The amygdala - the stress conductor

The amygdala (part of the limbic system) is the central instance for evaluating the threat potential of stressors and triggers the brain’s stress reactions.¹

Parts of the amygdala are:

• Lateral amygdala (LA)
• Basolateral amygdala (BLA) → calculated action
• Central medial amygdala (CMA) → impulse-driven emotional behavior

The amygdala receives information from many organs and systems about current stressors.

• 1. Signal input to amygdala (afferents)
• 2. Signal output from amygdala (efferents)

1. Signal input to amygdala (afferents)¶

The signal inputs of the amygdala are shown according to Rensing, Koch, Rippe, Rippe.²

→ means a transfer of information in the direction of the arrow.
An indented → indicates a transfer of information from the parent point.

• Monoamine systems
  • Dopamine → amygdala
  • Noradrenaline → Amygdala
  • Serotonin → amygdala
• Sensory stimuli
  • Aversive sensory stimuli:
    • → Spinal cord → Parabrachial nucleus → Amygdala
    • → Parabrachial nucleus (direct) → Amygdala
    • Thalamus (sensory and polymodal nuclei) → amygdala
  • Neutral / conditioned sensory stimuli
    • Thalamus (sensory and polymodal nuclei)
      • → Amygdala
      • → Cortex (primary sensory nuclei)
        • → Amygdala
        • Cortex (association areas)
          • → Amygdala
          • → primary insular cortex
            • → Amygdala
            • → Hippocampus
              • → Amygdala
  • Odors
    • Olfactory bulb of the cortex
      • → Amygdala
        due to the great importance of the sense of smell, this is the only stimulus that is directly connected to the medial amygdala³
  • Visual stimuli
    • Inferotemporal cortex → Amygdala⁴
  • Acoustic stimuli
    • Upper temporal lobe → amygdala⁵

2. Signal output from amygdala (efferents)¶

The signal outputs of the amygdala are shown according to Rensing, Koch, Rippe, Rippe.²

→ means a transfer of information in the direction of the arrow.

• Interstitial core of the stria terminalis
  • → Hypothalamus (paraventricular nucleus)
    • → HPA axis ⇒ The HPA axis / stress regulation axis
• Hypothalamus (lateral)
  • → rostroventrolateral medulla
    • → Sympathetic nervous system
      • → Increase in blood pressure
      • → Decrease in blood pressure
      • → Pupil dilation
      • → Skin resistance reduction
• Central cave gray
  • → Freezing
  • → Analgesia
• More motorized trigeminal and facial nucleus
  • → anxious or stressed facial expression
• Insular and prefrontal cortex
  • → subjective feeling
  • → Feeling unwell
  • → Fear
• Nucleus reticularis pontis caudalis
  • → Startle reaction
• Locus coeruleus
  • → Attention
  • → Arousal
  • → Vigilance
• Ventral tegmentum
  • → Attention
  • → Arousal
  • → Vigilance
• Raphe cores
  • → Attention
  • → Arousal
  • → Vigilance
• Vagus nerve (dorsal nucleus)
  • → Parasympathetic nervous system
    • → Bladder emptying / micturition
    • → Bowel movement / defecation
    • → Stomach ulcers
• Parabrachial nucleus
  • → Increase in respiratory rate (wheezing)
• Undisclosed mediation channel
  • → Pain perception⁶
  • → Perception of hunger⁶
  • → Thirst perception⁶