COORDINATION SYSTEM THE SENSES Ch.9/XI bil

Sensory system Sense organs or receptors are receptors, it functions to receive information These organs are designed to receive stimuli which make us aware of changes taking place in our environment Receptor is an external stimulus receiver Senses, which have special receptor cells to identify changes in the external environment, have function to provide information ( heat, cold,pressure, touch etc) Stimulus from external environment is carried by the somatic nerve.

Sensory system All the senses have highly specialized receptors enabling them to respond to stimuli – Chemoreceptors : chemical – Photoreceptors : light – Phonoreceptors : sound – Tangoreceptors : touch/pressure Exteroreceptors = detects stimuli originating outside the body Interoreceptors = detects stimuli originating inside the body Proprioreceptors = located within the body muscles, joints and bones (kinestetic)

Sense of touch The sense organ for touching and pressure is skin. The skin is richly supplied with nerve endings and these enable it to act as a sense organ Stimulation of nerve endings in the skin produces sensations related to temperature, pain and touch which are important for survival

Skin Type of receptors in skin  Merkel : touch corpuscle  Paccini : pressure corpuscle  Ruffini : heat (thermoreceptor)  Meissner : cold corpuscle  Free nerve endings : pain

Sense of taste The tongue is covered by projections called papillae on the surface. The papillae contain taste receptors – taste buds The taste receptor is a chemoreceptor because it can be stimulated by various chemical substances Sense of taste depends to the sense of smell

Tongue There are 4 main kinds of tastes :  Bitter : on the back  Sweet : on the tip  Sour : on the side to tip  Salty : on the sides

Sense of hearing The sense of hearing is concerned with the perception of sound The ear is the only organ of hearing and it is also concerned with balance There is a close relationship between the sense of hearing and speech

Ear structure Three parts of ear :  Outer ear (external) o Auricle/Pinna/flap : receive and collect the sounds o Auditory canal : is a canal, covered by hair, sebaceous and ceruminous glands – secretes cerumen (ear wax)  Middle ear o Tympanic membrane o Ear bones (ossicles): responsible for the transmission  Malleus (hammer)  Incus ( anvil)  Stapes (stirrup) o Eustachian tube : connect middle ear and pharynx

Ear structure  Inner ear (internal) o Oval window o Semicircular canal : balance organ Sacculus Utriculus Ampula o Cochlea : Sound receptor

Ear Middle ear

The inner ear Semicircular canal Cochlea

Anatomy of inner ear Within the cochlea, there is a fluid called perilymph and endolymph – Scala vestibuli – Scala media – Scala tymphani

Sound transmission

Sense of smell Smelling rods (olfactory rods) – bipolar cells – are located on the surface of the nasal cavity (upper part) The nose is both an organ of the respiratory system and sensory system The odor dissolves in the layer of moist mucous membrane covering the receptors in the upper nasal cavity. The impulses are transmitted to the brain for interpretation

The nose

Sense of sight This sense organs responsible for vision. Eye is the vision organ that composed of photoreceptor cells that receive light (intensity and colour) – visual receptors in the retina are highly sensitive to light Two different receptors – Cone cells : for vision in bright day and colours – Rod cells : for vision in low light /night Accomodation power = ability to change lens shape and focal length that enables the eye to receive clear images of objects

Eye structure

The eye External structure

The eye Internal structure

Photoreceptors

Physiology of vision

Light transmission

The senses (summary) Sense organreceptorsType of receptors Type of stimulus location Sense of touchNerve endingsexteroreceptortouchskin Sense of tasteTaste budsexteroreceptorchemicaltongue Sense of smellOlfactory cellexteroreceptorchemicalnose Sense of hearing Organ of cortiexteroreceptorsoundear Sense of sightRod and Conesexteroreceptorlighteye

Disorders and disturbances