Sympathetic nerve stimuli are responsible for the release of which of the following substances?

• A. Norepinephrine
• B. Serotonin
• C. Insulin
• D. Acetylcholine

Answer: (A)

Verified step by step guidance

1. Understand the role of the sympathetic nervous system: The sympathetic nervous system is part of the autonomic nervous system and is responsible for the 'fight or flight' response. It prepares the body to respond to stress or danger by increasing heart rate, dilating airways, and mobilizing energy stores.
2. Identify the neurotransmitters associated with the sympathetic nervous system: The primary neurotransmitter released by postganglionic sympathetic neurons is norepinephrine. This neurotransmitter acts on adrenergic receptors to elicit physiological responses.
3. Differentiate between the substances listed: Serotonin is primarily involved in mood regulation and is not released by sympathetic nerve stimuli. Insulin is a hormone secreted by the pancreas to regulate blood sugar levels and is unrelated to sympathetic nerve activity. Acetylcholine is the neurotransmitter released by preganglionic neurons in both the sympathetic and parasympathetic systems, but it is not the primary neurotransmitter of postganglionic sympathetic neurons.
4. Focus on norepinephrine: Norepinephrine is the correct answer because it is the substance released by postganglionic sympathetic neurons to activate adrenergic receptors in target tissues during sympathetic stimulation.
5. Conclude the reasoning: Based on the physiological role of the sympathetic nervous system and the neurotransmitters involved, norepinephrine is the substance released in response to sympathetic nerve stimuli.