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Prof. S. Aswin, MD, PhD

SOMATOMOTORIC SYSTEM. Somatomotoric cortex. Prof. S. Aswin, MD, PhD. (GENERAL SOMATIC EFFERENT/ GSE SYSTEM). GENERAL SOMATIC EFFERENT (GSE) SYSTEM. EFF. EFFECTOR (SKELETAL MUSCLE). PYRAMIDAL SYSTEM. (INFO.). (CONTRACTION). COORDINATED MOVEMENT. (instruction: CONSCIOUS). CNS

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Prof. S. Aswin, MD, PhD

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  1. SOMATOMOTORIC SYSTEM Somatomotoric cortex Prof. S. Aswin, MD, PhD (GENERAL SOMATIC EFFERENT/ GSE SYSTEM)

  2. GENERAL SOMATIC EFFERENT (GSE) SYSTEM EFF. EFFECTOR (SKELETAL MUSCLE) PYRAMIDAL SYSTEM (INFO.) (CONTRACTION) COORDINATED MOVEMENT (instruction: CONSCIOUS) CNS (BRAIN) CIRCUIT EXTRAPYRA- MIDAL SYSTEM BASAL GANGLIA/ CEREBELLUM/ THALAMUS/ CORTEX

  3. GENERAL FUNCTIONS & CHARACTERISTICSOF GSE SYSTEM 1. SKELETAL MUSCLE • SKELETAL MUSCLES GENERALLY FUNCTION TO ALLOW: • MOVEMENT • ADJUST POSTURE • PRODUCE BODY HEAT • THE CRUCIAL PROPERTIES OF THE MUSCLE TISSUE: • ITS ABILITY TO CONTRACT • BE EXCITED BY A STIMULUS • BE STRETCHED (RETURN TO ITS ORIGINAL SHAPE AFTER STRETCHING OR CONTRACTING) • GIVES SKELETON THE POWER TO MOVE • IS USUALLY CONTRACTED VOLUNTARILY AND CONSCIOUSLY (Except: reflex)

  4. 2. NERVOUS CONTROL (MNs, NMJ/MEP)* • THE CONTRACTION OF SKELETAL MUSCLE IS UNDER NERVOUS CONTROL, i.e., THE MUSCLE TISSUE ALONE CANNOT CONTRACT *(MN: motor neuron; NMJ: neuromuscular junction; MEP: motor-end plate) 3. NEUROTRANSMITTER • ITS CONTRACTION IS INITIATED BY A CHEMICAL (NEUROTRANSMITTER/NT: acetylcholin/ACh) RELEASED FROM A NERVE (NEURON) AXON TERMINAL

  5. SOMATOMOT. CORTEX: UMN Corticobulbar tract CST Somatomotoric cortex BULBUS LMN SKELETAL MUSCLE SKELETALMUSCLE MOTOR HOMUNCULUS LCS UMN (Area 4/motor stript/ motor homunculus) ACS SKELETALMUSCLE LMN SKELETAL MUSCLE ANT. HORN CST: CORTICOSPIN. TRACT LCS: LAT. CORTICOSPIN. TRACT ACS: ANT. CORTICOSPIN. TRACT MIDLINE

  6. Somatomotoric cortex MOTOR HOMUNCULUS

  7. STRUCTURAL & FUNCTIONAL ASPECTS OF THE GSE SYSTEM  THE BRAIN EXERTS ACTIVE AND SUBTLE INFLUENCE ON THE ACTIVITY OF SKELETAL MUSCLES THROUGH DESCENDING MOTOR PATHWAYS THAT MAKE UP THEUPPER MOTOR NEURONS (UMN) 1. UMN • ORIGINATING FROM CELL BODIES IN THE CEREBRAL CORTEX AND BRAINSTEM (Regulates/modulates) • FUNCTION: UMN LMN* (cranial/spinal nerves) *LMNs located in the BULBUS (pons + medulla), their fibers are sent (through cranial/spinal nerves) to the muscle fibers innervated Cortex: UMN Skeletal m. Bulbus:LMN.

