A&P2: Week One Videos.

Overview of the Endocrine System

Primary Function: Regulates metabolic processes within the body, including growth, development, and digestion.
Definition of Metabolic Processes: Encompasses all chemical reactions occurring within the body.
Comparison with Nervous System: Similar role in monitoring and adjustment, but focuses specifically on metabolic processes.

Ductless Glands: Secrete hormones directly into the bloodstream instead of through ducts.
Hormones as Chemical Messengers: Hormones travel through the bloodstream to target organs and induce physiological changes.

Function: Produces numerous hormones; often referred to in a joking manner due to its extensive activity.

Description: Small glands located on the thyroid, appearing as tiny spheres or candy-like shapes (6lets).
Typical Count: Usually 4 to 6 per individual, varies.

Significance: Often overlooked; plays an important role, especially in the immune system.

Position: Tucked behind the stomach; plays multiple roles including endocrine function.

Types: Ovaries (female) and testes (male); classified as gonads based on gender.

Dedicated Glands: Primarily concerned with endocrine functions.
Dual Purpose Glands: Serve multiple functions (e.g., hypothalamus and pancreas).

Released into the bloodstream where they exert effects on specific target organs. Each hormone has unique functions and interacts with its target cells.

Change Cell Permeability: Alters what substances can enter or exit the cell, exemplified by insulin allowing glucose entry.
Gene Regulation: Hormones can turn specific genes on or off, affecting protein synthesis.
Change Enzyme Activity: Hormones can activate or inhibit enzyme functions, impacting biochemical reactions.
Secretion of Other Hormones: Hormones can trigger the release of other hormones (e.g., TSH stimulates thyroid hormone release).
Promote Cell Division: Certain hormones induce cell division, significantly influencing growth (e.g., growth hormone on growth plates).

Types of Hormones: Divided into steroid (cholesterol-based) and protein (amino acid-based) hormones.
- Steroid Hormones: Nonpolar, can easily pass through cell membranes and utilize direct gene activation.
- Protein Hormones: Polar, cannot pass through cell membranes easily and instead utilize the second messenger system to convey signals into the cell.

Specificity: Each hormone binds to specific receptors which influences its effectiveness.
Affinity: Describes the attraction between a hormone and its receptor; high affinity means stronger bonding.

Upregulation: More receptors are produced if levels of the hormone are low, increasing sensitivity.
Downregulation: Fewer receptors are produced if hormone levels are high, decreasing sensitivity.

Permissiveness: One hormone's effectiveness depends on the presence of another hormone (e.g., growth hormone and thyroid hormone).
Synergism: Two hormones working together produce a greater effect than individually (e.g., a combined response greater than additive).
Antagonism: Hormones that oppose each other's actions (e.g., insulin and glucagon regulation of glucose levels).

Negative Feedback: Major regulator; a decrease in hormone leads to increased secretion to restore balance.
Humoral Stimuli: Chemical changes in blood trigger hormone release (e.g., changes in calcium or glucose levels).
Neural Stimuli: Direct responses from the nervous system stimulate hormone release.
Hormonal Stimuli: One hormone triggering another hormone's release (e.g., TSH acting on the thyroid).

The endocrine system coordinates vital bodily functions through hormone release and action, ensuring metobolic processes are regulated efficiently. The interactions and specificity of hormones and their receptors are crucial for maintaining physiological balance.