Neurology Physiology

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jknell
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Neurology Physiology
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  1. CNS/PNS Origins
    • Neuroectoderm:
    • -CNS neurons
    • -ependymal cells
    • -oligodendroglia
    • -astrocytes

    • Neural Crest Cells:
    • -PNS neurons
    • -Schwann cells

    • Mesoderm:
    • -Microglia

    "Microglia like Macrophages originate from Mesoderm"
  2. Neurons
    -signal-transmitting cells of nervous system

    -permanent cells (don't divide in adulthood, no progenitor stem cell population)

    • Dendrites: receive input (stain with Nissl: RER)
    • Axons: send output (no RER)
  3. Wallerian Degeneration
    • -injured axons
    • -degeneration distal
    • -axonal retraction proximal
    • -allow for potential regeneration if in PNS
  4. Astrocytes
    • Function:
    • -physical support, repair
    • -K+ metabolism
    • -removal of excess NT
    • -maintenance of BBB
    • -reactive gliosis in response to injury

    Marker = GFAP

  5. Microglia
    • Function:
    • -CNS Phagocytes (mesoderm)
    • -NOT visible in Nissl stain
    • -respond to tissue damage by differentiating into large phagocytic cells

    • Appearance:
    • -small irregular nuclei
    • -relatively little cytoplasm

    **HIV-infected microglia fuse to form multinucleated giant cells in CNS

  6. Myelin
    • Function:
    • -wraps and insulates axons
    • -increases conduction velocity and space constant
    • -saltatory conduction btwn nodes of ranvier

    • Made by:
    • -CNS: oligodendrocytes
    • -PNS: Schwann cells
  7. Oligodendroglia
    • Function:
    • -myelinates multiple CNS axons (up to 50)
    • -predominant glial cell in white matter

    • Appearance:
    • (on Nissl stain)
    • -small nuclei with dark chromatin and little cytoplasm
    • -fried egg on H&E

    **destroyed in Multiple Sclerosis

  8. Schwann Cells
    • Function:
    • -myelinates 1 PNS axon
    • -promotes axonal regeneration
    • -derived from neural crest
    • -increased conduction velocity

    **destroyed in Guillain Barre

    Acoustic Neuroma: schwannoma of CNVIII

  9. Sensory Corpuscles
    • 1. Free nerve endings
    • 2. Meissner's corpuscles
    • 3. Pacinian corpuscles
    • 4. Merkel's discs
  10. Free Nerve Endings
    • C: slow, unmyelinated fibers
    • A delta: fast, myelinated fibers

    • Location:
    • -all skin, epidermis
    • -some viscera

    • Senses:
    • -pain and temperature
  11. Meissner's Corpuscles
    • Large, myelinated fibers
    • **adapt quickly

    • Location:
    • -glabrous (hairless) skin

    • Senses:
    • -dynamic fine/light touch
    • -position sense
  12. Pacinian Corpuscles
    Large, myelinated fibers

    • Location:
    • -deep skin layers
    • -ligaments
    • -joints

    • Senses:
    • -pressure
    • -vibration
  13. Merkel's Discs
    • Large, myelinated fibers
    • **adapt slowly

    • Location:
    • -Hair follicles

    • Senses:
    • -pressure
    • -deep static touch (shapes, edges)
    • -position sense
  14. Endoneurium
    -single nerve fiber layers ("inner")

    **Inflammatory infiltrate in Guillain Barre
  15. Perineurium
    -surrounds a fascicle of nerve fibers ("around")

    **must be rejoined in microsurgery for limb attachment

    "Perineurium = Permeability barrier"
  16. Epineurium
    • -dense connective tissue
    • -surrounds entire nerve ("outer")

    **surrounds fascicle and blood vessels
  17. Neurotransmitters
    • 1. NE
    • 2. DA
    • 3. 5-HT
    • 4. ACh
    • 5. GABA
  18. Norepinephrine
    • Synthesis:
    • -Locus ceruleus (pons) ("stress and panic")

