Chapters 23 24 Tripple

Special Senses „

Will only take 1 lecture, not 2, so we’ll be caught up with regard to the syllabus.

Olfaction „

Olfactory epithelium … In

mucous membrane on roof of nasal cavity … Humans: microsmatic „

„

Small surface area

3 types of cells … Receptor

cells cells … Basal cells … Supporting

Olfaction „

Receptor cells … …

Bipolar Single dendrite „ „

Knoblike expansion 10-20 cilia …

… … …

Receptors are in cilia

Axon forms olfactory nerve (CN I) Continually lost Continually replenished from basal cells

„

Support cells

„

Bowman’s Glands

… … … … …

Support receptor cells Aid in mucous movement Located below epithelium Secrete mucous Dissolves odorous substances

1

Olfaction „

What makes a smell? … Volatility „

Moves through air

… Water „

… Lipid „

„

solubility

Diffuse through mucous

solubility

Interact with lipids of olfactory receptor membranes

Smells adapt quickly to a continuous stimulus

Anosmia Lack of smell „ Affects taste too „

Taste „

Taste buds … Epithelium … Receptor „ „

Clear vesicles Dense vesicles …

„ „

Glycosaminoglycans

Microvilli 4-20 receptors per bud

… Support „

cells

Support and secrete substance bathing microvilli

… Basal „

in the mouth cells

cells

Replace lost taste buds (1014 days)

2

Taste „

4 basic tastes … Sour … Salty … Sweet … Bitter

„

Tip of tongue

„

Sides and back

… Sweet … Sour

& salty

and bitter

Taste Pathway

Retina „

Pigment epithelium … Support,

nutrients, absorb light

„

Rods & Cones … Photoreceptors … No

dendrites vs color … Dark current … Light

„

External limiting membrane … Fenestrated

for connection between photosensitive processes and rest of cell body

Light

3

Retina „

Outer nuclear layer … Cell

bodies of rods & cones

„

Outer plexiform layer … Synaptic … Axons

of rods & cones … Dendrites of bipolar cells … Axons & dendrites of horizontal cells

Light

Retina „

Inner nuclear layer … Bipolar „

Next stage after rod/cone

… Horizontal

Dendrites – cone axons „ Axons – rod & cone axons „

… Amacrine „

Twilight vision

Light

Retina „

Inner Plexiform layer … Synaptic … Axons

of bipolar cells, dendrites of ganglion cells, axons/dendrites of amacrine cells

„

Ganglion cell layer … M(idget) „

cells

Single bipolar cell

… P(olysynaptic) „

cells

Light

Several bipolar cells

4

Retina „

Optic nerve layer … Axons

of ganglion cells … Unmyelinated „

Internal limiting membrane

Light

Blindspot Where the optic nerve leaves the retina „ Starts at ganglion cell layer, piercing through the other layers „ No receptors, or other cells, in this region „

Retinal Circuitry

5

Night Blindness „ „

Nyctalopia Vitamin A deficiency … Used

to form visual pigment sensitivity to light of both rods & cones

… Decrease

Color Blindness Lack a cone „ Red-green „

… Most … Esp.

common in males

Visual Pathways: Clinical Correlates

6

Visual Pathways: Clinical Correlates

Hearing

Organ of Corti Hair cells „ Endolymph „ Tectorial membrane „

7

Sound transmission „

Ossicular route

„

Air route

… Normal

route

… Disease/damage

to ossicles on round window … Poor sound transmission … Air

„

Bone route … Bones

of skull to perilymph

Deafness „

Conductive … Obstruction … Middle

„

by wax ear diseases

Sensorineural … Damaged … Damaged

„

hair cells auditory nerve

Tell them apart by a tuning fork

Vestibular Sensation „

Saccule & utricle

„

Semicircular canals

… Linear

acceleration

… Angular „

„

acceleration

Head/body turns

Required for coordination of motor responses, eye movements and posture

8

Disorders „

Vertigo

„

Nystagmus

… Illusory

motion

9