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NERVOUS SYSTEM

NERVOUS SYSTEM. General Organization CNS (Brain + Spinal Cord) Peripheral NS (= PNS) Afferent Efferent Somatic Autonomic Sympathetic Parasympathetic. Protection of CNS Meninges (Dura Mater, Arachnoid Mater, Pia Mater)

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NERVOUS SYSTEM

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  1. NERVOUS SYSTEM

  2. General Organization CNS (Brain + Spinal Cord) Peripheral NS (= PNS) Afferent Efferent Somatic Autonomic Sympathetic Parasympathetic

  3. Protection of CNS Meninges (Dura Mater, Arachnoid Mater, Pia Mater) Blood-Brain Barrier (hypothalamus is “outside”)

  4. Cerebral Cortex Organization Layers I-VI Vertical columns Four lobes (Frontal, Parietal, Temporal, Occipital)

  5. Parietal Lobes Sensory input from body surface (touch, pressure, heat, cold, pain, proprioception) Sensory homunculus Anatomical distortions Frontal Lobes Voluntary movements, speech Motor homunculus Brain plasticity

  6. Some specific cortical areas Broca’s area (vocal formation of words) Wernicke’s area (speech recognition) Association areas Prefrontal association cortex Parietal-temporal-occipital association cortex Limbic association cortex (in temporal lobe)

  7. Subcortical Structures Basal nuclei (= basal ganglia) Lesions cause resting tremors Thalamus Hypothalamus Limbic system (includes parts of cerebral cortex, basal nuclei, thalamus and hypothalamus)

  8. MEMORY Short term (seconds to 6 hours) Long term (days to decades) Consolidation Amnesia Retrograde Anterograde

  9. CEREBELLUM Motor coordination: Fine movements (writing, playing musical instrument) Coarse movement (posture, walking) Lesions cause intention tremor, poor balance, poor muscle tone, poor coordination

  10. Brain Stem Connects cerebrum and cerebellum to spinal cord Includes areas that control respiration, heart rate, arterial pressure, gastrointestinal activities Cranial nerves (12 pair; vagus) Reticular formation and reticular activating system Controls alertness and level of attention (arousal) States of arousal: Maximal alertness, wakefulness, sleep, coma

  11. Spinal Cord Gray matter inside, white matter outside Ascending and descending tracts Spinal reflex arc

  12. PNS: Afferent Receptors as transducers Sensations vs perceptions How receptors work Stimulation usually increases Na permeability This lessens negativity of receptor cell When receptor is a neuron, this is a receptor potential When receptor isn’t a neuron, this is a generator potential Receptor and generator potentials are graded at low levels of stimulus strength

  13. Coding of Stimulus Strength Frequency coding Population coding Adaptation Phasic receptors (respond to change in stimulus strength) Tonic receptors (pain; proprioception)

  14. Somatic vs Special Senses Labeled lines, referred pain and phantom pain Receptive fields and sensory acuity

  15. Pain and Analgesia Nociceptors: A-Delta fibers (fast; sensitive to heat and mechanical stimuli) C-Fibers (slow; sensitive to chemical stimuli) Analgesia and endorphins Central pain Chronic inflammation following injury to peripheral nerve Uninterrupted except by sleep http://www.practicalpainmanagement.com/critical-necessity-diagnose-pain-centralized

  16. PNS – Efferent General Autonomics Architecture of systems preganglionic and postganglionic cells) Sympathetic trunk (= sympathetic ganglion chain) Collateral ganglia in sympathetic system Parasympathetic ganglia Transmitters in autonomics Preganglionic fibers are cholinergic Postganglionic fibers are cholinergic in parasympathetics, adrenergic in sympathetics

  17. Resting outputs and autonomic tone Autonomic dominance Sympathetic (flight or fight) Parasympathetic (vegetative)

  18. Somatic Nervous System Voluntary, not necessarily conscious One neuron from CNS to effector cell (unlike autonomic) Stimulation only, no inhibition: final common pathway

  19. Neuromuscular Junction Many terminal branches on neuron Axon terminal = “bouton” (“button”) Motor end plate Neuromuscular junction analogous to synapse Usually, each action potential in motor neuron -> one action potential in muscle cell

  20. Toxins Black widow venom (releases ACh from cholinergic neurons) Botulinum toxin (“botox”; blocks ACh release from boutons) Curare (competes with ACh for cholinergic receptors) Cholinesterase inhibitors (many insecticides, chemical warfare agents). Prevent muscles from relaxing

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