Special Senses

1
Special Senses

• Olfaction, Gustatory Sense,
• Vision

2
Olfaction Sense of Smell

• Well-developed in other mammals,
• orientation
• individual recognition
• Less developed in primates
• Arboreal mammals, less to smell up there

3
Olfaction

• Receptors in epithelium of nasal cavity
• Supporting cells
• Olfactory receptor cells
• Bipolar neurons
• Dendrites protrude into mucus
• Axons olfactory nerves, end in olfactory bulb

4
Gustatory Sense

• Taste buds on tongue, soft palate, throat
• Most buds on papillae
• Taste bud
• Supporting cells form capsule
• Gustatory receptor cells with microvilli

5
Vision

• Eye converts electromagnetic radiation (light) to
  action potentials
• Impulses carried over optic nerves optic tracts
  to primary visual cortex

6
Eye Accessory structures

• Eyebrow
• Eyelids
• Eyelashes

7
Eye Accessory structures

• Orbicularis oculi muscle closes eye
• Conjunctiva
• Mucous membrane under lid and over surface of
  sclera

8
Eye Accessory structures

• Lacrimal apparatus
• Lacrimal gland
• Excretory ducts
• Lacrimal punctum
• Lacrimal canal
• Nasolacrimal duct

9
Eye Extrinsic Muscles

• Six muscle aim each eye
• Superior rectus
• Inferior rectus
• Medial rectus

• Lateral rectus
• (abducens)
• Superior oblique
• (trochlear)
• Inferior oblique

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Eye

• Three layers (tunics)
• Fibrous tunic
• Sclera
• Cornea
• Vascular tunic
• Choroid
• Ciliary body
• Iris
• Sensory tunic Retina

11
Eye

• Anterior segment
• Aqueous humor secreted by ciliary body
• Drained through scleral venous sinus (Canal of
  Schlemm)
• Posterior segment
• Vitreous humor

12
Eye Refraction

• Cornea
• More refraction
• Fixed (not focusable)
• Lens
• Connected to ciliary body by suspensory ligaments
• Changes shape to focus
• Flatten for distance
• Thicken for near vision

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Focusing, Accomodation

• Lens changes shape to focus
• Flatten for distance
• Thicken for near vision

14
Regulating Light Intensity

• Bright light stimulates parasympathetic reflex to
  constrict pupils
• Dim light stimulates sympathetic reflex to dilate
  pupils
• Atropine (Norepinephrine mimic) used to dilate
  pupils

15
Eye

• Sensory tunic Retina
• Extension of brain
• Optic disc
• Attachment, origin of optic nerve
• Central artery vein
• Macula lutea fovea centralis

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Eye Retina

• Retina built backwards
• Light passes through 3-4 layers of cells before
  reaching photoreceptors
• Retinal cells
• Ganglion cells
• Cell bodies of optic nerve fibers
• Bipolar cells
• Rods
• Cones

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Eye Retina

• Rods Cones absorb light energy, secrete
  neurotransmitter to bipolar cells
• Photopigments
• Retinal opsin
• 4 kinds of opsins (protein)

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Eye Retina

• Rods
• Retinal opsin ? rhodopsin
• Absorbs light across whole visual spectrum
• Cant distinguish color
• Sensitive to dim light
• Few rods in macula lutea
• More concentrated in peripheral parts of retina

19
Eye Retina

• Cones
• 3 kinds of cones with three opsins
• Each absorbs most in part of visual spectrum
• Used to see color
• Concentrated in macula lutea fovea centralis

20
Impulse transmission from Retina

• Retinal cells have high metabolic activity
• Dark
• Depolarized
• Release of neurotransmitter
• IPSP in bipolar cells
• Light
• Hyperpolarized
• No neurotransmitter release to bipolar cells,
  inhibition removed
• Bipolar cells stimulate ganglion (optic n.) cells