The neurovascular unit (NVU) is a group of closely related cells and extracellular matrix components that function in the homeostatic haemodynamic response of cerebral hyperaemia. Cerebral hyperaemia is a fundamental central nervous system mechanism of homeostasis that increases blood supply to neural tissue when necessary. This mechanism controls oxygen and nutrient levels using the methods of

vasodilation Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstricti ...

and

vasoconstriction Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood ve ...

in a multidimensional process involving the many cells of the neurovascular unit. The cells of the NVU sense the neural needs of oxygen and glucose and trigger the appropriate vasodilatory or vasoconstrictive responses. Thus the NVU plays a vital role of neurovascular coupling of neural activity and cerebral blood flow.

Imaging Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the formation of an image). Imaging technology is the application of materials and methods to create, preserve, or duplicate images. ...

has shown that areas of neural activity in the brain are supplied with an increased blood flow while blood flow to inactive regions is restricted. Dysfunction of the NVU has been seen to be associated with neurodegenerative diseases. However, the mechanisms are not well understood. One factor may be related to

astrocyte Astrocytes (from Ancient Greek , , "star" + , , "cavity", "cell"), also known collectively as astroglia, are characteristic star-shaped glial cells in the brain and spinal cord. They perform many functions, including biochemical control of e ...

dysfunction.

Function

Cells of the neurovascular unit include

neuron A neuron, neurone, or nerve cell is an membrane potential#Cell excitability, electrically excitable cell (biology), cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous ...

s, blood-brain-barrier epithelial cells, myocytes and pericytes. Other components come from the

extracellular matrix In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide struc ...

. The brain has a very high energy need and no storage support which means that it has to take oxygen and glucose from the dynamic blood supply. Imaging has shown that areas of brain activity are supplied with an increased flow of blood. The cells of the NVU sense the needs of neural tissue and release many different mediators that engage in signaling pathways, and effector systems such as the myogenic effect; these mediators trigger the vascular smooth muscle cells to increase blood flow through vasodilation or to reduce blood flow by vasoconstriction. This is recognized as a multidimensional response that is acknowledged to operate across the cerebrovascular network as a whole.

Clinical significance

The NVU concept with its involvement with neurology was made formal in the NINDS ''Stroke Progress Review Group'' in 2001. Dysfunction in the NVU is associated with neurodegenerative diseases including Alzheimer's disease, and

Huntington's disease Huntington's disease (HD), also known as Huntington's chorea, is a neurodegenerative disease that is mostly inherited. The earliest symptoms are often subtle problems with mood or mental abilities. A general lack of coordination and an uns ...

though its mechanism is not well understood. However, it is recognised that maintaining the health of the cerebrovascular system promotes good health for the brain.

References

{{Reflist Neurology