Neuroanatomy Exam 3 Study Guide.pdf

Neuroanatomy Exam 3 Study Guide Cerebellum: Approximately 10 questions: Cerebellum Anatomy → Embryologically related to the pons (Rhombencephalon → Metencephalon) - Important structures including fissures, lobes, peduncles, etc. Cerebellar Peduncles: White matte...

Neuroanatomy Exam 3 Study Guide Cerebellum: Approximately 10 questions: Cerebellum Anatomy → Embryologically related to the pons (Rhombencephalon → Metencephalon) - Important structures including fissures, lobes, peduncles, etc. Cerebellar Peduncles: White matter axons allowing info into and out of the cerebellum from Myelincephalon and Metencephalon - Superior - Middle - Inferior Vermis: Rounded elongated central part of cerebellum lying in midline between lateral masses of the cerebellum (Cerebral Hemispheres) Horizontal Fissure: Separates cerebellum into superior and inferior parts Anterior Lobe: Toward the brainstem Posterior Lobe: Toward the back of the head Flocculonodular Lobe: Flocculus and Nodulus - Most primitive - Posterolateral fissure separates from posterior lobe Primary Fissure: Separates anterior and posterior lobe Functional Areas and their associated lobes (spinocerebellar, cerebrocerebellar, Flocculonodular) Spinocerebellar: Anterior lobe, vermis & paravermis (intermediate) - Spine to cerebellum - Ascending, sensory - Unconscious proprioception through spinocerebellar pathways - Coordinate and correct trunk movements Cerebrocerebellum: Posterior lobe (lateral hemispheres) - Cerebrum to Cerebellum - Descending, motor - Initiation, planning and coordination of movement determining strength and scope of movement; streamline cortical output Vestibulocerebellum: Flocculonodular lobe (Oldest Primitive Part of Brain) - Vestibulocochlear nerve to cerebellum - Ascending, sensory - Receive input from primary vestibular afferents and projects to vestibular nuclei - Govern eye movement and body equilibrium Criteria of a Neurotransmitter 1. Substance must be present within presynaptic neuron 2. Substrate must be released in response to presynaptic depolarization and release is Ca2+ dependent 3. Specific receptors for substance must be present on postsynaptic cell Main Excitatory and Inhibitory neurotransmitters Neurotransmitter Function Deficit  Acetylcholine Somatic muscle control Alzheimers & MG Parasympathetic function Dopamine Reward (Pleasure) & movement regulation Parkinson’s Glutamate Principal excitatory neurotransmitter in the Epilepsy/Seizures (Too Much) CNS Fundamental in synaptic plasticity (important for learning and memory), formation of neural networks during development and repair of the CNS GABA Primary Inhibitory Neurotransmitter in the Epilepsy/Seizures Anxiety (Too Little) CNS Reduce neuronal excitability by inhibiting nerve transmission Serotonin Mood stabilizer, sleep patterns Depression (Too Little) Cerebellar cortex/laminae (3 layers, superficial to deep) - What type of cells are in each; What type of function (excitatory or inhibitory) do these cells have on each other? Utilize schematic and summary chart Molecular Layer: Most superficial - Axons of granule cells (parallel fibers) - Dendrites of purkinje cells - Stellate cells - Basket cells Purkinje Layer: - Single layer of neuronal purkinje cell bodies - Highly dendritic extending into molecular layer Granular Layer: Deep - Granule cells - Golgi cells - Axons from mossy fibers Cell Type Neurotransmitter Affects Climbing Fibers Glutamate + (Excitatory) Purkinje Cell Mossy Fibers Glutamate + (Excitatory) Granule & Golgi Cells Granule Cells Glutamate + (Excitatory) Stellate & Basket Cells  Golgi Cells GABA - (Inhibitory) Granule Cells Stellate Cells GABA - (Inhibitory) Purkinje