Human Hormones
& The Endocrine
System
Comprehensive Study Guide & Exam Prep
Chemical Classifications
Endocrine vs. Nervous System.
Over and under-secretion effects
Action Mechanisms
Practice Exercises
, Human Hormones & The Endocrine System
Definition of Hormones
A hormone is a chemical messenger produced and secreted by endocrine glands into the
bloodstream, where it travels to specific target cells to regulate physiological processes.
Characteristics of Hormones
Transported via blood stream
Effective in very small concentrations
Act only on target cells with specific receptors
Regulate body homeostasis
Types of Hormones (Based on Chemical Nature)
A. Peptide/Protein Hormones
Made of amino acids
Water-soluble
Bind to membrane receptors
Example: Insulin, Growth Hormone
B. Steroid Hormones
Derived from cholesterol
Lipid-soluble
Cross cell membrane
Bind to intracellular receptors
Example: Estrogen, Testosterone, Cortisol
C. Amine Hormones
Derived from amino acids (tyrosine)
Example: Thyroxine, Adrenaline
Transport of Hormones to Target Cells
Hormones are secreted by endocrine glands directly into the bloodstream. The circulatory system
distributes them throughout the body. Although hormones reach many tissues, only target cells
possessing specific receptors can respond. The binding of a hormone to its receptor initiates signal
transduction pathways, resulting in physiological changes.
Similarities between Endocrine System and Nervous System
Maintain homeostasis
Endocrine system usually complements the nervous system
They work together, whereby certain parts of nervous system stimulate or inhibit the release of
hormones while some hormones promote and inhibit the generation of nerve impulses
Differences between Endocrine System and Nervous System
& The Endocrine
System
Comprehensive Study Guide & Exam Prep
Chemical Classifications
Endocrine vs. Nervous System.
Over and under-secretion effects
Action Mechanisms
Practice Exercises
, Human Hormones & The Endocrine System
Definition of Hormones
A hormone is a chemical messenger produced and secreted by endocrine glands into the
bloodstream, where it travels to specific target cells to regulate physiological processes.
Characteristics of Hormones
Transported via blood stream
Effective in very small concentrations
Act only on target cells with specific receptors
Regulate body homeostasis
Types of Hormones (Based on Chemical Nature)
A. Peptide/Protein Hormones
Made of amino acids
Water-soluble
Bind to membrane receptors
Example: Insulin, Growth Hormone
B. Steroid Hormones
Derived from cholesterol
Lipid-soluble
Cross cell membrane
Bind to intracellular receptors
Example: Estrogen, Testosterone, Cortisol
C. Amine Hormones
Derived from amino acids (tyrosine)
Example: Thyroxine, Adrenaline
Transport of Hormones to Target Cells
Hormones are secreted by endocrine glands directly into the bloodstream. The circulatory system
distributes them throughout the body. Although hormones reach many tissues, only target cells
possessing specific receptors can respond. The binding of a hormone to its receptor initiates signal
transduction pathways, resulting in physiological changes.
Similarities between Endocrine System and Nervous System
Maintain homeostasis
Endocrine system usually complements the nervous system
They work together, whereby certain parts of nervous system stimulate or inhibit the release of
hormones while some hormones promote and inhibit the generation of nerve impulses
Differences between Endocrine System and Nervous System
