Human Body Communication Systems

Overview

Nervous System: Functions through neurons, releasing chemical signals to specific locations.
Endocrine System: Releases chemical signals (hormones) throughout the body via bloodstream to target cells with specific receptors.

Hormones activate a cell's actions through specific receptors, fitting together like a lock and key.
Hormones are released by various glands and tissues such as the thyroid gland, pancreas, fat tissue, and heart tissue.
Functions include regulating metabolism, blood pressure, fluid levels, electrolyte balance, and protein synthesis for growth and repair.

Steroidal Hormones: Made of lipids (e.g., testosterone, estrogen, cortisol)
- Steroid hormones bind to carrier proteins to circulate in the blood.
- Easily pass through the cell membrane (lipid bilayer).
- Bind to receptors near or in the nucleus, affecting DNA to produce mRNA and create new proteins within the cell.
Non-Steroidal Hormones: Made of proteins or amino acids (e.g., glucagon, insulin, growth hormone, thyroxine, melatonin)
- Do not require carrier proteins; circulate easily in blood.
- Bind to cell membrane receptors, initiating secondary messengers to amplify signals and modify existing proteins.
Prostaglandins: Pseudo-hormones derived from arachidonic acid.
- Act locally (neighboring cells), primarily involved in immune response (e.g., swelling, inflammation).
- Example: Cyclooxygenase, targeted by drugs like ibuprofen.

Negative Feedback: Most hormones use this mechanism. Increased hormone levels result in actions that reduce further release of the hormone (cyclic pattern).
Positive Feedback: Rare, amplifies the release (e.g., childbirth hormones).
Concentration in blood is measured, but receptor availability is also crucial for hormone response.
- Down-Regulation: Fewer receptors, reduces response.
- Up-Regulation: More receptors, increases response.

Initial increase and then gradual decline in blood glucose and muscle glycogen levels.
Glucagon: Releases liver glycogen to maintain blood glucose levels.
Insulin: Activates GLUT4 transporters for glucose uptake; decreases during exercise but GLUT4 can be activated by muscle contraction.
Epinephrine/Norepinephrine: Released from the sympathetic nervous system, increasing heart rate and stroke volume during exercise.
Maintaining Blood Volume: Release of renin, ADH, and aldosterone to prevent dehydration and retain electrolytes and water.

Increase in norepinephrine, epinephrine, glucagon, and cortisol (after 15-25 minutes).
Decrease in insulin release, increased cell sensitivity to insulin, and increased GLUT4 activation.
Hormones promoting metabolism, cardiovascular function, and fluid retention.

30-45 minutes post-exercise: High norepinephrine, epinephrine, cortisol, growth hormone, and testosterone levels, promoting lipolysis and muscle repair.
80 minutes post-exercise: Continued high levels of growth hormone and testosterone focusing on tissue repair.

Hormones play a crucial role in the body's communication system, especially in regulating various bodily functions and responses to exercise. Understanding how different hormones function and interact is key to understanding overall bodily health and performance.