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The Senses

The Senses. Special vs General. Special: characterized by Large and complex organs Localized grouping of specialized receptors Eye Nose Ears Taste buds. General. Exist as individual cells or receptor units Widely distributed throughout the body Free nerve endings

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The Senses

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  1. The Senses

  2. Special vs General • Special: characterized by • Large and complex organs • Localized grouping of specialized receptors • Eye • Nose • Ears • Taste buds

  3. General • Exist as individual cells or receptor units • Widely distributed throughout the body • Free nerve endings • Messiners corpusles • Ruffini’s corpusles • Pacinian corpuscles • Krause’s End Bulbs • Golgi tendon receptors • Muscle spindles

  4. Converting Stimulus into Sensation • Stimuli: light, sound, temperature change, mechanical pressure, or taste & smell • Changed into an electrical signal or nerve impulse transmitted over a nervous system pathway • To the Brain, where interpretation takes place

  5. Special Sense Organs: Eye • 3 layers form eyeball: sclera, choroid, retina • Cornea, is part of the sclera: window of the eye • Iris: colored part of the eye, • Conjunctiva: mucous membrane that lines the eyelids and covers the sclera in front • Lacrimal gland: located in upper lateral portion of the orbit

  6. EYE cont’ • Choroid: middle layer of the eyeball: contains dark pigment to prevent scattering of incoming light rays • 2 involuntary muscles: • Ciliary muscle and Iris • Pupils dilate and constrict according to light. • Lens: lies directly behind the pupil, held in place by a ligament attached to ciliary muscle.(responsible for focus)

  7. Retina • Innermost layer of the eye • Contains rods and cones • Rods: receptors for night vision • Cones: receptors for day and color vision • Connected to the Optic nerve • Visual perception occurs in the visual cortex of the cerebrum

  8. Ear • Functions in hearing and equilibrium • Divided into 3 sections: • Inner, middle and outer ear • Outer: Auricle: pinna • External auditory canal: 2.5cm in length • Contains ceruminous glands=ear wax • Ends at tympanic membrane

  9. Ear: cont’ • Middle Ear: Houses ossicles, that is • Malleus (hammer) • Incus (anvil) • Stapes (stirrup) • Ends in the oval window • Auditory (eustachian) tube connects the middle ear to the throat • Inflammation: Otitis Media

  10. Ear….cont’ • Inner ear: Bony Labrinth filled with perilymph(fluid) • Subdivided into: vestibule, semicircular canals, and cochlea • Specialized hair cells in the “organ of Corti” respond when bent by movement of the endolymph(fluid)set in motion by sound waves.

  11. Taste • Tongue: covered with tiny, different sized bumps, known as papillae. • approximately 10,000 of these papillae, which are made up of taste buds. • Taste buds contain the specialized receptor cells which allow us to distinguish the different tastes that we know. • Four different taste-sensitive areas on the surface of the tongue: • sour, salt, bitter and sweet.

  12. Areas of Taste

  13. Smell • Smells are detected in the nose by the specialized receptor cells of the olfactory epithelium. • These are called olfactory receptor neurones. • Neurones send chemical message to olfactory nerve, which in turn is sent to the brain for analysis.

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