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Understanding Synapses of the Brain

written by: Andrea Campbell • edited by: Elizabeth Stannard Gromisch • updated: 1/9/2012

How can something that is too small to be seen possibly perform functions that affect everything we do? The synapses of the brain are part of a network of mini conductors that help to channel how we move, react and think. These cell elements create chemical reactions that signal those movements.

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    Science Behind The Matter

    RoyandSherrington 1893 You know how when something is not too hard, people will say, “It’s not brain science!” Well, here are explanations that are brain science and which will help you to understand what the synapses of the brain are, where they are located, how they connect and work, and what they do.

    Englishman Sir Charles Scott Sherrington was a neurophysiologist, meaning he studied nervous function in the brain, and won a 1932 Nobel Laureate prize in Medicine for his work. Sherrington and his colleagues made up the word, “synaptein,” which is the combination of a Greek word meaning syn—together—and haptein, meaning to clasp. (Photo at left: Charles Smart Roy & Charles Scott Sherrington.)

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    Cells and Molecules

    mad.scientist4 Our bodies are made up of cells. We know that there are molecules found on the surface of cells in the body and brain. Each and every molecule is composed of small units of atoms like carbon, hydrogen and nitrogen bonded together—and these elements are chemicals. Invisible forces attract one molecule to another so they glom together. This invisible force can be overcome if enough energy is applied to the substance. For example, heat can melt ice, turning it into water and eventually steam—and while the molecules break loose and fly apart, the chemical formula for water, remains the same.

    Now there are receptor molecules that respond to energy and chemical cues by vibrating. They shimmy, wiggle, bend and change from one shape to another. In a living organism, they are found attached to a cell floating on the cell’s surface or membrane. A typical nerve cell can have millions of receptors on its surface (picture a lily pad on water). The receptor molecules have proteins, tiny amino acids inside crumpled chains.

    Just as our fingers have sense organs and can sense something when we touch it, receptors function as sensing molecules. They hover in the membranes of cells dancing and wiggling, waiting to pick up messages from other little creatures that diffuse through the fluids surrounding each cell.

    Remember, all receptors are proteins and they wait for the right chemical keys to swim through the extracellular fluid and bind with them.

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    Synaptic Connections

    Mouse cingulate cortex neurons Brain cells communicate with one another by chemicals through synaptic connections. The human brain contains billions of neurons and each neuron has a large amount of synaptic connections to other neurons. Each synapse itself contains a variety of those receptor proteins that can alter the gross firing pattern of a neuron. (See: Mouse cingulate cortex neurons at left.)

    This chemical key that docks onto the receptor and causes it to dance is called a ligand. It tickles the cell and the disturbance makes the molecule rearrange itself, changing shape as information enters the cell.

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    Receptors

    brainsynapses The receptor, now receiving a message, transmits it from the surface of the cell deep into the interior and a chain reaction occurs—biochemical events—and tiny machines directed by the ligands, make any number of activities happen, such as manufacturing new proteins, making decisions about cell division, opening or closing ion channels, and adding or subtracting energetic chemical groups.

    The human brain contains billions of nerve cells or neurons, the information processing system.

    A neuron has:

    • Dendrites (inputs)
    • Cell body
    • Axon (output)

    A synapse is the place where two neurons join in such a way that a signal can be transmitted from one to the other. Basically, the axon of one neuron activates a second neuron and like a chain reaction, makes a synapse with one of its dendrites or within the cell body. The two types of synapse reactions are: electrical or chemical.

    A neuron receives input from other neurons and the neuron discharges an electrical pulse that travels from the body, down the axon, to the next neuron or other receptors. The axon endings are close to the dendrites or cell body of the next neuron. Transmission of an electrical signal from one neuron to the next is effected by neurotransmitters, chemicals which are released from the first neuron which bind to receptors in the second. This link is called a synapse.

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    Synapse Function

    Our brains learn by altering the strength of connections between neurons, and by adding or deleting connections between neurons. The ability of a synapse can change with experience, providing us with memories. One way this happens—called potentiation—is through release of more neurotransmitters. Synapses are affected by drugs such as curare, strychnine, cocaine, morphine, alcohol, LSD and many other chemicals. These drugs have different effects on synaptic function, either exciting them or inhibiting them. There are also diseases which inhibit proper synapses of the brain, such as Alzheimer's.

    For an excellent example of "The effects of drugs and disease on synaptic transmission," visit: http://outreach.mcb.harvard.edu/animations/synapse.swf

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    Reference & Resource

    Pert, Candace B. Ph.D, Molecules of Emotion: Why You Feel the Way You Feel, Scribner, 1997.

    A Brief Introduction to The Brain, http://www.ifc.unam.mx/Brain/segunda.htm

    Image Credit: Chemical synapse schemas, http://www.nia.nih.gov/Alzheimers/Publications/UnravelingtheMystery/

    Image Credit: 1893 Photograph of Sir Charles Sherrington and Professor Charles Smart Roy from Wikimedia.org, http://commons.wikimedia.org/wiki/File:Roy_Sherrington_1893_01.jpg

    Image Credit: neuron, http://www.flickr.com/photos/neurollero/17873944/in/set-366106/ Creative commons generic use

    Photo: Mad scientist, Clipart.com

    For a large size picture of the Synapse Schema, go to: http://images.brighthub.com/media/4B3030_brainsynapses.jpg

All About the Human Brain

Study up on the human brain, from basic anatomy to neurotransmitters and left vs. right brain thinking. Our science study guides provide all the hints you need to score high on your next test!
  1. Study Guide for Left and Right Brain Learning
  2. Study Guide for the Parts of the Brain
  3. Study Guide for the Function and Structure of Neurons
  4. Study Guide for the Neurotransmitters in the Brain
  5. Understanding Synapses of the Brain

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