Define Stress

"a perceived threat to homeostasis"

"an event or stimulus that causes an often abrupt but always large change in autonomic activity and hormone secretion, particularly cortisol secretion"

Hypothalamus Nuclei - Wiki

RegionAreaNucleusFunction
Anterior (supraoptic)PreopticPreoptic nucleusThermoregulation
Anterior (supraoptic)PreopticVentrolateral preoptic nucleusSleep
Anterior (supraoptic)MedialMedial preoptic nucleusRegulates the release of gonadotropic hormones from the adenohypophysis Contains the sexually dimorphic nucleus, which releases GnRH, differential development between sexes is based upon in utero testosterone levels Thermoregulation
Anterior (supraoptic)MedialSupraoptic nucleusVasopressin release Oxytocin release
Anterior (supraoptic)MedialParaventricular nucleusthyrotropin-releasing hormone release corticotropin-releasing hormone release oxytocin release vasopressin release somatostatin round arousal (wakefulness and attention) appetite
Anterior (supraoptic)MedialAnterior hypothalamic nucleusthermoregulation panting sweating thyrotropin inhibition
Anterior (supraoptic)MedialSuprachiasmatic nucleusCircadian rhythms
Anterior (supraoptic)LateralLateral nucleusSee Lateral hypothalamus § Function – primary source of orexin neurons that project throughout the brain and spinal cord
Middle (tuberal)MedialDorsomedial hypothalamic nucleusblood pressure heart rate GI stimulation
Middle (tuberal)MedialVentromedial nucleussatiety neuroendocrine control
Middle (tuberal)MedialArcuate nucleusGrowth hormone-releasing hormone (GHRH) feeding Dopamine-mediated prolactin inhibition
Middle (tuberal)LateralLateral nucleusSee Lateral hypothalamus § Function – primary source of orexin neurons that project throughout the brain and spinal cord
Middle (tuberal)LateralLateral tuberal nucleiEmpty cell
Posterior (mammillary)MedialMammillary nuclei (part of mammillary bodies)memory
Posterior (mammillary)MedialPosterior nucleusIncrease blood pressure pupillary dilation shivering vasopressin release
Posterior (mammillary)LateralLateral nucleusSee Lateral hypothalamus § Function – primary source of orexin neurons that project throughout the brain and spinal cord
Posterior (mammillary)LateralTuberomammillary nucleusarousal (wakefulness and attention) feeding and energy balance learning memory sleep

Cortisol Effects

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Draw HPA Axis

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How the HPA Axis Helps with Stress

  1. Detects stressors via the limbic system ( amygdala , hippocampus ).

  2. Hypothalamus ( PVN ) releases CRH , signaling the pituitary gland

  3. Anterior pituitary releases ACTH , which stimulates the adrenal cortex

  4. Adrenal cortex secretes cortisol , which :

    • Increases glucose availability ( energy boost )

    • Suppresses non-essential functions ( immune , digestion , reproduction )

    • Enhances alertness and behavioral adaptation

  5. Negative feedback loop : Cortisol eventually inhibits CRH & ACTH release to prevent excessive stress response

How the HPA Axis Can Go Wrong

Cytokines Effects on Nervous System

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Define Hyperalgesia and Allodynia