The Nervous System. The NERVOUS SYSTEM controls and coordinates functions throughout the body and responds to internal and external stimuli. NEURONS are cells that transmit messages, called IMPULSES , through the nervous system.
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NEURONSare cells that transmit messages, called IMPULSES, through the nervous system
The AXON carries impulses away from the cell body. The axon is covered in a membrane called the MYELIN SHEATH. There are gaps in the myelin sheath, called NODES. The signal can jump from node to node, increasing the speed of the impulse.
A RESTING NEURON is one that is not transmitting an impulse. Na+/K+ gates pump three Na+ ions out of the cell membrane and two K+ ions in through the cell membrane, creating a net negative charge inside the cell. This charge configuration is called the RESTING POTENTIAL of the neuron.
When the neuron receives a signal from the environment or another neuron, the ion gates at the leading edge of the cell open and Na+ is pumped into the the axon, and K+ is pumped out. This creates an ACTION POTENTIAL, which creates a current that moves down the axon.
In order for a neuron to send an impulse in response to a stimulus, the stimulus must overcome the THRESHOLD POTENTIAL, the minimum potential needed in order to create an action potential.
A neuron can transfer a signal to another cell at locations called SYNAPSES. At the synapse, chemicals called NEUROTRANSMITTERS are released, which sends the impulse to receptors in an adjacent cell.
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