Special Senses Lecture 1 Flashcards
What are receptors in the senses characterized by?
The type of energy used to activate them
What do Mechanoreceptors recognize?
Hearing, balance and touch
What do Thermoreceptors recognize?
Temperature
What do Chemoreceptors recognize?
Taste and smell
What do Photoreceptors recognize?
Vision
What do Osmoreceptors recognize?
Osmolarity of body fluids
What do Nociceptors recognize?
Pain
What occurs in sensory perception?
Energy from the outside world is converted in to a form that the body can understand: Electrochemical
What is the Adequate Stimulus?
When sensory endings respond to a particular type of energy applied to them
What is Primary Transduction Process?
When energy applied to a sensory receptor is converted into electrochemical energy
What is involved in the Primary Transduction process of the Visual system?
Photons of light are converted to a change in membrane potential
What is involved in the Primary Transduction process of the Hearing system?
Air pressure waves in air is converted to the bending of hair
What is a Generator Potential?
A non-propagated, graded potential that is usually depolarizing and recorded from a sensory nerve
What is the magnitude of a generator potential propotional to?
The strength of the stimulus
What is do we need to know to determine how many stimuli can be discriminated?
The range of the sensory system
What is the range in wavelength that humans can detect light?
Between 390 and 700 nm
What is the Sclera?
The tough white fibrous part of the eye
What is the Cornea?
The clear covering of the eye
What is a Conjunctiva?
A thin protective membrane covering the eye
What is the Cornea continuous with?
The sclera
What is the most important part of the light focusing power of the eye?
The Cornea
What is the Cornea important for?
Light focusing power of the eye
What sits behind the Cornea?
The Anterior Chamber
What is the Anterior Chamber filled with?
Aqueous humor
What is the Aqueous Humor secreted by?
The ciliary body
What is the Aqueous Humor drained by?
The Canal of Schlemm
Where is Aqueous Humor found?
The Anterior and Posterior chambers
What sits immediately behind the Anterior Chamber?
The Crystalline Lens
What is the shape of the surface of the Crystalline lens?
It is convex
What does the fluid filled anterior chamber allow for?
The cornea to act as a unit
What is behind the lens?
A chamber called the Vitreous chamber
What is the Vitreous chamber filled with?
A gelatinous substance called Vitreous Humor
What is the function of Vitreous Humor?
Maintain the shape of the eye
What is at the back of the eye?
The Retina
What does the Retina contain layers of?
- Receptor cells (rods and cones)
* Processing cells (bipolar, amacrine and ganglion cells)
What is behind the Retina?
The Choroid Layer
What is the Choroid layer?
A layer of pigment cells that contain melanin
What is the passage of light starting from the cornea?
Cornea Anterior Chamber Pupil Lens Vitreous Chamber Retina
What is the function of the Choroid?
To absorb pigment
What is Accommodation?
The process by which the curvature of the lens is increased
When does Accomodation occur?
During near vision
Which curvature of the lens is most affected during Accomodation?
The anterior curvature of the lens
What is the lens held in place by?
Suspensory ligaments
What are the Suspensory ligaments of the eye attached to?
A sphincter like muscle called the ciliary muscle
What flattens the lens of the eye?
The ciliary muscle being relaxed and tension of suspensory ligaments is increased
What must the shape of the lens be for distance vision?
Flat
What causes the lens to be rounder and thicker?
Contraction of the ciliary muscle and the tension of the ligaments is reduced
When is the eye set for close vision?
When the eye is rounder and thicker
What is Refraction?
The deflection from a straight path undergone by a light ray in passing obliquely from one medium to another
What is the Focal Distance?
The distance from the refractive surface to the point where parallel light rays converge
What does the reciprocal of the focal distance give?
the diopter
What is the Diopter?
The reciprocal of the focal distance that tells the refractive power
What is Myopia?
Nearsightedness
What is the cause of Myopia?
The eye is too long
What is Hyperopia?
Farsightedness
What is the cause of Hyperopia?
The eye is too short
What is Presbyopia?
A stiff lens due to age
What is an Astigmatism?
When the corneal surface is more curved in one plane than an another causing a difference in refraction between the two planes
What fixes a Myopia?
A Negative (concave) lens
What fixes Hyperopia?
A positive (convex) lens
How is an Astigmatism fixed?
With cylindrical shaped lenses which focuses light into a line instead of a point
