the senses Flashcards
types of sensory receptors
chemoreceptors
mechanoreceptors
photoreceptors
thermoreceptors
nociceptors
name some diseases that affect the eye
Diabetic retinopathy
Age Related Macular Degeneration
Cataracts
Colour blindness
Night blindness
Dry eye
Glaucoma
Retinal Detachment
Allergic conjunctivitis
Viral, fungal and bacterial infections of the eye
Cancers of the eye: Retinoblastoma
Genetical conditions: Retinitis pigmentosa
the two main areas of sensory physiology
sensation
sensory perception(how the signals are interpreted)
sensation is a physiovhemical process and perception is a psycological process
functions of the thalamus
Relay Station for Sensory Information
sensory integration
helps regulate sleep and consciousness
the three concentric layers of the eye body
Fibrous Tunic (Outer Layer): cornea, sclera
Vascular Tunic (Middle Layer): iris, ciliary body, choroid
Nervous Tunic (Inner Layer or Retina): retina, macula, optic disk
note that each of these layers has components of it’s own that contribute to eye function
function of the ciliary muscle
changes lens shape by relaxing/contracting muscle
the central point of the retina
FOVEA
part of the eye that contains photoreceptors
retina
cataracts
the clouding of the lens in the eye, leading to a decrease in vision quality
how many smooth muscles does the iris have, name them
2
Inner circular muscle (involved in constriction)
Outer radial muscle (involved in dilation)
the cells in the iris that determine the colour of the iris are called?
melanocytes
what happens during the parasympathetic and sympathetic stimulations of the cilary muscle
parasympathetic stimulation leads to ciliary muscle contraction, which facilitates accommodation for near vision(like reading), while sympathetic stimulation results in ciliary muscle relaxation, adapting the eye for distance vision
note that c.muscle contraction affects the suspensory ligaments
the two main types of of photoreceptors in the retina
cones(3 types of that) and rods(1 type of that)
the lens is more flattened in near vision and more rounded in distance vision, true or false
false
what happens to the suspensory ligaments attached to the lens as the ciliary muscle contracts and vice-versa?
they relax during c. muscle contraction and contract during it’s relaxation
how is the pupil reflex test important
Can be used to assess Integrity of sensory and motor function of the eye
when carried out…: both pupils constrict regardless of which eye is being stimulated
how many layers of neurons does the retina contain, name them
3
Inner layer (contains neurons called ganglion cells)
Middle layer (contains neurons called bipolar cells)
Outer layer (contains photoreceptors: rods + cones)
the retina layers are in reverse order, true or false
note that this means Light has to Pass Through Inner & Middle Layers and blood vessels before reaching the photoreceptors
true
outline some differences between rods and cones
photoreceptors in the retina
responsible for black and white vision while responsible for colour vision
Highest Conc. periphery of retina while Highest Conc. fovea
Low Visual Acuity while High Visual Acuity
Convergence with Bipolar cell: High while Convergence with Bipolar cell: Low
High Sensitivity while Low Sensitivity
low light conditions while high light conditions
which photoreceptor is stimulated in low light conditions
rod
rhodopsin
a light-sensitive pigment in the rods of the retina, crucial for low-light vision
the two components of rhodopsin
Rhodopsin consists of a protein called opsin and a light-absorbing molecule called retinal
remember that cones are photoreceptors
the three types of photopigments in cones
Cone Red Light
Cone Green Light
Cone Blue Light
rhodopsin is not destroyed by bright light, is this true?
no, it is
is rhodopsin regenerable
yes
rubin’s vase
an optical illusion that depicts either a vase or two faces in profile, depending on how one perceives the image. It was created by the Danish psychologist Edgar Rubin in 1915.
before light strikes the back of the retina, it is modified in two ways, outline these 2 ways
the light is first modulated by the pupils
Process where lens changes shape to adjust refractive power so image is focussed on retina (this is known as accomodation)
the modulation of pupil size helps optimize vision in different lighting environments.
the mechanism of accomodation is reliant on the sympathetic nervous system, true or false
note that accomodation is when the lens of the eye can change its shape to focus on objects at different distances
false, it is reliant on the parasympathetic nervous system
for distant vision, is there a parasympathetic stimulation of the ciliary muscle?
no
note that for near vision, this statement would be right
cones are photoreceptors
high stimulus levels are required to use the cones , true or false
true
the role of convergence of signals from rods in the detection of low light
convergence is the coordinated movement of both eyes inward, towards each other, to focus on a near object.
COnvergence allows multiple rod cells to synapse onto a single bipolar cell, which then transmits the signal to ganglion cells and eventually to the brain. This pooling of signals increases the likelihood of detecting a weak stimulus, enhancing the sensitivity of the visual system in dim light.
rhodospin bleaching
the process where light breaks down rhodopsin pigment in the eye, leading to temporary vision loss.
the largest component of the eye, and what is it filled with
vitreous chamber
the vitreous humor (a gel-like substance)
outline the spectral properties of the three types of cones
cone blue lights have a short wavelength
cone green lights have a medium wavelength
cone red lights have a long wavelength
tritanopia
type of color vision deficiency, often referred to as blue-yellow color blindness.
Individuals with tritanopia have difficulty distinguishing between shades of blue and green, as well as between yellow and red. This condition is caused by a malfunction or absence of the S-cone photoreceptors in the retina, which are responsible for perceiving short-wavelength light, primarily blue hues.
deuteranopia
a form of color vision deficiency, commonly known as red-green color blindness.
individuals with deuteranopia have difficulty distinguishing between shades of red and green. This condition is caused by the malfunction or absence of M-cone photoreceptors in the retina, which are responsible for perceiving medium-wavelength light, particularly green hues
protanopia
a type of color vision deficiency, commonly referred to as red-blindness
Individuals with protanopia have difficulty perceiving red hues due to the absence or malfunction of L-cone photoreceptors in the retina, which are responsible for perceiving long-wavelength light, particularly red hues
