The Nueron
What are many axons covered with?
A myelin sheath.
What is a neuron?
A specialized cell used to transmit information to other nerve, muscle, or gland cells.
What does the flow of ions produce?
An electrical current that creates a tiny amount of voltage across teh cell membrane.
How many neurons does the mammalian brain have?
Between 100 million and 100 billion neurons.
Where are dendrites located?
Dendrites extend from the cell body and receive messages from other neurons.
How do neurons transmit messages?
Electrical impulses along their axons.
How long can axons be?
From a fraction of an inch to three feet.
What does the myelin sheath do?
It accelerates the transmission of electrical signals across the axon.
What are cells within the nervous system called?
Nuerons
What is the basic working unit of the brain?
Nuerons.
What are the glia in the brain called?
Oligodendrocytes.
What do these receptors act as?
On and off switches for the next cell.
What are glia in the peripheral nervous system called?
Schwann cells.
What are ion channels?
Selectively permeable, water-filled molecular tunnels that pass through the cell membrane and allow ions or small molecules to enter or leave the cell.
What is the myelin sheath made up of?
Specialized cells called glia.
What are synapses?
Synapses are contact points where one neuron contacts another, and dendrites are covered with them from other axons.
How much more glia than neurons does the brain contain?
Ten times more.
Where is the axon?
The axon extends from the cell body and often gives rise to similar branches ending at nerve terminals.
What are neurotransmitters?
The brain's chemical messengers.
What does the cell body contain?
The nucleus and cytoplasm.
What happens to neurotransmitters?
They are released at the nerve terminals, diffuse across the synapse, and and bind to receptors on the target cell.
What do glia do?
They transport nutrients to neurons, clean up brain debris, digest parts of dead neurons and help hold neurons in place.
What happens when the voltage change reaches the end of a axon?
They trigger the release of neurotransmitters.
How do nerve impulses form?
Through the opening and closing of ion channels.
How do these transmitters work?
When the transmitter is in place in the specifically shaped receptor, it alters the target cell's membrane process, causing an action to occur.
What does each neuron consist of?
A cell body, dendrites, and an axon.
How does a nerve impulse work?
A dramatic reversal in the electric potential of a neuron from negative to positive occurs, and this action potential fires up the axon's membrane to the end, making several impulses per minute possible.