    • INCREASED IN:
    • -anxiety

    • DECREASED IN:
    • -depression
  19. Dopamine
    • Synthesis:
    • -Ventral Tegmentum
    • -Subthalamic Nucleus (midbrain)

    • INCREASED IN:
    • -schizophrenia

    • DECREASED IN:-Parkinson's
    • -Depression
  20. 5-HT
    • Synthesis:
    • -Raphe nucleus (pons)



    • DECREASED IN:
    • -anxiety
    • -depression
  21. ACh
    • Synthesis:
    • -Basal nucleus of Meynert (pons)



    • INCREASED IN:
    • -REM sleep

    • DECREASED IN:
    • -Alzheimer's
    • -Huntington's
  22. GABA
    • Synthesis:
    • -Nucleus accumbens (reward center, pleasure, addiction, fear)

    • DECREASED IN:
    • -Anxiety
    • -Huntington's
  23. Blood Brain Barrier
    • Formed by:
    • 1. Tight junctions between nonfenestrated capillary endothelial cells
    • 2. Basement membrane
    • 3. Astrocyte foot processes

    • Functions:
    • -helps prevent bacterial infections
    • -restricts drug delivery to brain

    • Glucose and AAs:
    • -cross slowly by carrier-mediated transport

    • Nonpolar/lipid soluble substances:
    • -cross rapidly by diffusion

    • Areas with no BBB:
    • -fenestrated capillaries and no BBB
    • -OVLT: osmotic sensing
    • -Area postrema: vomiting after chemo
    • -Neurohypophysis: ADH release

    Infection/Neoplasm destroy tight junctions --> vasogenic edema

    Hypothalamic inputs and outputs permeate the BBB
  24. Hypothalamus
    • "The hypothalamus wears TAN HATS"
    • Thirst and water balance
    • Adenohypophysis control
    • Neurohypophysis (releases hormones)
    • Hunger
    • Autonomic regulation
    • Temperature regulation
    • Sexual urges

    • Inputs:
    • -OVLT (osmolarity changes)
    • -area postrema (response to emetics)

    • Supraoptic nucleus makes ADH
    • Paraventricular nucleus makes oxytocin

    ADH and oxytocin are made in the hypothalamus but stored and released by posterior pituitary
  25. Areas of Hypothalamus and Functions
    • 1. Lateral area
    • 2. Ventromedial area
    • 3. Anterior hypothalamus
    • 4. Posterior hypothalams
    • 5. Suprachiasmatic nucleus
  26. Lateral nucleus of hypothalamus
    HUNGER

    • -destruction leads to anorexia/failure to thrive (infants)
    • -inhibited by leptin

    "If you zap your lateral nucleus you shrink laterally"
  27. Ventromedial nucleus of hypothalamus
    SATIETY

    -destruction (ie: by craniopharyngioma) leads to hyperphagia

    "If you zap your ventromedial nucleus you grow ventrally and medially"
  28. Anterior Hypothalamus
    • COOLING
    • -pArasympathetic

    "A/C = anterior cooling"
  29. Posterior Hypothalamus
    • HEATING
    • -Sympathetic

    "If you zap your posterior hypothalamus, you become a piokilotherm (cold-blooded like a snake)"
  30. Suprachiasmatic Nucleus
    CIRCADIAN RHYTHM

    "You need sleep to be charasmatic"
  31. Posterior Pituitary
    • Receives hypothalamic projections
    • -supraoptic nucleus (ADH)
    • -paraventricular nucleus (oxytocin)

    Neurohypophysis
  32. Thalamus
    • -major relay for all ascending sensory information except olfaction

    • VPL
    • VPM
    • LGN
    • MGN
    • VL
  33. VPL
    • Input:
    • -Spinothalamic tracts
    • -Dorsal Columns/Medial lemniscus

