Adrenalin
Explanation
The endocrine system regulates physiological processes through chemical messengers called hormones. Specific hormones are released by the adrenal glands to prepare the body for immediate physical exertion in response to external threats or stress.Analysis of Options:
- Insulin: Incorrect. Insulin is secreted by the beta cells of the pancreas (Islets of Langerhans). Its primary function is to regulate blood glucose levels by facilitating the uptake of glucose into cells, thereby lowering blood sugar. It is not the primary hormone for acute stress responses.
- Thyroxine: Incorrect. Thyroxine is secreted by the thyroid gland. It regulates the Basal Metabolic Rate (BMR) and plays a key role in protein synthesis and growth. Its effects are metabolic and developmental rather than immediate stress management.
- Adrenalin: Correct. Adrenalin (also known as Epinephrine) is secreted by the medulla of the adrenal glands. It is termed the "emergency hormone" or the hormone of "fight or flight." During acute stress, it rapidly increases heart rate, strength of heart contraction, breathing rate, and blood glucose levels to supply energy for immediate action.
- Growth Hormone Growth Hormone: Incorrect. Growth Hormone (Somatotropin) is secreted by the anterior pituitary gland. It stimulates growth, cell reproduction, and cell regeneration in humans and other animals.
Key Takeaway: Adrenalin is the primary hormone responsible for the "fight or flight" response, enabling the body to adjust to acute stress or emergency situations.