Neurons and Neurotransmitters

Nervous System

Central nervous system (CNS):BrainSpinal cord

Peripheral nervous system (PNS):Sensory neuronsMotor neurons (somatic and autonomic)

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The Nervous SystemCentral Nervous System (CNS)BrainSpinal CordPeripheral Nervous System (PNS)Sensory NeuronsMotor NeuronsSomatic Nervous Systemvoluntary movements via skeletal musclesAutonomic Nervous Systemorgans, smooth musclesSympathetic- Fight-or-Flight responsesParasympathetic - maintenanceThe Nervous System

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Divisions of the autonomic nervous system

The Nervous SystemA physical organ system like any other

2 main kinds of cells NeuronsGlia

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 cells100 billion neurons10x more glial cellsGlial cellsSupport neurons (literally, provide physical support, as well as nutrients)Cover neurons with myelinClean up debrisHousewives

Astrocytes Regulate external environment (ions, etc.) Most abundant glial cell May contribute to blood-brain barrier and to synapses

Three main types of neuronsSensory Neurons

Interneurons

Motor Neurons

Sensory (Afferent) vs. Motor (Efferent)e.g., skine.g., muscleGrays 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 organs

The Withdrawal Reflex

Neuron Anatomy and Neural Communication

NeuronsAxon of another neuronDendrites of another neuron

Neural 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 glands

Neural 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 movie

Specific Parts: The NeuronStructure

Specific 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 buttons

W. W. Norton

Relay RaceAction Potential starts at dendriteThrough cell bodyDown AxonAxon TerminalsHow does it get to the next cells dendrites?

Neurons dont touchSynapse = millionth inch gapIn synapse = vesicles w/ neurotransmittersChemical messengers that transmit info

CommunicationImpulse releases neurotransmitter from vesicles

Neurotransmitter enters synaptic gap

Neurotransmitter binds to receptors on the receiving neuron

Myelin Sheath

Fatty material made by glial cellsInsulates the axonAllows for rapid movement of electrical impulses along axonNodes of Ranvier: gaps in myelin sheath where action potentials are transmittedMultiple sclerosis is a breakdown of myelin sheathSpeed of neural impulse Ranges from 2 200+ mph

Myelinization clipMyelin conduction clip

Neurotransmitters

chemical 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 impulse

Neurotransmitters (>60)Acetylcholine (ACh)1st substance identified as NTLinks motor neurons and muscles (contract or relax)e.g. curare vs black widow spiderAlso involved in memory, learning, sleep, dreaming(acetylcholine movie)Endorphins (the brains own morphine)1973 injected rats with morphineBound like NTsBrain had receptors for exogenous substance?Brain must produce its own morphineReleased during pain and discomfort

More neurotransmitters Receptor binding movie

Figure 3.20 on page 89The sympathetic division of the nervous system prepares the body for action, whereas the parasympathetic returns it to a resting state.Figure 2.5B from:Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall.Figure 2.6 from:Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall.Source:Figure 2.6 from:Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall.Source:Figure 2.7 from:Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall.Source: