PERCEPTION TO STIMULI a.3 SL/HL Biology

SKILL: LABEL A DIAGRAM OF THE HUMAN EYE

RECEPTORS DETECT CHANGES
Pain receptors are a type of chemoreceptor that respond to chemicals released by damaged tissues!!
Olfactory receptors respond to smell because of molecules released into the air! Some people can detect smells that others cannot because of our unique DNA.

RODS AND CONES
Photoreceptors located in the retina of the eye
Rods: respond to dim light; give us black and white vision
Cones: respond to bright light; give us color vision

SKILL: ANNOTATE A DIAGRAM OF THE RETINA

ANNOTATING THE DIAGRAM OF THE RETINA:
Rod Cells: photoreceptors sensitive to dim light (black and white)
Cone Cells: photoreceptors activated by bright light (color)
Bipolar neurons: cells in the retina that carry impulses from a rod or cone to a ganglion cell of the optic nerve
Ganglion cells: synapse (connect) with the bipolar neurons and send impulses to the brain via the optic nerve

RED-GREEN COLOR BLINDNESS
Normal vision uses three cones: red, green, blue (“Trichromatic vision“)
Some individiuals are dichromatic and have red-green color blindness.
 Sex-linked trait: sons inherit the defect from their mother
 Very rare for female to have this trait
Can be caused by the presence of blue and green cones with NO red cones (red-blindness) OR by blue and red cones with NO green cones (green-blindness).
Test 1 Test 2

FIELD OF VISION
Remember: information from the RIGHT field of vision from BOTH eyes is sent to the LEFT part of the visual cortex (and vice versa)
Both eyes send information to both sides of the brain
How does this work? Are images upside down?

SKILL: LABEL A DIAGRAM OF THE HUMAN EAR

HOW IS SOUND PERCEIVED?
>>The ear is an example of a mechanoreceptor in action! Air vibrations are converted to action potentials.
1.
Sound waves are vibrations of air molecules detected by the pinna
2.
This causes ear drum vibrations (pressure changes)
3.
Structures in the middle ear are stimulated; transmit and amplify sound by 20x
4.
Oval window transmits vibrations from middle ear bones to cochlea
5.
Fluid causes tiny hairs in cochlea to act as receptors for individual wavelengths of sound
6.
The tiny hairs (mechanoreceptors) release a chemical neurotransmitter to the auditory nerve
7.
Vibrations are transformed into nerve impulses; stimulate the sensory nerve and transmit to the brain
8.
The round window releases pressure so fluid in the cochlea can vibrate

HOW GOOD IS YOUR HEARING?
How do we perceive sound?
The Ultimate Hearing Test

WHAT’S WITH THESE TINY EAR HAIRS?
The cochlea has 32,000+ hairs
We have three semi-circular canals in each inner ear that control our equilibrium and give our brain a 3D report of our vision
The canals contain fluid and hair cells
Movement of the fluid over the hair cells detects movement of our head–
Are we upside down? Are we falling? This helps us maintain balance!

COCHLEAR IMPLANTS
Used when a hearing aid is not a solution (profound hearing loss)
Cochlear implants convert sound into electrical signals that are sent directly to the brain
1.
An external processor is worn behind the ear or attached to the hair
2.
The microphone in the external processor picks up the sound signal
3.
The external processor digitalizes the sound and transfers the electrical signal to the implant, which is surgically placed into the cochlea
4.
This acts like a mini-computer, deciphering the sound and transferring it into electrical signals
5.
The brain interprets the signal as sound!