Medical Neuroscience Notes - 1st Lecture (September 2024) PDF

Medical Neuroscience 1st lecture September 2024 Figure 6.14 A Pure Hemiparesis; Pure hemiparesis B Hemiparesis No sensory loss with Additional Deficits Thalamocapsular...

Medical Neuroscience 1st lecture September 2024 Figure 6.14 A Pure Hemiparesis; Pure hemiparesis B Hemiparesis No sensory loss with Additional Deficits Thalamocapsular lacune Figure 6.14 A Pure Hemiparesis; B Hemiparesis Unlikely cortical, as lesion would involve entire motor strip; high risk for sensory involvement with Additional Deficits Not muscle or peripheral: involvement face + entire body half would be required Not medulla + spinal cord: face would be spared Unlikely thalamus: somatosensory functions spared Locations in: ?? Thalamocapsular lacune Figure 6.14 A Pure Hemiparesis; B Hemiparesis Unlikely cortical, as lesion would with Additional Deficits involve entire motor strip; high risk for sensory involvement Not muscle or peripheral: involvement face + entire body half would be required Not medulla + spinal cord: face would be spared Unlikely thalamus: somatosensory functions spared Locations in: Corticospinal + corticobulbar Contralateral Thalamocapsular lacune  Unlikely cortical, as lesion would involve entire motor strip; high risk for sensory involvement Not muscle or peripheral: involvement face + entire body half would be required Not medulla + spinal cord: face would be spared Unlikely thalamus: somatosensory functions spared Locations in: Corticospinal + corticobulbar Contralateral Thalamocapsular lacune Figure 2.2 Embryological Development of the Central Nervous System (Part 1) Figure 2.2 Embryological Development of the Central Nervous System (Part 2) Figure 2.2 Embryological Development of the Central Nervous System (Part 3) Figure 2.2 Embryological Development of the Central Nervous System (Part 3) Mesencephalon Myelencephalon + pons = Metencephalon Epithalamus: Pineal body  Anatomical organization: various ways of subdividing the nervous system Peripheral versus central Autonomic versus somatic Gray matter versus white matter Gray matter: cortical and subcortical areas White matter: fiber tracts Tractus: a bundle of nerve fibres Fascicle: small bundle of nerve fibres Funiculus: a bundle of one or more fascicles Capsula: ascending and descending fibres Lemniscus: bundle of secondary sensory fibers Table 2.1 Main Parts of the Human Nervous System Peripheral nervous system (PNS) – Cranial nerves and ganglia – Spinal nerves and dorsal root ganglia – Sympathetic and parasympathetic nerves and ganglia – Enteric nervous system Central nervous system (CNS) – Brain – Spinal cord Figure 2.1 Parts of the Human Nervous System Figure 2.1 Parts of the Human Nervous System  Anatomical organization: various ways of subdividing the nervous system Peripheral versus central Somatic versus autonomic Gray matter versus white matter Gray matter: cortical and subcortical areas White matter: fiber tracts Tractus: a bundle of nerve fibres Fascicle: small bundle of nerve fibres Funiculus: a bundle of one or more fascicles Capsula: ascending and descending fibres Lemniscus: bundle of secondary sensory fibers Figure 2.21 Neural Circuit for Deep Tendon (Muscle Stretch) Reflex Figure 2.9 Autonomic Nervous System (Part 1) Figure 2.9 Autonomic Nervous System (Part 2) pupilconstriction lacrimal glands, salivary glands parotid gland heart, lung, digestive tract digestive tract lower part Figure 2.9 Autonomic Nervous System (Part 2) pupilconstriction lacrimal glands, salivary glands parotid gland heart, lung, digestive tract digestive tract lower part  Anatomical organization: various ways of subdividing the nervous system Peripheral versus central Somatic versus autonomic Gray matter versus white matter Gray matter: cortical and subcortical areas White matter: fiber tracts Tractus: a bundle of nerve fibres Fascicle: small bundle of nerve fibres Funiculus: a bundle of one or more fascicles Capsula: ascending and descending fibres Lemniscus: bundle of secondary sensory fibers Figure 2.7 Gray Matter and White Matter in the Central Nervous System Gray matter versus white matter Figure 2.8 The Spinal Cord (Part 1) Increased amount of gray matter FIGURE 6.4 Myelin-Stained Sections through Different Levels of the Spinal Cord  Anatomical organization: various ways of subdividing the nervous system Peripheral versus central Somatic versus autonomic Gray matter versus white matter Gray matter: cortical and subcortical areas White matter: fiber tracts Fascicle: small bundle of nerve fibres (axons) Tractus: a bundle of nerve fibres Funiculus: a bundle of one or more fascicles Capsula: ascending and descending fibres Lemniscus: bundle of secondary sensory fibers Figure 6.9 Internal Capsule (Part 1) 85% of pyramidal tract fibers cross over 15%: ipsilateral: anterior cortical spinal tract Figure 7.1 Posterior Column–Medial Lemniscal Pathway Medical Neuroscience Friday September 13 2024 Figure 2.22 Brainstem and Cranial Nerves (Part 1) Figure 2.22 Brainstem and Cranial Nerves (Part 2) Figure 2.22 Brainstem and Cranial Nerves (Part 3) Figure 2.11 Detailed Labeled