Human Anatomy Unit 4 NERVOUS SYSTEM: GENERAL AND SPECIAL SENSES Receptors •  Receptor sensi4vity –  Each receptor has a characteris4c sensi4vity •
•
•
•
Pressure Pain Temperature Chemical sensi4vity •  Recep4ve field Structural Classifica4on •  Naked nerve endings •  Encapsulated nerve endings •  Neuroepithelium –  epithelium modified for some neuron func4ons General Senses •  Nociceptors –  involved in “pin prick” sensa4on, itching, 4ckling •  Thermoreceptors –  Respond to changes in temperature •  Mechanoreceptors –  Respond to physical distor4on, contact, pressure on their plasmolemma •  Chemoreceptors –  Monitor chemical composi4on of body fluids –  Respond to presence of specific chemicals Nociceptors •  Loca4ons –  Numerous in superficial areas of skin –  Joint capsules –  Periostea of bone –  Walls of blood vessels –  Few in deep 4ssue, organs •  Respond to –  Temperature –  Mechanical damage –  Dissolved chemicals •  Sensa4ons –  Fast pain •  Prickling pain (cuts) –  Slow pain •  Burning, aching –  Referred pain Referred Pain •  Impulses from certain viscera mapped to other sites in dermatomes of skin •  Mapped to ‘most likely source’ •  Usually follows sympathe4c nerve pathways (can also follow parasympathe4c pathways) Thermoreceptors •  Loca4ons –  Dermis of skin –  Skeletal muscles –  Liver –  Hypothalamus •  Cold more numerous than hot •  Free nerve endings Mechanoreceptors •  Respond to: –  Stretch –  Compressional force –  Tensile force –  Distor4on •  Types –  Tac4le receptors –  Barroreceptors –  Proprioceptors Chemoreceptors •  Detect small changes in the concentra4on of specific chemical or compounds •  Dissolved in fluid (plasma) •  Caro4d/Aor4c bodies Olfac4on Gusta4on •  All taste quali4es are tasted everywhere on tongue •  Some areas are more sensi4ve to certain quali4es •  Can change in an individual with 4me •  Chemoreceptors located in tongue •  Five primary sensa4ons –  Sweet, sour, salty, biZer, and umami (savory) Gusta4on Equilibrium and Hearing •  External Ear –
–
–
–
Auricle/Pinna External auditory meatus Tympanic membrane Ceruminous glands •  Middle Ear –  Tympanic cavity –  Eustacian tube –  Auditory ossicles •  Malleus •  Incus •  Stapes –  Muscles •  Tensor tympani •  Stapedius muscle •  Inner Ear –  Membranous labyrinth •  Contains specialized cells that detect sound and monitor equilibrium –  Bony labyrinth •  fluid filled cavity of the petrous por4on of the temporal bone –  Cochlea •  Organ of Cor4 –  Ves4bule •  Semicircular canals •  Utricle •  Saccule –  Hair cells –  Suppor4ng cells Anatomy of the Ear The Middle Ear Ves4bular Apparatus •  Semicircular canals –  3 canals at right angles to each other (anterior, posterior, lateral) –  each contains 2 ampullae with receptors –  sense angular rota4on •  Utricle and Saccule –  receptors for sta4c equilibrium changes –  Detect linear accelera4on Semicircular Canals and Ducts Semicircular Canals and Ducts The Maculae of the Ves4bule The Cochlea and Organ of Cor4 The Cochlea and Organ of Cor4 Vision Sec4onal Anatomy of the Eye Sec4onal Anatomy of the Eye Accessory Structures of the Eye Lacrimal Apparatus Extrinsic Eye Muscles Tunics of The Eye •  Fibrous Tunic –  Fibrous outer tunic –  composed of sclera proper and cornea •  Vascular tunic –  choroid •  Neural tunic –  Re4na Fibrous Tunic •  Structures –  Sclera –  Cornea •  Func4ons –  Mechanical support –  Physical protec4on –  AZachment for extra‐occular muscles –  Assist in accomoda4on (focusing) Vascular Tunic •  Choroid –  Posterior to lens –  Network of capillaries –  Heavily pigmented with melanin •  Ciliary body –  heavily pigmented –  has a muscle and processes •  Iris –  Pigmented muscle –  2 smooth muscle layers •  Sphincter pupillae muscle •  Dilator pupillae muscle –  Pupil = hole in middle •  Func4ons –  Route for blood vessels, lympha4cs –  Regulates the amount of light that enters the eye –  Secre4ng and reabsorbing queous humor –  Controlling the shape of the lens (accomoda4on) Vascular Tunic •  Choroid –  Posterior to lens –  Network of capillaries –  Heavily pigmented with melanin •  Iris –  Pigmented muscle –  2 smooth muscle layers •  Pupillary sphincter muscle •  Pupillary dilator muscle –  Pupil = hole in middle •  Ciliary body –  heavily pigmented –  Ora serrata –  Ciliary body •  Ciliary muscle •  Ciliary processes –  Suspensory ligaments Vascular Tunic Neural Tunic •  Func4on of the re4na = photorecep4on •  Pigmented layer •  Neural layer – re4na –  Photoreceptors •  Rods, cones –  Macula lutea –  fovea centralis •  in line with the visual axis •  “focus point” –  op4c disc •  blind spot •  Exit site for blood vessels and op4c nerve Re4nal Organiza4on Re4nal Organiza4on The Chambers of the Eye •  Anterior cavity –  Anterior chamber –  Posterior chamber –  Aqueous humor –  Canal of Schlemm –  Lens •  Posterior Cavity –  Vitreous chamber The Lens •  Composed of alpha crystalline protein •  Flexible •  Bi‐convex lens •  Accommodates –  focus at different distances