Receptors Flashcards
pacinian corpuscle
single sensory neurone surrounded by layers (lamallae) of tissue, separated by a gel
found in skin
when pressure is applied
pressure deforms the layers surrounding the neurone
deforms and stretches the membrane of the neurone
stretch mediated sodium ion channels
stretching opens channels and sodium ions diffuse into neurone
influx of Na+ depolarises membrane and generator potential is formed
if threshold is reach, AP passed to brain
heartbeat
myogenic as the contraction is initiated within the muscle itself (SAN)
SAN sends wave of electrical impulses across atria, causing atrial systole
impulse to AVN
delayed to allow atria to fully contract + ventricles to fill
AVN sends impulse down bundle of HIS
ventricles contract from base up- ventricular systole
changing heart rate
controlled by cardioregulatory centre (CRC) in medulla
symp NS- secretes noradrenaline at synapse with SAN
SAN increase frequency of impulses/electrical activity
para NS- secretes acetylcholine at synapse with SAN
SAN decreases frequency of impulses/ electrical activity
chemoreceptors
found in carotid artery and aorta
chemoreceptors- detect changes in pH usually caused by CO2 dissolving to form carbonic acid
during exercise
-increase in muscle activity, more CO2 produced by AR
-lowers blood pH
-detected by chemoreceptors, increase frequency of impulses to CRC
-CRC increases frequency of impulses to SAN via SNS
-SAN increases HR so blood flows to flush co2
barorecptors
pressure receptors which detect changes in blood pressure
blood pressure lower- receptors send more impulses to CRC in medulla, to increase frequency of impulses to SAN via SNS to increase HR
blood pressure higher- receptors send more impulses to CRC, increase frequency of impulses to SAN via PNS to decrease HR
human retina
light receptors - photoreceptors are found at the retina of the eye
include rods and cones
optic nerve- sensory neurone that carries impulse between eye and brain
rods
detect low intensity light so images are in black and white
only one type of rod
more rods than cones
located at periphery of retina + absent at the fovea
rhodopsin
light sensitive pigment in rod cells
bleached (broken down) into retinal and opsin by light energy
can be resynthesises using ATP
re-synthesis takes a long time which is why it is hard to adjust to low light
threshold can be reached even in very low light as it doesn’t need much light energy to be broken down + lots of rod cells connect to single bipolar cell
poor visual acuity
lots of rod cells connect to single bipolar cell
spatial summation of rod cells at one bipolar cell
single set of impulses to brain
brain cannot map contributions of each of rod cells as a part of the image so is blurry
cones
detect high intensity light so less sensitive than cone cells
3 types which view green, blue or red - depending on type of iodopsin
different types (blue green red) sensitive to light of a different wavelength
images seen in colour
concentrated at fovea
iodiopsin
pigment in cone cells
only broken down at high intensities
generates action potential if threshold is reached
high visual acuity
one cone cell connects to one bipolar cell, no spatial summation
separate set of impulses to brain from each cell
brain can map contribution of that cell to a part of an image
distribution of cells
uneven distribution
most cone cells are located near the fovea - directly opposite the lens- as they respond to high light intensities
rod cells are further away as they respond to lower light intensities
blind spot where there are no rod or cone cells
how we see light
light bleaches pigment in photoreceptor cell
triggers an action potential
NT released across the synapse
if there is sufficient NT, depot will occur in bipolar cell + threshold will be reached
act potential generated in bipolar cell
seeing different colour afterimages
certain cone cells eg red and blue are stimulated for a long time
they become exhausted and stop working
afterimage due to green cells now working instead
