receptors Flashcards
what are the 2 different types of receptors
1) cells - cells that connect to the nervous system
2) proteins on cell surface membranes
what are Pacinian corpuscles, what do they detect and where are they found
mechanoreceptors that detect mechanical stimuli such as pressure and vibrations, found in your skin
what is lamellae
connective tissue that surround the sensory nerve ending that’s in the centre of the Pacinian corpuscle
what happens when the Pacinian corpuscle is stimulated
the lamellae are deformed and press on the sensory nerve ending, this deforms the stretch-mediated sodium ions channels, the channels open and sodium ions diffuse into the cell which creates an action potential if its big enough to reach the threshold
what controls how much light enters the eye
controlled by the muscles of the iris
how are the light rays focused
by the lens onto the retina which contains the photoreceptor cells which detect light
what is the fovea
an area of the retina which contains lots of photoreceptors
how are the nerve impulses carried from the retina to the brain
by the optic nerve
what is the area called where the optic nerve leaves the eye
the blind spot - there are no photoreceptor cells here so its not sensitive to light
how do photoreceptors convert light into electrical impulses (steps)
1) light enters the eye and hits the photoreceptors and is absorbed by light-sensitive pigments
2) light bleaches the pigment which causes a chemical change and alters the membrane permeability to sodium ions
3) a generator potential is created and If it reaches the threshold a nerve impulse is sent along the bipolar neurone - bipolar neurones connect the photoreceptors to the optic nerve which takes the impulse to the brain
what 2 types of photoreceptors does the human eye have, what are their properties and where are they found
1) rods - found in the peripheral parts of the retina, only give information in black and white (monochromatic vision)
2) cones - found packed together in the fovea, give information in colour (trichromatic vision)
what 3 types of optical pigment does the cone have
1) red sensitive
2) green sensitive
3) blue sensitive
when they’re stimulated in different proportions you see different colours
what are the different optical pigments in the eye sensitive to
different wavelengths of light
why do rods work better in dim light
because many rods join one neurone, so many weak action potentials combine together to reach the threshold and trigger an action potential
why do cones work better in bright light
cones are less sensitive than rods so they work better in bright light, this is because one cone joins one neurone so it takes more light to reach the threshold and trigger an action potential