Cells Basket Cells GABA - (Inhibitory) Purkinje Cells Purkinje Cells GABA - (Inhibitory) Deep Cerebellar Nuclei (DCN) Define: Neural Sharpening Repetition of an object stimulus results in faster and better recognition of this object - Neuronally associated with a reduced firing rate of neurons called repetition suppression - When better at a task, need less feedback Cerebellar Homunculus: (somatotopic representation: For example: The trunk is represented in the vermis) Vermis: Axial skeleton, trunk, neck and head Paravermis: Appendicular skeleton, limbs Lateral Hemispheres: Posterior lobe 4 Deep Cerebellar Nuclei “Don’t Eat Greasy Foods” Dentate Nucleus: Main output from the cerebellum - Regulates fine control of voluntary movements, cognition, language and sensory Emboliform Nucleus Globose Nucleus Fastigial Nucleus: Coordination of trunk, head and neck - Oldest nuclei What might cerebellar dysfunction present with clinically? - Balance problems - Gait disorders/ataxia - Uncoordinated movement (especially dysmetria) - Speech problems (dysarthria) - Visual problems (nystagmus) - Vertigo Rapid and Alternating Movements - Dysdiadochokinesia: Successive pronation and supination of the hands, rapid rapping of the fingers - Causes may include: MS or cerebellar abnormalities Accessory Movements - Scanning speech: Causes enunciation of individual syllables - Nystagmus: Fast phase toward side of cerebellar lesion → Fast eye movement Dysmetria - Touch nose: Perform eyes open and eyes closed - Assess for dysmetria (hypo or hyper) and smoothness of movement/intention tremor Ataxia - Cerebellum assists in balance and equilibrium - Wider-base tottering gate - Unable to perform tandem gait Rebound Phenomenon - Rebound Phenomenon (top) - Patient resist force and abruptly stop - Positive sign seen is spastic limb where exaggerated rebound occurs in opposite direction (hitting face or stuck extended) - Pronator Drift (bottom) - Patient closes eyes and extend both arms at 90 with palms up, patient tries to maintain position for 20-30 seconds - Positive sign hand pronates or turns downward Spinal cord/ gray matter: approximately 10 Q. What are dentate ligaments Bilateral extensions of pia mater that attach the spinal cord to the dura Spinal nerves: - How many pairs? 31 pairs - How many in each region? (4 regions) - 8 Cervical - 12 Thoracic - 5 Lumbar - 5 Sacral - 1 Coccygeal - Function: (Sensory, motor, or both?)  - All spinal nerves are BOTH sensory and motor - Where do they exit the vertebral column: - All spinal nerves (EXCEPT C1-C7) Exit BELOW their corresponding vertebrae - T1 exits below T1 vertebrae - C1-C7 exit ABOVE their corresponding vertebrae - C8 exits between C7 and T1 Grey matter columns: Locations and their general associated functions 1. Dorsal Horn: a. Location: All spinal levels of spinal cord b. General function: Contain neurons that receive somatosensory information from the body 2. Ventral Horn: a. Location: All spinal levels of spinal cord b. General function: Largely contain motor neurons that exit the spinal cord to innervate skeletal muscle 3. Intermediate Column: a. Location: All spinal levels of spinal cord b. General function: Contain autonomic neurons that innervate visceral and pelvic organs 4. Lateral Horn: a. Location: T1-L2 b. General function: Contain autonomic neurons that innervate visceral and pelvic organs Gray Matter Nuclei;(general location and related function/modality) emphasis on: - Marginal zone Location: Tip of Dorsal Horn Function: Relay pain & temperature sensation  - Substantia Gelatinosa Location: Top of the Dorsal Horn Function: Relay pain, temperature & light touch - Dorsal Nucleus of Clarke Location: Most dorso-medial