Are particular types more important than others in various diseases, and can we target them for therapies? The ongoing genetic revolution has made these questions more addressable than ever before, yet we still have a long way to go.
Once you appreciate this diversity and combine it with the fact that there are 86 billion neurons plus at least as many glia! QBI newsletters Subscribe. Help QBI research Give now. Skip to menu Skip to content Skip to footer.
Site search Search. Site search Search Menu. How do neurons work? Home The Brain Brain functions. Figure 1 : Synapses are tiny gaps between neurons, across which the neurons talk to each other. An action potential here yellow lightning causes neurotransmitter to be released. The neurotransmitter travels across the gap to activate receptors on the receiving neuron.
Figure 2: A neuron spikes when a combination of all the excitation and inhibition it receives makes it reach threshold. 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. Explain the brain to your students with a variety of teaching tools and resources. Engage local scientists to educate your community about the brain.
For Educators Log in. Also In Anatomy. Sex Differences in the Brain. The Mysterious, Multifaceted Cerebellum. Einstein's Brain. Spinal Cord. Purkinje Cells. Trending Popular articles on BrainFacts. When one neuron wants to share a message with another, it sends an electrical impulse, called an action potential, down its axon until it reaches the axon terminal, at the end of the axon.
Think of an axon terminal as an airport terminal. An airport terminal is filled with passengers waiting to depart, whereas an axon terminal is filled with neurotransmitters waiting to travel to the next neuron. When the action potential reaches the axon terminal, some of the neurotransmitters in the terminal are dumped into a tiny gap between the terminal and the dendrite of another neuron.
This gap is called a synapse—it is so tiny that it is measured in nanometers or billionths of a meter. The neurotransmitter crosses the synapse and binds to a specialized site, called a receptor, on the other side. Each neurotransmitter binds only to its specific receptor, just as a key fits only in a particular lock. Depending on the neurotransmitter, it either stimulates the other neuron or inhibits, making it either more likely or less likely to fire an action potential of its own.
All these happens with very high precision and is repeated again and again. Some neurotransmitters, especially one kind called neuropeptides , are different. Neuropeptides are released from many parts of a neuron, including the dendrites. Rather than being released into the tiny synapse between an axon terminal and another neuron, they are released into the fluid that fills the spaces between neurons, and they diffuse through the brain to reach receptors that are on distant targets.
One way of thinking about diffusion is to consider making your way through a forest Figure 2. To go from one point to another when no trees are around would be very simple and fast.
Once you have a lot of trees, going from one point to another would take much longer time, because you must go around the trees. So this sort of signaling is much slower than signaling at synapses, but eventually the neuropeptides will reach most parts of the brain. However, only brain areas that have the right receptors can respond to the neuropeptides.
Let me use another example. The neuropeptides, oxytocin and vasopressin, are made by large neurons in the hypothalamus , a part of the brain that is important in regulating many physiological processes of the body.
These large neurons have one axon that goes all the way to a specialized gland, the pituitary gland , which is attached to the bottom of the brain. From there, the neuropeptides are released from the axon terminals directly into the blood. Oxytocin travels through the body and has a role in childbirth and breastfeeding. But both neuropeptides are also released into the brain, where they control several sorts of behavior.
For example, oxytocin helps a mother to bond with her child, and vasopressin affects memory and aggression. However, the brain areas that control these behaviors are sometimes far from the cells that make the neuropeptides. The oxytocin and vasopressin released from the axon terminals into the blood cannot re-enter the brain because of a strange structure called the blood—brain barrier.
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