Introduction

1. Introduction Chapter 1

2. The language of anatomy and physiology is usually derived from Greek or Latin origins. • Anatomy: Study of the structures of the human body • (Greek: ana = up; tome = to cut) • Physiology: Study of the functions of the organs • (Greek: physis = nature; logia = to study)

3. Today we know that all matter, including the human body, is composed of tiny particles called atoms.

4. Levels of Structural Organization Subatomic Particles – electrons, protons, and neutrons Atom – smallest unit of an element (hydrogen atom, lithium atom, etc.) Molecule – particle of 2 or more atoms (water molecule, glucose molecule, etc.) Macromolecule– very large molecule (protein, DNA, etc.) Organelle –carry on specific activities within a cell (mitochondrion, Golgi apparatus, nucleus, etc.) Continued…

5. Levels of Structural Organization…continued Cell–basic unit of life Humans = 50 -100 trillion cells (muscle cell, nerve cell, etc.) Tissue – group of similar cells that perform a specialized function (epithelia, connective, muscle and nerve) Organ – Groups of different tissue (skin, femur, heart, kidney, etc. ) Organ System – Group of organs that function together (skeletal system, digestive system, etc.) Organism – the human

6. All organisms share several characteristics of Life • Responsiveness – organisms are able to detect changes in the environment and respond to them • Metabolism – is the sum of all chemical reactions in a cell • Reproduce – DNA replication, Cell Division, Sexual Reproduction • Growth – increase in size of body or organ • Respiration – releases energy from food • Digestion – break down of food

7. All organisms share several characteristics of life • …Continued • Development – Living things become more complex • Absorption – passage of substances across membranes and • into bodily fluids • Assimilation – Changing substances into different chemical forms • Excretion – Removal of wastes

8. Humans depend on 5 requirements for life. • Water - Essential for transportation & metabolic processes • Food - Source of energy and used as building blocks for growth and repair • Oxygen – required to release energy from metabolism • Heat – form of energy, drives chemical reactions • Pressure – a force required for breathing and circulation

9. Homeostasis • Homeostasis is a process in which a stable internal environment of an organism is maintained. • Homeostatic Control Mechanisms – monitor the internal environment and corrects conditions as needed. Vital Signs measure the ability to maintain homeostatic mechanisms: e.g. heart rate, blood pressure, pH, body temperature, respiratory rate, ect. Vital signs assess the conditions of homeostatic mechanisms

10. 3 components of a Homeostatic Mechanism • Receptor – monitors the environment and provides information about • changes in the conditions • Control Center – Region in body that sets the normal range • Set-Point: target value that is maintained by the control center • (e.g. Body temperature = 98.6°F, or 37°C) • Effector – Produces a response that alters conditions in the environment • (usually a muscle or a gland) *The control center receives input from receptors and sends output to effectors when changes are needed.

11. Control of Homeostatic Mechanisms Homeostasis is maintained through regulatory processes called feedback loops A feedback loop is a cycle of events in which a body condition (such as body temperature) is continually monitored and adjusted to be within specific limits Figure 1.6 a homeostatic mechanism monitors a particular aspect of the internal environment and corrects any changes back to the value indicated by the set-point

12. There are 2 types of feedback loops • Negative Feedback Loop –reduces the deviation of conditions from a set-point • Most common way to maintain homeostasis • Effectors act to lessen or counteract the stimulus • Positive Feedback Loop –increases the deviation of conditions from a set-point • Effectors respond by reinforcing the stimulus • Drives systems away from equilibrium (runaway train) • Not a way to maintain homeostasis

13. Example of Homeostasis and Negative Feedback Stimulus Negative Feedback Receptors Control Center Effectors

14. Control of Homeostatic Mechanisms Negative Feedback restores conditions back towards set-point. • As conditions return towards normal, negative feedback gradually shuts down the effectors. This prevents a correction from going to far.

15. Figure 1.8 The homeostatic mechanism that regulates body temperature

16. Positive Feedback • As a stimulus moves conditions away from the set-point, positive feedback further increases the deviation. • Positive feedback produces unstable conditions that are usually short-lived. • Example: The increase in uterine contractions during childbirth

17. effectors positive feedback stimulus Positive feedback cycle child birth receptor control center

18. Positive Feedback & Childbirth • Positive feedback continues to increase the strength of contractions. The cycle ends only after the baby is born and the cervix is no longer stretched. End of Chapter 1