KAAP220 Exam 3 – Hypothalamus, Pituitary & Feedback Loops

What connects the hypothalamus and anterior pituitary by blood?

The hypophyseal portal system.

What connects the hypothalamus and posterior pituitary?

Axons of hypothalamic neurosecretory neurons.

What is the anterior pituitary also called?

Adenohypophysis; it is glandular tissue.

What is the posterior pituitary also called?

Neurohypophysis; it is neural tissue.

Where are ADH and oxytocin synthesized?

In hypothalamic nuclei, including the supraoptic and paraventricular nuclei.

What does the posterior pituitary do with ADH and oxytocin?

Stores and releases hormones made in the hypothalamus.

How do hypothalamic releasing hormones reach the anterior pituitary?

Through blood in the hypophyseal portal system.

What would portal-system blockage primarily disrupt?

Delivery of hypothalamic regulators to the anterior pituitary.

Would portal-system blockage directly stop axonal release from the posterior pituitary?

Not necessarily; posterior release uses axons rather than portal blood.

What is a trophic hormone?

A hormone that stimulates another endocrine gland to secrete hormones.

What does CRH stand for?

Corticotropin-releasing hormone.

What does ACTH stand for?

Adrenocorticotropic hormone.

What does the hypothalamic PVN release in the HPA axis?

CRH into the hypophyseal portal system.

What does the anterior pituitary release in response to CRH?

ACTH into systemic circulation.

Which adrenal cortex zone is stimulated by ACTH in the HPA axis?

Zona fasciculata.

What hormone does the zona fasciculata release?

Cortisol.

Trace the HPA axis in order.

PVN releases CRH → anterior pituitary releases ACTH → zona fasciculata releases cortisol.

How does cortisol provide negative feedback?

Elevated cortisol inhibits further CRH and ACTH release.

What is long-loop negative feedback?

A target-gland hormone feeds back to inhibit the pituitary and/or hypothalamus.

What is short-loop negative feedback?

A pituitary hormone feeds back to inhibit hypothalamic hormone release.

What is negative feedback?

A response reduces the original stimulus and helps maintain homeostasis.

What is positive feedback?

A response amplifies the original stimulus until a specific event is completed.

How does oxytocin support positive feedback during labor?

Cervical stretch triggers oxytocin, which increases contractions and further stretch.

How does oxytocin support lactation?

Nipple stimulation triggers oxytocin release, causing milk ejection and reinforcing suckling.

Why is oxytocin during labor not a standard negative-feedback loop?

Contractions amplify cervical stretch and oxytocin release until delivery.

What is the main difference between anterior and posterior pituitary hormones?

Anterior hormones are made by pituitary cells; posterior hormones are made in the hypothalamus.