Neurons and Neurotransmitters Nervous 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 The Nervous System The The Nervous Nervous System System Central CentralNervous NervousSystem System CNS CNS Brain Brain Peripheral PeripheralNervous NervousSystem System PNS PNS Spinal SpinalCord Cord Motor MotorNeurons Neurons Somatic SomaticNervous NervousSystem System voluntary voluntarymovements movementsvia via skeletal muscles skeletal muscles Sympathetic Sympathetic Fight or Flight Fight or Flight responses responses Sensory SensoryNeurons Neurons Autonomic AutonomicNervous NervousSystem System organs smooth muscles organs smooth muscles Parasympathetic Parasympathetic maintenance maintenance Divisions of the autonomic nervous system Copyright The McGraw Hill Companies Inc Permission required for reproduction or display The Nervous System A physical organ system like any other 2 main kinds of cells Neurons Glia Neurons 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 later Glial 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 Astrocytes Regulate external environment ions etc Most abundant glial cell May contribute to blood brain barrier and to synapses Three main types of neurons Sensory Neurons Interneurons Motor Neurons Sensory Afferent vs Motor Efferent sensory afferent nerve Neurons that send signals from the senses skin muscles and internal organs to the CNS e g skin motor efferent nerve Neurons that transmit commands from the CNS to the muscles glands and organs Gray s Anatomy 38 1999 e g muscle The Withdrawal Reflex Neuron Anatomy and Neural Communication Neurons Dendrites Cell Body Myelin Sheath Axon of another neuron Axon Dendrites of another neuron Neural Anatomy Dendrite the bushy branching extensions of a neuron that receive messages and conduct impulses toward the cell body Axon the extension of a neuron ending in branching terminal fibers through which messages are sent to other neurons or to muscles or glands Neural Anatomy and communication Synapse junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron tiny gap at this junction is called the synaptic gap or cleft Synapse movie Specific Parts The Neuron Structure Specific Parts The Neuron Function 1 3 2 Neurons 3 functions Reception Conduction Transmission Action Potential When dendrites stimulated the delicate balance is altered Membrane breaks down Positively charged ions rush in depolarization Charge less negative Causes release of chemicals from terminal buttons W W Norton Relay 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 info Communication Impulse releases neurotransmitter from vesicles Neurotransmitter enters synaptic gap Neurotransmitter binds to receptors on the receiving neuron Myelin 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 mph Myelinization clip Myelin conduction clip Neurotransmitters chemical messengers that traverse the synaptic gaps between neurons when 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 impulse Neurotransmitters 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 discomfort More neurotransmitters Receptor binding movie
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