Chapter 17: Special Senses

What are the 5 special senses?

1. olfaction

2. gustatoon

3. vision

4. hearing

5. equilibrium

Constrast the general and special senses

general:

• somatic sensations (tactile, thermal, pain, proprioceptive) & visceral sensations

• scattered throughout body

• relatively simple

special:

• smell, taste, vision, hearing, equilibrium

• concentrated in specific regions of head

• anatomically distinct & have complex neural pathways

Where is olfactory apithelium located

• covers inferior surface of cribiform plate (of ethmoid bone)

• extends along superior nasal concha

What are the 3 types of olfaction cells. Briefly describe each

1. olfactory receptor cells (Bowman’s glands) → produce mucus to dissovle odor molecules for transduction

2. supporting cells (columnar epithelium) → located in mucus membrane; physical supprt, nourishment, insulation for olfactory receptor cells

3. basal cells → undergo mitosis to replace olfactory receptor cells

Describe the pathway of impulses along branches of olfactory (I) nerve

1. through cribiform plate (2 olfactory nerves)

2. synapse w/ olfactory bulbs

3. travel along olfactory tract

4. interpretation in primary olfactory area in cerebral cortex (temporal lobe)

Describe olfactory transduction

binding of an odorant molecle to olfactory receptor protein

1. chemical reactions involving cyclic AMP (cAMP) cause depolarization

2. action potential travels to primary olfactory area

3. impulse travels to frontol lobe for odor identification

Olfaction is the only sensory sytem that has direct _________

cortical projections w/o first going through relay stations in the thalamus

What are the 5 primary tastes (gustation)?

1. sour

2. sweet

3. bitter

4. salt

5. umami (meaty, savory)

Taste buds contain 3 kinds of epithelial cells:

1. supporting cells

2. gustatory receptor cells

3. basal stem stells

Describe the function of gustatory hairs

gustatory hairs → long microvillus

• projects from each receptor cell to the surface through the taste pore

Each gustatory receptor cell has a lifespan of about __ days

10

Taste buds are located in elevations on the tongue called ___.

papillae

What are teh 3 types of papillae that contain taste buds?

1. Vallate pillae → ~12 that contain 100-300 taste buds

2. Fungiform papillae → scattered on tongue w/ ~5 taste buds each

3. Foliate papillae → located in lateral tranches of tonuge (most of their taste buds degenerate in early childhood)

Describe filiform papillae

• cover entire surface of tonuge

• contain tactile receptors but NO taste buds

• increase friction to help tongue move food within mouth

Briefly describe the 3 cranial nerves involved in gustation

1. facial (VII) nerve → carries taste info from anterior 2/3 of tongue

2. glossopharyngeal (IX) nerve → carries tase info from posterior 1/3 of tongue

3. Vagus (X) nerve → carries taste info from taste buds on epiglottis & in throat

Trace the pathway of nerve impulses along the gustation cranial nerves

1. propogate along cranial nerves → gustatory nuceleus in medulla oblongata

2. acons carrying taste signals project into hypothalamus, luimbic system, & thalamus

3. taste is perceived consciously as signals from the thalamus arrive at the primary gustatory area in parietal lobe

List our sensitivity to different taste/substances from most sensitive to least

1. bitter

2. sour

3. salty/sweet

Describe how vision works

uses visible light

• part of electromagnetic spectrum w/ wavelengths from 400 → 700 nm

define wavelength

distance between two consecutive peaks of an electromagnetic wave

List the accessory structures of the eyes

• eyelids

• eyelashes

• eyebrows

• lacrimal apparatus

• extrinsic eye muscles

Which muscles control eyelid movement (1) and which muscles move the eyeball itself in all directions (2)?

1. palpebral muscles

2. extrinsic eye muscles

What is the conjunctiva?

thin, protective mucous membrane lining the eyelids & covering the sclera

what is the tarsal plate?

fold of CT that gives form to the eyelids

• contains row of sebaceous glands that keep eyelids from sticking

What is another name for the upper and lower eyelids?

upper & lower palpebrae (palpebra singular)

What produces & drains tears?

lacrimal apparatus

Trace the pathway for tears

1. lacrimal glands

2. lacrimal ducts

3. lacrimal puncta

4. lacrimal canaliculi

5. lacrimal sac

6. nasolacrimal ducts carry tears into nasal cavity

list the 6 extrinsic eye muscles

1. superior rectus

2. inferior rectus

3. lateral rectus

4. medial rectus

5. superior oblique

6. inferior oblique

When do watery eyes occur?

lacrimal fluid builds up when smth obstructs the nasolacrimal ducts (e.g. inflammation of nasal mucosa from a viral cold)

• overproduction of lacrimal fluid occurs in response to parasympathetic stimulation (emotional crying) → tears spill over edges of eyelids & drain into nasal cavity

List the 3 layers/tunics of the eyeball and what each are composd of

1. Fibrous tunic (outer) → sclera (white of the eye) & cornea (transparent epithelium)

2. Vascular tunic (middle) → choroid, ciliary body, iris

3. Nervous tunic (inner) → retina

Describe the function of