What is a neuron?Neurons, or nerve cells, are the basic unit of the nervous system. They transmit signals throughout the body to other neurons, muscles, or glands. Neurons communicate using electrical and chemical signals. There are three major types of neurons in the body: sensory neurons: sensory neurons, motor neurons, and interneurons, which connect the two.
GliaIn addition to neurons that carry action potentials, the nervous system also contains glial cells, which protect and nurture neurons. In the central nervous system (brain and spinal cord), there are four types of glial cells: astrocytes, microglia, schwann cells, and ependymal cells.
Astrocytes are star-shaped neurons that provide neurons with nutrients and regulate the blood brain barrier. Schwann cells create the myelin sheaths that insulate neuronal axons. Microglial cells mediate immune responses in the brain and clear debris. Ependymal cells produce cerebrospinal fluid and line the brain.
Neurotransmitters & The
A synapse is the connection between the axon terminal of one neuron and the dendrite of the next cell. When electric signals travel to the axon terminal, they cause neurotransmitters to diffuse into the synaptic cleft (gap between neurons). Neurotransmitters bind to receptors in the post-synaptic cell, and can cause one of two responses: excitatory (signal more likely to fire) or inhibitory (signal less likely to fire)
Additional ResourcesCheck out the links below for more information on neurons!
Lumen Learning: courses.lumenlearning.com/boundless-psychology/chapter/neurons/ Khan Academy: khanacademy.org/science/biology/human-biology/neuron-nervous-system/a/the-synapse |
StructureNeuronal structure is made of three primary components: the soma (cell body), which contains the nucleus and cellular components, the axon, which carries electrical signals to be passed to the next neuron, and dendrites, which receive chemical signals from the previous neuron. Axons can be up to one meter long, and they end in axon terminals, which secrete neurotransmitters into the synapse.
Neurons can be myelinated or unmyelinated. The myelin sheath is made up of fatty material, and it acts as insulation on the axon to help signals travel faster. Gaps in the myelin sheath are called nodes of Ranvier.
Signals & Action PotentialsNeurons transmit signals through secretion of neurotransmitters in the synapse and electrical signals in the neuron's axon. The synapse refers to the gap between adjacent neurons, and neurotransmitters from one neuron diffuse across to bind to the next neuron. This starts the passing of the electrical signal through the neuron, also called the action potential.
Neurons have a natural distribution of charge that makes the inside more negative than the outside. When neurotransmitters bind to receptors on the dendrites, channels open, causing the charge to change inside. This causes different channels to open, making the inside of the neuron momentarily positively charged, or depolarized. These depolarizations pass through the neuron as electrical signals, and they end with the secretion of neurotransmitters at the neuron's axon terminal.
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