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NERVOUS SYSTEM: GENERAL AND SPECIAL SENSES
Human Anatomy
Unit 4
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