nuclei Function: Unconscious proprioceptive information to the brain - Motor Neurons (Lateral and Medial) Location: Ventral Horn Function: Innervate viscera and skeletal muscles Rexed Laminas: I, II, VII, VIII, & IX General location, associated function/modality and tract pathway if applicable, Does it correlate with a specific nuclei? Lamina I:  Location Function Tract Pathway Associated Nuclei Tip of dorsal horn Responds to noxious (painful) Contralateral Marginal Zone stimuli Spinothalamic Tract Lamina II: Location Function Tract Pathway Associated Nuclei Substantia Sensation of noxious (pain) and Spinothalamic Substantia Gelatinosa of non-noxious (light touch) stimuli Gelatinosa Rolando Rolando & pain interpretation Lamina VII: Location Function Tract Pathway Associated Nuclei Majority of Relays motor information to the 1. Dorsal 1. Nucleus Dorsalis intermediate & viscera spinocerebellar tract (Clarke’s Nucleus) ventral grey column Gives rise to all cells involved in 2. Intermediolateral 1. Medial and ventral the autonomic system cell column (ILM) to dorsal horn (C8-L3) 2. Responsible for the formation 3. Sacral Autonomic of lateral horn in T1-L2 nucleus 2. Lateral portion of sympathetic intermediate zone 3. Consists of pre-ganglionic 3. Lateral part of parasympathetic neurons Lamina VII (S2-S4) Lamina VIII: Location Function Tract Pathway Associated Nuclei Medial aspect of Modulate ipsilateral and Termination site for Motor neurons ventral horn → More contralateral motor output to descending fibers prominent in cervical skeletal muscle including and lumbar vestibulospinal & enlargements reticulospinal tracts Lamina IX: Location Function Tract Pathway Associated Nuclei Anterior Horn Medial areas innervate axial Corticospinal Tract Phrenic nucleus (Motor) Cell musculature innervates the spinal accessory nucleus Spinal accessory Lateral areas innervate limbs of bilaterally nucleus muscles  Nucleus of Onuf - Expand on Lamina VII: - Dorsal Nucleus of Clarke: Function: Carry unconscious proprioception information from lower extremities - Composed of large neurons and axons that forms the dorsal spinocerebellar tract on the ipsilateral side Levels: C8 - L3 - Sacral Autonomic Nucleus: Function: Point and Shoot (erection and ejaculation) - Preganglionic parasympathetic neurons Levels: S2 - S4 - Intermediolateral cell columns: Function: Formation of Lateral horn in T1 - L2 sympathetic Levels: T1 - L2 - Expand on Lamina IX: - Alpha/Gamma neurons Alpha Motor Neurons: Extrafusal fibers of striated skeletal muscle - Muscle contraction Gamma Motor Neurons: Intrafusal fibers of neuromuscular spindles - Muscle proprioception - Phrenic Nucleus Function: Innervation of the diaphragm Levels: C2 - C5 - Spinal Accessory Nucleus: Function: Innervation of trapezius & sternocleidomastoid muscles Levels: C1 - C5 - Nucleus of Onuf: Function: Supply striated voluntary muscles of the pelvic floor Levels: S1 - S2 Spinal Tracts PowerPoint: approximately 20 Q. For tracts: Please know: Where each tract beings & ends; what its function is; if it decussates, where; how many order neurons do they have/where are they Dorsal Column Medial Lemniscal Pathway (DCML Pathway) → Fasciculus Gracilis Start End Decussate # neurons Function Dorsal Cortex medial Yes (medulla) 1. DRG Discriminative/Fine touch Columns lemniscus to 2. Gracile Nucleus sensation, vibration and (spine) 3. VPL of conscious proprioception Thalamus 3,1,2 Thalamus to SS (position sensation, kinesthesia) (somatosensory cortex from LOWER extremity cortex) Dorsal Column Medial Lemniscal Pathway (DCML Pathways) → Fasciculus Cuneatus Start End Decussate # neurons Function Dorsal Cortex medial Yes (medulla) 1. DRG Discriminative/Fine