Hypothalamic-Pituitary-Adrenal Gland Axis (HPA Axis) + Adrenal Cortex

The HPA axis is primarily part of which body system response?

Stress response

In the HPA axis, parvocellular neurons of the PVN release which hormone?

corticotropin-releasing hormone (CRH)

CRH is released into which system to reach the anterior pituitary?

Hypophyseal portal system

CRH binds to which cells in the anterior pituitary?

Corticotropes

What hormone is secreted by the anterior pituitary in response to CRH?

adrenocorticotropic hormone (ACTH)

Where does ACTH travel after entering systemic circulation?

Adrenal Cortex

What type of hormones does the adrenal cortex secrete?

Lipid-based steroid hormones

What is the general category name for adrenal cortex hormones?

Corticosteroids

What are the two main classes of adrenal corticosteroids?

Mineralocorticoids and glucocorticoids

What is the main mineralocorticoid mentioned?

Aldosterone

What triggers aldosterone secretion?

decline in blood volume or blood pressure

What is the main effect of aldosterone?

helps to increase blood pressure (Na+ retention)

What is the main glucocorticoid hormone?

Cortisol

What is the main function of cortisol?

helps the body deal with stressful situation (chronic stress)

Cortisol is produced in which zone of the adrenal cortex?

Zona fasciculata

Magnocellular neurons of the supraoptic nucleus produce which neurohormone?

Vasopressin

Vasopressin is released into which structure before entering circulation?

posterior pituitary

How is vasopressin released into the posterior pituitary?

Through direct neuronal release from magnocellular neurons

What is a major effect of vasopressin during traumatic blood loss?

Increases blood pressure

Vasopressin helps maintain what balance in the body?

Salt-water balance

What is the effect of vasopressin on sodium (Na⁺) in urine?

Prevents the secretion of Na⁺ into the urine

What is the effect of vasopressin on water in urine?

decreases water in urine

In the HPA axis stress response, neurons in the paraventricular nucleus primarily activate which system?

Sympathetic nervous system

A preganglionic neuron from the PVN is described as what type of neuron?

Cholinergic

Where do preganglionic cholinergic neurons from the PVN synapse?

Chromaffin cells in the adrenal medulla

What neurotransmitter is released by the preganglionic neuron onto chromaffin cells?

Acetylcholine (AcH)

Binding of ACh to chromaffin cells causes release of what?

Catecholamines

What are catecholamines released by the adrenal medulla?

Dopamine, norepinephrine, and epinephrine

Which of the following is the main catecholamine in the stress response?

Epinephrine

Epinephrine primarily binds to which receptor type?

β2-adrenergic receptors (GPCRs)

What is the main effect of epinephrine signaling?

a quick response in a target cell/tissue due to fast changes in intracellular signaling