Post on 26-Apr-2018
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