Section One

• Physiology is the study of how living organisms function
• Pathophysiology is the study of physiology that has gone wrong
• The level of organization of the body is divided into cells, tissues, organs, and organ systems
• Homeostasis is the constant internal environment that is a prerequisite for good health. In order to have good health, the body wants to be in homeostasis
• Homeostasis is a dynamic not a static process, where it can be predicted and fluctuates in a normal and narrow range. The normal value of a physiological variable is called its set point.
• Dynamic Constancy is when a given variable in the body that may vary over the short term, but it is stable and predictable over the long term
• Negative Feedback: an increase or decrease in the variable brings about a response that moves that variable in the opposite direction
• Feedforward regulation: changes in regulated variables are anticipated and prepared before they actually occur
• Positive Feedback: initial change in a particular variable leads to an even greater change or an "explosion" in that variable. Less important for homeostasis as it counteracts the goals of homeostatic set points
• Receptor: a way to measure the regulated variable
• Effector: Some way to alter or effect the regulated variable
• Integrating center: something linking the receptor and effector
• Smelling of food triggers nerve responses from odor receptors in the nose to cells in the digestive system. This induces saliva secretion in the mouth and sends signals to cause stomach churning and acid production. This is an example of feedforward regulation
• Blood clotting is an example of positive feedback in the body
• Cell membranes form the major structural element of cells. Some functions are to regulate the passage of substances into and out of the cell and between cell organelles and cytosol; and to detect chemical messengers arriving at the cell surface.
• About 60% of the human body mass is water
• Hydrogen bonds between adjacent water molecules are not long-lasting and easily broken. Loose bonding gives water unusually high surface tension and cohesiveness
• Water is a great solvent for ions due to its polarity
• LDL is known as "bad cholesterol"
• HDL is considered "good cholesterol"
• Cholesterol is slightly amphipathic because of a single polar hydroxyl group attached to the rest of the nonpolar structure
• Cholesterol decreases fluidity of a membrane
• The cell membrane has a low permeability to polar substances such as inorganic ions (Na+, K+, Cl-), and polar non-electrolytes (peptide hormones, sucrose, insulin)
• Cell membrane has a greater permeability to nonpolar substances such as steroid hormones (testosterone)
• Small polar molecules can pass through the cell membrane, but it will take a very long time due to the permeability
• All membranes contain lipids (phospholipids, cholesterol) and proteins (integral, peripheral)
• Integral proteins: Closely associated with the membrane lipids and cannot be extracted from the membrane without disturbing the lipid bilayer
• Peripheral Proteins: On one side of the membrane
• Integral proteins can serve as passive transport pores and channels (ex. aquaporins), active transport pumps (Ex. Na/K pump), membrane lined enzymes (Ex. ETC), and receptors
• An example of a peripheral protein is G-protein