Endocrine System Overview

Endocrine System Overview

• This system is responsible for regulating physiological processes.
• The system involves glands, endocrine cells, hormones, and target cells.
• Objectives include defining these components and understanding their roles in the body.

Levels of Understanding

• Know: Define endocrine gland, endocrine cell, hormone, and target cell
• Comprehend: Compare endocrine system's regulation to the nervous system's
• Apply: Identify major hypothalamic and pituitary hormones' functions
• Analyze: Describe physiological roles of growth hormone, thyroid hormone, and cortisol
• Synthesize: Discuss endocrine system integration with other body systems
• Evaluate: Design an experiment to prove a compound is a hormone

Chapter Sections

• Anatomy Overview: Provides foundational anatomical knowledge about the endocrine system.
• Patterns of Organization: Explores different ways endocrine tissues are arranged in the body.
• Regulation of Endocrine Tissues (Hypothalamus and Pituitary): Details how these tissues interact and regulate other endocrine organs.
• Endocrine Tissue: Hormone Activation Cascades: Focuses on signaling pathways initiated by hormones.
• Effects of Aging on the Endocrine System: Highlights how aging affects endocrine function and processes.

Endocrine Tissues: Diversity & Decentralization

• Endocrine tissues are diverse and decentralized
• They include hypothalamus, pituitary, pineal, thyroid, parathyroid, adrenal, adipose, heart, and various other organs.

General Properties of Hormones

• Released through many pathways (e.g., diffusion, plasma).
• Vary widely in chemical structure.
• Released in low quantities, reaching target cells.
• Bind receptors influencing target cells' response.
• Involved in maintaining homeostasis, activating through autocrine, paracrine mechanisms.

Hormone Regulation: Feedback Loops

• Negative feedback loops are common, adjusting hormone levels to maintain homeostasis.
• Positive feedback loops are also described, although less frequent for maintaining hormone balance.

Hormone Receptor Levels

• Hormone receptors can adjust their numbers (upregulation or downregulation) based on hormone levels.
• Permissiveness: One hormone can enhance responsiveness to another.

Hormone Release Modulation

• Hormone release primarily controlled through amplitude modulation.
• This means that the amount of hormone released fluctuates within a certain range.
• Unlike neurotransmitters, which show an "all-or-none" response.

Peptide/Protein Hormone Synthesis

• Peptide hormones are synthesized in an inactive form.
• They involve steps like preprohormone to prohormone to hormone for proper functions.

Other Peptide Hormones

• Some notable peptide hormones discussed include ACTH, Lipotropin, Endorphins, and MSH.

Amino Acid Derivative Hormones

• These hormones are synthesized from amino acids (e.g., epinephrine, norepinephrine).

Processes Influencing Hormone Secretion

• Hormone secretion affected by different factors such as physiological factors, the nervous system, and other hormones.

Hormone Transport and Excretion

• Fat-soluble hormones are mostly bound to transport proteins, versus water-soluble hormones.
• Hormonal excretion happens through various pathways (e.g., urine, GI tract), and their half-life influences the rate of this process

Hormone Metabolism Change

• Metabolism can alter hormone levels, a key point for maintaining endocrine homeostasis.

Hormone Action Mechanisms

• Videos provide further information on hormone mechanisms, including receptor types.

G-protein Coupled Receptors (GPCRs)

• GPCRs are integral membrane proteins that relay signals through a series of intracellular signaling steps.
• Features include cell membrane integration, extracellular hormone binding, and intracellular G-protein interaction.

Downstream Effects of GPCRs

• G-protein subunits have effects on different targets affecting cellular processes, involving cAMP, DAG and IP3.

One-Transmembrane Spanning Receptors

• One-TMS receptors are integral membrane proteins, and their intracellular portion activates enzymes directly.

Nuclear Receptors

• Nuclear receptors act as transcription factors inside the cell.
• They are generally cytoplasmic, bind hormones, then dimerize and translocate to the nucleus.

Diseases Caused by Receptor Mutations

• Specific mutations in hormone receptors have been linked to various diseases like Graves' disease, Jansen's metaphyseal dysplasia, and others.

Hypothalamus and Pituitary

• The hypothalamus and pituitary have distinct anatomical features (as discussed in various sections).
• Understanding the regulation between these tissues is crucial to comprehending hormone regulation.

Hypothalamic Hormones

• Various hypothalamic peptides/hormones affect anterior/posterior pituitary gland action.

Pituitary Gland (Anterior)

• Different pituitary hormones impact various body systems, including mammary glands, musculoskeletal system, thyroid, adrenal glands, and gonads.
• The mechanisms described include trophic hormones and feedback loops.

Pituitary Gland (Posterior)

• Posterior pituitary hormones – like vasopressin, oxytocin.
• Their functions include controlling water retention, milk production, and other processes.

Other Endocrine Tissues

• Other tissues (like the heart, the gastrointestinal tract, the immune system, the placenta) produce peptides regulating metabolic processes

Aging and Endocrine System

• Age-related changes affect hormone release (e.g., in growth hormone).
• This influences body composition, bone health, organ function, and cellular function.