Special Senses - Bio 122 - PDF

Special Senses By Dr. Youssef 1  1- Gustatory Sense {Taste} Taste Buds are localized mainly on the dorsal surface of tongue along the walls of projections called papillae Chemo receptors are stimulated by chemicals in food & are sensitive t...

Special Senses By Dr. Youssef 1  1- Gustatory Sense {Taste} Taste Buds are localized mainly on the dorsal surface of tongue along the walls of projections called papillae Chemo receptors are stimulated by chemicals in food & are sensitive to at least 4 different taste sensations: salt, sour, sweet & bitter Afferent nerves from anterior 2/3 of tongue travel along (cn 7) facial nerve, while nerves from posterior 1/3 travel along glossopharyngeal nerve (cranial nerve 9) Gustatory cortex is in parietal lobe 2 3 4  2- Olfactory Sense {Smell} Olfactory neurons are concentrated in the superior region of the nasal cavity Chemo receptors are stimulated by chemical dissolved in liquids Afferent nerves pass through olfactory nerve (cn 1) to olfactory cortex in temporal lobe 5 6  3- Visual Sense Eyeball has three tunics: 1- Fibrous (outer layer) 2- Vascular (middle layer) 3- Nervous, Retina (inner layer) Two cavities: 1- Anterior Cavity (in front of lens) contains aqueous humor 2- Posterior Cavity (behind lens) contains vitreous humor (gelatinous material, maintains eye shape) 7 Tunics of the Eye 8 9 10  Pupil is opening in center of iris Pupillary reflex alters pupil size in response to light (bright light  constriction, dim light  dilation) 11 Iris Control of Pupil Diameter 12  Photoreceptors (rods & cones) are located in retina Visual impulses travel via optic nerve to visual cortex in occipital lobe 13  4- Auditory Sense (Hearing) & Equilibrium The ear is composed of: a- External Ear: Auricle (pinna) External Auditory Canal 14 15 b- Middle Ear: Begins at tympanic membrane Has an opening into Eustachian tube (auditory tube) that connects middle ear to throat & functions to equalize air pressure between the outside air & middle ear cavity Contains auditory ossicles: the smallest bones in the body (malleus, incus & stapes) 16 c-Inner Ear: Contains bony labyrinth ( interconnecting chambers) and membranous labyrinth (tubes inside bony labyrinth, filled with clear fluid called endolymph) Divided into vestibule, semicircular canals, and cochlea Vestibule & semicircular canals function in equilibrium sense Cochlea functions in hearing sense17 18  Hearing impulses travel from mechanoreceptors to auditory cortex in temporal lobe via cochlear branch of vestibulocochlrer nerve 19