Neurons
Neurons are the building block, and key to the functionality of the nervous systems. What would we be without neurons? Immobile blobs. See, neurons are key to the body's ability to move, react, and process information. They are the body's connection to the brain. They work in conjunctions with thousands of others to communicate signals thought the body , enabling all of the body's function.
Cool facts about neurons
What do you need to know?
Neurons have a core structure made up of the cell body, the nucleus, the axon and axon terminals. There are several other parts that you can see in the diagram below.
Neurons are the building block, and key to the functionality of the nervous systems. What would we be without neurons? Immobile blobs. See, neurons are key to the body's ability to move, react, and process information. They are the body's connection to the brain. They work in conjunctions with thousands of others to communicate signals thought the body , enabling all of the body's function.
Cool facts about neurons
- The human brain contains an estimated 100 billion neurons
- An octopus has 300 million neurons
- A neuron is about 4 to 100 microns in diameter
- Neurons transports signals at 250 mph
- During fetal development neurons develop at around a whooping 250,000 neurons per minute
What do you need to know?
Neurons have a core structure made up of the cell body, the nucleus, the axon and axon terminals. There are several other parts that you can see in the diagram below.
The cell body contains the nucleus and cytoplasm. The axon extends from the cell body and often gives rise to many smaller branches before ending at nerve terminals.
Dendrites extend from the neuron cell body and receive messages from other neurons. Synapses are the contact points where one neuron communicates with another. The dendrites are covered with synapses formed by the ends of axons from other neurons.
When neurons receive or send messages, they transmit electrical impulses along their axons, which can range in length from a tiny fraction of an inch (or centimeter) to three feet (about one meter) or more. Axons are covered with a layered myelin sheath, which accelerates the transmission of electrical signals along the axon. This sheath is made by specialized cells called glia, they are known as Schwann cells.
The brain contains at least ten times more glia than neurons. Glia perform many jobs. Researchers have known for a while that glia transport nutrients to neurons, clean up brain debris, digest parts of dead neurons, and help hold neurons in place. Current research is uncovering important new roles for glia in brain function.
Neural impulses are transmitted from one neuron to another via neurotransmitters. When an action potential reaches the terminal buttons of a neuron, neurotransmitter-filled synaptic vesicles fuse with the cell membrane, releasing neurotransmitter molecules into the synaptic cleft. These molecules link up with receptors on neighboring neurons and generate a voltage change or postsynaptic potential at the receptor site.
Dendrites extend from the neuron cell body and receive messages from other neurons. Synapses are the contact points where one neuron communicates with another. The dendrites are covered with synapses formed by the ends of axons from other neurons.
When neurons receive or send messages, they transmit electrical impulses along their axons, which can range in length from a tiny fraction of an inch (or centimeter) to three feet (about one meter) or more. Axons are covered with a layered myelin sheath, which accelerates the transmission of electrical signals along the axon. This sheath is made by specialized cells called glia, they are known as Schwann cells.
The brain contains at least ten times more glia than neurons. Glia perform many jobs. Researchers have known for a while that glia transport nutrients to neurons, clean up brain debris, digest parts of dead neurons, and help hold neurons in place. Current research is uncovering important new roles for glia in brain function.
Neural impulses are transmitted from one neuron to another via neurotransmitters. When an action potential reaches the terminal buttons of a neuron, neurotransmitter-filled synaptic vesicles fuse with the cell membrane, releasing neurotransmitter molecules into the synaptic cleft. These molecules link up with receptors on neighboring neurons and generate a voltage change or postsynaptic potential at the receptor site.
Action potential/ Threshold/ Resting potential
An action potential is part of the process that occurs during the firing of a neuron. During the action potential, part of the neural membrane opens to allow positively charged ions inside the cell and negatively charged ions out. This process causes a rapid increase in the positive charge of the nerve fiber. When the charge reaches +40 mv, the impulse is sent down down the nerve fiber.
This is continued through a series.
When an impulse is sent out from a cell body, the sodium channels open and the positive sodium cells surge into the cell. Once the cell reaches a certain threshold, an action potential will fire, sending the electrical signal down the axon. Action potentials either happen or they don't; there is no such thing as a partial firing of a neuron. This is known as the all or none law.
After a neuron fires, there is a period of time where it cannot fire again. During this time, the potassium channels reopen and the sodium channels close, gradually returning the neuron to its resting potential.
This is continued through a series.
When an impulse is sent out from a cell body, the sodium channels open and the positive sodium cells surge into the cell. Once the cell reaches a certain threshold, an action potential will fire, sending the electrical signal down the axon. Action potentials either happen or they don't; there is no such thing as a partial firing of a neuron. This is known as the all or none law.
After a neuron fires, there is a period of time where it cannot fire again. During this time, the potassium channels reopen and the sodium channels close, gradually returning the neuron to its resting potential.
How does a reflex work?
The external stimuli alerts the sensory neurons, which then proceeds to sent a signal of what it is through the nervous system and it is processed by the sensory cortex and sent through the motor cortex sending an action signal to the appropriate motor neurons in the body, triggering an action.
Light you finger on fire? Neurons make and send the signal for you to saw OWWWWWWWWWWWWWWW!.
Light you finger on fire? Neurons make and send the signal for you to saw OWWWWWWWWWWWWWWW!.
Tip
Think of a hand! The fingers are dendrites, the palm is the cell body, and that has the nucleus. The arm is the axon, and the elbow (use your imagination) has the axon terminals.