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| The basic structure of a neuron |
Neurons – Building Blocks of the Nervous System
The nervous system consists of billions of specialized cells called neurons. About one third of your neurons are organized into a complex communication network to carry information from your sense organs to your brain and from your brain back to your muscles. The rest of your neurons form the structures in your brain.
A neuron is a specialized and elongated cell that transmits an electro-chemical signal from one end to the other. A neuron receives signals through delicate branching structures called dendrites located near the cell nucleus. A nerve cell has one longer extension, an axon. And at the far end of the axon, there are more branches. A single neuron can receive signals though many of its dendrites and can transmit signals to many other neurons through its axon branches. If a strong nerve impulse arrives at a dendrite, or a weaker signal arrives at a number of dendrites, then an electrochemical signal is generated that propagates along the axon and then off to the dendrites of one or more nearby neurons.
There is a tiny but important gap, called a synapse, between the dendrites and axons of neighbouring neurons. A nerve impulse can only jump this gap with the assistance of specialized chemicals called neurotransmitters. Neurotransmitters are created and released at a synapse as a nerve impulse approaches the end of an axon. If enough neurotransmitter has been generated before the nerve impulse arrives, then the impulse can cross the synapse and continue down the dendrite of the next nerve. An impulse has a greater chance of being transmitted if the signal in a single axon is stronger, or if an impulse has been duplicated and is travelling along several neighbouring neurons at the same time. A synapse can also act as a filter by blocking weaker signals. After an impulse reaches the end of an axon, neurotransmitters are quickly broken down so they will not interfere with the next set of nerve impulses.
Neurons outside of the brain are bundled to form nerve fibres that look like white cords or wires. Signals typically travel from dendrites and down the axon of a nerve fibre at speeds up to one hundred metres per second, depending on the overall structure of the nerve bundle. Although neurons are carefully protected and nourished by support cells, they are unable to undergo cell division or to repair any significant damage. Any neural damage tends to be permanent.
The nervous system consists of billions of specialized cells called neurons. About one third of your neurons are organized into a complex communication network to carry information from your sense organs to your brain and from your brain back to your muscles. The rest of your neurons form the structures in your brain.
A neuron is a specialized and elongated cell that transmits an electro-chemical signal from one end to the other. A neuron receives signals through delicate branching structures called dendrites located near the cell nucleus. A nerve cell has one longer extension, an axon. And at the far end of the axon, there are more branches. A single neuron can receive signals though many of its dendrites and can transmit signals to many other neurons through its axon branches. If a strong nerve impulse arrives at a dendrite, or a weaker signal arrives at a number of dendrites, then an electrochemical signal is generated that propagates along the axon and then off to the dendrites of one or more nearby neurons.
There is a tiny but important gap, called a synapse, between the dendrites and axons of neighbouring neurons. A nerve impulse can only jump this gap with the assistance of specialized chemicals called neurotransmitters. Neurotransmitters are created and released at a synapse as a nerve impulse approaches the end of an axon. If enough neurotransmitter has been generated before the nerve impulse arrives, then the impulse can cross the synapse and continue down the dendrite of the next nerve. An impulse has a greater chance of being transmitted if the signal in a single axon is stronger, or if an impulse has been duplicated and is travelling along several neighbouring neurons at the same time. A synapse can also act as a filter by blocking weaker signals. After an impulse reaches the end of an axon, neurotransmitters are quickly broken down so they will not interfere with the next set of nerve impulses.
Neurons outside of the brain are bundled to form nerve fibres that look like white cords or wires. Signals typically travel from dendrites and down the axon of a nerve fibre at speeds up to one hundred metres per second, depending on the overall structure of the nerve bundle. Although neurons are carefully protected and nourished by support cells, they are unable to undergo cell division or to repair any significant damage. Any neural damage tends to be permanent.
