You’re babysitting some children in a strange house. You’ve been receiving creepy phone calls all night, and, getting sick of the harassment, you report the incidents to the police. You receive a phone call some time later from the police with the worst possible news – they tracked the number. The calls were coming from inside the house. Terror starts to build inside you.
Your pupils dilate when you hear the news. Your erector pili muscles are triggered, causing goose bumps and your hair to stand on end. Cranial nerve VIII takes the afferent sensory information from the voice you hear over the phone into your pons. Sympathetic nervous activity would induce several reactions. Extensive neural divergence allows everything to happen at once. This afferent information leaves the pons through the lateral horns, down the preganglionic neuron, and out the spinal nerves T1-L2 to the short postganglionic fiber.
Desperately, you try to think of a way out of the situation. Your sympathetic nervous system begins to work on overdrive as your fight or flight reflex kicks in. Do you run, or do you stay and fight? You become drastically more alert because of the catecholemines that have been released into your system, specifically NE and E. You realize that you have begun to hyperventilate. The rapid breathing causes an excessive loss of carbon dioxide, spiking your pH levels. This causes cerebral vasoconstriction, and you start to feel faint and dizzy. You realize your skin has gone pale with fright. Your integumentary system is not nearly as important for your survival right now. Dermal blood vessels constrict because of NE’s binding with alpha adrenergic receptors. The blood is better used elsewhere.
Sympathetic nervous output from the superior mesenteric ganglion also affects your urinary system. The output goes into the kidneys and influences the rate of filtration and urine production. You suddenly have an intense urge to go to the bathroom, but you push the thought aside because you have more important issues to deal with at hand. Slowly, you back away from the phone. Output from the hypothalamus and brainstem slows your parasympathetic activity. This would mean decreases in digestive function through adrenergic receptors mediated by NE. You are too focused on the situation at hand for your body to be dealing with these functions — you subconsciously deem them unnecessary.
You remember the child – you need to get him out of the house. Blood is pumping through your circulatory system at a much faster rate. Your heart rate increases through adrenergic receptors mediated by NE, therefore increasing blood pressure and cardiac output. Efferent motor information from the precentral gyrus of the frontal lobe is sent to the skeletal muscles, which are now ready to contract because of the vasodilation around the myofibrils. You tense up. Your body is preparing itself to run away.
With sweaty palms, you frantically search the room for something that could pass as a weapon to defend yourself. The increase in sympathetic activity causes the myoepithelial cells of your merocrine sweat glands to contract and squeeze out sweat. You barely notice this new diaphoresis because your mind is in survival mode. Luckily, you come across a metal fireplace rod. Clutching it to your side, you sprint up to the child’s room, pull him out of bed, and sprint out of the house.
Hours later, the police show up to the house. The intensity of the situation has died down, but your heart is still pumping, your breathing rate is still elevated, and you still feel tense and nervous. The sympathoadrenal system stimulates the release of NE and E. The endocrine system – more specifically, the adrenal glands — is what allows these effects to last hours after. This mixture causes the prolonged sympathetic effects.
Unfortunately, whoever was in the house was long gone. They left behind no evidence or indication of where they went. To this day, you still don’t know who it was in the house that night or what they planned on doing to you. If only your knowledge of crime scene investigation techniques matched your hyperawareness of your body’s physiological response to stimuli…