Where is adrenaline secreted? 

Adrenal medulla 

The correct answer is option 3. Adrenal medulla.

Adrenaline, also known as epinephrine, is a hormone and neurotransmitter that plays a critical role in the body's response to stress or danger. It is primarily secreted by a specialized region of the adrenal glands called the adrenal medulla.

Adrenal Glands: The adrenal glands are small, triangular-shaped glands located on top of each kidney. Each adrenal gland consists of two main regions: the outer adrenal cortex and the inner adrenal medulla.

Adrenal Medulla: The adrenal medulla is the innermost portion of the adrenal gland. It is composed of specialized cells called chromaffin cells, which are neuroendocrine cells that release hormones directly into the bloodstream in response to nervous system stimulation.

Stress Response: When the body experiences stress, whether physical, emotional, or psychological, the sympathetic nervous system is activated. This activation triggers a series of physiological responses collectively known as the fight-or-flight response.

Release of Adrenaline: The sympathetic nervous system stimulates the adrenal medulla to release adrenaline into the bloodstream. Adrenaline acts as a hormone when released into the bloodstream, affecting target organs throughout the body. It also acts as a neurotransmitter when released at nerve endings, affecting nearby cells.

Physiological Effects: Adrenaline has various effects on the body that help prepare it for action in response to stress or danger. Some of the key effects include:

Increased Heart Rate: Adrenaline increases heart rate (positive chronotropic effect) and the force of heart contractions (positive inotropic effect), leading to increased cardiac output and blood flow to vital organs.

Dilation of Airways: Adrenaline relaxes the smooth muscles in the airways, leading to bronchodilation and increased airflow into the lungs.

Mobilization of Energy: Adrenaline stimulates the breakdown of glycogen into glucose in the liver (glycogenolysis) and the release of fatty acids from adipose tissue (lipolysis), providing additional energy sources for the body.

Pupil Dilation: Adrenaline causes dilation of the pupils (mydriasis), improving vision and increasing alertness.

Vasoconstriction: Adrenaline constricts blood vessels in non-essential organs (such as the skin and digestive system) while dilating blood vessels in essential organs (such as the muscles and brain), redirecting blood flow to where it is needed most.

In summary, adrenaline is primarily secreted by the adrenal medulla in response to stress, and it plays a crucial role in the body's fight-or-flight response by increasing heart rate, dilating airways, mobilizing energy stores, and enhancing overall readiness for action.