receptors Flashcards
(37 cards)
what are receptors
group of specialised cells that detects a specific stimulus and generates a response
how do receptors work
specific stimulus causes depolarisation of membrane potential producing generator potential
the more intense the stimulus, the larger the generator potential, the more frequent the action potentials
if membrane potential exceeds threshold value, action potential is generated
often part of sensory neurones / associated with them
what is a mechanoreceptor
receptor that responds to mechanical pressure
what type of receptor are pacinian corpuscles
mechanoreceptor
where are pacinian corpuscles found
skin, especially in the fingers, soles of the feet, and genitalia
what are stretch mediated sodium channels
sodium channels that only open when enough pressure is applied
describe the structure of the pacinian corpuscles
made of many layers of membrane or connective tissue separated by gel containing sodium ions
how is a generator potential produced once pressure has been applied to parcinian corpuscles
layers of membrane becomedistortedand stretch-mediated sodium channelsin axon membraneopen
influx of sodium ions into axon via facilitated diffusion causes depolarisation
what are the parcinian corpuscles like at rest
stretch mediated channels closed
inside of neurone negatively charged
why are parcinian corpuscles important
convert mechanical stimulus (pressure) into electrical impulse which the nervous system can process → nervous transmission for survival and response
what receptors are in the eye
photoreceptors
what are the two types of receptors in the eye and where are they found
rods on the periphery of the retina
cones in the fovea
what pigment is in rod cells
rhodpsin
how is an action potential generated in rod cells
when light hits rhodopsin it breaks down (bleaches)
generator potential triggered
if potential large enough action potential generated
what is the journey of impulses from the receptor along the CNS
photoreceptor -> bipolar neurone -> optic nerve -> brain
what is retinal convergence in relation to rod cells
spatial summation of multiple rod cells forming a synapse with 1 bipolar neurone
why is spatial summation required for rod cells
individual small generator potentials combined to produce larger potential that may reach threshold for action potential
why do rod cells have low visual acuity
rod cells are very sensitive to low light but because many rods feed into one bipolar neurone, brain can’t tell which specific rod was stimulate
what pigment is found in cone cells
three types of iodopsin
red, green and blue sensitive
how do we see in full colour vision with only three types of cone cells
light enters eye stimulating different cone cells depending on wavelength
brain interprets colour according to proportion of type of cone stimulated
what is colour blindness
where a person lacks one or more types of cone cells, or iodopsin pigment is dysfunctional
how is colour blindness inherited
genetic, usually sex linked disorder -> more common in males
how do people have red green colour blindness
caused by faulty or missing red or green cone cells so person cannot distinguish between red and green shades
what is visual acuity
sharpness of vision and ability to distinguish between two close objects
