The Role of Neuropeptides and the Dorsal Horn in Psoas Function
The psoas muscle is not just a physical structure; it plays a dynamic role in the body’s emotional and physiological regulation. Its deep connection to the autonomic nervous system (ANS), the limbic system (our emotional brain), and the spinal cord's dorsal horn provides a fascinating insight into how stress, emotions, and movement are interwoven.
Neuropeptides: The "Molecules of Emotion"
Neuropeptides are chemical messengers that influence communication between cells, modulating everything from emotion and pain to immune function and tissue health. Dr. Candace Pert, a leading researcher in this field, described neuropeptides as the "molecules of emotion" due to their ability to encode and transmit emotional states throughout the body.
Where Neuropeptides Reside:
Limbic System: The brain's emotional centre, including areas like the amygdala, is rich in neuropeptides. This explains the emotional resonance of physical experiences and vice versa.
Brainstem and Reticular Activating System (RAS): These areas are critical for alertness and fear response, further linking neuropeptides to the fight-or-flight response.
Dorsal Horn of the Spinal Cord: The dorsal horn, particularly in the T10-L2 segments, is a key site for sensory processing and neural feedback to the psoas muscle.
Neuropeptides in the Psoas Context:
Neuropeptides such as neuropeptide Y (NPY), corticotropin-releasing hormone (CRH), and endogenous cannabinoids modulate stress responses and have a direct role in the fear reflex.
These chemical messengers influence the connective tissue surrounding the psoas, either exacerbating chronic tension or promoting release, depending on the state of the nervous system.
Dorsal Horn Connection to the Psoas
The dorsal horn of the spinal cord acts as a hub for sensory information processing and reflex integration, directly affecting the psoas through the following mechanisms:
Segmental Reflex Loops:
The dorsal horn receives afferent signals (sensory information) from the psoas and surrounding tissues. These signals, especially from tight or inflamed fascia, are processed and transformed into efferent motor responses, perpetuating a cycle of contraction.
In states of chronic stress or trauma, this loop becomes overactive, creating a constant low-level alert signal that keeps the psoas in subtle contraction.
Hypertonicity Development:
Repeated activation of the dorsal horn at T10-L2 can cause hypertonicity (increased tension) in muscles associated with those spinal segments, including the psoas.
This hypertonicity is often linked to feelings of physical or emotional insecurity, further highlighting the psoas's role as a somatic reflection of the fear response.
Inflammatory Pathways:
When stress is unresolved, neuropeptides involved in inflammation, such as substance P, may accumulate in the dorsal horn. This can amplify pain signals and perpetuate tension in the psoas.
The Psoas and Fascial Communication
Recent research highlights that communication in the body is not solely dependent on nerve impulses. Electrical and biochemical signaling through fascia plays a significant role in psoas function:
Electrical Impulses:
Fascia transmits electrical signals faster than nerves, providing a rapid pathway for communication between the psoas, other muscles, and the CNS.
Neuropeptides and Fascia:
The fascia enveloping the psoas is influenced by neuropeptides, which can modulate its tension and sensitivity. For example, excessive cortisol from chronic stress may lead to stiff, reactive fascia, further deepening the contracted state of the psoas.
Therapeutic Implications
Understanding the neuropeptide and dorsal horn connection to the psoas sheds light on why holistic approaches are so effective:
Restoring Neural Balance:
Techniques like hypopressives and breathwork calm the sympathetic nervous system, reducing excitatory input to the dorsal horn and interrupting the reflex loop keeping the psoas in contraction.
Facilitating Neuropeptide Regulation:
Practices that promote parasympathetic activation (e.g., diaphragmatic breathing, craniosacral therapy) can help regulate neuropeptide levels, reducing inflammation and tension.
Engaging the Fascial System:
Myofascial release and gentle stretching target both the psoas muscle and its surrounding fascia, addressing the biochemical and structural contributors to chronic dysfunction.
Key Takeaway
The psoas muscle is more than a physical connector between the spine and legs—it is a vital player in the body's emotional, physiological, and neurological health. The dorsal horn, neuropeptides, and fascial communication pathways intertwine to reflect and amplify the state of our nervous system, making the psoas both a messenger and a mirror of our inner world. Addressing its dysfunction requires a multifaceted approach, integrating physical, emotional, and biochemical perspectives for true healing.
