topic 8

Question 1

what is a stimulus

Answer 1

any change in the internal or external environment

Question 2

what is a receptor

Answer 2

they detect stimuli

Question 2

what’s an effector

Answer 2

produce responses to stimuli

Question 3

what is the nervous system

Answer 3

send information as electric impulses, made of a complex network of neurones

Question 4

what are the three types of neurones

Answer 4

sensory, motor, relay

Question 5

what do sensory neurones do

Answer 5

transmit electrical signals from receptors to the CNS

Question 6

what do motor neurones do

Answer 6

transmit electrical impulses from the CNS to the effector

Question 7

what do relay neurones do

Answer 7

transmit electrical signals between sensory and motor neurones

Question 8

how are the nervous and hormonal system different

Answer 8

hormonal- chemical, slow, widespread response
nervous- electrical impulses, fast, localised response

Question 9

what are photoreceptors and where are they located

Answer 9

in the eye, they are receptors that react to visual stimuli

Question 10

how do photoreceptors convert light energy into an electric impulse

Answer 10

light enters the eye, hits the photoreceptor and is absorbed by light-sensitive pigments
light bleaches the pigments causing a chemical change, triggering a move impulse along the bipolar nerve

Question 11

name the two types of photoreceptor

Answer 11

rod cell, cone cells

Question 12

what do rod cells do and where are they located

Answer 12

found in the peripheral parts of the retina, only give information in black and white (monochromatic vision)

Question 13

what do cone cells do and where are they located

Answer 13

they are packed together in the fovea, they give information in colour (trichromatic vision)

Question 14

what are the three types of cone cells

Answer 14

red sensitive, blue sensitive, green sensitive

Question 15

what do rod cells when stimulated by light

Answer 15

hyperpolarise

Question 16

what pigment do rod cell contain and what is it made up of

Answer 16

rhodopsin- made of two chemicals joined together- retinal and opsin

Question 17

what happened when its dark

Answer 17

rod cells aren’t stimulated-
sodium ions are pumped out of the cell, diffuses back into the cells through the open channel, this makes the cell slightly negative depolarising it, this releases neurotransmitters, the neurotransmitters inhibit the bipolar neurone, no action potential

Question 18

what happens when its light

Answer 18

rod cells are stimulated-
light breaks apart rhodopsin, this causes the sodium channel to close, sodium ions leave the cell, but can’t diffuse back in, the cell is more negative on the outside making it hyperpolarised, this stops neurotransmitters being released, meaning there’s no inhibition of the bipolar, action potential

Question 19

what is the structure and function of a motor neurone

Answer 19

many short dendrites carry impulses from CNS to cell body, one long axon carries impulses from cell body to effector cells

Question 20

what is the structure and function of a sensory neurone

Answer 20

on long dendron carries impulse from receptor cells to cell body which is located in the centre of the cell, on short axon carries nerve impulses from cell body to CNS

Question 21

what is the structure and function of a relay neurone

Answer 21

many short dendrites carries impulse from sensory neurone to cell body, an axon carries impulse from cell body to motor neurone

Question 22

name the steps of stimulation.

Answer 22

stimulus, depolarisation, depolarisation, hyper polarisation, resting potential

Question 23

what happens when a stimulus is detected

Answer 23

this excites the neurone cell membrane causing sodium ion channels to open. the membrane becomes more permeable to sodium, so sodium ions diffuse into the neurone. making the inside of the neurone less negative

Question 24

what happens at depolarisation

Answer 24

if the potential difference reaches the threshold more sodium ion channels open, more sodium diffuses into the cell

Question 25

what happens at repolarisation

Answer 25

at a potential difference of +30 the sodium ion channels close and potassium ion channels open. this makes the potassium ions diffuse out of the cell returning the membrane to resting potential

Question 26

what is hyper polarisation

Answer 26

potassium ion channels are slow to close, leading to an overshoot where too many potassium ions leave this makes the potential difference to negative

Question 27

how does the membrane return to resting potential

Answer 27

the sodium potassium pump returns it to resting potential

Question 28

how does an action potential move along a wave

Answer 28

as a wave of depolarisation

Question 29

what happens during the refractory period

Answer 29

ion channels are recovering so can’t be opened, the refractory period acts as a time delay between action potentials

Question 30

what are myelinated neurones

Answer 30

neurones with feline sheath

Question 31

what does myeline sheath do

Answer 31

is an electrical insulator, made up of Schwann cells, they cause action potentials to move faster