Sensory system

1. Sensory system Human Anatomy Dept. Biomedical Engineering

2. INTRODUCTION • Millions of bodliy sensory organs receive signals from outer environment to be sent to CNS • These organs are divided into 2 main groups • GENERAL SENSORY ORGANS - for touch, heat & pain sessitivity - for guarding homeostasis • SPECIAL SENSORY ORGANS vision, hearing, balance, taste & smell sesnsitivity

3. RECEPTORS OF SENSORY ORGANS • This specially designed apparatus receives signals from the outer & inner environment and transforms them into signal to be sent to the nervous system Eg. Vision or hearing allows to sense the danger of outer environment Pain, changes in blood pressure, hunger and thurst sensations allow to preserve homeostasis (i.e. İnner environment)

4. Working principle of receptors • Receptor defines the stimuli and transforms it into signal, acceptable by the nervous system • Continuous stimulation of receptors causes their adaptation, which slow down signal formation . Eg.: lost of the sense to parfumes after long exposition time.

5. Distribution of receptors • Special sesnsory organs are located on specific areas • General sensory receptors are located through the body • Distribution of the latter vary from area to area (compare touch sensors on the fingertip and on the back of the body

6. Receptor’s classification based on location • Eksteroceptor (skin receptors) work to register pressure, touch, pain, heat • Viseroceptor (located within internal organs) define hunger-thurst, blood pressure, traction, chemical changes • Proprioceptor (felt in space and during intoxication)are located within skeletal muscles, tendons and joints and work during movement, orientation & muscle stretching.

7. Classification of receptors on the base of signal type • Mechanoreceptor • Chemoreseptor • Thermoreceptor • Nociceptor • Photoreceptor

8. Mechanorceptor • Reacts on mechanical impact • E.g. Pressure or traction of the skin, muscle & vessel

9. Chemoreceptor • Reacts on changes in chemical composition E.g. Work to register smell, taste, pH, blood glucose or CO2 concentration changes.

10. Photo- & thermoreceptors • Thermoreceptor – detects heat changes • Photoreceptor – provides with vision

11. Nociceptor • Switches on when any stimuli is strong enough to cause damage • Reacts on toxins, excessive light, noise, pressure or heat. • The sense of pain appears.

12. Special sensory systems • Smell sensory system • Taste sensory system • Hearing sensory system • Balance sensory system • Vision sensory system

13. Smell sesnsory system • Molecules of smelling compounds are dissolved in the mucus of the nasal cavity, which causes the irritation of olfactory nerve. • Generated signal propagates towards CNS

14. Taste sensory system • Taste chemoreceptors within the taste buds on the tongue provide CNS with signals after contact with compounds.

15. Systems for hearing and balance • External ear • Mid ear (composed of 3 bones), which receive & send signal to the cochlear nerve. • Inner ear – special labyrinth contains fluid with otoliths, which dislocation during movement causes vestibular nerve irritation & signal formation

16. Vision sensory system Structure of the eye • Cornea-external cover of the eye • İris-diaphagm of the eye, which regulates light entrance to the eye • Lense – focuses light to the back wall of the eye • Retina – back wall of the eye, contating photoreceptors.