Neurons carry messages throughout the body, including sensory information from external stimuli and signals from the brain to different muscle groups in the body. In order to understand exactly how a neuron works, it is important to look at each individual part of the neuron. The unique structures of the neuron allow it to receive and transmit signals to other neurons as well as other types of cells.
Characteristics
Have many dendrites, or only one dendritAre short and highly branchedTransmit information to the cell body
Most neurons possess these branch-like extensions that extend outward away from the cell body. These dendrites then receive chemical signals from other neurons, which are then converted into electrical impulses that are transmitted toward the cell body. Some neurons have very small, short dendrites, while other cells possess very long ones. The neurons of the central nervous systems have very long and complex dendrites that then receive signals from as many as a thousand other neurons. If the electrical impulses transmitted inward toward the cell body are large enough, they will generate an action potential. This results in the signal being transmitted down the axon.
Characteristics
Contains numerous organelles involved in a variety of cell functionsContains a cell nucleus that produces RNA that directs the synthesis of proteinsSupports and maintains the functioning of the neuron
Think of the cell body as a small factory that fuels the neuron. The support structures of the cell include mitochondria, which provide energy for the cell, and the Golgi apparatus, which packages products created by the cell and dispatches them to various locations inside and outside the cell. The axon hillock acts as something of a manager, summing the total inhibitory and excitatory signals. If the sum of these signals exceeds a certain threshold, the action potential will be triggered and an electrical signal will then be transmitted down the axon away from the cell body. This action potential is caused by changes in ion channels which are affected by changes in polarization.
Characteristics
Acts as something of a manager, summing the total inhibitoryPossesses an internal polarization of approximately -70mV in normal resting state
When a signal is received by the cell, it causes sodium ions to enter the cell and reduce the polarization. If the axon hillock is depolarized to a certain threshold, an action potential will fire and transmit the electrical signal down the axon to the synapses. Some axons are covered with a fatty substance called myelin that acts as an insulator. These myelinated axons transmit information much faster than other neurons.
Characteristics
Most neurons have only one axonTransmit information away from the cell bodyMay or may not have a myelin coveringRange dramatically in size, from 0.1 millimeters to over 3 feet long
The myelin surrounding the neurons protects the axon and aids in the speed of transmission. The myelin sheath is broken up by points known as the nodes of Ranvier or myelin sheath gaps. Electrical impulses are able to jump from one node to the next, which plays a role in speeding up the transmission of the signal. Axons connect with other cells in the body including other neurons, muscle cells, and organs. These connections occur at junctions known as synapses.
Characteristics
Contain vesicles holding the neurotransmittersConvert the electrical impulses into chemical signalsCross the synapse where they are received by other nerve cellsResponsible for the reuptake of any excessive neurotransmitters released during this process
A Word From Verywell
Neurons serve as basic building blocks of the nervous system and are responsible for communicating messages throughout the body. Knowing more about the different parts of the neuron can help you to better understand how these important structures function as well as how different problems, such as diseases that impact axon myelination, might impact how messages are communicated throughout the body.
