system
Given the following post, respond as if you're commenting on Reddit:
human
What happens during a hypoglycemic episode? (Symptoms, brain function, etc)
gpt
There are two main mechanisms behind the symptoms of hypoglycaemia; the first resulting from the body's attempts to restore glucose balance, the second being directly caused by the lack of glucose supplied to the brain (neuroglycopenia).

Glucose-sensitive neurons are constantly monitoring the levels of glucose in the blood, and changes in the glucose level causes changes in the rate that these neurons generate impulses, feeding back information about glucose levels to the brain. Normal glucose levels can usually be maintained by altering the rate of secretion of the hormone glucagon from the pancreas, but excessive hypoglycaemia results in increased activity of the sympathetic nervous system, releasing the hormones adrenaline (epinephrine) and noradrenaline (norepinephrine) into the blood. This is what causes some of the common initial symptoms of hypoglycaemia; sweating, tremors, rapid heart rate, bounding pulse; as the body puts itself into what is basically a 'survival' mode. Patients that are prone to hypoglycaemic episodes often rely on these symptoms to warn them of their low glucose levels while they're still able to do something about it, but they can become desensitised in some cases.

As glucose levels continue to fall, the brain loses its supply of energy. Compared with other tissues, the brain has difficulty readily utilising proteins and fats to produce the energy needed for cell functions, and is much more reliant on a consistent level of glucose being maintained in the blood. Neurons maintain their ability to conduct electrical impulses by maintaining specific, highly-regulated levels of ions (Na^(+), K^(+), Ca^(2+)) both inside and outside the cell via ion channels and pumps. Without glucose to provide energy, the neurons can no longer maintain the correct ion levels and lose their ability to generate or carry nerve impulses, causing deficits in whatever function those neurons usually carry out. The effects of neuroglycopenia can vary widely between individuals depending on which parts of the brain are affected first, but can include drowsiness, confusion, loss of coordination, dysfunctional speech, changes in senses and behavioural changes. As the glucose levels drop further, communication between the different areas of the brain becomes impaired and symptoms progress through to loss of consciousness and coma. 

Restoring glucose levels will often rapidly resolve even patients that have fallen into a hypoglycaemic coma, but extended and/or repeated episodes of hypoglycaemia can result in permanent damage to the brain. 

Sources: Oxford Textbook of Medicine 5e (Ch. 13.11.2), Guyton and Hall Textbook of Medical Physiology 13e (pp. 794, 998-999)