structure and function of the nervous system 1. 2 central nervous system: brain spinal cord...
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Structure and Structure and Function of the Function of the Nervous SystemNervous System
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Central Nervous System:
Brain
Spinal cord
Peripheral Nervous System:
Cranial nerves (12 pairs)
Spinal nerves (31 pairs)
Afferent (ascending) – sensory
Efferent (descending) – motor
Central Nervous SystemCentral Nervous System
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Peripheral Nervous System
Somatic Nervous Autonomic Nervous System System
Operates with conscious control Usually without conscious control
Controls skeletal muscle Regulates body’s internal environment
Releases Acetylcholine at synapses Releasesacetylcholine or norepinephrine at
synapses
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Autonomic Nervous System
Sympathetic Parasympathetic Nervous System Nervous System
Originates in the thoracic Originates in the brain stemand lumbar segments (cranial nerves) and sacralof the spinal cord : segments of the spinal Thoracolumbar system cord: Craniosacral system
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Sympathetic Parasympathetic Nervous System Nervous System
Effect is wide spread Effect is local
"Fight-or-Flight" - Bear "Feed and Breed” - Book emergency, excitement, exercise, salivation, lacrimation, urination, embarrassment defecation
Postganglionic fibers Postganglionic fibers release norepinephrine release Ach
Preganglionic fibers of both release ACh
Cells of the Nervous Cells of the Nervous SystemSystem
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Neurons – the primary cell of the nervous system
Supporting cells – Neuroglial cells
NeuronsNeurons
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Each neuron is adapted for a specialized function.
Detect environmental changes
Process information
Initiate body responses
Fuel source is mostly glucose
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Saltatory conductionSaltatory conduction
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Neuroglia – “Nerve Neuroglia – “Nerve glue”glue”
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Schwann cells form the myelin sheathes of axons in the peripheral nervous system.
AstrocytesOligodendrocytesMicrogliaEpendymal cells are found in the CNS
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Generation of nerve Generation of nerve impulsesimpulses
Action potentials are generated when Action potentials are generated when stimulus is greater than threshold.stimulus is greater than threshold.
Action potential is an all-or-none Action potential is an all-or-none responseresponse
Axon has a resting potentialAxon has a resting potential Opening of voltage gated channels Opening of voltage gated channels
propagates current down axonpropagates current down axon At end of axon, neurotransmitters At end of axon, neurotransmitters
released from synaptic knobs into released from synaptic knobs into synaptic cleftsynaptic cleft 2121
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Neurons interact with other Neurons interact with other neuronsneurons
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Synapse – region between two neurons
Presynaptic → Postsynaptic
Neurotransmitters:
Excitatory – Excitatory postsynaptic potentials (depolarize)
Inhibitory – Inhibitory postsynaptic potentials (hyperpolarize –more difficult to reach threshold)
NeurotransmittersNeurotransmitters
At least 30 knownAt least 30 known AcetylcholineAcetylcholine Amino acids – GABAAmino acids – GABA Biogenic amines – catecholamines – Biogenic amines – catecholamines –
norepinephrine, epinephrine, dopaminenorepinephrine, epinephrine, dopamine– Also serotonin and histamineAlso serotonin and histamine
Neuropeptides – opiates such as Neuropeptides – opiates such as enkephalins and endorphinsenkephalins and endorphins
Gases – Nitric oxide (NO)- vasodilationGases – Nitric oxide (NO)- vasodilation
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BrainBrain
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Divisions of BrainDivisions of Brain
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Forebrain - cerebral hemispheres, thalamus and hypothalamus
Midbrain - corpora quadrigemina and cerebral peduncles
Hindbrain - cerebellum, pons, medulla oblongata
Reticular formation
Reticular activating system
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Gyri - convolutions
Sulci - grooves
Gray matter – nerve cell bodies and dendrites (unmyelinated)
White matter – myelinated axons
Spinal cordSpinal cord
Lies in vertebral canal protected Lies in vertebral canal protected by vertebral columnby vertebral column
Connects brain and bodyConnects brain and body Somatic and autonomic reflexesSomatic and autonomic reflexes Begins at medulla oblongata and Begins at medulla oblongata and
ends at conus medullaris at L1 or ends at conus medullaris at L1 or L2L2
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Protective StructuresProtective Structures
CraniumCranium Meninges:Meninges:
– Dura Mater – “Tough mother”Dura Mater – “Tough mother” Periosteum and meningeal layerPeriosteum and meningeal layer Falx cerebri, Falx cerebelli, and Falx cerebri, Falx cerebelli, and
Tentorium cerebelliTentorium cerebelli– Arachnoid – “Spider web-like”Arachnoid – “Spider web-like”
Subarachnoid space – CSF flowsSubarachnoid space – CSF flows– Pia mater – “Gentle mother”Pia mater – “Gentle mother”
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Blood-Brain BarrierBlood-Brain Barrier
Capillaries have tight junctionsCapillaries have tight junctions Aided by astrocytesAided by astrocytes Selectively permeableSelectively permeable Important when we want to get Important when we want to get
antibiotics or other antibiotics or other chemotherapeutic agents into chemotherapeutic agents into the brain.the brain.
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