Physiology Chapter 2: Hypothalamic Hormones

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Questions and Answers

Which hormone significantly increases during late pregnancy and delivery?

Oxytocin

CRH (correct)

Somatostatin

GHRH

Where are GHRH secreting neurons primarily located?

Ventromedial nucleus

Lateral hypothalamus

Arcuate nuclei (correct)

Paraventricular nucleus

What is the primary function of GHRH?

Inhibit GH release

Stimulate somatotropes to release GH (correct)

Inhibit insulin secretion

Increase glucagon levels

How many amino acids does GHRH contain?

44 Signup and view all the answers

What is the half-life of somatostatin?

2-3 minutes Signup and view all the answers

Which of the following hormones is NOT inhibited by somatostatin?

Corticotropin-releasing hormone Signup and view all the answers

Which family of peptides includes GHRH?

Secretin family Signup and view all the answers

Where is the hypothalamus located?

At the base of the brain in the diencephalon Signup and view all the answers

What mechanism do hypothalamic hormones commonly use to exert their action?

Binding to specific receptors on plasma membrane Signup and view all the answers

What is the primary function of the hypothalamic median eminence?

Serves as the vascular link between the hypothalamus and the anterior pituitary Signup and view all the answers

Which part of the pituitary is known as the adenohypophysis?

Anterior pituitary Signup and view all the answers

What type of hormones are primarily regulated by the hypothalamus?

Anterior pituitary trophic hormones Signup and view all the answers

What is the average weight of the pituitary gland?

0.5 g Signup and view all the answers

During which biological conditions does the pituitary gland weigh double?

Puberty or pregnancy Signup and view all the answers

What type of circulation connects the median eminence of the hypothalamus and the anterior pituitary?

Hypothalamo-pituitary portal system Signup and view all the answers

Which primary functions are regulated by the hypothalamus?

Breathing depth and rate, and digestive tract motility Signup and view all the answers

What is the primary inhibitory hormone for prolactin secretion?

Dopamine Signup and view all the answers

Where are the TRH-secreting neurons primarily located?

Paraventricular nuclei Signup and view all the answers

Which of the following hormones stimulates the release of LH and FSH?

Gonadotropin releasing hormone Signup and view all the answers

What is the half-life of Gonadotropin releasing hormone?

2-4 minutes Signup and view all the answers

From which part of the developing anatomy does the anterior pituitary arise?

Primitive oral cavity Signup and view all the answers

Which part of the hypothalamus is associated with CRH secretion?

Anterior portion of the paraventricular nuclei Signup and view all the answers

What is the role of oxytocin concerning ACTH secretion?

Inhibits ACTH secretion Signup and view all the answers

Which characteristic applies to the arcuate nucleus?

It forms a functional entity with the median eminence. Signup and view all the answers

Study Notes

Hypothalamic Hormones and Their Functions

Hypothalamic hormones regulate anterior pituitary trophic hormones, which determine target gland secretion.
The hypothalamus is located at the base of the brain in the diencephalon, housing neurons critical for hormone regulation.
The hypothalamic median eminence forms the vascular link between the hypothalamus and the anterior pituitary gland.

The Pituitary Gland

The pituitary gland, referred to as the "master gland," resides in the sella turcica of the sphenoid bone and weighs approximately 0.5 g.
Its weight can double during puberty or pregnancy.
The pituitary is divided into two parts:
- Adenohypophysis (anterior pituitary) - accounts for 75% of gland weight.
- Neurohypophysis (posterior pituitary) - originates from the brain as an outgrowth from the hypothalamus.

Vascular Connection

The hypothalamic-hypophysial portal system links the hypothalamus to the anterior pituitary, facilitating the transport of hormones.
The anterior pituitary is the most vascularized tissue in mammals, receiving 0.8 ml/g/min from arterial blood supplied via internal carotid arteries.

Hypothalamic Hormones Regulating the Anterior Pituitary

Thyrotropin Releasing Hormone (TRH):
- A tripeptide composed of glutamic acid, histidine, and proline, with a structure of 242 amino acids.
- Stimulates the release of Thyroid Stimulating Hormone (TSH).
- Located in the medial portions of the paraventricular nuclei, with a half-life of 6 minutes.
Gonadotropin Releasing Hormone (GnRH):
- A linear decapeptide that stimulates LH and FSH secretion, dependent on its pulse frequency.
- Secreting neurons reside in the preoptic area of the anterior hypothalamus, with a half-life of 2-4 minutes.
Dopamine:
- Produced in the arcuate nuclei, acting as the primary inhibitor of prolactin release (PRL).
- Has a half-life of 1-2 minutes.
Corticotropin Releasing Hormone (CRH):
- A 41-amino acid peptide that undergoes extensive synthesis, increasing during late pregnancy and delivery.
- Regulates ACTH secretion, with neurons located in the paraventricular nuclei.
Growth Hormone Releasing Hormone (GHRH):
- A peptide hormone comprising 108 amino acids, stimulating GH release from somatotrophs in the anterior pituitary.
- Contains a major isoform of 44 amino acids and has a half-life of 3-7 minutes.

Other Hormones and Their Actions

Somatostatin:
- A tetradecapeptide with 14 amino acids, inhibits multiple hormones including GH, TSH, insulin, and glucagon.
- Found in delta cells of pancreatic islets, with a half-life of 2-3 minutes.

Mechanism of Action

Hypothalamic hormones bind to specific plasma membrane receptors on target cells, triggering intracellular signaling pathways.
They activate phosphatidylinositol metabolism and the adenylate cyclase system, elevating intracellular calcium levels.
The actions of hypothalamic hormones are regulated by various negative-feedback systems to maintain homeostasis.

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Description

Explore the critical role of hypothalamic hormones in regulating the secretion of anterior pituitary trophic hormones in this quiz. Understand how these hormones influence target gland activity and the intricate connections between the hypothalamus and the pituitary gland. Test your knowledge on this essential topic in physiology!