Unit 2: Neurotransmission
“I have kids participating who never would have thought of raising their hands before. And the recall of some of the children whom I never would have figured would be tracking is just amazing - what they remember from last year, what they remember from last week or last month. It’s really good.” 4th Grade Teacher B Neurotransmission Unit: Background Information
Neurons: Neurotransmission: Structure and Function Neurons Sending Messages
he human brain contains Neurons in the spinal cord directly approximately 100 billion nerve control our muscles, and the basic Tcells, which are also called neurons. concepts of neurotransmission will be There are many different types of neurons introduced though this neuro-muscular in the nervous system that differ in communication. Neurons whose cell appearance. However, all neurons have bodies are located in the spinal cord some common structural features that project their axons directly to skeletal allow them to transmit and receive muscles. These cells are called motor messages. The basic parts of neurons are neurons and receive messages from the the cell body, dendrites, axon, and axon motor cortex, as described in general terms terminal. in the reactions time lessons. The axon terminal of the motor neuron comes in The cell body and dendrites very close proximity to the muscle cell, but function as the “receptive” part of the cell. dose not directly contact the muscle. There The axon and axon terminal are involved is a very small space between the axon in transmission of messages to other cells. terminal and the muscle cell that is known A single neuron can cell can receive as the synaptic cleft. This small region messages from thousands of other that includes the axon terminal, synaptic neurons. Neuroscientist have discovered a cleft, and adjacent part of the muscle cell is great deal about how neurons called the synapse. communicate with one another and believe that the intricate communication among The motor neuron gets excited these cells is responsible for our thoughts, electrically by receiving a series of memories, feelings, and sensory chemical messages from the motor cortex. perception. Very little is known about how When a threshold level of excitation is the interactions of neurons actually create reached in the cell body, a burst of our human experience. However, much is electrical activity is produced in the axon known about how nerve cells stimulate that is propagated to the axon terminal. muscle cells, and thus control our This burst of electrical excitation is called movements. The basic principals involved the action potential. When the action in the transmission of messages from potential reaches the axon terminal, a neurons to muscles are the same as those release of chemicals (molecules) known as between nerve cells n e u ro t r a n s m i t t e r s is induced. T h e neurotransmitter molecules travel across the synaptic cleft and bind to specialized
Grade 4: Neurotransmission Unit UNC-CH Brain Explorers May be reproduced for non-profit educational use only. Please credit source. B
receptors on the muscle cell. When the neurotransmitter binds to the receptor, electrical activity is induced in the muscle and this causes a complex series of biochemical events to occur within the muscle cell that results in muscle contraction and movement of body parts. This sequence of events is summarized schematically below. (This animation was created in Hyperstudio, as a part of a technology extension unit for fourth grade.)
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Watch that axon terminal!
Grade 4: Neurotransmission Unitt UNC-CH Brain Explorers May be reproduced for non-profit educational use only. Please credit source. B Notes
Grade 4: Neurotransmission Unit UNC-CH Brain Explorers May be reproduced for non-profit educational use only. Please credit source.