Homeostasis: Central Command

A nod to Dictator (DK’Tronics, 1983), Don Priestley’s strategy game for the ZX Spectrum. Instead of keeping a dictatorship together, you keep a body together. You don’t control what your human does: they pull all-nighters, eat triple burgers, go to the gym and skip lunch. Each day you decide how the body copes, and you have a few hormones to call on, which don’t come back once used. Survive as long as you can.

The science

• Homeostasis is the body keeping its inside steady (temperature, blood sugar, water, pH) while the outside changes, mostly through negative feedback. Much of the control sits in the hypothalamus, which steers the nervous system and, through the pituitary gland, the endocrine system.
• The hormones. Adrenaline, from the adrenal glands, drives the fight-or-flight response. Cortisol raises blood glucose and dampens the immune system. Insulin, from the pancreas, helps cells take up glucose. Endorphins are the body’s own painkillers. Melatonin, from the pineal gland, signals night-time and helps set the circadian rhythm, the body clock that jet lag upsets.
• Some of the events. Muscles store glucose as glycogen and run short on a long run. Shivering and brown fat make heat in the cold. Hay fever is the immune system overreacting to pollen, with histamine. At altitude, the kidneys release erythropoietin to make more red blood cells. Sunlight lets the skin make vitamin D, and caffeine keeps you alert by blocking adenosine receptors.

Where the game cuts corners

• The body doesn’t run out of hormones; the limited doses are a game rule, to make you choose.
• Real homeostasis works all the time and all at once, mostly without you noticing: the brain doesn’t get a menu of choices each morning. (If yours does, it may be time for a coffee and a chat with a doctor.)