    • Info:
    • -Pain and Temperature
    • -Pressure, Touch, Vibration, Proprioception

    • Destination:
    • -primary somatosensory cortex
  34. VPM
    • Input:
    • -Trigeminal
    • -Gustatory

    • Info:
    • -face sensation
    • -taste

    • Destination:
    • -primary somatosensory cortex

    "Makeup goes on the face (VPM)"
  35. LGN
    • Input:
    • -CNII

    • Info:
    • -Vision

    • Destination:
    • -Calcarine Sulcus

    "Lateral - Light"
  36. MGN
    • Input:
    • -Superior olive and inferior colliculus of tectum

    • Info:
    • -Hearing

    • Destination:
    • -Auditory cortex of temporal lobe

    "Medial = Music"
  37. VL
    • Input:
    • -basal ganglia

    • Info:
    • -Motor

    • Destination:
    • -Motor Cortex
  38. Limbic System
    • Functions:
    • Emotion
    • Long term memory
    • Olfaction
    • Behavior Modification
    • ANS system function

    • Structures:
    • -hippocampus
    • -amygdala
    • -fornix
    • -mamillary bodies
    • -cingulate gyrus

    • "the famous 5Fs"
    • Feeding
    • Fleeing
    • Fighting
    • Feeling
    • Fornicating
  39. Cerebellum
    • Functions:
    • -modulates movement
    • -aids in coordination and balance

    • Input:
    • -contralateral cortex via MCP
    • -Ipsilateral proprioceptive info via ICP from spinal cord (input nerves = climbing and mossy fibers")

    • Output:
    • -Purkinje neurons --> deep nuclei of cerebellum --> SCP --> contralateral cortex

    • Deep Nuclei:
    • "Don't Eat Greasy Foods" (lateral to medial)
    • Dentate
    • Emboliform
    • Globose
    • Fastigial
  40. Basal Ganglia
    • Functions:
    • -voluntary movements and making postural adjustments
    • -receives cortical input, provides negative feedback to cortex to modulate movement

    • Striatum: putamen (MOTOR) + caudate (COGNITIVE)
    • Lentiform: putamen + GP
  41. Basal Ganglia Pathways


    • 1. Excitatory Pathway
    • 2. Inhibitory Pathway

  42. Basal Ganglia: Dopamine Pathways


    • DA binds:
    • -D1 (stimulating excitatory pathway)
    • -D2 (inhibiting inhibitory pathway)

    --> increased movement
  43. Basal Ganglia: Inhibitory Pathway


    • -cortical inputs stimulate the striatum
    • -disinhibits STN via GPe
    • -STN stimulates GPi/SNr which inhibit the thalamus

    DECREASED MOTION
  44. Basal Ganglia: Excitatory Pathway


    • -cortical inputs stimulate the striatum to release GABA
    • -disinhibits the thalamus by GPi/SNr

    INCREASED MOTION
  45. Cerebral Cortex Functions
    • Precentral gyrus: primary motor cortex
    • Postcentral gyrus: primary sensory cortex
    • Occiptal lobe (above and below calcarine sulcus): primary visual cortex
    • Transverse Temporal Gyri: primary auditory cortex
    • Posterior Superior Temporal gyrus: Wernicke's Area
    • Posterior Inferior Frontal gyrus: Broca's Area
    • Arcuate Fasciculus: connects Wernickes and Brocas
  46. Homunculus


    Topographical representation of sensory and motor areas of cerebral cortex
  47. Cerebral Arteries
    • ACA: anteromedial surface (medial frontal lobe, superior medial parietal lobe)

    MCA: lateral surface

    PCA: posterior and inferior surface (medial occipital, medial and inferior temporal)

    • Watershed zones:
    • -ACA/MCA
    • -PCA/MCA
  48. Regulation of Cerebral perfusion
    • -tight autoregulation
    • -perfusion driven primarily by CO2



