Chromaffin cells are specialized neuroendocrine cells that primarily secrete catecholamines (such as epinephrine and norepinephrine) and other hormones into the bloodstream. They are crucial for the body's "fight-or-flight" response.
Where are Chromaffin Cells Located?
The primary location of chromaffin cells is within the adrenal medulla, which is the inner part of the adrenal glands located above the kidneys. They can also be found in sympathetic ganglia throughout the body, though this is less common. These extra-adrenal chromaffin cells are particularly important during fetal development.
Function of Chromaffin Cells:
The main function of chromaffin cells is the synthesis, storage, and release of catecholamines, including:
- Epinephrine (Adrenaline): A powerful hormone that increases heart rate, blood pressure, and blood sugar levels. It is released in response to stress, excitement, or danger.
- Norepinephrine (Noradrenaline): Similar to epinephrine, but also plays a role in attention and focus.
When stimulated by the sympathetic nervous system, chromaffin cells release these hormones directly into the bloodstream, causing a cascade of physiological effects to prepare the body for action. This includes increasing alertness, redirecting blood flow, and mobilizing energy reserves.
How Chromaffin Cells Work:
- Nervous System Stimulation: Pre-ganglionic sympathetic nerve fibers directly innervate chromaffin cells.
- Acetylcholine Release: When stimulated, the nerve fibers release acetylcholine, a neurotransmitter.
- Hormone Secretion: Acetylcholine binds to receptors on the chromaffin cells, triggering the release of catecholamines into the bloodstream via exocytosis.
Significance of Chromaffin Cells:
Chromaffin cells play a vital role in:
- Stress Response: Mediating the body's immediate response to stress.
- Blood Pressure Regulation: Helping to maintain stable blood pressure.
- Glucose Metabolism: Influencing blood sugar levels.
Tumors of Chromaffin Cells:
Pheochromocytomas are tumors that arise from chromaffin cells, typically in the adrenal medulla. These tumors can cause excessive production of catecholamines, leading to symptoms such as high blood pressure, rapid heart rate, sweating, and anxiety. Diagnosis usually involves measuring catecholamine levels in urine and blood, followed by imaging studies to locate the tumor.
