Damnjanović Ivana

The Sensory System

Introduction Our “senses” continually provide us with

information about our surroundings. Sense organs are complex organs like

the eye or specialized receptors in areas such as the nasal mucosa or tongue.

Introduction Conversion of a stimulus to a sensation:

Stimuli (light, sound, temperature, etc. are changed into an electrical signal or nerve impulse.

Cutaneous Sensations Receptors of the general sense organs

are found in almost every part of the body.Encapsulated nerve endings – located in the

dermis; touch and pressure.Free nerve endings – mainly in the dermis of

the skin, mucosa, internal organs. They sense pain or crude touch.

Encapsulated nerve endings

Sense of Touch

The nerve endings in your skin can tell you if something is hot, cold, smooth or rough . They can also feel if something is hurting you. Your body has different types of nerve endings that all send messages to your brain.

Sense of Taste Taste buds – chemical receptors that

generate nervous impulses resulting in the sense of taste. There are about 10,000 microscopic taste buds located on the papillae of the tongue.

Gustatory cells

Sense of Taste Taste Sensations

Sweet, sour, bitter, saltyOther flavors results from a combination of

taste bud stimulations and olfactory receptor stimulation.

Magnified

tastebud

Papillae

Microscopic view oftaste buds (x100)

brain

food

sensory cell

Sense of Smell Olfactory receptors – chemical receptors

responsible for the sense of smell are located in the upper part of the nasal cavity.

The Ear Sense organ associated with hearing

and equilibrium and balance. 3 main parts

ExternalMiddleInner

Ear Brain

External Middle Inner

The Ear External ear Pinna External Auditory canal – a curving tube about one

inch long; extends into the temporal bone and end at the tympanic membrane (eardrum)

Middle ear Tympanic membrane 3 tiny bones called ossicles (bones) transmit

sound waves.

External Auditory canal

tympanic membrane

3 tiny bones

The EarInner Ear – contains mechanoreceptors that are activated by vibration and generate nerve impulses that result in hearing and equilibrium. -Cochlea is the auditory portion of the inner ear

Vestibule – membranous sacs (utricle and saccule) adjacent to the oval window and between the semicircular canals. Contains receptors for equilibrium.

semicircular canals

cochlea

The Eye Contains receptors for vision and a

refracting system that focuses light rays on the receptors in the retina.

Eyelids – contain skeletal muscle that allow us to close them and totally cover the exterior eyeball.

Eyelashes – help to keep dust out of our eyes. Tears

The Eye Cranial Nerves

Optic – visionOculomotor – eye movment

The eye contains 3 layers

The Eye Structure of the eyeball

Sclera – tough fibrous tissue.○ Front surface is the “white” of our eyes and

the cornea. The cornea is transparent ○ Sclera is covered by the conjunctiva in the

front of the eyeball.

The Eye Structure of the eyeball

Choroid - contains a dark pigment to prevent scattering of light that enters the eyeball. Also contains blood vessels and 2 involuntary muscles.○ Iris

○ Ciliary body (muscle)

The Eye Structure of the eyeball

Lens – composed of transparent, elastic protein; no blood supply

Retina – contains microscopic receptor cells called rods and cones○ Rods ○ Cones ○ Fovea