A.P. Biology
Sense Organs
Sensory Reception
Type of Sensory Receptor
Mechanoreceptor
Thermoreceptor
Pain Receptor
Chemoreceptor
Photoreceptor
Stimulus
Pressure, position, acceleration (balance)
Heat
Tissue damage
Chemicals (taste, smell)
Light (vision)
Brain’s assessment of a stimulus depends on:
1. Which nerve pathway is carrying the stimulus (i.e. optic nerve—assessed as vision)
2. Frequency of action potentials (receptors “fire” more frequently for a “stronger” stimulus)
3. Number of axons stimulated (stronger stimulus recruits more receptors)
Sense Organs
= concentrations of sensory receptors Examples: Eye, Ear, Nose etc.
Taste—Chemoreceptors in taste buds on the tongue
Chemicals bind to receptors on taste cells, generating nerve impulses in sensory neurons
Smell—Chemoreceptors in the nose (olfactory cells) detect chemicals (odors)
Two types of Photoreceptors—Located in the Retina
Rod Cells—B/W vision
Cone Cells –Color vision
Stimulation of the photoreceptors generates nerve impulses optic nerve brain
Lens focuses images onto the retina
Muscles/ ligaments change the shape of the lens
Vision Problems and their Corrections
Hearing & Balance
HearingSound waves enter auditory canalVibrate the Tympanic MembraneMalleus, Incus, StapesVibrates Oval WindowMoves fluid in the CochleaHair cells move, stimulating nerve
cells in the auditory nerve (mechanoreceptors)
Balance/MovementFluid movement in the Semi-circular
Canals
