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