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)
Today we know that all matter, including the human body, is composed of tiny particles called atoms.
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…
Levels of Structural Organization…continued Cell –basic unit of life Humans = 50 -100trillion 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
All organisms share 6 characteristics of Life Responsiveness – ability to detect changes in the environment and respond to them Metabolism – sum of all chemical reactions in a cell Reproduce – cells divide producing new cells A sperm may fertilize an egg to create a new organism Growth – increase in size of body or organ Respiration – releases energy from food Digestion – break down of food
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
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. Homeostatic Mechanisms maintain a stable heart rate, blood pressure, pH, body temperature, respiratory rate, ect.
Vital signs assess the conditions of homeostatic mechanisms
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.
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
There are 2 types of feedback loops
1. 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
2. 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
Example of Homeostasis and Negative Feedback Stimulus
Negative Feedback
Body temperature drops below the set-point (37째C)
Body temperature returns towards the setpoint.
Receptors thermoreceptors send signals to the hypothalamus
Control Center
Effectors
The skeletal muscles contract rapidly (shivering) generating body heat
hypothalamus detects the change in temperature
The hypothalamus sends signals to the skeletal muscles
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.
Figure 1.8 The homeostatic mechanism that regulates body temperature
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
effectors
Uterine muscles contract.
Muscles push baby against cervix.
positive feedback
stimulus
Oxytosin promotes additional uterine contractions
Baby stretches the cervix
receptor Stretch receptors from cervix
Hypothalamus promotes
send a signal to the hypothalamus
the secretion of Oxytocin
control center Hypothalamus detects stretching of cervix
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