Unit 2:Neurotransmission

“I have kids participating who never would havethought of raising their hands before. And the recall ofsome of the children whom I never would have figured

would be tracking is just amazing - what they rememberfrom last year, what they remember from last week or

last month. It’s really good.”4th Grade Teacher

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Grade 4: Neurotransmission Unit UNC-CH Brain Explorers May be reproduced for non-profit educational use only. Please credit source.

Neurotransmission Unit: Background Information

Neurons: Structure and Function

The human brain containsapproximately 100 billion nervecells, which are also called neurons.

There are many different types of neuronsin the nervous system that differ inappearance. However, all neurons havesome common structural features thatallow them to transmit and receivemessages. The basic parts of neurons arethe cell body , dendrites, axon, and axonterminal.

The cell body and dendritesfunction as the “receptive” part of the cell.The axon and axon terminal are involvedin transmission of messages to other cells.A single neuron can cell can receivemessages from thousands of otherneurons. Neuroscientist have discovered agreat deal about how neuronscommunicate with one another and believethat the intricate communication amongthese cells is responsible for our thoughts,memories, feelings, and sensoryperception. Very little is known about howthe interactions of neurons actually createour human experience. However, much isknown about how nerve cells stimulatemuscle cells, and thus control ourmovements. The basic principals involvedin the transmission of messages fromneurons to muscles are the same as thosebetween nerve cells

Neurotransmission:Neurons Sending Messages

Neurons in the spinal cord directlycontrol our muscles, and the basicconcepts of neurotransmission will beintroduced though this neuro-muscularcommunication. Neurons whose cellbodies are located in the spinal cordproject their axons directly to skeletalmuscles. These cells are called motorneurons and receive messages from themotor cortex, as described in general termsin the reactions time lessons. The axonterminal of the motor neuron comes invery close proximity to the muscle cell, butdose not directly contact the muscle. Thereis a very small space between the axonterminal and the muscle cell that is knownas the synaptic cleft. This small regionthat includes the axon terminal, synapticcleft, and adjacent part of the muscle cell iscalled the synapse.

The motor neuron gets excitedelectrically by receiving a series ofchemical messages from the motor cortex.When a threshold level of excitation isreached in the cell body, a burst ofelectrical activity is produced in the axonthat is propagated to the axon terminal.This burst of electrical excitation is calledthe action potential. When the actionpotential reaches the axon terminal, arelease of chemicals (molecules) known asn e u ro t r a n s m i t t e r s is induced. T h eneurotransmitter molecules travel acrossthe synaptic cleft and bind to specialized

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Grade 4: Neurotransmission Unitt UNC-CH Brain Explorers May be reproduced for non-profit educational use only. Please credit source.

receptors on the muscle cell. When the neurotransmitter binds to the receptor, electricalactivity is induced in the muscle and this causes a complex series of biochemical eventsto occur within the muscle cell that results in muscle contraction and movement of bodyparts. This sequence of events is summarized schematically below. (This animation wascreated in Hyperstudio, as a part of a technology extension unit for fourth grade.)

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Watchthat axonterminal!

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Grade 4: Neurotransmission Unit UNC-CH Brain Explorers May be reproduced for non-profit educational use only. Please credit source.