touch Columns lemniscus to 2. Cuneatus sensation, vibration and (spine) Nucleus conscious proprioception Thalamus 3,1,2 3. VPL of (position sensation, kinesthesia) (somatosensory Thalamus to SS from UPPER extremity cortex) cortex Ventral Spinothalamic Pathways Start End Decussate # neurons Function Spine (DRG) Thalamus Yes (Level of 1. DRG Light touch and pressure entrance) 2. Substantia Gelatinosa (Lamina Ascends II) contralaterally 3. VPL of Thalamus to SS Cortex Lateral Spinothalamic Pathways Start End Decussate # neurons Function Spine (DRG) Thalamus Yes (Level of entrance) 1. DRG Pain and Temperature Lissauer’s tract 2. Substantia Gelatinosa Contralaterally (Lamina II) ascending into central 3. VPL of grey, white commissure Thalamus to SS and lateral Cortex spinothalamic tract into thalamus Dorsal Spinocerebellar Pathways (Lower) → Cuneocerebellar (Upper) Start End Decussate # neurons Function Spine (Type Cerebellum No 1. DRG Unconscious proprioception 1a muscle (Inferior 2. Clarke’s Column from lower limbs spindles and cerebellar Dorsal (nucleus golgi tendon peduncle) Doesn’t dorsalis/Lamina VII) Clarke’s Nucleus Golgi organs) at Decussate Ascends ipsilaterally to Tendon Organs and Musclle Clarke’s cerebellum Spindles nucleus Clarke is unconscious in the back Ventral Spinocerebellar Pathways (Lower) → Rostral Spinocerebellar (Upper) Start End Decussate # neurons Function Spine (NOT Cerebellum YES (DOUBLE 1. Decussate in central Unconscious proprioception at Clarke’s (Superior CROSS) → commissure and ascend from lower limbs nucleus) cerebellar Appears to contralaterally peduncle) ascend 2. Superior cerebellar NO Clarke’s Nucleus Golgi ipsilaterally peduncle decussation a tendon organs and muscle second time to reach spindles cerebellum - Rostral Spinocerebellar enters through inferior and superior cerebellar peduncles (Upper extremity) Lateral Corticospinal Pathways Start End Decussate # neurons Function Primary motor Anterior horn Yes; 85% 1. Cortex (Cells of Betz) Voluntary motor cortex 4,6 spine, Lamina 9 decussate in 2. Anterior horn Lamina 9 medulla Ventral Corticospinal Pathways Start End Decussate # neurons Function Primary motor Anterior horn No; 15% don’t decussate 1. Cortex (Cells of Voluntary motor cortex 4,6 spine, Lamina 9 → eventually does further Betz) down in anterior white 2. Anterior horn commissure in spinal cord Lamina 9 Medial Vestibulospinal Pathways Start End Decussate # neurons Function Pons; Medial Anterior horn No 1. Medial Vestibular Stabilizing head position, vestibular spine, Lamina 7 nucleusi in especially in relation to eye nuclei; &8 brainstem movements w/ vestibular stimuli  Descends bilaterally in 2. Anterior horn Reflexive adjustments of MLF spine, Lamina 7 & posture in response to head 8 movements - HEAD & EYE Lateral Vestibulospinal Pathways Start End Decussate # neurons Function Pons; Lateral Anterior horn No 1. Lateral Vestibular Anti-gravity muscles; vestibular spine, Lamina 7 nucleus (Dieter’s maintain balance and nuclei; &8 nucleus) in brainstem upright posture for Descends unanticipated movements Ipsilaterally 2. Anterior horn spine, made by body Lamina 7 & 8 Dieter’s Nucleus NOT AS IMPORTANT: “Rubrospinal” Start End Decussate # neurons Function Red nucleus Spine Yes - 2 Assist in fine motor control (mainly Immediately at flexors) Locomotion & Posture, midbrain Cervical/Upper limb “Tectospinal” Start End Decussate # neurons Function Nucleus in Spine (cervical) Yes - 2 Reflexive HEAD & NECK superior Immediately at movement in response to colliculus in midbrain environmental stimuli Midbrain “Reticulospinal” Start End Decussate # neurons Function Reticular Interneurons of 2 Locomotion and postural control