ATI TEAS (Test of Essential Academic Skills) Version 7ScienceEasy
A research team is studying the effects of a new drug on the sympathetic nervous system. They administer the drug to a test subject and observe an increase in heart rate, dilation of pupils, and inhibition of digestion. Which neurotransmitter's activity is most likely being enhanced by this drug?
- AAcetylcholine
- BSerotonin
- CNorepinephrine
- DGABA
Show answer & explanationAnswer & explanation
Correct answer: C. Norepinephrine
Norepinephrine is the primary neurotransmitter released by postganglionic sympathetic neurons, mediating the 'fight or flight' response. The observed effects—increased heart rate, pupil dilation, and inhibited digestion—are classic sympathetic responses.
Why the other options are wrong
- A. Acetylcholine is the primary neurotransmitter of the parasympathetic nervous system and preganglionic sympathetic neurons.
- B. Serotonin is involved in mood, sleep, and appetite regulation, not directly in acute sympathetic responses.
- D. GABA (gamma-aminobutyric acid) is an inhibitory neurotransmitter in the central nervous system.
Norepinephrine
A neurotransmitter and hormone primarily involved in the 'fight or flight' response, increasing alertness, heart rate, and blood flow to muscles.
- Released by most postganglionic sympathetic neurons.
- Acts on adrenergic receptors.
- Also functions as a hormone from the adrenal medulla.
Memory trick: Norepinephrine Navigates the 'Now or Never' Response.