All parts of the brain › Functions › Stress response

What part of the brain controls the stress response?

The hypothalamus, which starts both arms of the response. [1][2][3]

The 3D brain needs JavaScript. The list of parts still says what each one does for the stress response.

Lit: whole parts; region borders not drawn.

Slice

All 7 parts are lit together. Drag to turn, pinch or scroll to zoom, tap a part on the brain or a name in the list to focus it; .

In the fast arm, signals from the hypothalamus and brainstem run down the sympathetic nerves, and the adrenal medulla releases adrenaline and noradrenaline (the fight-or-flight response). In the hormonal arm, the hypothalamic–pituitary–adrenal (HPA) axis, the hypothalamus releases corticotropin-releasing hormone (CRH) and vasopressin, the pituitary gland answers with ACTH, and the adrenal cortex releases cortisol. The amygdala pushes the response on; cortisol acting through the hippocampus helps shut it off again. [1][2][3]

The paraventricular nucleus is a region on the hypothalamus, not a separate shape. The 3D model has no shape for it, so the whole hypothalamus is lit; the region’s exact border is not drawn.

The locus coeruleus is a region on the pons, not a separate shape. The 3D model has no shape for it, so the whole pons is lit; the region’s exact border is not drawn.

Stress response: 7 parts lit

Hypothalamus, pituitary gland, amygdala, hippocampus, prefrontal cortex, pons and medulla oblongata. Tap one to see where it is and what it does.

The parts and their roles

Its paraventricular nucleus holds the neuroendocrine neurons that make CRH and vasopressin, the first step of the HPA axis; CRH reaches the anterior pituitary through the portal blood vessels of the pituitary stalk. Signals from the hypothalamus also start the sympathetic arm that drives the heart, blood vessels and adrenal medulla. [1][2] Where is the hypothalamus?
CRH and vasopressin act together on the corticotrope cells of its anterior lobe, which release stored adrenocorticotropic hormone (ACTH); the blood carries ACTH to the adrenal cortex, where it rapidly starts the making of cortisol, the major stress hormone. [1] Where is the pituitary gland?
Sensory information arrives at its lateral part and is passed to its central nucleus, which projects to the parts of the brain that run the response to threat; at the hypothalamus these signals activate both the sympathetic nervous system and the HPA axis. For a threat that is only expected, its GABA neurons start the response by silencing the cells that normally hold the paraventricular nucleus back. [1][3] Where is the amygdala?
One of the brakes: it carries high levels of glucocorticoid receptors, and cortisol acting on limbic structures such as the hippocampus inhibits the HPA axis, part of the negative feedback that ends a stress response. [4][3] Where is the hippocampus?
Wired with the amygdala, hippocampus and hypothalamus, it is one of the regions that regulate the HPA and sympathetic responses, and it holds top-down control of attention, action and emotion; during acute stress, extra noradrenaline and dopamine released in it rapidly weaken its excitatory connections, so working memory and that control weaken. [1][5] Where is the prefrontal cortex?
Houses the locus coeruleus, the brain’s main noradrenaline nucleus, which mediates many of the sympathetic effects of stress: activated by stress, it raises noradrenaline release, which changes thinking through the prefrontal cortex, activates the HPA axis and increases sympathetic discharge through the brainstem. [6][7] Where is the pons?
Its rostral ventrolateral medulla is a primary regulator of the sympathetic nervous system, sending fibres down to the sympathetic neurons of the spinal cord; and sensory relays in the brainstem drive the paraventricular nucleus directly with noradrenaline when the body’s own balance is upset. [8][3] Where is the medulla oblongata?

Named areas on the lit gyri

The paraventricular nucleus, on the : A nucleus of the hypothalamus whose neuroendocrine neurons make and secrete CRH and vasopressin; the release of CRH from its neurons is what primarily drives the HPA stress response. [1][3]
The locus coeruleus, on the : A nucleus in the pons of the brainstem involved with physiological responses to stress; it is the main source of the brain’s noradrenaline and part of the reticular activating system. [6][7]

How they work together

The fast arm: sympathetic nerves fire, and the adrenal medulla releases the catecholamines adrenaline and noradrenaline. Heart rate and blood pressure rise, blood flows to the muscles, heart and brain, and adrenaline acting on the liver releases glucose for energy. [2][7]
The hormonal arm: CRH and vasopressin leave the hypothalamus at the median eminence, ACTH leaves the pituitary, and cortisol leaves the adrenal cortex. Cortisol makes more glucose available, helps turn fatty acids into usable energy and damps the immune system’s demanding processes, redirecting energy to the demand at hand. [1][2]
Two kinds of trigger use different routes: a reactive response to an upset of the body’s own balance is driven straight onto the paraventricular nucleus by sensory relays in the brainstem; an anticipatory response to a threat that is only expected runs through limbic structures such as the amygdala. [3]
The response switches itself off: cortisol circulates back and inhibits the hypothalamus and pituitary, lowering CRH and ACTH (negative feedback), and it also acts on the paraventricular nucleus rapidly through receptors on the cell membrane. Afterwards the parasympathetic system, whose vagal fibres leave the medulla, brings back the “rest and digest” state. [1][3][2]
The HPA axis also keeps a daily rhythm without any stress at all: in healthy people cortisol rises rapidly after waking, peaks within 30–45 minutes, then falls through the day to its lowest point in the middle of the night. [1]
An honest limit: the adrenal glands, the small organs on top of the kidneys that actually make cortisol, adrenaline and noradrenaline, are outside the brain and outside this model, and the paraventricular nucleus and locus coeruleus are too small for this atlas, so the hypothalamus and pons that hold them are lit whole. How strongly a person responds also depends on genetics, early life experience, sex, age and surroundings, which no map of parts shows. [1][3]

The feeling of fear and the stress response often start from the same alarm: the amygdala’s signal to the hypothalamus. [1][2] What part of the brain controls fear?

The HPA axis is one of the hypothalamic–pituitary chains, beside the thyroid and gonadal axes, that all start with a releasing hormone from the hypothalamus. [9] What part of the brain controls hormones?

Sources

Facts describe anatomy and normal function only. A part lit here takes part in the stress response; it does not do it alone, and it does other jobs too. The 3D model is the adult male BodyParts3D brain (credits and licence); on it the brainstem includes the midbrain, pons and medulla, so lighting the brainstem lights all three.