NERVOUS SYSTEM III SENSES

INTRODUCTION General Senses: are those with receptors widely distributed throughout the body EX. Skin, various organs and joints Special senses: more specialized receptors and arise from receptors located primarily in the head. EX. Eyes and ears

Receptors, Sensation and perception Chemoreceptors- respond to changes in concentration of chemicals Olfactory (smell) receptors Detect changes in cerebrospinal fluid pH Pain receptors (nociceptors)- respond to tissue damage.

Receptors, Sensation and perception Thermoreceptors- sense temperature change Mechanoreceptors- respond to touch, pressure, vibration, and stretch Photoreceptors- detect changes in light intensity, color, and movement

Receptors, Sensation and perception The brain interprets input from sensory receptors as perception. Sensation- Conscious awareness of incoming sensory information Sensory adaptation- ability to ignore unimportant stimuli EX. Not constantly noticing/sensing your socks around your ankles

General Senses Touch is the only one of the five senses that is considered a general sense Detected by mechanoreceptors and thermoreceptors and pain receptors

Special Senses Vision: Eyeball has outer, middle, and inner tunic (layers) The outermost tunic of the eyeball is the sclera The transparent anterior portion of the sclera is the cornea Choroid Coat- Middle tunic Retina- the inner tunic of the eye 


Special Senses Vision: Detected by photoreceptors The blink reflex is designed to. D. keep the eyes moist. The contractile structure that surrounds the pupil is the iris. Lacrimal glands: constantly produce a fluid called tears.


Special Senses Hearing: inner ear-contains the sense organs for hearing and balance 
 The external ear terminates at the tympanic membrane.
 
 The auditory tube equalizes air pressure between the middle ear and outside air. The malleus, incus, and stapes transmit vibrations from the eardrum to the oval window. 


Special Senses Hearing: Order of structures in the ear that vibrate when a sound wave enters the ear. Eardrum Ossicles Oval window Perilymph Endolymph Inner ear bones from lateral to medial: Malleus
 Incus Stapes


Special Senses Taste: The sense of taste is called gustation. Primary taste sensations: Sweet 
 Salty Sour
 Bitter 
 umami

Special Senses Smell: Smell is the special sense relayed directly to the cerebral cortex without going to the thalamus Detected by chemoreceptors called olfactory receptors

Special Senses Smell: In order for a molecule to be detected by the olfactory neurons, it must be dissolved in fluid covering the olfactory epithelium. Inhaling deeply and slowly through the nose help to identify an odor because more air containing the odor is brought into contact with the olfactory epithelium A person's nose run when he cries because tears drain into the nasal cavity via the nasolacrimal duct.


Special Senses Equilibrium: Static equilibrium- maintenance of balance when the head and body are not moving Dynamic equilibrium- maintenance of balance when the head and body are suddenly moved or rotated

Special Senses Equilibrium: Maintained by inner ear structures The position of the head with respect to gravity is determined by the movements of otoliths in response to gravity.