Surface View of Cerebral Cortex (Part 3) Irregular respiration Hypertension Bradycardia (slow heart rate) Intact: CN IV: superior oblique muscle: intorsion CN VI: lateral rectus muscle: abduction Figure 2.12 Primary Sensory and Motor Cortical Areas Figure 2.13 Somatotopic Maps in the Cortex Figure 2.16 Overview of Corticospinal Tract Figure 2.17 Overview of Basal Ganglia and Cerebellar Circuits Figure 2.19 Spinothalamic Sensory Pathway: Pain and Temperature (Part 2) Figure 2.18 Posterior Column Sensory Pathway: Vibration and Joint Position Sense (Part 2) Figure 2.20 The Thalamus Somatosensory cortex Figure 2.23 Simplified Depiction of Brainstem, Thalamic, and Cortical Circuits Important for Maintaining Consciousness Figure 2.26 Blood Supply to the Brain (Part 1) Figure 2.26 Blood Supply to the Brain (Part 2) Figure 2.26 Blood Supply to the Brain (Part 3) FIGURE 6.1 Motor and Somatosensory Cortical Areas (Part 1) FIGURE 6.1 Motor and Somatosensory Cortical Areas (Part 2) FIGURE 6.2 Somatosensory and Motor Homunculi Chapter 6 Opener FIGURE 6.9 Internal Capsule (Part 2) FIGURE 6.9 Internal Capsule (Part 1) 85% of pyramidal tract fibers cross over 15%: ipsilateral: anterior cortical spinal tract (face, head, and neck) Figure 12.13 Upper Motor Neuron versus Lower Motor Neuron Facial Weakness FIGURE 6.10 Somatotopic Organization of Corticobulbar and Corticospinal Tracts (Part 1) FIGURE 6.10 Somatotopic Organization of Corticobulbar and Corticospinal Tracts (Part 2) FIGURE 6.10 Somatotopic Organization of Corticobulbar and Corticospinal Tracts (Part 3) Figure 6.7 Somatotopic Organization of Medial and Lateral Motor System Projections to Anterior Horn Cells TABLE 6.3 (1) Lateral and Medial Descending Motor Systems Site of decussation Levels of Tract Site of origin (where relevant) termination Function LATERAL MOTOR SYSTEMS Lateral corticospinal Primary motor Pyramidal Entire cord Movement of tract cortex and other decussation, at the (predominantly at contralateral limbs frontal and parietal cervicomedullary cervical and areas junction lumbosacral enlargements) Rubrospinal tract Red nucleus, Ventral tegmental Cervical cord Movement of magnocellular decussation, in the contralateral limbs division midbrain (function is uncertain in humans) FIGURE 6.11 Descending Motor Pathways (Part 1) Fine movements of contralateral limbs (flexion legs) FIGURE 6.11 Descending Motor Pathways (Part 2) Functions uncertain in human (flexion arms) TABLE 6.3 (2) Lateral and Medial Descending Motor Systems Site of decussation Levels of Tract Site of origin (where relevant) termination Function MEDIAL MOTOR SYSTEMS Anterior corticospinal Primary motor cortex and — Cervical and upper Control of bilateral axial tract supplementary motor thoracic cord and girdle muscles area Vestibulospinal tracts (VSTs)a Medial VST Medial and inferior — Cervical and upper Positioning of head and vestibular nuclei thoracic cord neck Lateral VST Lateral vestibular nucleus — Entire cord Balance Reticulospinal tracts Pontine and medullary — Entire cord Automatic posture and reticular formation gait-related movements Tectospinal tract Superior colliculus Dorsal tegmental Cervical cord Coordination of head and decussation, in the eye movements midbrain (uncertain in humans) FIGURE 6.11 Descending Motor Pathways (Part 3) Bilateral axial and girdle muscles FIGURE 6.11 Descending Motor Pathways (Part 4) Positioning head and neck Balance Lateral: extension legs Medial: extension arms FIGURE 6.11 Descending Motor Pathways (Part 5) Reticulospinal: automatic posture and gait-related movements Pontine: extension arm/legs Medullary: flexion arm/legs Tectospinal: uncertain in humans Figure 3.5 Posturing and Triple Flexion Decorticate Decerebrate Triple flexion Signs of lower motor neuron lesions: ?? Signs of lower motor neuron lesions: Muscle weakness Atrophy Fasciculations Decreased tone hyporeflexia Signs of upper motor neuron lesions: ? In acute phase? Signs of upper motor neuron lesions: Muscle weakness combined with increased tone Hyperreflexia Spasticity (lesions descending inhibitory pathways) Abnormal reflexes (e.g. Babinsky) In acute phase: flaccid paralysis with decreased tone with decreased reflexes TABLE 6.4 Signs of Upper Motor Neuron and Lower Motor Neuron Lesions Sign Upper motor neuron lesions Lower motor neuron lesions Weakness Yes Yes Atrophy Noa Yes Fasciculations No Yes Reflexes Increasedb Decreased Tone Increasedb Decreased a Mildatrophy may develop due to disuse. b With acute upper motor lesions, reflexes and tone may be decreased. TABLE 6.5 (1) Terms Commonly Used to Describe Weakness Term Definition Example Example clinical symptoms Denoting severity Paresis Weakness (partial Hemiparesis Weakness of one side of body (face, paralysis) arm, and leg) Plegia No movementa Hemiplegia No movement of one side of body (face, arm, and leg) Paralysis No movementa Leg paralysis No movement of the leg Palsy Imprecise term for Facial palsy Weakness or paralysis of face weakness or no muscles movement a Inupper motor neuron lesions causing paralysis or plegia there is no voluntary movement of the limb, but reflexes may be present.