  8. Skeletal m. LMN Ant. horn of the spinal cord Alpha MN Gamma MN 2. LMN** • ALPHA MNs EXTRAFUSAL MUSCLE FIBERS • GAMMA-EFFERENT MNs INTRAFUSAL MUSCLE FIBERS ** LMNs located in the anterior horn of the spinal cord (through the spinal nerves) sent to the muscle fibers innervated

  9. Fig.10.7 NEUROMUSCULAR SPINDLESENSORY RECEPTOR THAT MONITORS THE EXTENTAND RATE OF MUSCLE LENGTHENING (STRETCHRECEPTOR) Gamma- efferent MN Alpha MN Neuromuscular spindle (fusus neuromuscularis) Soma cells of gamma efferent MN and alpha MN located in the anterior horn of the spinal cord

  10. MOTOR UNIT Motor neuron together with muscle fibers (myofibers) it innervates NEUROMUSCULAR JUNCTION (NMJ)/ MOTOR-END PLATE (MEP): The junctin of a motor unit and muscle fibers In humans: A single motor unit causes the contraction of 6-30 fibers (small MU: in some eye muscles) to over 1,000 fibers (largeMU: in powerful leg muscles)

  11. CHARACTERISTICS OF MOTOR UNIT (MU) • SMALL MU: • Fast movement • Weak movement • Easily fatigue (e.g., external eye muscles) • LARGE MU: • Slow movement • Strong movement • Not easily fatigue (e.g., muscles of upper arm and upper leg/thigh)

  12. NEUROMUSCULAR JUNCTION (NMJ) (Fig.10.5) • THE JUNCTION BETWEEN A MOTOR NEURON ENDING ON A MUSCLE FIBER • THE END BRANCHES OF THE MOTOR NEURON (AXON TERMINALS) GAIN ACCESS TO THE MUSCLE FIBER THROUGH THE ENDOMYSIUM • AT THE JUNCTION BETWEEN THE MUSCLE FIBER AND THE AXON TERMINALS: THE MUSCLE FIBER MEMBRANE FORMS A MOTOR END PLATE (MEP) (MEP: • THE SPECIALIZED PORTION OF THE SARCOLEMMA (PLASMA MEMBRANE) OF A MUSCLE FIBER • IT SURROUNDS THE SYNAPTIC END BULBS OF THE AXON)

  13. MEP

  14. NEUROMUSCCULAR JUNCTION MEP

  15. Electrochemical process Action potential NT release interaction of NT + receptor MEP

  16. COMPONENTS OF THE MOTOR SYSTEM: PYRAMIDAL & EXTRAPYRAMIDAL CEREBRAL CORTEX Pyramidal syst. Extrapyr. syst. BG THAL. Basal ganglia BG Ext. amyg., HPT Cere- bell. BRAIN STEM Cerebellum, BG, thalamus: involve in the extrapyramidal circuits that influence pyramidal activities SPINAL CORD

  17. MOTOR AREA (4,6+8, 3,1,2, 5,7) Cerebral cortex efferent (descendens) pathways 1.Corticobulbar tract 2. Corticorubral 2. Corticonuclear 3. Corticospinal tract Cerebral cortex 1 2 Bulbus 3 Nuc. ruber Nuc. cran. Ant. horn of the spin. cord MIDLINE

  18. CORTICOBULBAR TRACT Cerebral cortex Bulbus Pons Med.oblongata

  19. 1.CORTICOSPINAL TRACT: 1A. Anterior corticospinal tract (10% of fibers) 1B. Lateral corticospinal tract (pyramidal tract) (90% of fibers) 1 pyramis Pyramidal decussation 1B 1A

  20. Pons Med. obl. Bulbus: medulla oblongata + pons

  21. SOMATOMOTORIC SYSTEM • INITIATION • VOLUNTARY • NONSTEREOTYPIC (specific, smooth, precise, skilled) INDIVIDUAL MUSCLE MOVEMENT PYRAMIDAL SYST. EXTRAPYRAMIDAL SYST. • BODY POSITION (rough) • TONUS • INHIBITION/ACTIVATION GROUP OF MUSCLES MOVEMENT* LOWER MOTONEURONS (LMNs)* SKELETAL MUSCLES * e.g., extensors, flexors COORDINATED MOVEMENT (* LMN: Motoric neuron which axon directly innervate the effector/skeletal muscle)

  22. BASAL GANGLIA/NUCLEI 2B • 1. Lenticular nuc.: • Globus pallidus • Putamen • 2. Caudate nuc.: • A. Caput • B. Corpus • C. Caudate • 3. Amygdala 2A 1 2C 3

  23. PYRAMIDAL SYSTEM • PART OF SOMATOMOTORIC SYST. ORIGINATED FROM SPECIAL AREAS* OF THE CEREBRAL CORTEX WHICH DESCENDS THROUGH THE PYRAMID/PYRAMIS OF THE MEDULLA OBLONGATA AND TERMINATES ON MOTONEURON * Pyramidal areas/cortex (4, 3,1,2,6,8, 5,7)

  24. CYTOARCHITECTURAL MAP OF THE HUMAN CEREBRAL CORTEX (52 AREAS) • Somatomotoric cortex/area • Primary (Motor stript): 4 • Secundary/premotoric: 6,8 • Supplement:

