Why We Shake: Exploring the Amygdala’s Role in Fight-or-Flight

caulocare
Jun 17
4 min read

By Dr. Phumlarp Caulo | Caulo Care, Forest Hills, New York| June 17, 2025

You step onto the stage, your heart hammering in your chest. The spotlight’s glare overwhelms your vision, and dozens of expectant eyes fix upon your trembling form. In that electrifying moment, every fiber of your being screams for escape. Your legs feel like jelly, quivering uncontrollably beneath the weight of your fear. As the audience holds its breath, you find yourself asking: What mysterious force within your brain and body drives this visceral reaction?

The Discovery of the Brain’s Fear Center

Modern neuroscience locates a “fear center” in the brain known as the amygdala. Two landmark eras of research paved the way:

Heinrich Klüver & Paul Bucy (1937)
In experiments on rhesus monkeys, Klüver and Bucy surgically removed portions of the temporal lobes—areas encompassing the amygdala. The animals displayed marked “tameness” and a profound loss of fear toward novel stimuli. This was the first evidence implicating regions around the amygdala in the regulation of fear responses.
Joseph E. LeDoux (Early–Mid 1990s)
LeDoux’s work on fear conditioning in rodents demonstrated that the amygdala serves as the principal structure for encoding and storing fearful memories. His experiments mapped a rapid “low-road” neural pathway that channels sensory input straight to the amygdala, triggering the release of stress hormones and priming the body’s fight-or-flight response.

Together, these investigations established the amygdala’s central role in fear processing—a concept first suggested by Klüver and Bucy and later confirmed and expanded by LeDoux.

1. Traditional Chinese Medicine Perspective

Fear (恐, Kǒng) Damages the Kidneys
- In TCM theory, fear is classified as an emotional excess that injures the Kidneys (腎).
- The Kidneys house the Essence (精, jīng), which underpins all vital activity. When Kidney energy is depleted, muscular control and joint stability suffer.
Kidney Qi Sinking (腎氣下陷)
- A downward deficit of Kidney Qi undermines the body’s foundational support.
- The legs, hips, and lower back lose their “grand strength,” leading to instability and trembling.
Qi Reversal Under Fear
- Fear can force Qi to “recede” (逆氣), disrupting its harmonious flow in the torso and limbs.
- This imbalance manifests as superficial muscle tremors in the legs.
The Water Element and Muscles
- The Water element, embodied by the Kidneys, governs the tendons, muscles, and joints.
- When Kidney (Water) energy falters, tendons and muscles weaken, producing tremors.
Supportive TCM Therapies
- Herbal Tonics: Rehmannia (熟地黃, Shú Dì Huáng) and Cornus (山茱萸, Shān Zhū Yú) to nourish the Kidneys.
- Acupuncture Points: KI3 (Taixi) and BL23 (Shenshu) to fortify Kidney Qi.
- Dietary Recommendations: Foods that support the Water element—such as Chinese red dates and black sesame seeds—to build Blood and Qi.

2. Modern Medical Perspective

Activation of the Autonomic Nervous System
- When we perceive a threat, the amygdala signals the sympathetic division of the autonomic nervous system.
- The adrenal glands then surge stress hormones—epinephrine and norepinephrine—into the bloodstream.
Effects of Epinephrine on Muscle Fibers
- Epinephrine increases motor neuron firing rates, resulting in rapid cycles of muscle contraction and relaxation.
- These high-frequency micro-contractions present visually as trembling or shaking.
Redistribution of Blood Flow
- Blood is shunted toward essential muscles (e.g., respiratory and locomotor muscles) to prepare for fight or flight.
- Peripheral muscles in the legs may become transiently under-perfused, contributing to localized weakness and tremor.
Physiological Versus Pathological Tremor
- Fear-induced shaking is a physiologic tremor, arising from normal interactions between the central nervous system and peripheral nerves.
- This contrasts with pathologic tremors (e.g., Parkinsonian tremor), which stem from specific neurotransmitter deficiencies or structural brain lesions.
Management Strategies
- Breathing Techniques: Slow, diaphragmatic breathing to dampen sympathetic overactivity.
- Progressive Muscle Relaxation: Systematically tensing and releasing muscle groups to reduce baseline tension.
- Mindfulness Meditation: Cultivating awareness to modulate the fight-or-flight response.
- Pharmacologic Support: In some cases, β-blockers (e.g., propranolol) may be prescribed to blunt the peripheral effects of epinephrine.

Months later, you stand beneath the same spotlight, calm, centered, and grounded. Through a harmonious blend of ancient TCM practices that nourish your Kidney Qi and modern techniques that soothe your amygdala’s overdrive, you have transformed what was once a paralyzing tremor into a testament to your resilience. As you deliver your message with steady legs and a clear mind, you recognize that understanding the roots of fear has not only silenced your shakes but also empowered you to meet life’s challenges with unwavering strength.

Dr. Phumlarp Caulo LAc,MsAc,OM,DAHM,Pre-RN

Integrative Medicine Practitioner, bridging Eastern and Western Wisdom.

“Rooted in ancient wisdom, guided by modern science

On this page, we look back at history so you can move forward with health.

I believe in Mother of the Earth, the timeless healer of body and soul.”

This information is only educational and should not be construed as medical advice.

Everything must be balanced, and the suggestions may not apply to you.

A specialist doctor should be consulted for any medical advice or diagnosis.

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Dr. Phumlarp Caulo LA,c, MAc. OM, DAHM