    Hypoxemia increases cerebral perfusion pressure when ONLY when PO2 < 50 mmHG
  49. Dural Venous Sinuses


    Large venous channels that run through the dura and empty into internal jugular vein

    • Functions:
    • 1. Drain blood from cerebral veins
    • 2. Receive CSF from arachnoid granulations
  50. Ventricular Systems


    Intraventricular foramina of Monroe: connect lateral and third ventricles

    Cerebral Aqueduct (of Sylvius): connects third and fourth ventricle

    Foramina of Luschka (Lateral): connects fourth ventricle to subarachnoid space

    Faramen of Magendie (Medial): connects fourth ventricle to subarachnoid space

    **CSF made by ependymal cells of choroid plexus
  51. Spinal Nerves
    • 31 total (just like flavors of Baskin Robins!)
    • -8 cervical
    • -12 thoracic
    • -5 lumbar
    • -5 sacral
    • -1 coccygeal

    • C1-C7 exit above vertebrae
    • All others exit below
  52. Lower Spinal Cord
    In adults the spinal cord extends to L1 - L2

    Subarachnoid space extends to S2

    Lumbar puncture: L3-L4, L4-L5 (cauda equina)

    "To keep the cord alive keep the spinal needle between L3 and L5"
  53. Spinal Cord and Associated Tracts


    • 1. Dorsal Columns
    • 2. Lateral Spinothalamic Tract
    • 3. Intermediate Horn Sympathetics
    • 4. Anterior Spinothalamic Tract
    • 5. Lateral Corticospinal Tract
  54. Dorsal Column Tract


    Pressure, vibration, fine touch, proprioception

    • First Order Neuron:
    • -Sensory neuron with cell body in DRG
    • -ascends ipsilaterally in dorsal column

    • Synapse 1:
    • -ipsilateral nucleus cuneatus or gracilis

    • Second Order Neuron:
    • -Decussates in medulla
    • -ascends contralaterally in medial lemniscus

    • Synapse 2:
    • -VPL (thalamus)

    • Third Order Neuron:
    • -Sensory cortex

    **Dorsal column organized as you are with arms outside and legs inside
  55. Spinothalamic Tract


    • Lateral: pain, temperature
    • Anterior: crude touch, pressure

    • First Order Neuron:
    • -sensory nerve (Adelta and C fibers) with cell body in dorsal root ganglion

    • Synpase 1:
    • -ipsilateral gray matter at the level it enters

    • Second Order Neuron:
    • -decussates at anterior white commisure
    • -ascends contralaterally

    • Synapse 2:
    • -VPL

    • Third Order Neuron:
    • -Sensory Cortex

    **Legs are lateral
  56. Lateral Corticospinal Tract


    Descending voluntary movement of contralateral limbs

    • First Order Neuron:
    • -UMN: cell body in primary motor cortex
    • -descends ipsilaterally through internal capsule, decussates in the pyramids of the medulla, descends contralaterally

    • Synapse 1:
    • -cell body of anterior horn in spinal cord

    • Second Order Neuron:
    • -LMN: leaves spinal cord

    • Synapse 2:
    • -NMJ

    **Legs are Lateral in Lateral corticospinal tract
  57. Dermatomes


    C2: posterior skull cap

    C3: high turtle neck shirt

    C4: low collar shirt

    • T4: nipple line
    • "T4 at the teat pore"

    T7: xiphoid process

    • T10: umbilicus (early appendicitis referral)
    • "T10 at the belly butten"

    • L1: inguinal ligament
    • "L1 is IL (Inguinal Ligament)

    • L4: includes kneecaps
    • "Down on ALL 4s (L4)"

    • S2-S4: erection, sensation of penile and anal zones
    • "S2, 3, 4 keep the penis off the floor"
  58. Clinical Reflexes
    • Biceps: C5 nerve root
    • Triceps: C7 nerve root
    • Patella: L4 nerve root
    • Achilles: S1 nerve root

