Neurons and Neurotransmitters

Nervous System Central nervous system (CNS): Brain Spinal cord Peripheral nervous system (PNS): Sensory neurons Motor neurons (somatic and autonomic)

The Nervous System The Nervous System Central Nervous System (CNS) Peripheral Nervous System (PNS) Brain Spinal Cord Motor Neurons Sensory Neurons Somatic Nervous System voluntary movements via skeletal muscles Autonomic Nervous System organs, smooth muscles Sympathetic - “Fight-or-Flight” responses Parasympathetic - maintenance

Divisions of the autonomic nervous system Rest Action Figure 3.20 on page 89 The sympathetic division of the nervous system prepares the body for action, whereas the parasympathetic returns it to a resting state.

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”

Three main types of neurons Sensory Neurons Interneurons Motor Neurons

The Withdrawal Reflex Figure 2.5B from: Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall.

Neuron Anatomy and Neural Communication

Dendrites of another neuron Neurons Cell Body Dendrites Axon Myelin Sheath Dendrites of another neuron Axon of another neuron

Neural Anatomy Dendrite Axon 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 Figure 2.6 from: Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall. Source:

Specific Parts: The Neuron Function 1. 3. 2. Figure 2.6 from: Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall. Source: 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

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

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