The amygdala - the stress conductor

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

Parts of the amygdala are:

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

1. Signal input to amygdala (afferents)

The signal inputs of the amygdala are shown after Rensing, Koch, rib.²

→ means in each case an information transfer in the direction of the arrow.
An indented → means an information transfer from the parent point.

Monoamine systems
- Dopamine → Amygdala
- Norepinephrine → amygdala
- Serotonin → Amygdala
Sensory stimuli
- Aversive sensory stimuli:
  - → Spinal cord → Nucleus parabrachialis → 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
  - Bulbus olfactorius of the cortex
    - → Amygdala
      due to the great importance of the sense of smell, this is the only stimulus that is directly wired to the medial amygdala³
- Visual stimuli
  - Inferotemporal cortex → amygdala⁴
- Acoustic stimuli
  - Upper temporal lobe → amygdala⁵

The signal outputs of the amygdala are shown after Rensing, Koch, rib.²

→ in each case means an information transfer in the direction of the arrow.

Interstitial nucleus of the stria terminalis
- → hypothalamus (paraventricular nucleus)
  - → HPA axis ⇒ stress The HPA axis / stress regulation axis
Hypothalamus (lateral)
- → rostroventrolateral medulla
  - → Sympathetic nervous system
    - → Blood pressure increase
    - → Blood pressure decrease
    - → pupil dilation
    - → Skin resistance reduction
Central cave gray
- → Freezing
- → Analgesia
Motor trigeminal and facial nucleus
- → anxious or stressed facial expression
Insular and prefrontal cortex
- → subjective feeling
- → malaise
- → Fear
Nucleus reticularis pontis caudalis
- → Startle reaction
Locus coeruleus
- → Attention
- → Arousal
- → Vigilance
Ventral tegmentum
- → Attention
- → Arousal
- → Vigilance
Raphe seeds
- → 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)
Unnamed mediation channel
- → Pain perception⁶
- → Hunger perception⁶
- → Thirst perception⁶