Senses

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Lecture 16

• Senses

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• What do we respond to?
• Stimulus
• Pain
• Mechanical
• Temperature
• Chemicals
• Electromagnetic
• Awareness of stimulus _______________
• Where are sensory receptors located?
• Interoceptors
• Exteroceptors

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• An interoceptor which monitors changes in blood
  pressure
• What kind of stimulus do these respond to?

• A chemoreceptor monitoring changes in hydrogen
  ion concentration within the body

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• Mechanoreceptors
• Respond to distortion of cell membrane
• Baroreceptors changes in internal pressure
• Proprioceptors position of limbs, extension of
  muscle
• Hearing and equilibrium inner ear
• Tactile touch, etc. integument

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• Receptors in the Integument
• Nonencapsulated
• Naked nerve endings
• Merkel Discs
• Encapsulated
• Meissners Corpuscles
• Tactile
• Dermal papillae hairless skin
• Pacinian corpuscles lamellated corpuscles
• Dermis/hypodermis deep pressure
• Joint capsules
• Ruffini endings flattened capsule
• Deep dermis, joints
• Continuous deep pressure

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Pain Sensations

• Nociceptors pain receptors
• Tissue injury compounds
• Free nerve endings
• Stimulus
• excessive distension, muscle spasm, inadequate
  blood flow
• Little adaptation occurs
• Acute (fast) vs. chronic (slow)

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• Exteroceptors - Chemoreception
• Taste - Gustatory
• Tongue, mouth pharynx and larynx
• 4-5 chemical categories
• Olfactory
• Nasal passages
• Response to many different compounds

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• Smell - Olfactory
• Olfactory cells - epithelium in the upper nasal
  cavity
• bind to specific odor molecules
• cerebral cortex processes input
• Limbic associations occur (It smells like)

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Numbers- 5 million olfactory receptors. Size and
Shape- similar to a postage stamp. Location- roof
of the nasal cavity. Cell Division- replaced
every 60 days. Sensitivity- 1,000 different types
of receptors
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• Odorants bind to receptors ?Depolarization
• Olfactory glands ? mucus
• Rapid adaptation
• 50 1 min
• Highly sensitive

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• Gustatory Taste
• Dissolved substances
• 10,000 taste buds found on tongue, soft palate
  larynx
• sides of circumvallate fungiform papillae
• 3 cell types supporting, receptor basal cells
• Four responses
• Sweet okay
• Salty - okay
• Sour ??
• Bitter ?! poison?
• umami
• water

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Gustatory Pathway

• First-order gustatory fibers found in cranial
  nerves
• VII (facial) serves anterior 2/3 of tongue
• IX (glossopharyngeal) serves posterior 1/3 of
  tongue
• X (vagus) serves palate epiglottis
• Signals travel to thalamus or limbic system
  hypothalamus
• Taste fibers extend from the thalamus to the
  primary gustatory area on parietal lobe of the
  cerebral cortex
• providing conscious perception of taste

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• Ear -Mechanoreceptors
• Sound - hearing
• Orientation and motion in space equilibrium
• Gravitational equlib
• rotational equilibrium
• VIII cranial nerve
• ? name

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• Ear 3 regions
• External ear
• Auricle
• External acoustic meatus ? ear drum
• Ceruminous glands ? cerumen
• Middle ear
• Tympanic membrane
• Auditory ossicles
• Auditory tube
• Inner ear
• Bony labyrinth encloses membranous labyrinth

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• Middle ear
• Ossicles malleus, incus, stapes
• ? oval window of inner ear
• Auditory tube

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• Inner Ear
• Bony labrynth w/i petrous portion of temporal
  bone
• Membranous labrynth contain endolymph
• Vestibular complex
• Utricle saccule static gravitational
  equilib.
• Hair cells located at maculae embedded in
  gelatinous mass containing CaCO3 crystals
  otoliths
• Semicircular canals rotational equilibrium
• Hair cells in ampullae cilia embedded in cupula

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Cristae within ampulla

• When head moves, the attached semicircular ducts
  and hair cells move with it
• endolymph fluid does not
• Cilia of hair cells enclosed cupula bend

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Close-up of Macula

• Otolithic membrane slides ? Movement of
  stereocilia kinocilium alters release of
  neurotransmitter onto the vestibular branches of
  the vestibulocochler nerve

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• Cochlea 3 fluid filled channels
• scala vestibuli, scala tympani and cochlear duct
• Sound tranduced by Organ of Corti

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Section thru one turn of Cochlea

