Human nervous system two major parts central nervous system and peripheral nervous system Nervous System Organization Brain Spinal cord Central Nervous System Nervous System Organization All neurons outside the CNS ID: 1009775
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1. The Nervous SystemMillions of interconnected neurons form the nervous systemHuman nervous system two major parts: central nervous system and peripheral nervous system
2. Nervous System OrganizationBrainSpinal cordCentral Nervous System
3. Nervous System OrganizationAll neurons outside the CNS31 pairs spinal nerves12 pairs of cranial nervesPeripheral Nervous System
4. The Brain - 3 Major AreasCerebrum (telencephalon, diencephalon,)CerebellumBrainstem (midbrain, pons, medulla oblongata)
5. CerebrumComposed of Telencephalon (Cerebral Cortex) and DiencephalonCerebral Cortex is gray matter because nerve fibers lack white myelin coating
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7. Cerebral Cortex - 4 Major LobesParietalFrontalTemporalOccipital
8. Functions of the Cerebral CortexIntellectual processes: thought, intelligence.Processes sensory information and integrates with past experience to produce appropriate motor response.
9. Diencephalon - 2 Major PartsThalamusRelays stimuli received from all sensory neurons to cortex for interpretationRelays signals from the cerebral cortex to the proper area for further processingHypothalamusMonitors many parameterstemperature, blood glucose levels, various hormone levelsHelps maintain homeostasisSignals the pituitary via releasing factorsSignals the lower neural centers
10. Diencephalon
11. CerebellumLocated behind the brainstemHelps monitor and regulate movementIntegrates postural adjustments, maintenance of equilibrium, perception of speed, and other reflexes related to fine tuning of movement.
12. BrainstemComposed of midbrain, pons, and medulla oblongataMaintains vegetative functioningWhere is respiratory control center?Where is cardiovascular control center?Reflexes
13. Brain Stem
14. Spinal CordContains both gray and white matterGray matter is H-shape in core of cord
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16. Gray MatterRegions of brain and spinal cord made up primarily of cell bodies and dendrites of nerve cellsInterneurons in spinal cordsmall nerves which do not leave the spinal cordTerminal portion of axons
17. White MatterContains tracts or pathways made up of bundles of myelinated nervesCarry ascending and descending signalsAscending nerve tract from sensory receptors through dorsal root, up cord to thalamus, to cerebral cortexPyramidal tract transmits impulses downward eventually excites motoneurons control muscles.Extrapyramidal originate in brain stem descend to control posture.
18. Descending Nerve TractsAscending: dorsalDescending: lateral, ventro-medial tracts
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20. Peripheral Nervous SystemThirty-one pairs of spinal nerves & 12 pairs of cranial nerves.Each spinal nerve is a mixed nerve containing:Somatic afferentVisceral afferentSomatic efferentVisceral efferentWhich is a motor fiber?
21. Somatic Nervous SystemSomatic afferent (sensory): carry sensations from periphery to spinal cord. Includes exteroceptive (pain, temperature, touch) & proprioceptive.Somatic efferent (motor): communicate from spinal cord to skeletal muscles.
22. Autonomic Nervous System SubdivisionsSympatheticresponsible for increasing activity in most systems (except GI)adrenergic fibers release epinephrineParasympatheticresponsible for slowing activity in most systems (except GI)cholinergic fibers release acetylcholine
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24. Autonomic ReflexMonosynaptic reflex arcKnee jerk response
25. Complex ReflexesInvolve multiple synapsesCrossed extensor reflex
26. Motor UnitA single motor neuron and all of the muscle fibers which it innervates. Represents functional unit of movement.Ratio of muscle fibers to nerve relates to muscle’s movement function.
27. NeuronsTwo basic typesMotorSensoryThree basic partsAxons DendritesSoma or Cell Bodies
28. Sensory NervesEnter the spinal cord on the dorsal sideCell bodies lie outside the spinal cord in Dorsal Root Ganglia
29. Motor NervesExit the spinal cord on the ventral sideCell bodies lie within grey matter of spinal cordSomatic innervates skeletal muscleAutonomic (visceral)innervates organs / smooth muscle
30. Neuron Part: AxonsCarry impulses away from the cell body
31. MyelinSchwann cells wrapped around the axon of some neuronsappear as multiple lipid-protein layersare actually a continuous cellincrease the speed of action potential conduction
32. Nodes of RanvierGaps between Schwann Cellsimpulse jumps from node to nodesaltatory conduction
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34. Neuron Parts: Dendrites and Cell bodyDendrite: receives stimuli and carry it to the cell bodyCell body: site of cellular activity
35. SynapseJunction between the dendrites of one neuron and the axon of a second neuronNerves communicate by releasing chemical messenger at synapse
36. SynapseImportant neurotransmitters:MonoaminesNeuropeptidesNitric oxide
37. Motor Nerves - SizeAlpha motor nervesLarger fibersConduct impulses fasterInnervate regular muscle fibersGamma Motor nervessmaller fibersconduct impulses more slowlyInnervate proprioceptors such as muscle spindles
38. Nerve Properties Related to FunctionIrritabilityable to respond to stimuliConductivityable to transmit electrical potential along the axon
39. Resting Membrane PotentialDifference in charge between the inside and outside of the cellsodium in greater concentration outsidepotassium in greater concentration insideanions in greater concentration insidemembrane permeability greater for potassium than sodiumNa+ / K+ pump moves sodium out, potassium in
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41. Generating Action PotentialsVoltage gated ion channels sodium channels open --- sodium rushes insodium channels close --- stops inward flow of sodiumpotassium channels open --- potassium rushes outNet effect - Depolarization then Repolarizationelectrical flow created by ionic flow, not electron flow
42. Na+ / K + PumpMembrane bound proteinsUtilizes ATPMaintains resting membrane potentialEstablishes sodium & potassium concentration gradients
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44. Neuromuscular JunctionMotor neuron cell body and dendrites in gray matter of spinal cordAxons extend to muscleAxon’s terminal end contains a synaptic knobSynaptic knob has synaptic vesicles containing acetylcholine
45. Neuromuscular JunctionAxon leaves spinal cord.Extends to skeletal muscle.Terminal branches end in synaptic knob.
46. Motor End PlateArea beneath the terminal branches of the axonsContains acetylcholine receptor complexesAcetylcholine binding opens the receptor complexCholinesterase degrades acetylcholine into acetate and choline
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48. Tension Generating CharacteristicsAll or None Lawwhen a neuron reaches threshold it generates an action potential which is conducted the length of the axon without any voltage changewhen the nerve fires, all the muscle fibers it innervates contract
49. Summation of Local Graded PotentialsTemporal Summationadditive effect of successive stimuli from an axon Spatial Summationadditive effect of stimuli from various axons
50. Gradation of ForceForce of muscle varies from slight to maximal:Increase number of motor units recruitedIncrease frequency of motor unit discharge.
51. ProprioceptorsMuscle SpindlesGolgi Tendon OrgansPacinian CorpusclesRuffini Endings
52. Muscle SpindlesEncapsulated fibers within the muscle bellyMonitor changes in muscle lengthMonitor the rate of change in muscle lengthRespond by causing muscle contraction
53. Golgi Tendon OrgansEncapsulated receptors Located at the musculotendinous junctionMonitor tension within the tendonRespond by causing the muscle to relax
54. Pacinian Corpuscles & Ruffini EndingsEncapsulated receptors Located near joints, in muscle, tendon, and bone