The nervous system is made up of billions of neurons, which associate between one another. Neurons are responsible for manipulating information, doing so involves changes in the bio electrical and/or biochemical properties of a cell, and these changes require large amounts of energy. The nervous system is therefore the greatest consumer of oxygen and glucose. These energy requirements arise directly from the metabolic demand placed on cells-which have a large surface area and concentrate bio molecules and ions against the energy gradient. Each Neuron Also:
1) Receives information from the environment, or other nerve cells.
2) Processes information
3) Sends information to other neurons or effector tissues.
Dendrites:
Dendrites are tiny branch like extensions on a neuron. These dendrites are usually numerous in numbers, and are located at the top of the neuron, protruding away from the cell body. Dendrites are specialized for receiving information and are always opposite the Axon Terminals, which they form synaptic contacts with. When the Dendrites make contact with the axon terminal, a connection is made, allowing for the nerve impulses to be transferred between the neurons. Dendrites are absolutely crucial to the neuron because with out them, the individual neurons will be unable to form the intricate network, which allows us to feel and send direction s from our brain to the rest of our body.
Nucleus:
The Nucleus is essentially the “brain” or control center for the neuron. It holds all the genetic information in it.
Axon:
The axon is a long thin wire like part which comes off of the cell body, and extends to the axon terminals. The axon is covered by sheaths of myelin, which allows for the electrical signals to be transferred easier and faster. The electrical signal is transferred down the axon, from the dendrites to the axon terminals, where they then connect to a dendrite from another neuron to transfer information.
Myelin Sheath:
The Myelin Sheath is a soft white fatty substance which sheaths the axon. This sheet insulates the axon, and allows for the electrical signal to be transferred more efficiently along the axon, towards the axon terminals, as well as allow the impulse to travel at a faster rate.
Axon Terminals:
The Axon Terminals are very closely linked with the Dendrites. They are as crucial to the transfer of electrical signals and impulse. The axon terminal transfers the electrical impulse from them to the dendrites, when they make contact with each other. This contact allows for the impulse to travel from one neuron to another neuron.
Interesting Facts:
Average number of neurons in the human brain: 100 billion
Average number of neurons in an octopus brain: 300 billion
Rate of neuron growth during development of a fetus (in the womb): 250,000 neurons/minute
Diameter of a neuron: 4 to 100 microns
Longest axon of a neuron: around 15 feet (Giraffe primary afferent axon from toe to neck)
Velocity of a signal transmitted through a neuron: 1.2 to 250 miles/hour
