![]() Finally, there are interneurons, which process the sensory input from our environment into meaningful representations, plan the appropriate behavioral response, and connect to the motor neurons to execute these behavioral plans. There are motor neurons that allow us to initiate movement and behavior, ultimately allowing us to interact with the world around us. ![]() Not all neurons are created equal! There are neurons that help us receive information about the world around us, sensory neurons. We will discuss the role of receptors in more detail later in the module. Neurotransmitters are released from the presynaptic terminal button, travel across the synaptic gap, and activate ion channels on the postsynaptic spine by binding to receptor sites. In the presynaptic terminal button, there are synaptic vesiclesthat package together groups of chemicals called neurotransmitters(see Figure 3). There are 1,350,000 nm in the thickness of a dime. To give you a better idea of the size, a dime is 1.35 mm (millimeter) thick. Here we will focus specifically on synapses between the terminal button of an axon and a dendritic spine however, synapses can also form between the terminal button of an axon and the soma or the axon of another neuron.Ī very small space called a synaptic gapor a synaptic cleft, approximately 5 nm (nanometers), exists between the presynaptic terminal button and the postsynaptic dendritic spine. Synapsesform between the presynaptic terminal button (neuron sending the signal) and the postsynaptic membrane (neuron receiving the signal see Figure 3). At the end of the axon is a terminal button, which forms synapses with spines, or protrusions, on the dendrites of neurons. The axon splits many times, so that it can communicate, or synapse, with several other neurons (see Figure 2). Typically, the axon of a neuron is covered with an insulating substance called a myelin sheaththat allows the signal and communication of one neuron to travel rapidly to another neuron. The place at which the axon of one neuron comes in close contact to the dendrite of another neuron is a synapse(see Figures 2–3). The axon is a process that extends far away from the soma and carries an important signal called an action potential to another neuron. The main source of output of the neuron is the axon. The nucleus, which is located within the soma, contains genetic information, directs protein synthesis, and supplies the energy and the resources the neuron needs to function. Dendrites receive information from thousands of other neurons and are the main source of input of the neuron. Dendritesare processes that extend outward from the soma, or cell body, of a neuron and typically branch several times. Each neuron has three main components: dendrites, the soma, and the axon (see Figure 2). There are approximately 100 billion neurons in the human brain ( Williams & Herrup, 1988). ![]() ![]() The Structure of the Neuron Basic Nomenclature ![]()
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