A.P. Biology Sense Organs

Sensory Reception Mechanoreceptor Thermoreceptor Pain Receptor 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: Which nerve pathway is carrying the stimulus (i.e. optic nerve—assessed as vision) Frequency of action potentials (receptors “fire” more frequently for a “stronger” stimulus) 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 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 Hearing Sound waves enter auditory canal Vibrate the Tympanic Membrane Malleus, Incus, Stapes Vibrates Oval Window Moves fluid in the Cochlea Hair cells move, stimulating nerve cells in the auditory nerve (mechanoreceptors)

Balance/Movement Fluid movement in the Semi-circular Canals