    • "1,2 buckle my shoe; 3,4 kick the door; 5,6 pick up sticks; 7,8 shut the gate"
  59. Primitive Reflexes
    • -present in infant but absent in normal adult
    • -disappear in 1 year
    • -inhibited by mature frontal lobe
    • *may reemerge in frontal lobe lesions

    • Moro Reflex:
    • -"hang on for life"
    • -abduct/extend limbs when startled, then draw together

    • Rooting Reflex:
    • -move head toward side if cheek or mouth is stroked (nipple seeking)

    • Sucking Reflex:
    • -suckling when roof of mouth touched

    • Palmar Reflex:
    • -curl fingers if palm stroked

    • Plantar Reflex:
    • -Babinski sign
    • -dorsiflex big toe, fanning of other toes

    • Galant reflex:
    • -stroke along one side of spine if baby is face down causes lateral flexion of lower body toward side
  60. Ventral Brain Stem
    • Optic Chiasm
    • Infundibulum
    • Anterior perforated substance
    • Tuber cinereum
    • Mammillary body
    • Cerebral peduncle (crus cerebri)
    • Pons
    • MCP
    • Pyramid

    • CNs that lie medially at brain stem: III, VI, XII:
    • 3(x2) = 6(x2) = 12
    • Motor = Medial
  61. Dorsal Brain Stem


    Pineal Gland: melatonin secretion, circadian rhythms

    Superior Colliculi: conjugate vertical gaze center

    Inferior Colliculi: auditory

    "Your eyes are above your ears, and the superior colliculus (visual) is above the inferior colliculus (auditory)"
  62. Cranial Nerves (mnemonics)
    • "Oh, Oh, Oh To Touch And Feel Virgin Girls' Vaginas, Ahhhh, Heaven"
    • Olfactory
    • Optic
    • Oculomotor
    • Trochlear
    • Trigemnial
    • Abducens
    • Facial
    • Vestibulochochlear
    • Glossopharyngeal
    • Vagus
    • Accessory
    • Hypoglossal

    • "Some Say Marry Money But My Brother Says Big Brains Matter Most"
    • S=sensory
    • M=motor
    • B=both

    • Foramina:
    • "Cleaners Only Spray Smelly Stuff Right On Smelly Idiots In J. Jonah Jameson High"
    • Cribiform plate (CNI)
    • Optic canal (CNII)
    • Superior orbital fissure (CNIII)
    • Superior orbital fissure (CNIV)
    • Superior orbital fissure (CNV V1)
    • Foramen Rotundum (CNV V2)
    • Foramen Ovale (CNV V3)
    • Superior orbital fissure (CNVI)
    • Internal Auditory meatus (CNVII)
    • Internal Auditory meatus (CNVIII)
    • Jugular foramen (CNIX)
    • Jugular foramen (CNX)
    • Jugular foramen (CNXI *enters through FM)
    • Hypoglossal canal (CNXII)
  63. Cranial Nerve I
    Olfactory

    • Function:
    • -smell

    • Type:
    • -sensory

    • Foramen:
    • -cribiform plate

    *only CN without thalamic relay to cortex
  64. Cranial Nerve II
    Optic

    • Function:
    • -sight

    • Type:
    • -Sensory

    • Foramen:
    • -optic canal
  65. Cranial Nerve III
    Occulomotor

    • Function:
    • -SR, IR, MR, IO
    • -pupillary constriction
    • -accomodation
    • -levator palpebrae

    • Type:
    • -motor

    • Foramen:
    • -superior orbital fissure
  66. Cranial Nerve IV
    Trochlear

    • Function:
    • -SO

    • Type:
    • -Motor

    • Foramen:
    • -superior orbital fissure
  67. Cranial Nerve V
    Trigeminal

    • Function:
    • -facial sensation (ophthalmic, maxillary, mandibular)
    • -somatosensation to anterior 2/3 tongue
    • -muscles of mastication

