CHAPTER 6: THE EYE Flashcards
What is sensation?
Involves cells in the nervous system that are specialized to detect stimuli from the environment.
What is perception?
Conscious experience and interpretation of information from the senses.
What allows the eye to detect light stimuli?
photoreceptors in the eye
What wavelength of electromagnetic radiation is visible to us?
between 380 nm and 760 nm.
What wavelength of electromagnetic radiation is visible to us?
between 380 nm and 760 nm.
What is hue?
dominant wavelength
What is brightness?
intensity
What is saturation?
purity
At what speed does light travel?
300 000km per second
Slower oscillations= ….. wavelengths?
longer
What happens if the radiation contains all visible wavelength ?
no sensation of hue, appears white.
What is a sensory receptor?
- specialized neuron
- detects a particular category of physical events
What is sensory transduction?
process by which sensory stimuli are transduced into slow, graded receptor potentials-
What is a receptor potential?
-Slow- graded electrical potential produced by a receptor cell in response to a physical stimuli
What part of the eye must the image be focused on?
- the retina
- focus is aided by bones and muscles surrounding the eye.
What are the eyes suspended in ?
the orbits
How is the eye help in place and moved?
-by extraocular muscles attached to the sclera
What are the conjunctiva?
mucous membranes that line the eyelid and fold back to attach to the eye.
What is responsible for regulating the amount of light entering the eye?
pupils
What is responsible for accomodation?
- the lens
- control by ciliary muscles
What are the three cellular layers of the retina?
From BACK to FRONT:
- photoreceptive (rods and cones)
- bipolar cells
- ganglion cells
Are there more rods or cones in the retina?
more rods than cones
What are rods responsible for?
-low intensity light vision
What are cones responsible for?
acuity, colour vision, daytime vision
What is the fovea?
- central region of the retina
- contains only cones
- most acute vision.
What is the optic disk?
- back of the eye
- no receptors
- blind spot
- exit point of axons
What is transduction?
- process by which energy from the environment is converted to a change in membrane potential in a neuron
- converts external stimuli into internal stimuli
What are photopigments?
- responsible for transduction
- embedded in lamella (layer of membrane)
- consist of an opsin and a retinal.
How many photopigments a rod contain?
10 million
What is a receptive field?
place a visual stimulus must be located to produce a response in a neuron
What does the location of the receptive field of a particular neuron depend on?
location of photoreceptors that provide it with visual information.
What are vergence movements ?
cooperative movement that keep eyes both on the same target.
What are saccadic movements?
shift of gaze abruptly from one point to another
What are pursuit movements?
movement that eyes make to maintain an image of a moving object on the fovea.
What are pursuit movements?
movement that eyes make to maintain an image of a moving object on the fovea.
What are the optic nerves?
- back of the eye
- bundles of axons of ganglion cells
- convey info to dorsal lateral geniculate nucleus (LGN)
- join together at base of brain to form optic chiasm
What are the main steps of the visual pathway?
- photoreceptors of the retina
- info sent to rest of brain via optic nerves to LGN
- neurons in LGN send axons to primary visual cortex
- info sent to visual association cortex
