Special Senses

General Senses Involve the action of receptors throughout the body

Somatic sensations arise from sensory neuron receptor endings in skin, skeletal muscles or near the joints (pain)

Visceral sensations arise from sensory receptors in the walls of internal organs (feeling that bladder or stomach are full)

Commonly recognized sensory systems are those for vision, hearing, touch, olfaction (smell) and taste

Arise from receptors located in specific sensory organs

Special Senses

Types of Sensory Receptors

Thermoreceptors: respond to heat or cold

Mechanoreceptors: detect touch, position relative to gravity and movement

Nociceptors (pain receptors): detect injury

Chemoreceptors: detect concentrations of specific chemicals

Photoreceptors: incorporate light-sensitive pigments that respond to light energy

Ø  Hundreds of olfactory receptors (chemoreceptors) in the lining of the nasal cavity

Ø  Each responding to a different type of odorant molecule

Ø  An average person can discriminate between and remember about 10,000 different odors

Sense of Smell

Sense of Smell

When you recognize an odor, you are responding to a distinctive mix of odorant molecules § Excite a unique subset of the nose’s sensory neurons § Trigger a unique pattern of excitation in the cerebral cortex

Sense of Taste

Taste buds embedded in the upper surface of the tongue

Sense of Taste Perceived taste arises from a combination of signals produced by the taste receptors (chemoreceptors)

Taste receptors responding to sweetness, sourness, saltiness, umami and fattiness

Vision

Detection of light in a way that allows the brain to form an image of objects in the environment

Both the cornea and lens bend incoming light so that rays converge on the retina The image formed on the retina is upside down

Rod cells: most abundant photoreceptors, detect dim light and respond to changes in light intensity Cone cells: daytime vision and color differentiation

Visual Accommodation

Refractive problems/ how light is focused when it enters the eye

Nearsightedness: eyeball is too long Farsightedness: eyeball is too short

Conjunctivitis

Cataracts

Color blindness

Age related macular degeneration (AMD)

Glaucoma

Hearing Detection of sound (a form of mechanical energy)

Vibrations cause pressure variation in the air, water or other media Pressure waves are created

How loud the sound is The pitch of the sound

Outer Ear

Collects sound waves and funnel them inward

Middle Ear

Sound waves traveling down the auditory canal make the eardrum vibrate

Inner Ear

Hearing and balance

Cochlea contains fluid and small nerve endings (hairs of Corti) Sound vibrations cause the fluid to move, stimulating the hairs of Corti Hairs of Corti transmit impulses to the brain via the auditory nerve