1. Central Nervous System Dr. Mohammad Alzoghiabi

2. Organization of the Nervous System  Central nervous system 1.Brain 2.Spinal cord  Peripheral nervous system 1.Sensory receptors 2.Sensory nerves 3.Ganglia

4. Central Nervous System Functions:  Has information about environment  Organizes reflexes  Plans & execute voluntary movement  Memories, thinking & learning

5. Central Nervous System  Types of nerves 1.Sensory or afferent division 2.Motor or efferent division

6. Spinal cord TTTThe most caudal portion of CNS FFFFrom the base of the skull to 1st lumbar vertebra CCCContain 31 pairs of spinal nerves

7. Spinal cord and nerves SSSSensory verves: carry information to spinal cord from different organs via dorsal root and cranial nerve ganglia MMMMotor nerves: carry information from spinal cord to periphery, include both: Somatic Autonomic

8. Brain Stem  Medulla breathing, blood pressure, swallowing, coughing and vomiting reflexes  Pons participates with medulla in regulating breathing gets information from cerebral hemispheres to cerebellum  Midbrain Controls eye movements contains neucli of auditory and visual system

9. Cerebellum  Functions: i.Coordination of movements ii.Planning and execution of movements iii.Maintenance of posture iv.Coordination of head and eye movements

10. Thalamus and Hypothalamus  Thalamus processes all sensory and motor informations  Hypothalamus contains centers to regulate 1. Body temp 2. Water balance 3. Pituitary gland 4. ADH and oxytocin  Known as Diencephalon “between brain”

11. Motor Cortex AAAAnterior to the central cortical sulcus divided into: 1- primary motor cortex 2- premotor area 3- supplementary motor area

12. Primary Motor Area (MI)  Right front of the central sulcus  Laterally in the sylvian fissure  Superiorly to the top of the brain  Inferiorly to the longitudinal fissure  Topographical representations of the body areas in an inverted manner

16. Primary Motor Area (MI)  Main origin of the pyramidal tract  More than half of motor area concerned with the hands and muscle of speech  Excitation of a single motor neuron causes the excitation of a specific pattern of movement but not a single muscle  Contains upper motorneurons which project directly to spinal cord  Lesion in MI leads to flaccid paralysis

17. Premotor Area  Anterior to the primary motor cortex  Superiorly to the longitudinal fissure  Inferiorly to the sylvian fissure  Same topographical organization as the motor cortex  Responsible for more complex patterns of movement

18. Supplementary Motor Area  Has another topographic organization  Contraction often bilateral - bilateral grasping movements (climbing) - attitudinal movements - fixation movements - positional movements of head and eyes

19. Other Motor Regions  Bronca’s Area: responsible for vocalization  Voluntary eye movement field: controls the eye movement to certain objects and blinking  Head rotation area  Area of hand skills destruction  motor apraxia

20. White Matter of Spinal Cord  Posterior faniculus  Anterior faniculus  Lateral faniculus Tract: Tract: Composed of nerve fibers sharing a common origin, destination and functions

21. Posterior funiculus  Contains one ascending fibers concerned with two modalities - kinesthesia - discriminative touch  Lesion of this area causes loss of: - vibration sense - position - two point discrimination - fine touch (tested by piece of cotton) - weight perception

23. Lateral & Anterior funiculi Ascending Tracts:  Dorsal spinocerebral tract  Ventral spinocerebellar tract  Spinocervical thalamic tract  Lateral spionothalamic tract  Anterior spinothalamic tract

24. Lateral & Anterior funiculi  Desending Tracts  Corticospinal tract  Rubrospinal tract  Lateral vestibulospinal tract  Medial vestibularspinal tract  Reticulospinal tract  Descending autonomic pathway

25. Ascending Tracts  Dorsal spinocerebellar tract: conveys impulses from muscle spindle, golgi organ via (DRG) to cerebellum  Ventral spinocerebellar tract: conveys impulses to cerebellum from golgi organ

26. Ascending Tracts  Spinocervical thalamic tract: conveys impulses to thalamus; carries the kinesthesia & discriminative touch  Laeral spinothalamic tract: transmits pain & temperature sensations to thalamus  Anterior spinothalamic tract: transmits light touch sensations to brain stem & thalamus

28. Descending Tracts 1. Corticospinal tract (pyramidal)  From motor cortex to medulla as follow:  30% from the motor cortex to the muscles  30% from the premotor and supplementary cortex to the muscles  40% from somatosensory areas  divided into: 1.Crossed (lateral corticospinal tract) 2.Uncrossed fibers (anterior corticospinal tract)

29. Corticospinal Pathway (pyramidal) Corticospinal Pathway (pyramidal)  From the cortex  internal capsule  thru brain stem  via medulla where majority of the fibers cross in the lower medulla  lateral coticospinal tract of the cord  interneurons (few in dorsal horn and very few in anterior motor neurons)  N.B. also a few of fibers do not cross but pass ipsilaterally in ventral corticospinal tract

32. Corticospinal tract (pyramidal) Corticospinal tract (pyramidal)  3% of pyramidal fibers with 16  m myelinated  Originate from betz cells in the motor area  Impulses conveyed are facilitatory to flexor motor neurons  Terminates in internurons laminae IV-VII  Lesion:  Homolateral paralysis  Contralateral paralysis In addition to: spasticity, hyperactive myotatic reflexes and clonus

33. Descending Tracts 2. Rubrospinal tract  Neuronal origin is in red nucleus (midbrain)  Terminates similarly as pyramidal tract  Indirect corticospinal tract  Facilitates flexor motor neurons 3. Lateral vestibulospinal tract  Neuronal origin lie in pons (lateral vestibular nucleus)  Terminates at laminae VII & VIII  Facilitates extensor motor neurons

35. Descending Tracts 4. Medial vestibularspinal tract:  From media vestibular nucleus in pons  Terminates as latera tract  Facilitates flexor motor neurons 5. Reticulospinal tract: a. pontine reticulospinal tract from pons terminates at laminae VII & VIII facilitates extensor motor neurons b. medullary reticulospinal tract terminates at VII & IX facilitates flexor motor neurons

36. Descending Tracts 6. Descending autonomic pathway:  Neuronal origin at hypothalamus  Small caliber fibers  Project into intermediolateral of column