Lecture 5 - Photoreceptors and Photoreceptors

Endocrinology

The branch of medicine and biology that studies hormones, the endocrine glands that produce them, and their effects on the body’s functions, including metabolism, growth, and reproduction.

Paracrine

A form of cell communication in which signaling molecules are released by a cell and affect nearby target cells without entering the bloodstream.

Endocrine gland

A gland that secretes hormones directly into the bloodstream to regulate various bodily functions, such as growth, metabolism, and reproduction. Examples include the pituitary gland, thyroid gland, and adrenal glands

Neuroendocrine cells

Specialized cells that receive signals from the nervous system and release hormones into the bloodstream in response. They play a key role in regulating physiological processes like metabolism, stress response, and digestion.

Target cells

Specific cells that respond to a particular hormone, drug, or signaling molecule because they have the necessary receptors to bind to it.

Pituitary gland

A small, pea-shaped endocrine gland located at the base of the brain. It regulates various bodily functions by releasing hormones that control growth, metabolism, stress response, and other endocrine glands like the thyroid and adrenal glands.

Hypophysis

A small, pea-shaped endocrine gland located at the base of the brain. It regulates various bodily functions by producing and releasing hormones that control growth, metabolism, and other glands in the endocrine system.

Anterior pituitary

The front part of the pituitary gland that produces and releases hormones regulating growth, metabolism, stress response, and reproduction. It secretes hormones like growth hormone (GH), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), prolactin (PRL), luteinizing hormone (LH), and follicle-stimulating hormone (FSH), in response to signals from the hypothalamus.

Posterior pituitary

The part of the pituitary gland that stores and releases hormones produced by the hypothalamus, specifically oxytocin and vasopressin (antidiuretic hormone, ADH). It does not produce its own hormones but acts as a storage and release site for these essential regulators of water balance, blood pressure, and reproductive functions.

Infundibulum

Stalk-like structure that connects the hypothalamus to the pituitary gland. It serves as a pathway for neurohormones, allowing communication between the hypothalamus and both the anterior and posterior pituitary.

Hypophyseal portal system

A network of blood vessels that connects the hypothalamus to the pituitary gland. It allows hormones released by the hypothalamus to directly influence the pituitary, regulating important bodily functions such as growth, metabolism, and reproduction.

Thyrotropin releasing hormone

TRH

A hormone produced by the hypothalamus. It stimulates the anterior part of the pituitary gland to release thyroid-stimulating hormone (TSH).

TRH plays a key role in maintaining the balance of thyroid hormone levels in the body.

Corticotropin releasing hormone

CRH

A peptide hormone produced by the hypothalamus. It plays a key role in the body's response to stress by stimulating the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary.

CRH is also involved in the regulation of various physiological processes, including mood and behavior.

Gonadotropin releasing hormone

GnRH

Promotes secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

Growth hormone releasing hormone

GHRH

Promotes secretion of growth hormone (GH)

Prolactin inhibiting hormone

PIH

Inhibits secretion of prolactin (PRL).

Somatostatin

Inhibits secretion of growth hormone (GH) and thyroid-stimulating hormone

Oxytocin

(OT)

Target organ or tissue: uterus, mammary glands

Principal effects: Labor contractions, milk release

Antidiuretic hormone

ADH

target organ or tissue: Kidneys

Principal effects: water retention

Follicle stimulating hormone

FSH

Target organ or tissue: ovaries, testes

Principal effects: f: growth of ovarian follicles, m: sperm production

Luteinizing hormone

Target organ or tissue: ovaries, testes

Principal effects: f: ovulation, m: testosterone production

Thyroid stimulating hormone

TSH

Target organ or tissue: thyroid gland

Principal effects: growth of thyroid, secretion of thyroid hormone

Adrenocorticotropic hormone

ACTH

Target organ or tissue: Adrenal cortex

Principal effects: growth of adrenal cortex

Prolactin

PRL

Target organ or tissue: mammary glands

Principal effects: milk synthesis

Growth hormone

GH

Target organ or tissue: Liver, bone, cartilage, muscle

Principal effects: widespread tissue growth

What are four methods of cell-to-cell communication?

1. Gap junctions: direct connections

2. Neurotransmitter: Carries signal from one cell to another

3. Paracrine: released from a cell then binds to a nearby cell (local)

4. Hormones: Enter the blood, access to whole body.

How many Hypothalamic and pituitary hormones?

Hypothalamic: 6

Pituitary: anterior—>6, posterior —> 2

Where are posterior pituitary hormones synthesized

Posterior pituitary hormones are synthesized in the hypothalamus. The hypothalamus is a part of the brain that controls the secretion of hormones from the pituitary gland. 

Dehydroplandrosterone

DHEA - adrenal cortex

Erythropoietin

EPO - kidneys, liver

Insulin-like growth factors

IGFs - liver

Parathyroid hormone

PTH - parathyroids

Triiodothyrine

T3 - thyroid

Thyroxine

T4 - thyroid

Thyroid hormone

TH - Thyroid

Thyrotropin-releasing hormone

TRH - Hypothalamus