Hormones Released During a Fight or Flight Condition

The fight or flight response is a physiological reaction to perceived harmful events, attacks, or threats to survival. This response activates a series of hormonal and neural systems to prepare the body for action. Let's explore the hormones and their roles in this crucial stress response.

Understanding the Fight or Flight Response

When the body perceives a threat, the sympathetic nervous system is triggered, initiating a cascade of hormonal responses. These responses are mediated primarily by the hypothalamus, the paraventricular nucleus (PVN) in the hypothalamus, the adrenal glands, and the pituitary gland. This complex system ensures that the body is prepared for rapid action.

The Role of CRH and ACTH

Corticotropin-Releasing Hormone (CRH)

When the hypothalamus senses a threat, it releases Corticotropin-Releasing Hormone (CRH). CRH travels through the portal vein to the anterior pituitary gland, where it stimulates the release of Aclinogastrin (ACTH).

ACTH and Adrenal Glands

The (ACTH) then acts on the adrenal glands to produce and release Cortisol, commonly known as the stress hormone. Cortisol helps regulate metabolism, immune function, and the body's response to stress.

Adrenaline and Noradrenaline/Norepinephrine

Adrenaline and Noradrenaline/Norepinephrine

At the same time, the hypothalamus also stimulates the sympathetic nervous system, which releases Adrenaline (epinephrine) and Noradrenaline (norepinephrine). These hormones work in conjunction with CRH and ACTH to prepare the body for action. They are responsible for the following physiological changes:

Widening the Pupils: Noradrenaline activates the M3 receptors on the iris, leading to pupil dilation (mydriasis). Increased Heart Rate: Adrenaline binds to beta-adrenergic receptors on the cardiac muscle, causing the heart rate to increase. Raised Blood Pressure: Both hormones enhance vasoconstriction, increasing blood pressure. Improved Blood Flow: Blood flow is redirected to muscles and away from non-essential organs like the digestive system to ensure that the body is ready for immediate action.

Nature of the Sympathetic and Parasympathetic Nervous Systems

The sympathetic nervous system acts in opposition to the Parasympathetic Nervous System. This antagonism is crucial for the body's stress response. The parasympathetic system typically promotes homeostasis by regulating functions such as digestion, while the sympathetic system prepares the body for immediate responses to stressors.

During a fight or flight scenario:

Smooth Muscles of the Bronchial Tubes Relax: This increases airflow into the lungs, enabling more oxygen to reach the bloodstream. Gut Calms Down: This ensures that blood is redirected away from the digestive system to the muscles, which need more oxygen and nutrients for immediate action.

In summary, the fight or flight response is a complex and finely-tuned system of hormones and neural pathways that prepares the body for immediate action in the face of perceived threats. Understanding these mechanisms is crucial for comprehending the physiological reactions that occur during stress and how they impact overall health and well-being.

References

For further reading and research, please refer to the following sources:

McEwen, B. S. (2007). Physiology and neurobiology of stress and adaptation: Central role of the brain. Physiological Reviews, 87(3), 873-904. Pickering, R. J. (2019). The Neurobiology of Stress. Sciencedirect. Retrieved from [URL]