2 Minute Neuroscience: The HPA Axis

Overview

• The Hypothalamic Pituitary Adrenal (HPA) Axis is crucial for the body's stress response.
• Comprises hormone-secreting glands from the nervous and endocrine systems:
  • Hypothalamus
  • Pituitary gland
  • Adrenal glands

Components of the HPA Axis

Hypothalamus

• Small neuroendocrine structure located above the brainstem.
• Controls hormone release from the pituitary gland.

Pituitary Gland

• Hormone-secreting gland located below the hypothalamus.
• Releases hormones into the bloodstream to affect various targets.

Adrenal Glands

• Endocrine glands located on top of the kidneys.
• Secrete hormones in response to signals from the pituitary gland.

Function of the HPA Axis

• Regulates the stress response.

Hormonal Pathway

1. Stressful Event Occurs
   • Hypothalamus releases corticotropin-releasing hormone (CRH).
2. CRH Effect
   • Signals the pituitary gland to secrete adrenocorticotropic hormone (ACTH) into the bloodstream.
3. ACTH Effect
   • Travels to adrenal glands, prompting cortisol release from adrenal cortex.

Effects of Cortisol

• Mobilizes energy (e.g., glucose) to deal with stress.

Negative Feedback Mechanism

• High cortisol levels are detected by brain receptors (hypothalamus and hippocampus).
• Leads to the shutting off of the stress response to prevent excessive cortisol levels.