Nervous System III PDF

Nervous System III PALM 207  Learning Objectves Review: spinal cord, spinal roots, spinal nerves, vertebral levels, spinal levels of major nerve plexuses (cervical, brachial, lumbar, sacral) Identfy the anatomy of the blood supply to the spinal cord Distnguish bet...

Nervous System III PALM 207  Learning Objectves Review: spinal cord, spinal roots, spinal nerves, vertebral levels, spinal levels of major nerve plexuses (cervical, brachial, lumbar, sacral) Identfy the anatomy of the blood supply to the spinal cord Distnguish between ascending and descending tracts (locaton, functon), and provide specifc examples of each type Describe the pathways of common refexes Apply knowledge of structure/functon of spinal cord to clinical situatons.  Spinal Cord and Spinal Roots Ctntral canalvery small for CSF fow Whitt mattr contains Gray mattr contains mostly axons mostly ctll bodits. Vtntral root > - anterior side Dorsal root ganglion posterior side to roots converge Rootltts contain bundlts of axons tnttring or txitng spinal ↳Dorsal root dorsal side / posterior. cord  combined sensory a motor - 31 Pairs of Spinal Nerves Vtntral roots and dorsal roots join to form spinal ntrvts posterioris Vtntral ramus Canterior side ↳Dorsal posterior ramus Each spinal ntrvt dividts into dorsal rami and vtntral rami Art tht structurts labtltd on this slidt part of tht ctntral ntrvous systtm or ptriphtral ntrvous systtm? Central ✅ X mess Peripheral ↳ by webranched o a A ✅ X Spinal Cord Segments and Spinal Nerves are Named for the Vertebral Level Where Spinal Nerves Emerge Ctrvical (C1-C8) Note: due to diferental growth, spinal cord stops at vertebral levels L3 in Thoracic (T1-T12) newborns, and L1-L2 in adults. Lumbar (L1-L5) Spinal nerves are named for where they EMERGE from the vertebral column. Sacral (S1-S5) Coccygtal (Cx1) = 31  Spinal Nerve Plexuses: Networks of Adjacent Primary Rami Cervical Plexus C1-4 nerves to neck muscles and diaphragm Phrenic nerve C3-5 (C3,4,5 keeps you alive)  -(arm) Brachial Plexus C5-T1 – upper limb (LrL) Lumbar Plexus L1-L4 – inguinal region and lower limb Sacral Plexus L4-S4 –pelvis and lower limb Blood Supply to the Spinal Cord Vtrttbral arttrits down anterior of spinal cord go Anttrior spinal arttry (1) & Posttrior spinal arttrits (2) from each one referral artery What is the name of the hole in cervical vertebrae where the vertebral artery passes? Transverse foramen  Spinal Cord: Gray Mater Gray matter – “buterfy” shape – Dorsal horns posterior projections sensory neurons enter – Ventral horns anterior projections somatic motor neurons exit – Surrounds central canal  Spinal Cord: White Mater White matter – Three regions Posterior (or dorsal) column Lateral column Anterior column – Columns contain fber tracts dorsal columns (posterior Lateral Lateral Canteriors ventaens  Spinal Tracts Generally named for origin and destination Two general types – Ascending tracts carry sensory informaton to the brain – Descending tracts carry motor informaton to peripheral structures Located in one of three columns of spinal cord – Anterior Dontneeda – Posterior – Lateral  Ascending Tracts Sensory tracts Two to three neurons (usually 3) in pathway First-order neuron – sensory receptor in periphery – cell body in dorsal root ganglion – extends to spinal cord Second-order neuron – cell body in spinal cord – usually crosses over (decussaton) – extends to brain ↳(thalamus, brainstem, cerebellum) it can places go Third-order neuron (not always present) – cell body in thalamus (projects to cortex) Somatc Sensory Cortex Post-central gyrus  Descending Tracts Motor tracts – two types – Pyramidal: cell body in cortex of brain – Extrapyramidal: cell body someplace other than cortex Two neurons – Upper motor neuron: cell of origin in brain – Lower motor neuron cell body in gray matter of spinal cord neuronal processes in peripheral nerves Primary Motor Cortex Pre-central gyrus  Examples of Ascending Tracts Posterior column (2 grooves ↓ – Fasciculus gracilis (from trunk and legs) – Fasciculus cuneatus (from neck, arms and upper chest; ends at T6) Sensory Functons – Discriminatve touch (i.e., 2-point discriminaton) – Propriocepton (awareness of positon of body parts) – Weight discriminaton (assessing weight by feeling an object) – Vibratons Disclaimtr: As always, neural functons are complex. Functons provided are EXAMPLES, not complete lists.  Examples of Ascending Tracts Lateral column – Posterior spinocerebellar tract Sensory functons “Informs” cerebellum of movements/ coordinaton – Lateral spinothalamic tract Sensory functons Pain Temperature How could you ttst for spinal injury aftctng tht lattral spinothalamic tract? Brush with coton swab ! ✅ X Pinch or pin prick testoa ✅ All X needo Examples of Descending Tracts Pyramidal – Lateral corticospinal tract Motor functons Motor impulses from cortex to muscles on opposite side of body Precise, voluntary movements, esp. of distal extremities Ex typing , wiggling toes drawing straight , line , etc. Examples of Descending Tracts Extrapyramidal – Vestibulospinal tract Motor functons Motor impulses from one side of medulla to other side of body Regulates muscle tone in response to vestbular apparatus (in ear) Equilibrium & balance Ex after spinning for a while,.. you stop a get your palance  Refexes Basic feedback pathways enabling quick reactions to stimuli rely on stomatic nerves. Innate reflexes: mostly testing lower motor neuron circuits (descending pathway) Stretch Reflex Happingonpatientas Flexor reflex/Crossed Extensor Reflex Autonomic (Visceral) Reflexes Acquired reflexes: i.e., step on brakes as passenger in a car Clearnedthesereflen m LEARNED  Stretch Refex Deep tendon or Knee-jerk refex Response to stretch of a tendon Muscle that is stretched is the one catteren or that contracts heuron – Sensory neuron from muscle spindle motor – Synapse in spinal cord with motor Relaxa neurons to muscle & synergistc muscles – Inhibits motor neurons to antagonistc muscles  Flexor/Crossed Extensor Refex Withdrawal refex (i.e., response to pain) – Ipsilateral fexion (stmulate fexor muscles, inhibit extensor muscles) – Contralateral extension (stmulate extensor muscles, inhibit fexor muscles) Modulated by descending neurons in pyramidal pathway  Babinski Sign Non-painful stmuli can elicit fexor refex Loss of modulatory inhibiton from pyramidal tract In adults, indicatve of dysfuncton of pyramidal tract. In infants, normal untl fexor refex inhibiton developed.