• Partitions that separate the channels are Y
  shaped
• bony shelf of central modiolus
• vestibular membrane above basilar membrane
  below form the central fluid filled chamber
  (cochlear duct)
• Fluid vibrations affect hair cells in cochlear
  duct

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• Motion in vestibular/tympanic duct ? basilar
  membrane moved ? distortion of sterocilia against
  tectoral membrane ? neural impulse
• Pitch where in cochlea
• Amplitude force of motion

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• Eye Eyeball Accessory Structures
• Accessory Structures
• Eyelids palpebrae
• Tarsal glands secrete sebum
• Extrinsic muscles (6 of them)
• Lacrimal glands
• Conjunctiva epithelial layers covering anterior
  edges of eye eyelid to eyeball

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• Eye muscles
• Superior and Inferior rectus
• Lateral and medial rectus
• Superior and inferior oblique
• Control CN III, IV, VI

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• Conjunctiva
• Palpebral conjunctiva
• Bulbar conjunctiva
• Stratified squamous epith
• Mucous membrane

Conjunctiva
palpebrae
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• Eyeball
• Three Tunics
• Fibrous Tunic (outer layer)
• Sclera and cornea
• Vascular Tunic (middle layer)
• Iris and choroid
• Nervous Tunic (inner layer)
• Retina
• Cavities
• Anterior cavity aqueous humor
• Two cavities
• Drained via Canal of Schlemm
• lens
• Posterior cavity (vitreous chamber) vitreous
  humor

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• Radial muscles sympathetic dilate pupil
• Circular muscles parasympathetic constrict
  pupil

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• Avascular, crystalline protein
• Suspensory ligaments attach lens to ciliary
  process
• Ciliary muscle controls tension on ligaments
  lens

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Cataracts

• Leading cause worldwide of blindness.
• A lens becomes cloudy or opaque.
• Caused by
• Natural aging. 50 or over.
• Drug reactions.
• Injury.
• Diabetes.
• UVB damage.
• At risk
• Smokers (2X).
• Guys named Phil or Rupert.
• Treatment- surgery, removal and replacement of
  the lens.

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Nervous Tunic -- Retina

• Posterior 3/4 of eyeball
• Optic disc
• optic nerve exiting back of eyeball blindspot
• Central retina BV
• fan out to supply nourishment to retina
• visible for inspection
• hypertension diabetes
• Detached retina
• trauma (boxing)
• fluid between layers
• distortion or blindness

View with Ophthalmoscope
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• Rods Cones--Photoreceptors
• Rods----rod shaped 120 million
• shades of gray in dim light
• discriminates shapes movements
• distributed along periphery
• Cones----cone shaped 6 million
• sharp, color vision
• Concentrated at fovea of macula lutea

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Major Processes of Image Formation

• Refraction of light
• by cornea lens
• light rays must fall upon the retina
• Accommodation of the lens
• changing shape of lens so that light is focused
• Constriction of the pupil
• less light enters the eye

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Visual fields

• Left occipital lobe receives visual images from
  right side of an object through impulses from
  nasal 1/2 of the right eye and temporal 1/2 of
  the left eye
• Left occipital lobe sees right 1/2 of the world
• Fibers from nasal 1/2 of each retina cross in
  optic chiasm

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Accommodation the Lens

• Convex lens refract light rays towards each other
• Lens of eye is convex on both surfaces
• View a distant object
• lens is nearly flat by pulling of suspensory
  ligaments
• View a close object
• ciliary muscle is contracted decreases the pull
  of the suspensory ligaments on the lens
• elastic lens thickens as the tension is removed
  from it
• increase in curvature of lens is called
  accommodation

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Abnormalities of the Eye

• Distance Vision
• Nearsighted
• Close objects are seen clearly.
• Long eyeball causes image to focus in front of
  the retina.
• Farsighted
• Distant objects are seen clearly.
• Short eyeball causes image to focus behind
  retina.
• Astigmatism
• Image is blurred.
• Irregular curvature of the cornea or lens causes
  light rays to focus unevenly.

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Abnormalities of the Eye

• Color blindness
• Colors cannot be distinguished.
• 75 of people have poor green perception.
• 8-10 of males, lt1 females.
• X-Linked.
• A lack of or reduced number of one of the cone
  types.

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                                     4 Sex-Linked Traits
                                      1. Normal Color Vision A 29,  B 45,  C --,  D 26
                                      2. Red-Green Color-Blind A 70,  B --,  C 5,  D --
                                      3. Red Color-blind A 70,  B --,  C 5,  D 6
                                      4. Green Color-Blind A 70,  B --,  C 5,  D 2

Color Blindness Test do you see pink elephants?

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The End.