    • Type:
    • -Both

    • Foramen: "Standing Room Only"
    • -V1: superior orbital fissure
    • -V2: foramen rotundum
    • -V3: foramen ovale
  68. Cranial Nerve VI
    Abducens

    • Function:
    • -LR

    • Type:
    • -Motor

    • Foramen:
    • -Superior Orbital Fissure
  69. Cranial Nerve VII
    Facial

    • Function:
    • -Facial movement
    • -chordae tympani (taste to anterior 2/3 tongue)
    • -lacrimation
    • -salivation (submandibular, sublingual glands)
    • -obicularis oculi (eyelid closing)
    • -stapedius muscle (dampens loud sounds)

    • Type:
    • -Both

    • Foramen:
    • -Internal Acoustic Meatus

    **Facial nerve passes through the parotid gland but does NOT innervate it
  70. Cranial Nerve VIII
    Vestibulocochlear

    • Function:
    • -hearing
    • -balance

    • Type:
    • -Sensory

    • Foramen:
    • -internal acoustic meatus
  71. Cranial Nerve IX
    Glossopharyngeal

    • Function:
    • -taste (posterior 1/3 tongue)
    • -sensation (post 1/3 tongue)
    • -swallowing
    • -salivation (parotid gland)
    • -monitoring carotid body and sinus chemo and baroreceptors
    • -stylopharyngeus (elevates pharynx)

    • Type:
    • -both

    • Foramen:
    • -Jugular foramen
  72. Cranial Nerve X
    Vagus

    • Function:
    • -taste from epiglottic region
    • -swallowing
    • -palate elevation
    • -midline uvula
    • -talking
    • -coughing
    • -thoracoabdominal viscera
    • -monitoring aortic arch chemo and baroreceptors

    • Type:
    • -Both

    • Foramen:
    • -jugular foramen
  73. Cranial Nerve XI
    Accessory

    • Function:
    • -SCM (head turning)
    • -Trapezius (shoulder shrugging)

    • Type:
    • -Motor

    • Foramen:
    • -in through foramen magnum
    • -out through jugular foramen
  74. Cranial Nerve XII
    Hypoglossal

    • Function:
    • -tongue movement

    • Type:
    • -motor

    • Foramen:
    • -hypoglossal foramen
  75. Cranial Nerve Nuclei
    • -in brain stem tegmentum

    • Midbrain: CNIII, CNIV
    • Pons: CNV, VI, VII, VIII
    • Medulla: CNIX, X, XII
    • Spinal Cord: CNXI

    • Lateral Nuclei = sensory (aLar plate)
    • ------Sulcus Limitans--------
    • Medial Nuclei = Motor (basal plate)
  76. Cranial Nerve Reflexes
    • Corneal:
    • -Afferent = CNV1
    • -Efferent = CNVII

    • Lacrimation:
    • -Afferent: CNV1
    • -Efferent: CNVII
    • **loss of reflex does not preclude emotional tears

    • Jaw Jerk:
    • -Afferent: V3 (muscle spindle reflex)
    • -Efferent: V3 motor to masseter

    • Pupillary:
    • -Afferent: CNII
    • -Efferent: CNIII

    • Gag:
    • -Afferent: CNIX
    • -Efferent: CNX
  77. Cavernous Sinus
    • Function:
    • -drains blood from eye and superficial cortex
    • -drains into internal jugular vein

    • Nerves:
    • -CN III, IV, V1, V2, postganglionic sympathetic fibers
    • **nerves that control EOM + V1/V2

    • Arteries:
    • -Internal Carotid

    • **Cavernous Sinus Syndrome
  78. Muscles of Mastication
    • Close Jaw:
    • -Masseter
    • -teMporalis
    • -Medial pterygoid
    • "M's Munch"

    • Open Jaw:
    • -Lateral pterygoid
    • "Lateral Lowers"

    "It takes more muscles to keep your mouth shut"

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