THE FIGHT OR FLIGHT RESPONSE
Norepinephrine and acetylcholine neurotransmitters produce a fight or flight
response (see chart). In a fight response, eyes dilate so you can see better and
lungs inspire more oxygen while increasing your heart rate. Blood vessels con-
strict increasing blood pressure. Smooth muscles along the bladder and the GI
tract relax so that energy is not expended on digestion. Salivary glands reduce
the secretion of saliva giving the person the dry mouth feeling in an emergency.
The flight response is really a misnomer because it doesn’t help you run
away. Instead, the flight response is really the opposite of fight and allows the
individual to relax and function normally. In the flight response or the non-fight
mode, pupils constrict, the heart rate slows, the GI tract reduces function, and
breathing slows down.
CHAPTER 15 Nervous System Drugs^283
Sympathetic Depressants Parasympathetic Depressants
Sympatholytics (adrenergic blockers,
adrenolytics, or adrenergic antagonists)
Decrease blood pressure
Decrease pulse rate
Constrict bronchiolesParasympatholytics (anticholinergics,
cholinergic antagonists, or antispasmodics)
Increase pulse rate
Decrease mucus secretions
Decrease gastrointestinal motility
Increase urinary retention
Dilate pupils of eyesSympathetic (Fight) Parasympathetic (Flight)
Body Tissue/Organ Response Response
Eye Dilates pupil Constricts pupil
Lungs Dilates bronchioles Constricts bronchioles and
increases secretions
Heart Increases heart rate Decreases heart rate
Blood vessels Constricts Dilate
Gastrointestinal Relaxes smooth muscles Increases peristalsis
Bladder Relaxes bladder muscle Constricts bladder
Uterus Relaxes uterine muscle
Salivary gland Increases salivation