1. Brain stem & reticular formation Dr. Najam Siddiqi MBBS, PhD (Japan) Postdoc (USA)

2. What is brain stem ?  Medulla oblongata  Pons  Midbrain

3. What are contents of brain stem?  Ascending & descending tracts  Cranial nerve nuclei  Reticular formation nuclei and fibres forming a network  Other nuclei

4. Brain stem--Ventral view

5. Brain stem--Dorsal view

6. Midbrain at Superior Colliculus level

7. Oculomotor nerve (Pretectal & Edinger-Westphal nucleus)

8. Mid brain at Inferior colliculus level

9. Trochlear nerve (IV)

10. Pons Ventral viewDorsal view

11. Pons

13. Trigeminal nerve (V) (sensory/motor) Muscles of mastication, tensor tympani, tensor veli palatini, mylohyoid, digastric

14. Trigeminal nerve (sensory)

15. Abducent nerve (VI)

16. Facial nerve (VII) – Sensory/parasympathetic

17. Medulla oblongata

18. Facial nerve (motor) Muscles of facial expression, Post. belly of digastric, STAPEDIUS

19. Medulla oblongata

20. Glossopharyngeal nerve (IX)

21. Vagus nerve (X)  Parasympathetic nerve to the viscera: Gut, respiratory system, heart  Motor: muscles of palate, pharynx, larynx  Sensory: larynx, trachea, gut, aortic arch receptors, taste buds in post. oral cavity

22. Spinal accessory nerve (XI) Striated muscles of larynx, Sternocleido- mastoid, Trapezius

23. Hypoglossal nerve (XII) motor Intrinsic muscles of the tongue, hyoglossus, genioglossus, styloglossus

24. Olfactory nerve (I)

25. Optic nerve (II)

26. Vestibulocochlear nerve (VIII)

27. Reticular Formation (RF)  Resembles a net of neurons and nerve fibers from the spinal cord to the cerebrum  Separated by huge dendritic tree  Connected by immense number of afferent and efferent axons  Lie in brainstem tegmentum of midbrain, pons and medulla  Extent to thalamus, hypothalamus, cerebrum  Cranial nerve nuclei are not part of it  It influence skeletal muscle activity, somatic and visceral sensations, autonomic and endocrine functions and level of consciousness

28.  Arousal of the brain as a whole  Certain reticular neurons send continuous stream of impulses to cortex—keeps the cortex alert and conscious; this part is called Reticular Activating System (RAS)  RAS acts as a FILTER for the flood of sensory inputs. Disregard almost 99% of all sensory impulses as unimportant

29. Reticular Activating System (RAS)  RAS is inhibited by sleep centers located in hypothalamus  Depressed by alcohol, sleep inducing drugs, tranquilizers  Severe injury to RAS result in irreversible coma

33. Motor activity  Via reticulospinal tract, motor nuclei projects to motor neurons in the spinal cord to help control skeletal muscles  Other nuclei such as vasomotor, cardiac and respiratory centers of medulla are automatic centers regulate visceral motor functions

34. Nuclei of RF  Midline column: (Midline Raphe nuclei) extent the entire length of the median/paramedian plane of brainstem  Medial column: (Medial gigantocellular--large cell nuclei) pontomedullary tegmentum  Lateral column: (Lateral parvicellular small cell nuclei): from medullocervical region to midbrain  Cerebellar reticular formation nuclei: connected to cerebellum

35. Afferents  Ascending and descending pathways  Auditory and optic pathways  Spinal afferents includes spinoreticular tracts  Spinothalamic tract from thalamus, subthalamus, epithalamus, corpus striatum, limbic system  Brainstem afferents includes sensory tracts from Trigeminal, Cochlear, vestibular nuclei.  Tectoreticulat tract  Reticuloreticular tract  Cerebellar afferents

36. Afferents  Limbic afferents includes Habenular nuclei, mamillary bodies  Hypothalamus afferents  Basal ganglia afferents  Cerebral cortex afferents

37. Efferent projections  Reticulobulbar tract-cranial nerve nuclei  Reticulospinal tract—anterior horn cells of spinal cord  Reticulothalamic tract-- to thalamus, hypothalamus  Limbic system, cerebral cortex, red nucleus, corpus striatum, cerebellum, tectum,  To sympathetic and parasympathetic outflow

38. Functions 1. Control of muscle tone and reflexes: mediates postural reflexes through alpha and gamma motor neurons 2. Muscles of facial expression 3. Influence all ascending pathways: Central transmission of sensory impulses 4. Control of Autonomic nervous system: Respiration, Cardiovascular functions Respiration, Cardiovascular functions

39. Functions 5. Arousal and level of consciousness: Ascending reticular formation system: stimulation will arouse the sleeping person, mediates alerting responses and consciousness and maintain the cerebrum in a waking state 6. Influence on the biological clock--Sleep: serotonin-secreting neurons in raphe nuclei mediate non-REM sleep 7. Control of endocrine nervous system

40. Sleep disorders  Somnambuslim (sleep walking)  Enuresis  Narcolepsy  Cataplexy: an attack of paralysis of somatic muscles precipitated by bouts of laughter or crying/strong emotional stimuli

41. Hang on