Hypothalamus and Pituitary Gland Functions

Study Notes

Hypothalamus and Pituitary Gland

The hypothalamus plays a major role in controlling secretions from the pituitary gland.
The infundibulum (pituitary stalk) connects the hypothalamus to the pituitary gland.
Nerve cells in the hypothalamus produce chemical signals called releasing hormones and inhibiting hormones.

Pituitary Gland

Also known as the hypophysis, it is roughly 1 cm in diameter and weighs 0.5-1.0 g, and rests in the sella turcica of the sphenoid bone.
Hormones of the pituitary gland:
- Growth hormone (GH)
- Thyroid-stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
- Prolactin
- Melanocyte-stimulating hormone (MSH)

Posterior Pituitary

Antidiuretic hormone (ADH) targets the kidneys.
Oxytocin targets the uterus and mammary glands.

Biogenic Amines

Derivatives of the amino acid tyrosine, secreted by the thyroid and adrenal medullae.
Examples include thyroxine, triiodothyronine, epinephrine, and norepinephrine.

Mechanism of Action of Hormones

First step: binding to specific receptors at the target cell.
Cells without receptors do not respond to hormones.
Each receptor is usually highly specific for a single hormone.
Receptor locations:
- On the surface of the cell membrane (protein, peptide, and catecholamine hormones)
- In the cell cytoplasm (steroid hormones)
- In the cell nucleus (thyroid hormones)

Functions of the Endocrine System

Metabolism
Control of food intake and digestion
Tissue development
Ion levels
Water balance
Heart rate and blood pressure changes
Control of blood glucose and other nutrients
Control of reproductive functions
Uterine contractions and milk release
Immune system function

Hypothalamic Control of Anterior Pituitary

The hypothalamus regulates the anterior pituitary gland through hormones.

Parathyroid Gland

Located in the posterior part of each lobe of the thyroid gland, with four parathyroid glands present.
Parathyroid hormone (PTH) stimulates osteoclast activity, bone reabsorption, and the release of calcium and phosphate.

Oxytocin

Synthesized by neurosecretory neuron cell bodies in the paraventricular nuclei of the hypothalamus.
Stimulates uterine smooth muscle contraction during childbirth and during menses and sexual intercourse.
Responsible for milk ejection in lactating females.

Thyroid Gland

One of the largest endocrine glands, normally weighing 15 to 20 grams in adults.

Description

Learn about the crucial roles of the hypothalamus and pituitary gland in the endocrine system, including the production of releasing and inhibiting hormones. Understand the connections between these glands and how they regulate bodily functions.