Neurons and NeurotransmittersNervous SystemThe Nervous SystemDivisions of the autonomic nervous systemSlide 5NeuronsGlial cellsAstrocytesThree main types of neuronsSlide 10The Withdrawal ReflexNeuron Anatomy and Neural CommunicationSlide 13Neural AnatomyNeural Anatomy and communicationSpecific Parts: The Neuron StructureSpecific Parts: The Neuron FunctionAction PotentialSlide 19Relay RaceCommunicationMyelin SheathSlide 23NeurotransmittersNeurotransmitters (>60)More neurotransmittersNeurons and NeurotransmittersNervous System–Central nervous system (CNS):•Brain•Spinal cord–Peripheral nervous system (PNS):•Sensory neurons•Motor neurons (somatic and autonomic)Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Central Nervous System (CNS)Central Nervous System (CNS)BrainBrainSpinal CordSpinal CordPeripheral Nervous System (PNS)Peripheral Nervous System (PNS)Sensory NeuronsSensory NeuronsMotor NeuronsMotor NeuronsSomatic Nervous System•voluntary movements via skeletal musclesSomatic Nervous System•voluntary movements via skeletal musclesAutonomic Nervous System•organs, smooth musclesAutonomic Nervous System•organs, smooth musclesSympathetic- “Fight-or-Flight” responsesSympathetic- “Fight-or-Flight” responsesParasympathetic - maintenanceParasympathetic - maintenanceThe Nervous SystemThe Nervous SystemThe Nervous SystemCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Divisions of the autonomic nervous systemThe Nervous System•A physical organ system like any other•2 main kinds of cells –Neurons–Glia Basic units of the nervous system Receive, integrate, and transmit information Operate through electrical impulses Communicate with other neurons through chemical signals More about neurons and neuronal anatomy laterNeuronsGlial cells•100 billion neurons•10x more glial cells•Glial cells–Support neurons (literally, provide physical support, as well as nutrients)–Cover neurons with myelin–Clean up debris–“Housewives”• Regulate external environment (ions, etc.)• Most abundant glial cell • May contribute to blood-brain barrier and to synapsesAstrocytesThree main types of neurons•Sensory Neurons•Interneurons•Motor NeuronsSensory (Afferent) vs. Motor (Efferent)Sensory (Afferent) vs. Motor (Efferent)e.g., skine.g., muscleGray’s Anatomy 38 1999sensory (afferent) nervemotor (efferent) nerveNeurons that send signals from the senses, skin, muscles, and internal organs to the CNS Neurons that transmit commands from the CNS to the muscles, glands, and organsThe Withdrawal ReflexNeuron Anatomy and Neural CommunicationNeuronsAxon of anotherneuronAxon of anotherneuronCell BodyCell BodyDendritesDendritesAxonAxonMyelinSheathMyelinSheathDendrites of another neuronDendrites of another neuronNeural AnatomyDendritethe bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell bodyAxonthe extension of a neuron, ending in branching terminal fibers, through which messages are sent to other neurons or to muscles or glandsNeural Anatomy and communicationSynapsejunction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neurontiny gap at this junction is called the synaptic gap or cleftSynapse movieSpecific Parts: The NeuronStructureSpecific Parts: The Neuron FunctionNeurons = 3 functions: Reception, Conduction, Transmission1.3.2.Action PotentialWhen dendrites stimulated, the delicate balance is alteredMembrane breaks downPositively charged ions rush in (depolarization)Charge = less negativeCauses release of chemicals from terminal buttonsW. W. NortonRelay Race•Action Potential starts at dendrite–Through cell body–Down Axon–Axon Terminals•How does it get to the next cell’s dendrites?•Neurons don’t touch–Synapse = millionth inch gap–In synapse = vesicles w/ neurotransmitters»Chemical messengers that transmit infoCommunication•Impulse releases neurotransmitter from vesicles•Neurotransmitter enters synaptic gap•Neurotransmitter binds to receptors on the receiving neuronMyelin Sheath–Fatty material made by glial cells–Insulates the axon–Allows for rapid movement of electrical impulses along axon–Nodes of Ranvier: gaps in myelin sheath where action potentials are transmitted–Multiple sclerosis is a breakdown of myelin sheath–Speed of neural impulse Ranges from 2 – 200+ mphMyelinization clipMyelin conduction clipNeurotransmitterschemical messengers that traverse the synaptic gaps between neuronswhen released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether it will generate a neural impulseNeurotransmitters (>60)•Acetylcholine (ACh)–1st substance identified as NT–Links motor neurons and muscles (contract or relax)•e.g. curare vs black widow spider–Also involved in memory, learning, sleep, dreaming(acetylcholine movie)•Endorphins (the brain’s own morphine)–1973 injected rats with morphine–Bound like NTs–Brain had receptors for exogenous substance?•Brain must produce its own morphine•Released during pain and discomfortMore neurotransmitters Receptor binding
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