PERIAQUEDUCTAL GREY Meaning and
Definition
-
The periaqueductal grey, also referred to as the PAG, is a region located in the midbrain of the central nervous system, specifically surrounding the cerebral aqueduct. It is a small area composed of gray matter that plays a crucial role in the regulation and modulation of various physiological responses.
Functionally, the periaqueductal grey serves as a significant component of the descending pain modulation system. It contains numerous neural circuits involved in the inhibition or modulation of pain signals, effectively decreasing the perception of pain. Additionally, it participates in the regulation of autonomic functions, including cardiovascular responses, respiration, micturition, and nociception.
Furthermore, the periaqueductal grey is crucial in defensive and reproductive behaviors. It is involved in the expression of instinctual defensive reactions, such as freezing, fleeing, and fighting, when an individual faces potential threats or danger. Additionally, the periaqueductal grey is associated with various aspects of sexual and reproductive behavior, including sexual arousal, copulation, and maternal behaviors.
The periaqueductal grey is a complex region with connections to other areas of the brain, particularly the hypothalamus, amygdala, and brainstem nuclei. It receives input from multiple sensory and emotional pathways, integrating and processing information to initiate appropriate responses. Consequently, dysfunction within the periaqueductal grey can lead to various disorders, such as chronic pain, panic disorder, and abnormal reproductive behaviors.
Etymology of PERIAQUEDUCTAL GREY
The word "periaqueductal grey" is made up of two components: "periaqueductal" and "grey".
The term "periaqueductal" refers to the region surrounding the aqueduct of Sylvius. The aqueduct of Sylvius, also known as the cerebral aqueduct, is a long, narrow channel within the brainstem that connects the third and fourth ventricles. The word "periaqueductal" is derived from Latin roots: "peri-" meaning "around" and "aqueductum" meaning "aqueduct". Thus, "periaqueductal" signifies "around the aqueduct".
The term "grey" refers to the color gray, which is commonly associated with the gray matter in the central nervous system.
