3. receptors

Question 1

specific

Answer 1

detect 1 particular stimulus

Question 2

receptors can be

Answer 2

cells e.g. photoreceptors

proteins e.g. cell surface membranes

Question 3

pacinian corpuscle

Answer 3

detect pressure
found in skin
contain end of sensory neurone
wrapped in layers of connective tissue called lamellae

Question 4

pacinian corpuscle stimulation

Answer 4

stimulated - lamellae deformed and press on sensory nerve ending
sensory neurones cell membrane stretches - stretch-mediated sodium ion channels deformed
channels open +ve sodium ions diffuse in creating generator potential
generator potential reaches threshold = action potential

Question 5

eye

Answer 5

light enters pupil
amount controlled by muscles of iris
focused by lens onto retina (contains photoreceptor cells) foeva area where losts of receptors
nerve impulses carried from retina to brain

Question 6

photoreceptors

Answer 6

light enters hits photoreceptors and absorbed by light sensetive optical pigments
causes chemical change and alters permeability of membrane to sodium
generator potenial if reaches threshold sent along bipolar neurone
which connect photoreceptors to optical nerve

Question 7

rods

Answer 7

found in peripheral parts of retina
black and white
very sensitive (dim light) - many rods join to one neurone. weak action potentials combine to reach threshold
low visual acuity - many rods same neurone 2 points close together cant be told apart
rhodopsin

Question 8

cones

Answer 8

found packed together in fovea
colour
less sensetive (bright light) - one cone joins one neurone
high visual acuity - close together, 1 cone 1 neurone. light from 2 points hit 2 cones both action potenitail - distinguish two seperate points
iodopsin