Lab 6 - Sensory Receptors

The five main senses

sight, hearing, taste, smell, touch

Additional sensory modalities

temperature, pain, vibration, joint position, proprioreception

Sense

a system that consists of a sensory cell type that correspond to a defined region within the brain where signals are received and intercepted

Adaptation

process by which a sensory system becomes insensitive to a continuing stimulation

nocirecptors

pain receptors

Vision

the ability to detect electromagnetic energy

visible range of electromagnetic energy in humans

380 nm to 750 nm

Other animals with different ranges of vision

insects - can see further into the UV then humans

snakes - have organs that allow them to see infrared energy

Cones

cells responsible for color differentiation; found predominantly in the fovea

Rods

cells responsible for contrast resolution; not found in the fovea, but distributed evenly throughout rest of retina

optic disc

where the nerves and retinal blood vessels enter the eye; no rods or cones here leading to a blind spot

Why we see color

eyes have three sets of cones with peak sensitivities at different wavelengths (red at 564, green at 534, and blue at 420 nm); light at any wavelength in the visible range will excite one or more of these receptors; our perception of color is determined by extent of which receptors are activated

accommodation

eyes can change focus to accommodate for near or far vision by varying the shape of the lens

achromotopsia

rare condition where you cannot see ANY color and can only see in shades of gray, associated with lazy eyes, nystagmus(small, jerky eye movements), severe light sensitivity, and extremely poor vision

genetic element of color blindness

typically X-linked but has been found that mutations causing colorblindness are fond on at least 19 different chromosomes and 56 different genes

Protan

defect in red cone

protanomaly

a problem with red cones

protanopia

a complete red cone deficiency

deutan

a defect in the green cones

deutanomaly

a problem with green cones

deutanopia

a complete deficiency in green cones

tritan

a defect in blue cones

tritanopia

a complete deficiency in blue cones (tritanomaly does not exist)

hearing

the sense of sound perception

why we hear

tiny hair fibers in inner ear detect motion from the membrane (ear drum) which vibrates in response to changes in pressure

hearing range in humans

perfect hearing is 20-20000 Hz

other ways to detect sound

vibrations through the body by tactition; only way lower and higher frequency sounds can be heard

equilibrioreception

perception of balance by the vestibular system in the inner ear

semicircular canals filled with endolymph

responsible for detecting rotary movements of the head; each ampulla contains a receptor apparatus called a crista appulluris which consists of a gelatinous wedge shaped structure that blocks ampulla and prevents flow of endolymph; cilia of receptors cells are embedded in this gel and when the head moves, the gel moves, and the cilia bend relaying that the head has moved

utricle and saccule

detect linear acceleration and effects of gravity; each have ototlith organs; cilia of receptor cells are embedded in a gel containing calcium carbonate cyrstals called octontia; weigh of octonia allows detection of gravitational forces

audiometer

piece of equipment that generates sounds at selected frequencies and intensities

Romberg’s test

a test designed to test a person’s balance

Touch

the sense of pressure perception; several types of specialized cells are found in the skin, muscle and viscera; different intensities and pressure are detected by different cells

thermoception

the sense of heat and cold

cold receptors

activated at lower than 37 degrees C

warm receptors

activated from 37-45 degrees celsius

sensing freezing or hot temperatures

above 45 degrees C, nocireceptors are activated; body will adapt between 20 and 40 degrees celsius, but above or below we will not adapt to prevent injury due to prolonged exposure

homeostatic thermoreceptors

detect the internal body temperature; found need the hypothalamus in the brain