Disclaimer: I am not a medical professional, but will happily accept any corrections on my statements below with good sources :) You've seen it often in TV shows and movies - Star Trek is notorious for it; our hero sees an enemy approaching, hides behind a corner, and nails the target with a single strike to the head, or the back of the neck; the target drops down unconscious, and our hero continues undetected. Unfortunately, while this has the superb effect of showing the hero as a strong and decisive fighter, this technique pretty much never works A single blow to the head would need excruciatingly convenient circumstances to knock an adult unconscious, and if you're writing stories about smashing little kids in the noggin - well it would work, but shame on you! Furthermore, in situations where it is a friendly character who is knocked out, or in situations where the hero knocked a person out because they didn't want to seriously injure someone, they consistently void that intent by simply walking away from them afterwards Kids, if someone is struck down and loses consciousness in real life, your first move is to call an ambulance, ASAP. They could have a concussion and slip into a coma; they could have internal bleeding - possibly in the brain if they were struck in the head; they could have a cracked skull, they may have damaged their spine! If someone has lost consciousness, they are seriously injured and require medical attention immediately. Losing consciousness is not like taking a nap; even if it didn't result from a blunt force trauma (for example, someone losing consciousness after succumbing to a sleeper hold is a result of a rapid decrease in blood flow to the brain) - it's extremely dangerous! If someone is knocked out and the characters walk away from them, leaving no one to attend to them in an immediate sense, they have in the best case scenario caused massive damage to their body; worst case scenario they've killed them. What is actually more likely to happen if you are struck in the head (ie: by a fist; situations would be far more dire if you fell on something head-first, or were hit with a weapon, or had been struck repeatedly): If you were struck in the face/front of the head: You will be knocked backward If struck in the nose, your eyes will water and your nose may be broken or fractured If struck in the eye, you will see stars and later, the eyelid and surrounding tissue may swell up and obstruct your vision; depending on how you were hit, your vision may be damaged or lost If struck in the jaw/mouth, you may have broken teeth, a dislocated or cracked jaw, split lip, and you may bite your tongue. In many of these cases, you will likely end up swallowing blood, which will make you vomit it later. If struck in the ear, your ears will ring and you may lose equilibrium and sense of balance if your inner ear is damaged. Your hearing may also be damaged. If you have ear piercings they may tear the ear and cause bleeding and infection. The blow will likely also cause your head and upper body to turn, temporarily disorienting you. If you were struck in the cheek, you may have a broken cheekbone, which makes pretty much every movement from a sniffle to a swallow extremely painful If you were struck in the forehead, you may be knocked down and backward, you will almost definitely have a headache, you may see stars, and if struck hard enough, the tissues between your brain and skull may be damaged and swell up. If your head was knocked backward with significant force, you may also suffer whiplash If you were struck in the neck/back of the head Depending on where you were struck and if your brain was damaged, you might have dizziness, trouble processing visual stimuli (colour, depth perception, blackout vision, etc) nausea, headache, a 'goose egg' (bump on your head), you may have a concussion or haemorrhaging. Your skull may be cracked, and if you were struck in the neck or at the base of the skull, your spine could be damaged, causing permanent spinal injury, lack of mobility, or even paralysis. Being struck with something that has the potential to break skin and cut the muscle and/or bone underneath is even more deadly; torn muscles cause instant immobility and take a long time to repair; rapid and extreme blood loss is almost guaranteed for deep or large wounds, cracking or crushing the skull causes almost certain brain damage. The object may also cut through nerves, which cause mobility problems and are difficult to repair. All of these are deadly and dangerous and not something you should wish on anyone, of course, but few of them, barring extreme force (more than just a really hard punch or karate chop) are likely to cause a loss of consciousness with a single hit. Your exercise is to write a scene where a character either strikes someone else in the head, or is struck in theirs. Write an appropriate reaction.If the blow results in a lack of consciousness, remember that the damage would have to be severe enough to cause it; (one blow is not going to do it unless your character is literally Superman), and that such a condition is extremely deadly.