Vision physiology Flashcards
What is a bareceptor?
a receptor sensitive to changes in pressure, e.g., these can be found in blood vessels and detected changes in blood pressure
What is a mechanoreceptor?
a receptor sensitive to mechanical stimuli such as touch and sound, e.g., Meissner’s Corpuscles
Thermoreceptor?
A receptor sensitive to temperature stimuli, e.g., found in the skin, liver, skeletal msucles etc.
Osmoreceptor
Receptor sensitive to sodium & water water balance levels; osmotic pressure
photoreceptor
receptor sensitive to light stimuli
Nocireceptor
a receptor sensitive to pain stimuli/threatning & dangerous threats
Somatic V Visceral
Somatic; regards external stimuli and responses to such
Visveral; regards internal stimuli and responses to such
somatosensory
relating to sensation, such as pain, temp, etc. which can occur anywhere in the body- in contrast to one localised sense organ, e.g., sight, balance, taste
Viscera
refers to internal body cavities and their organs, such as the guts within the abdomen
papillae
small structures (bumps) on the upper surface of the tongue which gives the muscle its characteristic rough texture/ they contain our taste buds and therefore vital in our perception of taste.
Meissner’s Corpuscles
cutaneous (relating to/affecting the skin) never ending responsible for transmitting the sensations of fine, discriminative touch and vibration.
Gustatory
concerned with tasting/the sense of taste, e.g., gustatory cells = taste cells
Olfactory
concerned with the sense of smell, e.g., olfactory cells
Lacrimal
this is a (tear-shaped) gland which has the primary function of secreting tears (fluid) onto the surface of the eyeball
Conjunctivae
a thin mucous membrane which provides the eye protection via its production of both mucus and tears. It lines the inside of the eyelids and provides a covering to the sclera
Sensory receptor
a structure which reacts to a physical stimulus in the environment, whether internal or external. The sensory nerve ending receives information, such as a stimulus, and conducts a process of generating nerve impulses to be transmitted to the brain for interpretation
Nerve impulse
an electrical signal that travels along a nerve fibre in response to a stimulus, and serves to transmit a record of sensation from a receptor or an instruction to act as an effector
Neurone
a nerve cell
Receptive field
a specific region of sensory space in which an appropriate stimulus can drive an electrical response in a sensory neurone
Nerve fibre
a long, slender projection of a neurone (nerve cell) which typically conducts electrical impulses (action potentials) away from one neurone’s cell body to the next
Adaption (of sensory neurones)
the decline of the electric responses of a receptor neurone over time in spite of the continued presence of an appropriated stimulus of constant strength. e.g., not being aware of the sensation of our clothes on our skin, or background noise in a room we’ve been in for a period of time
What section of the brain is smell translated
temporal lobe; which is also associated with memory and emotion
where are receptor cells for smell (olfactory cells) located?
olfactory nasal epithelium
Three processes involved in formation of an image of the retina
1.) refraction or bending of light rays
2.) formation of an inverted image on the retina for the brain to convert
3.) adjustments for close vision (accomodation)
Conjuntivitis
- eye condition caused by allrgies or infection
- also known as pink eye
- usualluy affects both eyes
- redness, swelling, gritty sensation
- not contagious if caused by allergies
Cataract
when lens develops cloudy patches which become bigger and interfere with eyesight. older people likely to experience this
Myopia
short-sightedness. usually develops in kids 6-13
can get worse but stabalises when eye stops growing around age 20
hyperopia/hypermetropia (long-sightedness)
typically affects adults over age 40 but can affect anyone
astigamatism
- where eye is shaped more like a rugby ball than football
- blurred vision, eye strains, headaches
- common alongside myopia/hypermetropia
- may cause a lazy eye
- early identification is key for treatment
amblyopia (lazy eye)
- childhood condition where vision does not develop properly
- most common cause is imbalance in muscles which position the eyes (hence off-centred appearance)
- eyes are therefore prevented from wokring completely together
two types of photoreceptors
Cones; less sensitive than rods and therefore play a bigger role in our daytime vision. responsible for colour vision
Rods; due to their sensitivity, therefore work more in nightvision and are responsible for black and white vision
what is rhodopsin
a protein packed within rod and cone photoreceptors on the retina which is critical for light activation of rods
what vitamin is vital for vision?
vitamin A- which is necessary for rhodopsin and rods to do their job efficiently. where there is a deficiency in Vit A, nightvision would be greatly affected (negatively)
what is the macula lutea (fovea)
a (yellow) area of the retina responsible for sharp, detailed, central vision (also called visual aucity). here there is a high concentration of cones.
Gluacoma
where increased pressure within the eye can damage the optic nerve and therefore inhibit vision. e.g., the drainage system of aqueous humour is not working and compressing the vessels.
Visionretinopathy
prolonged exposure to high blood glucose (sugar) levels in the eye’s blood vessels, often because of uncontrolled diabetes
Macular Degeneration
A common age-related (50s & 60s) condition in which the middle part of one’s vision is affected. It does not cause total blindness but can make everyday activities such as reading and recognising faces difficult.
What is presbyopia?
the gradual loss of the eyes’ ability to focus on nearby objects. it is common as we age.
what part of the eye is affected with macular degeneration?
The macula lutea, which is located at the centre of the retina and in line with the pupil. degeneration of photoreceptors here means that central vision is blurry & obscured.
