THE SENSES
THE SENSES
• SENSORY INPUTS BECOME SENSATIONS AND
PERCEPTIONS IN THE BRAIN
– SENSATION
• AN AWARENESS OF SENSORY STIMULI
– PERCEPTION
• A MEANINGFUL INTERPRETATION OR CONCIOUS
UNDERSTANDING OF SENSORY DATA
THE SENSES
• SENSORY RECEPTOR CELLS CONVERT STIMULI
INTO ELECTRICAL ENERGY
– SENSORY TRANSDUCTION
• CELL CONVERTS A STIMULUS INTO AN ELECTRICAL SIGNAL
– RECEPTOR POTENTIAL
• GRADED CHANGE IN MEMBRANE POTENTIAL
– SENSORY ADAPTATION
• THE TENDENCY OF SENSORY RECEPTOR CELLS TO BECOME
LESS SENSITIVE WHEN THEY ARE STIMULATED REPEATEDLY
THE SENSES
• SPECIALIZED SENSORY RECEPTORS DETECT
FIVE CATEGORIES OF STIMULI
– FIVE RECEPTORS
• PAIN RECEPTORS
– RESPOND TO EXCESS HEAT, PRESSURE, DANGEROUS
CHEMICALS
• THERMORECEPTORS
– DETECT HOT OR COLD
THE SENSES
• SPECIALIZED SENSORY RECEPTORS DETECT
FIVE CATEGORIES OF STIMULI
– FIVE RECEPTORS
• MECHANORECEPTORS
– DETECT TOUCH,
PRESSURE,
STRETCHING,
MOTION AND SOUND
THE SENSES
• SPECIALIZED SENSORY RECEPTORS DETECT
FIVE CATEGORIES OF STIMULI
– FIVE RECEPTORS
• CHEMORECEPTORS
– ATTUNED TO CHEMICALS
THE SENSES
• SPECIALIZED SENSORY RECEPTORS DETECT
FIVE CATEGORIES OF STIMULI
– FIVE RECEPTORS
• ELECTROMAGNETIC RECEPTORS
– SENSITIVE TO ENERGY OF VARIOUS
WAVELENGTHS
– EX. PHOTORECEPTORS
THE SENSES
• THREE DIFFERENT TYPES OF EYES HAVE
EVOLVED AMONG INVERTEBRATES
– 3 TYPES
• EYE CUP
• COMPOUND EYE
– MANY TINY LIGHT-DETECTING UNITS
• SINGLE-LENS EYE
– SIMILAR TO CAMERA
THE SENSES
• VERTEBRATES HAVE SINGLE-LENS EYES
THE SENSES
• VERTEBRATES HAVE SINGLE-LENS EYES
– SCLERA
– CORNEA
– CHOROID
• IRIS
–
–
–
–
–
PUPIL
LENS
RETINA
VITREOUS HUMOR and AQUEOUS HUMOR
CONJUCTIVA
THE SENSES
• TO FOCUS, A LENS CHANGES POSITION OR
SHAPE
– MUSCLES ATTACHED TO THE CHOROIDS CHANGE
THE SHAPE OF THE LENS; FOCUSING LIGHT
APPROPRIATELY
THE SENSES
THE SENSES
• ARTIFICIAL LENSES OR SURGERY CAN
CORRECT FOCUSING PROBLEMS
– 3 COMMON PROBLEMS
• NEARSIGHTEDNESS (MYOPIA)
– EYEBALL TOO LONG
• FARSIGHTEDNESS (HYPEROPIA)
– EYEBALL TOO SHORT
• ASTIGMATISM
– MISSHAPEN LENS OR CORNEA
THE SENSES
• OUR PHOTORECEPTOR CELLS ARE RODS AND
CONES
– CONES
• STIMULATED BY BRIGHT LIGTH AND CAN DISTINGUISH
COLOR; DO NOT FUNCTION AT NIGHT
• PHOTOPSINS
– VISUAL PIGMENTS THAT ABSORB BRIGHT, COLORED LIGHT
THE SENSES
• OUR PHOTORECEPTOR CELLS ARE RODS AND
CONES
– RODS
• EXTREMELY SENSITIVE TO LIGHT AND ENABLE US TO
SEE IN DIM LIGHT AT NIGHT, THOUGH ONLY IN SHADES
OF GRAY
• RHODOPSINS
– VISUAL PIGMENT THAT
CAN ABSORB DIM LIGHT
THE SENSES
• THE EAR CONVERTS AIR PRESSURE WAVES
INTO ACTION
POTENTIALS THAT
ARE PERCEIVED AS
SOUND
THE SENSES
• THE EAR CONVERTS AIR PRESSURE WAVES INTO
ACTION POTENTIALS THAT ARE PERCEIVED AS
SOUND
– OUTER EAR  COLLECTS SOUNDWAVES TO EAR
DRUM
• PINNA  “EAR”; FLAP-LIKE STRUCTURE
• AUDITORY CANAL
– EARDRUM  SHEET OF TISSUE THAT SEPARATES
OUTER EAR FROM MIDDLE EAR
– MIDDLE EAR
• EARDRUM; HAMMER, ANVIL, STIRRUP, OVAL WINDOW
THE SENSES
• THE EAR CONVERTS AIR PRESSURE WAVES
INTO ACTION POTENTIALS THAT ARE
PERCEIVED AS SOUND
– INNER EAR
• CONTAINS COCHLEA
– THE ACTUAL HEARING
ORGAN
THE SENSES
• THE INNER EAR HOUSES OUR ORGANS OF
BALANCE
– SEMICIRCULAR CANAL 
• DETECT CHANGES IN THE HEAD’S RATE OF ROTATION OR
ANGULAR MOVEMENT
– UTRICLE AND SACCULE  HAIR CELLS THAT DETECT
THE
POSITION
OF THE HEAD
WITH RESPECT
TO GRAVITY
THE SENSES
• WHAT CAUSES MOTION SICKNESS?
– CONFLICTING SIGNALS FROM THE EYES AND
INNER EAR’S BALANCE MECHANISM
– SPIN AROUND OVER AND OVER, THEN SUDDENLY
STOP…WHAT HAPPENS?!?!?!?
THE SENSES
• ODOR AND TASTE RECEPTORS DETECT
CATEGORIES OF CHEMICALS
THE SENSES
• REVIEW: THE CENTRAL NERVOUS SYSTEM
COUPLES STIMULUS WITH RESPONSE
– NERVOUS SYSTEM LINKS STIMULUS RECEPTION
WITH RESPONSE
• STIMULI  RECEPTORS  SENSORY NEURONS  CNS
 INTEGRATION  MOTO NEURON  EFFECTOR 
RESPONSE
– REFLEX ARC
THE SENSES
• WHAT ABOUT OUR MUSCLES??
• SKA-DOOSH!!