1. Sensory Mechanisms

2. Sensory receptors and the brain
Sensation
Perception
Action potentials transmitted by sensory receptors to the brain
Sensory receptors
Specialized neurons/epithelial cells
Extero- and interoreceptors
Convert energy to changes in membrane potentials and transmit to brain
Functions: transduction, amplification, transmission, and integration
Interpretation of the stimuli by the brain
Ex. colors, taste, sound, smell

3. 1. Follow the movement of the rotating pink dot with your eyes. 2
1. Follow the movement of the rotating pink dot with your eyes. 2. Stare at the cross in the center. 3. Concentrate on the cross at the center for a long period of time.

4. Is the blue side in the front or back of the cube?

5. Types of sensory receptors
Mechanoreceptors
 Physical deformation
 Stretch receptors in muscles and hair cells
Pain receptors
 Excess heat, pressure, presence of chemicals, prostaglandins
 Naked dendrites called nociceptors
Thermoreceptors
 Heat or cold
 Skin receptors and interoreceptors in the hypothalamus
Chemoreceptors
 Presence and concentrations of chemicals in the environment
 Osmoreceptors in brain, gustatory and olfactory receptors, pheromone receptors in moth antennae
EM receptors
 EM energy
 photoreceptors: infrared in snakes, electroreceptors in eels, rods and cones in humans

6. Vision and photoreceptors
* All have pigment molecules that absorb light
Eye cup of planarians
Compound eyes of insects, crustaceans, polychaetes
Ommatidia are sensitive to movement!
Single lens eyes of jellyfish, polychaetes, spiders, mollusks
Single lens eyes of vertebrates

7. Structure of the human eye
Ciliary body
Iris
Suspensory ligament
Cornea
Pupil
Aqueous humor
Lens
Vitreous humor
Optic disk (blind spot)
Central artery and
vein of the retina
Optic nerve
Fovea (center of visual field,
most cones)
Retina with rods and cones
Choroid
Sclera
Structure of the human eye

8. Hearing and equilibrium in invertebrates
Ciliated receptor cells
Cilia
Statolith
Sensory nerve fibers
1 mm
Tympanic membrane
Statocysts in invertebrates

9. Hearing and equilibrium in mammals
Pinna
Auditory canal
Eustachian tube
Tympanic membrane
Stapes
Incus
Malleus
Skull bones
Semicircular canals
Auditory nerve, to brain
Cochlea
Oval window
Round window
Vestibular canal
Tympanic canal
Auditory nerve
Bone
Cochlear duct
Hair cells
Tectorial membrane
Basilar membrane
To auditory nerve
Axons of sensory neurons 1
Overview of ear structure 2
The middle ear and inner ear 4
The organ of Corti 3
The cochlea
Organ of Corti
Outer ear
Middle ear
Inner ear

10. Chemoreceptors and taste
Sensilla in insects
Taste buds in mammals

11. Chemoreceptors and smell
Brain
Nasal cavity
Odorant
Odorant receptors
Plasma membrane
Cilia
Chemoreceptor
Epithelial cell
Bone
Olfactory bulb
Action potentials
Mucus

12. Touch