Neurovascular coupling

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Cognitive Aging & Reserve
When activity rises in part of the brain, neurons, glial cells and blood vessels work together to send more blood there; this is called neurovascular coupling. Some researchers propose that with age the small arteries respond to these signals more slowly, so local blood flow lags, and the long, thin nerve fibers of the white matter are the most sensitive to a shortfall of blood. Part of the slowing of white matter in cognitive aging may come from this. The chain is still an inference and has not been shown directly.

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Blood follows nerve firing

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The brain keeps almost no energy in reserve, yet it never stops spending energy. Every time a neuron fires, ion pumps in its membrane burn (the cell's energy currency) to push the scrambled ions back into place. So sugar and oxygen have to be delivered as they are used. The body does not turn up the blood supply to the whole head. It opens the vessels next to the small patch that is working right now and lets blood flow catch up. This is called neurovascular coupling.

The signal to open the vessels is mostly sent ahead of need. As a synapse releases glutamate (the most common excitatory signal between neurons), nearby neurons and glial cells (brain cells that do not fire and instead look after neurons) start releasing molecules that relax the vessel wall. They do not wait for fuel to run low. Blood flow rises, bringing sugar and oxygen and carrying away waste such as carbon dioxide.

So the bright patch on a brain-scan color map is that surge of blood, not the firing itself. The electrical event is over within milliseconds; the blood arrives a beat later. A bright patch means the supply has caught up with the activity, not that the brain is congested or injured.

Educational content, not medical advice. See a clinician about your own case.

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Neurovascular coupling

Story

Connected to · 1

regulates · 1

Cognitive Aging & Reserve
When activity rises in part of the brain, neurons, glial cells and blood vessels work together to send more blood there; this is called neurovascular coupling. Some researchers propose that with age the small arteries respond to these signals more slowly, so local blood flow lags, and the long, thin nerve fibers of the white matter are the most sensitive to a shortfall of blood. Part of the slowing of white matter in cognitive aging may come from this. The chain is still an inference and has not been shown directly.

Read full story

Stop 1/4

Blood follows nerve firing

EVIDENCEREVIEW 2

READ THE ORIGINAL

The brain keeps almost no energy in reserve, yet it never stops spending energy. Every time a neuron fires, ion pumps in its membrane burn (the cell's energy currency) to push the scrambled ions back into place. So sugar and oxygen have to be delivered as they are used. The body does not turn up the blood supply to the whole head. It opens the vessels next to the small patch that is working right now and lets blood flow catch up. This is called neurovascular coupling.

The signal to open the vessels is mostly sent ahead of need. As a synapse releases glutamate (the most common excitatory signal between neurons), nearby neurons and glial cells (brain cells that do not fire and instead look after neurons) start releasing molecules that relax the vessel wall. They do not wait for fuel to run low. Blood flow rises, bringing sugar and oxygen and carrying away waste such as carbon dioxide.

So the bright patch on a brain-scan color map is that surge of blood, not the firing itself. The electrical event is over within milliseconds; the blood arrives a beat later. A bright patch means the supply has caught up with the activity, not that the brain is congested or injured.

Educational content, not medical advice. See a clinician about your own case.