6.1 Hormones

The cellular functions needed to be continuously regulated. The nerve fibres do not innervate all the cells of the body; a special kind of coordination system is thus required. The endocrine system serves the role to coordinate most body cells. The hormonal system is concerned with control of the different metabolic functions of the body, such as the rate of chemical reactions, the transport of substances through the cell membranes, growth, and secretions. This coordination is called chemical coordination.

Definition

Hormones: Hormones are organic chemicals secreted by a cell. They coordinate different functions in the body by carrying messages through blood to various organs and tissues.

Chemical Coordination: The coordination carried out by hormones through the blood to regulate different metabolic functions of the body is called chemical coordination.

Main Idea

• Cellular functions need continuous regulation.
• Nerve fibres do not innervate all cells.
• The endocrine system coordinates most body cells.
• The hormonal system controls metabolic functions.
• Coordination by hormones is called chemical coordination.
• Scientists have identified over 50 hormones in the human body so far.

Core Concept

• Hormones = organic chemicals secreted by cells
• Chemical coordination = coordination by hormones
• Endocrine system = coordinates body cells
• Hormones = carried through blood
• Hormones = control metabolic functions
• Over 50 hormones = identified in human body

Detailed Explanation

Hormones

Hormones are organic chemicals secreted by a cell. They coordinate different functions in the body by carrying messages through blood to various organs and tissues.

• Metabolism
• Homeostasis (constant internal balance), such as blood pressure and blood sugar regulation, fluid (water) and electrolyte balance and body temperature
• Growth and development
• Sexual function
• Reproduction
• Sleep-wake cycle
• Mood

• Hormones can stimulate changes in target cells even though they are present in extreme concentration.
• Chemically most hormones are either:
• Amines
• Peptides
• Proteins or glycoproteins
• Steroids

Summary Table of Hormone Functions

Chemical Nature of Hormones

Intermediate Level

Hormones

Functions Controlled by Hormones

Chemical Nature of Hormones

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. Cellular functions need continuous regulation.
• 2. Nerve fibres do not innervate all cells.
• 3. Endocrine system coordinates most body cells.
• 4. Hormonal system controls metabolic functions.
• 5. Coordination by hormones is called chemical coordination.
• 6. Hormones are organic chemicals secreted by a cell.
• 7. Hormones coordinate functions by carrying messages through blood.
• 8. Hormones act on various organs and tissues.
• 9. Scientists have identified over 50 hormones.
• 10. Hormones control metabolism.
• 11. Hormones control homeostasis.
• 12. Hormones control growth and development.
• 13. Hormones control sexual function.
• 14. Hormones control reproduction.
• 15. Hormones control sleep-wake cycle.
• 16. Hormones control mood.
• 17. Hormones can stimulate changes in target cells at extreme concentration.
• 18. Chemically, hormones are amines, peptides, proteins, glycoproteins, or steroids.
• 19. Hormones are essential for body functions.
• 20. Hormones maintain internal balance.

Remember

• - Hormones = organic chemicals secreted by cells
• - Chemical coordination = coordination by hormones
• - Endocrine system = coordinates body cells
• - Hormones = carried through blood
• - Hormones = control metabolic functions
• - Over 50 hormones = identified in human body
• - Functions = metabolism, homeostasis, growth, sexual function, reproduction, sleep-wake cycle, mood
• - Chemical types = amines, peptides, proteins, glycoproteins, steroids

Common Mistakes

• 1. Confusing hormones and neurotransmitters — Hormones travel through blood; neurotransmitters cross synapses.
• 2. Thinking hormones only control metabolism — They control many functions.
• 3. Forgetting the role of the endocrine system — It coordinates body cells.
• 4. Mixing up the chemical types — Amines, peptides, proteins, glycoproteins, steroids.
• 5. Thinking hormones are not effective at low concentrations — They are effective at extreme concentrations.
• 6. Forgetting the transport route — Hormones travel through blood.
• 7. Mixing up the functions — Metabolism, homeostasis, growth, etc.
• 8. Believing hormones act on all cells — They act on target cells with specific receptors.
• 9. Thinking there are only a few hormones — There are over 50.
• 10. Confusing endocrine and exocrine glands — Endocrine = ductless; exocrine = with ducts.

Quick Revision

The cellular functions needed to be continuously regulated. The nerve fibres do not innervate all the cells of the body; a special kind of coordination system is thus required. The endocrine system serves the role to coordinate most body cells. The hormonal system is concerned with control of the different metabolic functions of the body, such as the rate of chemical reactions, the transport of substances through the cell membranes, growth, and secretions. This coordination is called chemical coordination. Hormones are organic chemicals secreted by a cell. They coordinate different functions in the body by carrying messages through blood to various organs and tissues. Scientists have identified over 50 hormones in the human body so far. Hormones control many different bodily processes, such as metabolism, homeostasis, growth and development, sexual function, reproduction, sleep-wake cycle and mood. Hormones can stimulate changes in target cells even though they are present in extreme concentration. Chemically most hormones are either amines, peptides, proteins or glycoproteins and steroids.

60-Second Revision

• Hormones = organic chemicals secreted by cells
• Chemical coordination = coordination by hormones
• Endocrine system = coordinates body cells
• Hormones = carried through blood
• Hormones = control metabolic functions
• Over 50 hormones = identified in human body
• Functions = metabolism, homeostasis, growth, sexual function, reproduction, sleep-wake cycle, mood
• Chemical types = amines, peptides, proteins, glycoproteins, steroids
• Warning: Hormones act on target cells with specific receptors