  25. 1 2 • MOTOR CORTEX (MC) • Primary MC • (voluntary movement) • 2. Supplementary MC • (programming of complex movement) • 3. Premotor cortex • (complex movement) 3

  26. MOTOR HOMUNCULUS • Motor representation of the various parts of the body • Different parts of the body are represented in the cortex according to their functional importance • (Note the large areas devoted to the fingers, thumb, and face) SENSORY HOMUNCULUS

  27. THE COMPONENTS OF THE PYRAMIDAL SYST. SOMATOMOTORIC CORTEX CONTRIBUTION SOMATOMOTORIC CORTEX • AREA 4 40% (MOTOR STRIPT) HOMUNCULUS MOTORIS • AREA 3,1,2 20% (SOMAESTHETIC AREA) • AREA 6,8 (PREMOTORIC AREA) 40% • AREA 5,7 (PARASENSORIC AREA)

  28. MOTOR UNIT

  29. UPPER MOTONEURON (UMN)&LOWER MOTONEURON (LMN) 1. CEREBRAL CORTEX (Area 4; 6,8; 3,1,2;5,7) UMN CEREBRAL CORTEX MESENCEPHALON BRAIN STEM THE LOCATION OF ITS CELL BODY (SOMA) Corticospinal tract Corticobulbar tract Bulbus Spinal cord (Anterior horn)

  30. 2. MESENCEPHALON RUBER NUC. TECTAL NUC. INTERSTITIAL NUC. Rubrospinal Tectospinal Interstitiospinal tract tract tract SPINAL CORD (Anterior horn) 3. BRAIN STEM (truncus cerebri): Bulbus (Pons + med. Obl.) RETICULAR NUC. VESTIBULAR NUC. Reticulospinal Vestibulospinal tract tract SPINAL CORD

  31. LMN LOWER MOTONEURON (LMN) THE LOCATION OF ITS CELL BODY 1. BRAIN STEM MOTORIC NUCLEI OF CERTAIN CRANIAL NERVES (N III, N IV, N V, N VI, N VII, N IX, N X, N XII) N III N IV EXTRAOCULAR MUSCLES N VI N V N VII BRANCHIOGENIC MUSCLES * N IX VISCERAL ARCH I, II and III N X N XII TONGUE MUSCLES (* BRANCHIOGENIC MUSCLES: - Facial/mimic muscles - Sternocleidomastoid - Platysma - Laryngeal muscles - Trapezius - Pharyngeal muscles)

  32. 2. ANTERIOR HORN OF THE SPINAL CORD Alpha MN Gamma MN EXTRAFUSAL MUSCLE FIBERS INTRAFUSAL MUSCLE FIBERS

  33. SOMATOMOTORIC (DESCENDENT) SYSTEM MOTOR CORTEX (UMN) B A LMN BULBUS C UMN LMN SPINAL CORD (Anterior horn) MUSCULAR ACTIVITY (MOVEMENT) D A: CORTICOSPINAL TRACT D: SPINAL NERVES B: CORTICOBULBAR TRACT C: RETICULOSPINAL TRACT VESTIBULOSPINAL TRACT INTERSTITIOSPINAL TRACT

  34. PYRAMIDAL SYSTEM CORTICOSPINAL TRACT CORTICOBULBAR TRACT (PYRAMIDAL TRACT) LATERAL ANTERIOR (CROSSED) 90%) (10%)

  35. PYRAMIDAL CORTEX CRUS CEREBRI CORTICOSPINAL (MIDBRAIN) TRACT PONS PYRAMIS (MED. OBLONGATA) PYR. DECUSSATION LATERAL CORTICOSPINAL TRACT ANTERIOR CORTICOSPINAL TRACT LMN (ANTERIOR HORN OF THE SPINAL CORD) Lamina Rexed IV, V, VI, VII, IX LMN (ANT. HORN OF THE SPINAL CORD (LAM. REXED VIII) MIDLINE X I II III IV V VI VII IX VIII REXED LAMINA PYRAMIDAL SYSTEM

  36. CORTICOBULBAR TRACT UMN PYR. CORTEX CORTICOBULBAR TRACT PONS BULBUS MED. OBL. LMN 1 2 Characteristics of the bulbar nuclei innervation In general: crossed + uncrossed 1 & 2: nuclei in the bulbus

  37. LMN IN THE BULBUS MOTORIC NUCLEI OF: N III, N IV, N VI EXTRAOCULAR MUSCLES N V MASTICATORY MUSCLES N VII FACIAL (MIMIC) MUSCLES N IX, N X PALATUM MOLLE MUSCLES PHARYNGEAL MUSCLES (cranial LARYNGEAL MUSCLES part) ESOPHAGUS N XI TRAPEZIUS STERNOCLEIDOMASTOID (caudal LARYNGEAL MUSCLES part) PHARYNGEAL MUSCLES N XII TONGUE MUSCLES

