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The General & Special Senses. Chapter 18. Introduction. Senses – our perception of what is “out there” General senses Includes senses that are not specific Pass information through spinal nerves Special senses Found within complex sense organs to cerebral cortex

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  • Senses – our perception of what is “out there”
    • General senses
      • Includes senses that are not specific
      • Pass information through spinal nerves
    • Special senses
      • Found within complex sense organs to cerebral cortex
      • Pass information through cranial nerves to cerebral cortex
general senses
General Senses
  • Includes senses that are associated with skin
    • Temperature, pressure, touch, pain, vibration, proprioception
  • Pass information along the spinal nerves and pathways to specific areas of the cerebral cortex
special senses
Special Senses
  • Olfaction, gustation, equilibrium, hearing, & vision
  • Found within complex sense organs
  • Pass information along the cranial nerves to specific areas of the cerebral cortex.
  • Sensory receptors are transducers
    • Change stimuli into electro-chemical impulses
    • Specific receptors can transduce only certain types of stimuli
interpretation of sensory information
Interpretation of Sensory Information
  • Occurs in cerebral cortex
  • Depends on the area of the cerebral cortex that receives the information
central processing and adaptation
Central Processing and Adaptation
  • Sensory adaptation – the loss of sensitivity after continuous stimulation
    • Tonic receptors are always active
    • Phasic receptors only relay changes in the conditions they are monitoring
  • Role – prevents brain from being overloaded with unimportant information
  • Detect pain
    • Referred pain
    • Phantom pain
  • Respond to pressure & touch
    • Tactile receptors
    • Baroreceptors
    • Proprioreceptors
    • Thermoreceptors
tactile receptors
Tactile Receptors
  • Found in the dermis
  • Monitor changes in pressure
  • Detect chemicals in solution
    • Blood composition
olfaction the nose
Olfaction (the nose)
  • Olfactory receptors
    • Can detect at least 50 different primary smells
    • Located in the epithelium of roof of nasal cavity
olfactory receptors
Olfactory Receptors
  • Molecules dissolve in the mucus of the epithelium
  • Olfactory neurons pass through the roof of the nasal cavity and synapse in the olfactory bulb
  • Olfactory tracts go directly to the cerebral cortex
gustation the tongue
Gustation (the tongue)
  • Taste receptors are in the taste buds
  • 6 primary tastes
    • Sweet, sour, salty, bitter, water, umami
gustatory receptors
Gustatory Receptors
  • Located in papillae on the surface of the tongue
  • Contain the gustatory receptors
    • Molecules dissolve in saliva
pathway of gustatory sense
Pathway of Gustatory Sense
  • Cranial nerves relay sensory impulses to the cerebral cortex
    • All pass through the medulla & thalamus
equilibrium hearing the ear
Equilibrium & Hearing (the ear)
  • External ear
    • The auricle directs sound waves into the external auditory meatus to the tympanic membrane
the middle ear
The Middle Ear
  • Contains the auditory ossicles
  • Separated from the external ear by the tympanic membrane
    • Malleus
    • Incus
    • Stapes
  • Connected to the throat by the eustachian tube
the inner ear
The Inner Ear
  • Separated from the middle ear by the oval window
the inner ear1
The Inner Ear
  • Consists of a series of canals filled with fluid
the inner ear2
The Inner Ear
  • Consists of a series of canals filled with fluid
    • Vestibule
    • Semicircular canals
    • Cochlea contains
      • Organ of Corti
the vestibule
The Vestibule
  • Detects static position
  • Hair cells are embedded in a gelatinous material
otoliths at work
Otoliths at Work
  • Otoliths are balanced on top of gelatinous material
    • Slide when head tips
    • Bend hairs
    • Generates nerve impulse
the semicircular canals
The Semicircular Canals
  • Detect dynamic balance
  • Arranged at right angles to each other
  • Hair cells are embedded in gelatinous material with fluid over it
  • Movement of head
    • Bends the hairs
    • Creates nerve impulses
the cochlea
The Cochlea
  • Divided into 3 tunnels by membranes
    • Tunnels connect with the oval window and round window
    • Organ of Corti
the organ of corti
The Organ of Corti
  • Consists of hair cells on a basement membrane
  • Tips of hairs touch the tectorial membrane
  • Basement membrane vibrates
    • Hair cells bend
    • Sends a nerve impulse
summary of hearing
Summary of Hearing
  • Sound waves enter the external auditory meatus
  • Tympanic membrane vibrates
  • Auditory ossicles vibrate
  • Oval window vibrates
  • Fluid in cochlea moves
  • Basement membrane moves
  • Hairs rub against the tectorial membrane
  • Nerve impulse is sent along the auditory nerve to the brain
vision the eye accessory structures
Vision (the eye) – Accessory Structures
  • Eyelids protect the eye
    • Conjunctiva lines the eyelid
  • Lacrimal apparatus
    • Lacrimal gland produces tears
    • Lacrimal canals drain tears into lacrimal sacs
    • Nasolacrimal duct drains into the nasal cavity
  • Extrinsic muscles move the eyeball
structure of the eye 3 tunics
Structure of the Eye – 3 Tunics
  • Outer tunic
    • Includes cornea & sclera
  • Middle tunic
    • Includes choroid coat, ciliary body, lens, iris & pupil
  • Inner tunic (retina)
    • Contains photoreceptors
      • Rods & cones
    • Includes optic disc,macula lutea & fovea centralis
the cavities of the eye
The Cavities of the Eye
  • The lens separates the interior of the eye into 2 cavities
    • Anterior cavity
      • Contains aqueous humor
      • Glaucoma
    • Posterior cavity
      • Contains vitreous humor
the vascular tunic
The Vascular Tunic
  • Contains many blood vessels & nerves
  • The iris controls the size of the pupil
  • Suspensory ligaments attach the lens to the ciliary body
    • Controls the shape of the lens
  • Allows focusing on near & distant objects
  • Cataract
the retina
The Retina
  • Cones allow for sharp color vision in bright light
    • Contain pigments
    • Macula lutea
    • Fovea centralis
  • Rods provide for vision in dim light
    • Contain the pigment rhodopsin
    • Most dense at periphery of retina
summary of vision
Summary of Vision
  • Light rays enters through the pupil
  • Light rays cross in the lens
  • Retina receives reversed & upside down image
  • Rods & cones are stimulated
  • Optic nerve carries impulse to the brain
abnormal vision
Abnormal Vision
  • Myopia
  • Hyperopia
  • Presbyopia
  • Astigmatism