ب سم الله الرحمن الرحيم

1. بسم الله الرحمن الرحيم ﴿و ما أوتيتم من العلم إلا قليلا﴾ صدق الله العظيم الاسراء اية 58

2. Physiology of CNS Sensory System By Dr. Abdel Aziz M. Hussein Lecturer of Physiology Member of American Society of Physiology

3. Introduction • Body functions are regulated by 2 systems;

4. General Organization of NS

5. Anatomical Organization Central Nervous System (CNS) Peripheral Nervous System (PNS)

6. Central NS

7. Brain Prosencephalon (Forebrain) Mesencephalon (Midbrain) Rhombencephalon (Hindbrain)

8. Brain • Composed of 3 parts; I) Prosencephalon→ consists of • Telencephalon → 2 cerebral hemispheres • Diencephalon → include • Basal ganglia • Thalamus • Hypothalamus II) Mesencephalon: midbrain III) Rhombencephalon: include • Cerebellum , Pons, medulla oblongata

9. Telencephalon (Cerebral hemispheres) Thalamus Basal ganglia Diencephalon

10. Diencephalon

12. Spinal Cord • Composed of 5 regions; • Cervical regions → 8 segments • Thoracic segments → 12 segments • Lumbar segments → 5 segments • Sacral segments → 5 segments • Coccygeal segments → 1 segments

14. Peripheral N. System • Consists of nerves that arise from CNS to supply different parts of body; • Cranial nerves → 12 pairs • Spinal Nerves → 31 pairs (each pair arises from each segment of spinal cord)

15. Cervical Thoracic Lumbar Sacral Cocygeal

16. How Nervous System works?

17. Functional Divisions of NS • NS has 3 main functional divisions; a) Sensory division of NS: • Detects changes in internal and external environments and informs the CNS about them. b) Motor division of NS: • Initiates and controls the activities of skeletal muscles • Controls the activities of plain muscles, cardiac muscles and even glands. c) Intellectual division of NS: • Consciousness, memory, learning, thoughts, emotions

18. Functional Divisions of NS

19. SENSORY SYSTEM

20. Sensory System Def, • It is the division of the NS concerned with; • Detection of the stimuli (as regard nature, locality and intensity) • Informing specialized centers in CNS to adopt adequate responses

21. Stimuli CENTRAL NERVOUS SYSTEM Initiate reflexes Storage as in memory and learning Conscious perception of sensations

22. Component of Sensory System Centers Receptors Centers Afferents

23. Sensory Receptors

24. Receptors

25. Receptors • Def, • They are specialized microscopic structures present at the peripheral terminations of afferent or sensory neurons • Functions: • Detect stimuli e.g. thermal, chemical, electrical and convert it to nerve impulse • So, act as; • Detectors • Transducers

26. Receptors Stimulus Receptor potential Action potential

27. Types of Receptors

28. Classification of Receptors • According to the site of receptors: • 1) External receptors: • Present mainly in skin and body surfaces • e.g. Pacinian corpuscles • 2) Internal receptors: are 2 types; • a) Proprioceptors (deep receptors): • Present in structures deep to skin e.g. bones and muscles • e.g. Ms spindle receptors in the skeletal ms • b) Visceral receptors: • Present in the internal viscera • e.g. stretch receptors in the wall of hollow viscera

29. External Receptors

30. Proprioceptors

31. Classification of Receptors • B) According to nature of stimulus (Physiological classification): 5 classes: • 1) Mechanoreceptors: • Stimulated by the mechanical form of energy • Touch receptors in skin • Pressure receptors in skin and subcutaneous tissues e.g. Pacinian corpuscles • Tension receptors: golgi tendon organs in ms tendons • Stretch receptors in skeletal ms (ms spindle) and wall of viscera and arterial baroreceptors

32. Classification of Receptors B) According to nature of stimulus: 1) Mechanoreceptors: 5. Sound receptors : in inner ear (Organ of Corti) 6. Vestibular receptors (Macula and cristaampullaris)

34. Classification of Receptors • B) According to stimulus : • 2) Chemoreceptors: • Stimulated by chemical form of energy (stimuli) • External chemoreceptors:taste & smell receptors. • Internal chemoreceptors: • Peripheral chemoreceptors in the aortic and carotid bodies • Central chemoreceptors in medulla • Glucoreceptors and osmoreceptors in hypothalamus

35. Peripheral and Central chemoreceptors

36. Classification of Receptors • B) According to stimulus : • 3) Thermoreceptors: • Respond to thermal form of energy • e.g. cold and hot receptors4) Pain (nociceptors) receptors: • Respond to the injurious or noxious stimuli (tissue damage) • 5) Photoreceptors or light electromagnetic receptors: • Respond to the light waves as rods and cones in the retina.

37. THANKS