by formation spinal cord on influencing alpha or gamma motor both sides neurons through interneurons (Lamina 8) Spinal Cord Lesions: Approximately 10 Q. UMN versus LMN UMN Syndrome LMN Syndrome Type of Paralysis Spastic Paresis Flaccid Paralysis Atrophy No (Disuse) Atrophy Severe Atrophy Deep Tendon Reflex Increase Absent DTR Pathological Reflex Positive Babinski Sign Absent Superficial Reflex Absent Present Fasciculation and Fibrilation Absent Could be Present Blood supply to spinal cord: 1 anterior spinal artery, 2 dorsal spinal arteries Anterior Spinal Artery: Anterior ⅔ spinal cord - Housed in anterior median fissure Paired Posterior Spinal Arteries: Posterior spinal cord - Artery of Adamkiewicz Dominant segmental feeding vessel to the thoracic cord supplying the anterior aspect of the cord via the anterior spinal artery Characteristic hairpin turn on the cord surface as it first courses superiorly, then turns inferiorly Meets the anterior spinal artery Lesions: What tracts would be affected/what would that patient’ present with? - Anterior Spinal Artery Syndrome? Affects: Sudden occlusion of the anterior spinal artery by embolus - Only DCML intact Patient Presentation: Loss of pain and temperature below damage level - Intact vibration and conscious proprioception - Sensory Dissociation - LMNL at level and UMNL below level of injury - Tabes Dorsalis Affects: Dorsal columns bilaterally - DCML not able to send tract up from Fasciculus Cuneatus and Gracilis Patient Presentation: Loss of vibration and conscious proprioception - Intact pain, temperature and pressure - Positive Romberg sign (balance test with eyes closed) - Broad based stepping gait - Cauda Equina Syndrome Affects: Compression in cauda equina by space-occupying lesion like central disc herniation Patient Presentation: Saddle anesthesia with decreased bladder and bowel control - LMN in legs may be present - Spinal cord not affected - Spinothalamic lesion Affects: Lesioned part of spinal cord spinothalamic tract - Signal can’t get up from contralateral side Patient Presentation: Contralateral loss of pain and temperature BELOW the level of lesion - Syringomyelia Affects: Dilation of central canal of the spinal cord commonly in cervical region - 2nd order neuron from Substantia Gelatinosa can’t decussate in lateral spinothalamic pathway Patient Presentation: Loss of pain and temperature bilaterally in cape-like fashion - Intact vibration and proprioception - Associated with Arnold Chiari type 1 malformation - Central Cord Syndrome Affects: More lateral dilation of central canal than Syringomyelia - Affect descending lateral corticospinal tracts before synapsing (ipsilateral) Patient Presentation: Cape-like loss of pain and temperature - Seen more in elderly - Most common incomplete spinal cord syndrome - Upper motor neuron lesions in upper limb > lower limb - Horner’s syndrome may also be present → Parasympathetic’s dominant - Ptosis (Eyelid drooping) - Miosis (pupillary constriction) - Anhidrosis (No sweat production) - ALS Affects: Ventral horns and lateral corticospinal tracts  - 85% descending tracts do not descend Patient Presentation: Progressive degenerative motor neuron disease - Both UMN and LMN lesions in at least 3 of the 4 limbs - Ok above affected spinal level, affected below - Brown Sequard Syndrome Affects: Sudden destruction of half of the spinal cord - Decreased DCML ipsilateral side - Decreased Spinocerebellar Ipsilateral - Decreased Spinothalamic contralateral Patient Presentation: Contralateral loss of pain and temperature 1-2 dermatomes below lesion - Ipsilateral loss of vibration and proprioception - Ipsilateral LMN lesion at the level of damage and UMN lesions below