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Anatomy and Physiology of Domestic Animals
Veterinary Science 135

SENSORY SYSTEM

Sense organs are extensions of the central nervous system (CNS) that continuously monitor what is going on inside and outside the animal. At the heart of all sense organs are sensory receptors - various kinds of specially modified nerve endings. When triggered by an appropriate stimulus, a sensory receptor generates a nerve impulse that travels to the CNS and is interpreted as the appropriate sensation.

 

The sensory receptors of common domestic animals are sensitive to 4 general types of stimuli:

 

I. General terminology

II. General senses

A. Visceral sensations

B. Touch

C. Temperature

D. Proprioception

E.  Pain

            1. Nociceptors

            2. Nociception

                    a. Transduction

                    b. Transmission

                    c. Modulation

                    d. Perception

            3. Subjective consequences of severe/chronic pain

            4. Objective consequences of severe/chronic pain

                    a. Behavioral

                    b. Autonomic

                    c. Neuroendocrine

                    d. Metabolic

                    e. Immune

                    f. Morphologic

III. Special senses

A. Taste
1. Taste buds
a. Locations

b. Gustatory cells

c. Taste pore

B. Smell

1. Olfactory epithelium
a. Olfactory cells

b. Mucous layer

C. Hearing

1. External ear
a. Pinna

b. External auditory canal

c. Tympanic membrane

2. Middle ear

a. Function

b. Ossicles

i. Malleus

ii. Incus

iii. Stapes

c. Eustachian tube

i. Location

ii. Function

3. Inner ear

a. Cochlea
i. Location

ii. Structure

iii. Organ of Corti

(a). Hair cells

(b). Tectorial membrane

D. Equilibrium

1. Vestibule
a. Maculae

b. Otoliths

c. Functions

2. Semicircular canals

a. Crista

b. Function

E. Vision

1. Major layers of eyeball
a. Outer fibrous layer
i. Cornea

ii. Sclera

iii. Limbus

b. Middle vascular layer

i. Choroid
(a). Tapetum

ii. Ciliary body

iii. Iris

c. Inner nervous layer

i. Retina

2. Major compartments of eyeball

a. Aqueous compartment
i. Aqueous humor

ii. Anterior chamber

iii. Posterior chamber

b. Vitreous compartment

i. Vitreous body

3. Lens

a. Structure

b. Function

c. Attachments

d. Accommodation

i. Distant vision

ii. Close vision

4. Iris

a. Structure

b. Function

5. Retina

a. Function

b. Structure

i. Pigment layer

ii. Photoreceptors

(a) Rods

(b) Cones

iii Neurons, synapses, & nerve fibers

iv. Optic disk

6. Formation of a visual image

7. Extra-ocular structures

a. Conjunctiva
i. Palpebral conjunctiva

ii. Bulbar conjunctiva

b. Eyelids

i. Medial canthus

ii. Lateral canthus

iii. Tarsal glands

iv. Third eyelid

c. Lacrimal apparatus

i. Lacrimal gland

ii. Lacrimal puncta

iii. Lacrimal sac

iv. Nasolacrimal duct

d. Eye muscles

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