Chap 12 Flashcards
Sensory receptors
The nerve endings in cells that detect sensory information
•initiate neural impulses
- Different forms of energy stimulate the receptors
Sensation
Occurs when the neural impulses arrive at the cerebral cortex.
Ex) Face may detect warmth of a beam of sunlight and feel the warmth on at cheek
Perception
Each person has a UNIQUE perception.
-cerebral cortex interprets the meaning of the sensory information
Sensory adaptation
When the BRAIN filters out insignificant or REDUNDANT info.
• ex) sensory adaptation has occurred when you gone out clock ticking
Sensory receptors
Are specialized cells or neuron endings that detect specific stimulus.
Humans have 4 categories of receptors
•transduce, convert a form of NRG into electrochemical NRG
1) photoreceptors
Light stimulates this receptor.
•Eyes contains rods and cones in order to see and absorb light
-colours and shades
[damage: loss of associated sense]
2) Chemoreceptors
Stimulated by certain chemicals
-tongue: contains TASTEBUDS that detect various particles in food
3) Mechanoreceptors
Respond to mechanical forces from same form of pressure
•ex) hair cells in inner ear are activated by vibration of sound waves
•SKIN =pain, pressure and light touch
4) Thermoreceptors
In SKIN: detects heat and cold
Human eye: 3 layers
- external
- intermediate
- internal
External eye layer
Sclera and cornea
Sclera
External
•white of the eye/ touch and fibrous protective layer
cornea
LIGHT enters the eye
•clear/transparent dome of the eye
Intermediate layer of eye
Choroid
Iris
Pupil
Choroid
Intermediate
•ABSORBS stray light rays that ARENT detected by photoreceptors
•blood vessels= nourish eye
Iris
Front
Choroid forms DONUT shaped coloured iris
•allows light to enter via pupil
Pupil
Iris contains dark pupil
•dilated/expands
Adaptation
Light conditions
Ex) turning off lights, eyes adjust
Internal layer of eye
Ciliary muscles Retina Rods Cones Optic nerve fovea centralis
Ciliary muscle
Thickened choroid extending
•attaches to lens, focusing images on retina
Retina
Internal
•thin layer of tissue that contains photoreceptors (rod/cone)
Rods
Sensitive to light intensity
(Black and white)
-more than cones
Peripheral
Cones
Are sensitive to different colours
•pack most densely at back of eye
(FOVEA)
Optic nerve
Connects to brain and sends impulses from cones and rods
Suspensory ligaments
Attached to ciliary muscle and lens
1) anterior chamber
2) posterior chamber
1) aqueous humour
Clear fluid in antechamber
•maintains SHAPE of cornea and provides o2+nutrients
Glaucoma
Excess liquid builds up, ducts become plugged
•delicate blood vessels rupture
•cells of eye deteriorate due to lack of oxygen and nutrient
*BLINDNESS
2) vitreous humour
Clear jelly fluid in posterior chamber
•maintains shape of eyeball and supports surrounding cells
Focussing
Lens focussed light in particular direction
-rounded lens: ciliary contract suspensory relax
NEAR
-flattened lens: ciliary relax suspensory taut
FAR
Accommodation
Ability for lens to change shape in order to focus images clearly on retina
•reflex
•muscle fatigue~excess contraction or eye strain
Cataracts
Lens ages/protein structure degenerate
•grey/white spots form on lens
-surgically treated
Astigmatism
Inheritable condition impacting eyes FOCUS ability
•due to uneven curvature in cornea (blurry)
Myopia
Nearsighted people
•no trouble seeing CLOSE but not far
•elongated eyeball
-light in front of retina and not on
Hypermyopia
Common FARSIGHTED
•no trouble seeing FAR but not close
•shortened eyeball
•light doesn’t meet retina, focuses behind
Fovea centralis
Back of eye
-cones densely packed
Colour blindness
Deficiency in cones
(Red, green and blue)
More male
Blind spot
Ganglion cells merge to form optic nerve.
•areas do not contain photoreceptors
~incapable of detecting light
Binocular vision
3D
