The regulation of brain blood flow is crucial for understanding neural computation, interpreting functional imaging scans, and developing treatments for neurological disorders. Key mechanisms include neurotransmitter-mediated signaling, astrocyte mediation, oxygen modulation, and control by both arterioles and capillaries. Neuronal activity increases blood flow through feedforward mechanisms, such as glutamate signaling, which leads to the release of nitric oxide (NO) and arachidonic acid derivatives. Astrocytes, which surround synapses and envelop blood vessels, play a central role in neurovascular coupling by releasing potassium ions and metabolites of arachidonic acid. The relative importance of neuronal and astrocytic pathways varies across brain areas and neural pathways. Oxygen levels influence neurovascular coupling by affecting the synthesis of vasoactive messengers. Pericytes, cells surrounding capillaries, can also control blood flow at the capillary level. Functional hyperaemia, a disproportionate increase in blood flow relative to energy use, is essential for maintaining neuronal function during activity and is the basis of BOLD functional MRI. However, neurovascular coupling fails in pathological conditions like spreading depression and ischaemia, leading to neurological deficits and tissue damage. Understanding these mechanisms offers new opportunities for therapeutic interventions.The regulation of brain blood flow is crucial for understanding neural computation, interpreting functional imaging scans, and developing treatments for neurological disorders. Key mechanisms include neurotransmitter-mediated signaling, astrocyte mediation, oxygen modulation, and control by both arterioles and capillaries. Neuronal activity increases blood flow through feedforward mechanisms, such as glutamate signaling, which leads to the release of nitric oxide (NO) and arachidonic acid derivatives. Astrocytes, which surround synapses and envelop blood vessels, play a central role in neurovascular coupling by releasing potassium ions and metabolites of arachidonic acid. The relative importance of neuronal and astrocytic pathways varies across brain areas and neural pathways. Oxygen levels influence neurovascular coupling by affecting the synthesis of vasoactive messengers. Pericytes, cells surrounding capillaries, can also control blood flow at the capillary level. Functional hyperaemia, a disproportionate increase in blood flow relative to energy use, is essential for maintaining neuronal function during activity and is the basis of BOLD functional MRI. However, neurovascular coupling fails in pathological conditions like spreading depression and ischaemia, leading to neurological deficits and tissue damage. Understanding these mechanisms offers new opportunities for therapeutic interventions.