NERVOUS SYSTEM III SENSES INTRODUCTION General Senses are

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 Receptors: 1. Chemoreceptors- respond to changes in concentration of chemicals • Olfactory (smell) receptors • Detect changes in cerebrospinal fluid p. H 2. Pain receptors (nociceptors)- respond to tissue damage.

RECEPTORS, SENSATION AND PERCEPTION Receptors: 3. Thermoreceptors- sense temperature change 4. Mechanoreceptors- respond to touch, pressure, vibration, and stretch 5. 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 • Sensory structures that detect taste are taste buds. 


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.