripheral nervous system divided into

Answer 25

1. nervous system which carries nerve impulses form receptors towards the central nervous system
2. motor neurones which carries nerve impulses away form the central nervous system to effectors

Question 26

what is the motor nervous system divided into

Answer 26

1. voluntary nervous system which carries nerve impulses to body muscles
2. autonomic nervous system which carries nerve impulses to glands, smooth muscle and cardic muscle

Question 27

what is the spinal cord

Answer 27

a columm of nervous tissue that runs along the back and lies inside the vertebral column for protection

Question 28

what are the stages of a reflex arc

Answer 28

1. the stimulus ( heat from the hot object)
2. a receptor (temperature receptors in the skin)
3. sensory neurone (passes nerve impulses to the spinal cord)
4. a coordinator (links the sensory neurone to the motor neurone in the spinal cord)
5. motor neurone (carries nerve impulses form the spinal cord to a muscle in the upper arm)
6. an effector (the muscle in the arm which is stimulated to contract)
7. the response (pulling hand away from the hot object )

Question 29

what is the importance of reflex arc

Answer 29

• involuntary so do not require the decision making power of the brain so can carry out more complex response
• protect the body form harm, do not have to be learnt
• fast as the neuron pathway id short
• absence of decision making means the action is rapid