Endocrine System Overview

Gonads

• Ovaries in females and testes in males produce sex hormones.

Pineal Gland

• Regulates sleep patterns through the release of melatonin.

Types of Hormones based on chemical nature

• Three main hormone types: amino acid-based, steroids, and fatty acid derived.
• Most hormones are amino acid-based, including amines (dopamine & epinephrine) and polypeptide hormones (e.g., insulin, growth hormone).
• Steroid hormones are derived from cholesterol, such as gonadal and adrenocortical hormones.
• Fatty acid-derived hormones include eicosanoids, which are derived from arachidonic acid, such as leukotrienes and prostaglandins.

Intracellular Hormone Receptors and Activation of Genes

• Hormone receptors can be located in the cell membrane, cytoplasm, or nucleus.
• Cell membrane receptors are primarily for protein, peptide, and catecholamine hormones.
• Cytoplasmic receptors are primarily for steroid hormones.
• Nuclear receptors are for thyroid hormones.

Hormone Action

• Hormones circulate to all tissues but activate only target cells.
• Target cells have specific receptors for particular hormones.

G Protein–Linked Hormone Receptors

• A hormone (first messenger) binds to the receptor, which activates a G protein inside the cell.
• G protein then activates an enzyme called adenylyl cyclase.
• Adenylyl cyclase converts ATP to cyclic adenosine monophosphate (cAMP), which acts as a second messenger.
• cAMP then activates protein kinases.
• Protein kinases activate other proteins that ultimately produce a specific cellular effect.

Explore the functions and types of hormones produced by the gonads and pineal gland, including their chemical nature and mechanisms of action. Learn about hormone receptors and how they regulate gene activation in various cells. This quiz covers key concepts from the endocrinology chapter.