Chapter-21: Special Senses

Question 1

A role of olfactory /gustatory receptor, basal cell, and supporting cell in both olfactory and gustatory receptors

Answer 1

Olfactory receptor - first order neurons of olfactory pathway (smell)
gustatory cell - (taste)
basal cell - replace warn out/damaged receptor cells
supporting cells - support, nourishment, insulation to receptor cells, odor binding proteins

Question 2

Structure and function of the taste buds

Answer 2

can be found on soft palate, epiglottis and pharynx

number of taste buds declines with age

each taste bud consists of 3 kinds of epithelial cells
supporting, gustatory receptor, basal

supporting cells contain microvilli and surround gustatory receptory

gustatory microvilli (gustatory hairs)

Question 3

Different types of papillae and whether they are involved in gustation or not

Answer 3

3 types of papillae that contains taste buds
1) vallate (circular) papillae (100-300) - form inverted V shaped row at the back of the tongue

2) fungiform papillae (5 taste buds) - mushroom shaped elevations scattered over entire surface of tongue that contains about 5 taste buds each
3) foliate papillae - located on lateral margins of the tongue, but most of their taste buds are degenerate in early childhood

NOT INVOLVED IN GASTUATION
4) filiform papillae - contains tactile receptors but no taste buds, increase friction between tongue and food, making it easier for tongue to move food in oral cavity

Question 4

Neural pathways, i.e. the name of the cranial nerves that carry sensory information from receptors to the brain

Answer 4

taste -> gustatory receptor -> CN VII (facial), IX (glossopharyngeal) & X (vagus) -> gustatory nucleus (MO) -> thalamus -> parietal lobe (cerebral cortex) -> primary gustatory area -> perception of taste

gustatory nucleus (MO) -> limbic system and hypothalamus -> behavioral responses

Question 5

Structure and function of the accessory eye structures

Answer 5

Eyelids also called palpebrae
Levator palpebrae superioris muscle- a weak twitch
Palpebral fissure- space between eyelids/palpebrae
Lateral commissure and medial commissure
Lacrimal caruncle- contains sebaceous & sudoriferous glands
Tarsal plate-support the eyelids
Tarsal glands (Meibomian glands)-located in the tarsal plates
Chalazion- a tumor or cyst in tarsal glands
Conjunctiva
Palpebral conjunctiva- a thin protective mucous membrane
Bulbar conjunctiva
Sebaceous ciliary glands
Eyebrows and eyelashes

Question 6

Structure and function of the lacrimal apparatus

Answer 6

The lacrimal apparatus produces and drains lacrimal fluid or tears.
Lacrimal ducts
Lacrimal puncta
Lacrimal canaliculi lead into the lacrimal sac and the nasolacrimal duct.

Question 7

structures and function of the fibrous tunic: sclera, cornea and scleral venous sinus

Answer 7

Sclera- support, protection, shape of the eye & muscle attachment
Cornea- avascular collagenous tissue
Scleral venous sinus - collect the aqueous humor from the anterior chamber of the eyeball and deliver it to the veins of the eyeball

Question 8

Structures and function of the vascular tunics: choroid, ciliary body/process, iris, pupil, and lens

Answer 8

Choroid- vascular, melanocytes,
Ciliary body/process- melanocytes, aqueous humor
Iris- coloured portion of the eyeball, two smooth muscles
Pupil- opening in the iris, regulates light entrance
Lens - transmit light, focusing it on the retina

Question 9

Structure and function of the anterior and posterior chambers

Answer 9

Anterior cavity- controls the amount of light that enters the eye by opening and closing the pupil

Aqueous humor -bathes and nourishes the lens and maintains pressure within the eye

Anterior and posterior chambers -provides nourishment to the interior eye structures and helps to keep the eyeball inflated

Vitreous chamber - help the eyeball keep its shape

Vitreous body - maintain the round shape of the eye

Vitreal floaters -

Question 10

Structure and function of the retina

Answer 10

Pigmented layer
The melanin in the pigmented layer of the retina helps to absorb stray light rays

Neural (sensory) layer
Three layers of retinal neurons:
Photoreceptor layer
Bipolar cell layer
Ganglion cell layer

Cells present in bipolar cell layer: 
Horizontal cells
Amacrine cells
Rods
Cones
Photopigment molecules

Question 11

Neural pathways (cranial nerve) and the part of the brain lobe involved in the perception of vision and behavioral responses related to vision

Answer 11

IN ORDER
Bipolar cells
Optic (II) nerve
Optic chiasm
Optic tract 
Lateral geniculate nucleus-thalamus
Primary visual areas of Occipital lobe
Superior colliculi-visual reflexes
Pretectal nuclei-accommodation of reflexes