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General Organization
CNS (Brain + Spinal Cord)Peripheral NS (= PNS) Afferent Efferent Somatic Autonomic Sympathetic Parasympathetic
Protection of CNS
Mechanical Bony covering (skull, vertebrae) Meninges (dura mater, arachnoid mater, pia mater)
Chemical Blood-Brain Barrier (hypothalamus is “outside”)
Parietal Lobes
Sensory input from body surface (touch, pressure, heat, cold, pain, proprioception)
Sensory homunculus
Specific Cortical Areas
Broca’s area (formation of words)
Wernicke’s area (speech recognition)
Association areas Prefrontal association cortex Parietal-temporal-occipital association cortex Limbic association cortex (in temporal lobe)
Subcortical Structures
Basal nuclei (= basal ganglia). Lesions cause resting tremors
Thalamus
Hypothalamus
Limbic system (includes parts of cerebral cortex, basal nuclei, thalamus and hypothalamus)
MEMORY
Short term (seconds to 6 hours)
Long term (days to decades)
Consolidation
Amnesia Retrograde Anterograde
CEREBELLUM
Motor coordination: Fine movements (writing, playing musical instrument) Coarse movement (posture, walking)
Lesions cause intention tremor, poor balance, poor muscle tone, poor coordination
Brain Stem
Connects cerebrum and cerebellum to spinal cord
Includes areas that control “vital activities” (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
Spinal Cord
Gray matter inside, white matter outside
Ascending and descending tracts
Spinal reflex arc
Peripheral NS: 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 potentials at low levels of stimulus strength
Coding of Stimulus Strength
Frequency coding (afferent neuron generates action potentials at higher frequencies as stimulus strength increases)
Population coding (more afferent neurons generate action potentials as stimulus strength increases)
Adaptation Phasic receptors (respond to rate of change in stimulus strength) Tonic receptors (pain; proprioception)
Somatic vs Special Senses Special senses = taste, olfaction, vision, hearing Somatic senses are those originating on body surface (pressure, touch, heat, cold) and proprioception
Labeled lines, referred pain and phantom pain
Receptive fields and sensory acuity
Pain and Analgesia
Nociceptors (pain receptors): 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
Peripheral NS – 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
Resting outputs and autonomic tone
Autonomic dominance Sympathetic (flight or fight) Parasympathetic (vegetative)
Somatic Nervous System
Voluntary, not necessarily conscious
One neuron from CNS to effector cell (unlike autonomic)
Stimulation only, no inhibition. Motor neurons = final common pathway
Neuromuscular Junction
Many terminal branches on motor neuron (one can innervate many muscle cells)
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