(3)Anatomy and Physiology pt.3

• Because feedback mechanisms alter the original changes that triggered them, they are called feedback loops.
• Homeostasis in body temperature e.g.: If too warm, vessels dilate in the skin and sweating begins (a heat-losing mechanism). If too cold, vessels in the skin constrict and shivering begins (heat-gaining mechanism).
• Receptor: This is the structure that senses change in the body (e.g., stretch receptors above the heart that monitor blood pressure).
• Integrating (control) center: The control center that processes the sensory information, “makes a decision,” and directs the response (e.g. cardiac center of the brain).
• Effector: The cell or organ that carries out the final corrective action to restore homeostasis (e.g., the heart).
• Negative Feedback Loop: A type of feedback loop where the effector acts to counteract the initial stimulus so as to return the system to its normal state.
• Positive Feedback Loop: A type of feedback loop where the effector amplifies the initial stimulus so as to exaggerate the deviation from the normal state.
• Positive Feedback and Rapid Change include a self-amplifying cycle, and a normal way of producing rapid changes.
• Examples of positive feedback loops are labor contractions during childbirth, vomiting when nauseous, and sneezing when exposed to irritants.
• Self-amplifying cycle: Leads to greater change in the same direction, and the feedback loop is repeated(meaning change produces more change).
• Positive Feedback and Rapid Change can sometimes be dangerous, as it can lead to a runaway reaction e.g. a vicious circle of runaway fever.
• Gradient: This means a difference in chemical concentration, charge, temperature, or pressure between two points.
• Matter and energy tend to flow down gradients e.g. blood flows from a place of higher pressure to a place of lower pressure. Movement in the opposite direction is “up the gradient”, and movement in this direction ("up the gradient") requires spending metabolic energy.
• Chemicals flow down concentration gradients. Charged particles flow down electrical gradients. Heat flows down thermal gradients. Everything here moves from the highest concentration to the lowest concentration naturally.
• The History of Anatomical Terminology: About 90% of our current medical terms come from 1,200 Greek and Latin roots reflecting ancient past. The Renaissance brought progress but confusion as some of the same structures were named differently in varied countries while some structures were named after people (eponyms). In 1895 Anatomists established worldwide naming conventions, rejected eponyms, and used unique Latin names instead. In 1998 Terminologia Anatomica (TA) was developed. It provided Latin names and English equivalents and was adopted by anatomists in over 50 countries.
• When Analyzing Medical Terms, look for Terminology based on word elements, Scientific terms, and Acronyms.
• In Scientific terms, there is one root (stem) with a core meaning, combining vowels join roots into a word, and Prefixes and/or suffixes may modify the meaning of the root word.
• Acronyms are pronounceable words formed from the first letter (or first few letters) of a series of words. Example: PET scan
• The 3 components of a negative feedback loop are: Receptor, Intergrating (Control) Center, and Effector.