  38. CORTICOBULBAR TRACT (left) (right) CEREBRAL CORTEX CEREBRAL CORTEX (UMN) (UMN) IPSILAT. (uncrossed) A: BILATERAL CONTRALAT. (crossed) B: UNCROSSED (UNILATERAL) Innervation of nuclei in the bulbus A B

  39. Upper facial muscles Lower facial muscles N VII NUCLEI CHARACTERISTICS OF CORTICOBULBAR TRACT • IN GENERAL: CRANIAL NERVE NUCLEI RECEIVE BILATERAL INNERVATION FROM THE CEREBRAL CORTEX • EXCEPTIONS: - N VI: CROSSED ONLY (CONTRALATERAL) CORTEX A.CRANIAL (bilateral) - N VII: 2 NUCLEI B. CAUDAL (contralateral) CORTEX N VI NUCLEUS A B

  40. CLINICAL CORRELATION PARALYSIS/PLEGIA PARESIS (TOTAL PARALYSIS) (PARTIAL PARALYSIS) Severed A B Severed A B MONOPLEGIA HEMIPLEGIA PARAPLEGIA TETRAPLEGIA (One limb) (Half of the (Right + left (Four limbs) body: lower limbs) one upper limb (the same side) + one lower limb MUSCLE PLEGIA

  41. PARALYSIS / PLEGIAPYRAMIDAL TRACT LESION RIGHT (DEXTER) LEFT (SINISTER) A CORTICOSPINAL TRACT PYRAMIDAL DECUSSATION C LATERAL CORTICOSPINAL TRACT B D SUPERIOR EXTREMITY INFERIOR EXTREMITY LESION: A LEFT HEMIPLEGIA (HEMIPLEGIA SINISTRA) / CONTRALATERAL B RIGHT HEMIPLEGIA /IPSILATERAL C LEFT INFERIOR EXTREMITY PARALYSIS RIGHT SUPERIOR EXTREMITY PARALYSIS (HEMIPLEGIA CRUCIATA) LEFT SUPERIOR EXTREMITY LEFT INFERIOR EXTREMITY RIGHT SUPERIOR EXTREMITY RIGHT INFERIOR EXTREMITY TETRAPLEGIA D

  42. BROWN-SEQUARD SYNDROME • IPSILATERAL PARALYSIS • DEEP ANESTHESIA + CUTANEOUS IPSILATERAL HYPERESTHESIA • CONTRALATERAL CUTANEOUS ANESTHESIA • HEMISECTION OF THE SPINAL CORD

  43. LESION AT THE LATERAL PART OF PYR. DECUSSATION Hemiplegia cruciata

  44. HEMISECTION OF THE SPINAL CORD • BROWN-SEQUARD • SYNDROME: • Paralysis (ipsilat.) • Deep anesthesia • & cutaneous hyperesthesia (ipsilat.) • - Cutaneous anesthesia (contralat.)

  45. Hemiplegia

  46. EXTRAPYRAMIDAL SYSTEM

  47. EXTRAPYRAMIDAL S Y S T E M A SYSTEM CONSISTS OF TRACTS (SUPRASPINAL DESCENDENS), NUCLEI AND FEEDBACK CIRCUITS WHICH PRODUCES SIGNIFICANT INFLUENCES ON THE VOLUNTARY MUSCLES ACTIVITIES, OUTSIDE OF THE PYRAMIDAL SYSTEM THE COMPONENTS OF THE EXTRAPYRAMIDAL SYSTEM • EXTRAPYRAMIDAL CORTEX TELENCEPHALON BASAL GANGLIA • THALAMUS DIENCEPHALON SUBTHALAMUS • RUBER NUCLEUS SUBSTANTIA NIGRA BRAIN STEM RETICULAR FORMATION • CEREBELLUM • FEEDBACK CIRCUITS

  48. EXTRAPYRAMIDAL SYSTEM PYRAMIDAL SYSTEM POSTURAL ACTIVITY NONPOSTURAL ACTIVITY GROUP OF LARGE INDIVIDUAL MUSCLE MUSCLESADAPTATION SKILLED MOVEMENTS (Smooth, precise, specific, learned) MODULATION CIRCUIT LMN Pyramidal & extrapyramidal systems interact in harmony to produce normal and coordinated movement NORMAL & COORDINATED MOVEMENT

  49. AMYGDALA: Anatomically: part of basal ganglia Functionally: part of the limbic system GANGLIA BASALIA NUC. LENTICULARIS PUTAMEN GLOBUS PALLIDUS NUC. CAUDATUS CAUDA CAPUT CORPUS

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