This unit started with what is physiology? It is the study of how our bodies work. What a very complicated system we have.
When scientists want to learn more about something they apply a scientific method. There may be many different techniques but all methods share three attributes: 1) rational, 2) honesty and 3) humility (willingness to admit that we could be wrong).

HOMEOSTASIS: Our biological system maintaining constant conditions inside an environment while interacting with and making adjustments to changes around and inside the system. (Miller-Keane; Encyclopedia & Dictionary of Medicine, Nursing, & Allied Health; 5th Edition).

Other topics included in this chapter were the different kinds of primary tissues our body is composed of. These would include muscle, nervous, epithelial and connective tissues. With these different tissues organs and systems are developed.


For homeostasis to be maintained, certain elements are needed. As changes in the body happen sensors will send information to an integrating center in the body. These areas can be a part of the brain, spinal cord or an endocrine gland. They then figure out what is going on in a certain area of the body (set point). This information is sent to an effector (muscles or glands) which will produce a change by either increasing or decreasing an action to reverse the deviation from the set point and defend homeostasis. This process is called negative feedback. There is also positive feedback, which is not as common. The effectors will increase the changes that originally activated the effectors. Some examples of positive feedback are clotting of blood, ovulation and contractions of the uterus during childbirth.



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In order to have tissues there has to be cells, which are the basic unit of structure and function in the body. When the cells have a similar function in the body, this becomes a group of tissues. The four groups of tissues are: muscle, nervous, epithelial and connective. Muscle tissue is used for contraction. There are three kinds, skeletal, cardiac and smooth muscles. When a person thinks of skeletal, they would think of bone and this is where the skeletal muscle is attached. Tendons attached to bone and make it possible for us to move our leg when we want to—voluntary movement. Cardiac muscle is only in the heart. Smooth muscle is found in blood vessels, bronchioles, in ducts of the urinary and reproductive systems and the digestive tract. There are special circular arrangements and longitudinally arranged layers of smooth muscle in the digestive tract which are used in peristalsis.

Nervous tissue consists of nerve cells, which have three parts: cell body, dendrites and axon. These transport messages from one part of the body to another in the form of nerve impulses.

When a person thinks of epithelial tissue the word skin comes to mind. It is used to protect our body or provide a barrier between the external environment and the internal environment of our body. Epithelial tissue can have several layers and different shaped cells. This is how they are classified. One characteristic of epithelial membranes is the constant loss and renewal of cells. For this tissue to be strong the epithelial cells are packed very close together and are joined by a structure called junctional complexes. Nourishment of this layer has to come from underneath since there is no room for blood vessels.

People may not think of blood as a tissue but it is; it is connective tissue. The other types are connective tissue proper, cartilage and bone. Gristle is the common name for supportive and protective cartilage tissue, it is found in the joint surfaces of the bone.


Organs will have two or more primary tissues, with the skin being the largest. Organs are then grouped together by functions and are called systems. We have several systems: integumentary, nervous, endocrine, skeletal, muscular, circulatory, immune, respiratory, urinary, digestive, and reproductive. All of these need to work together to maintain life.

All information came from Human Physiology; Stuart Ira Fox; 12th Edition






My chosen career is nursing so knowing how the body and its systems work is important. With working in a clinic, we see many different things. Patients may come in with a laceration, needing sutures. Some cuts do get very deep. It is interesting watching the physician suture things back together. Other patients may come in with a lump, which ends up being a sebaceous cyst. The physician will open this up to relieve the pressure and expel the sebum. Usually the area is numbed first; then opened using a blade. Sometimes the pressure is so great that it doesn’t take much of an opening to get the sebum to fly across the room. The physician then will apply more pressure to expel more sebum. He may also use a hemostat to break up the sac under the skin. The area is left open so it can continue to drain. I like helping with these kinds of things.




Negative feedback is when something in the body increases;sensors indicate a higher blood sugar level after eating. The body then sends a message to the brain, the integrating center, that something needs to be done. The pancreas, the effector, releases insulin which takes the glucose to the cells that need it for energy. This will restore the blood sugar to a normal level or homeostasis.
When a person is fasting the body uses other sources to make sure the glucose level doesn't fall too much. Glucagon causes the liver to secrete glucose into the blood stream. As the blood sugar increases, insulin is produced by the pancreas. When the blood sugars start to decrease because of the insulin production, the body knows not to produce more insulin. Negative feedback inhibition is used to control sugars. If even one thing is not regulated properly, it will effect other parts of the body throwing everything else off. The body will try to respond to get things back in order but may have to work harder to get the job done. This could lead to an organ or system failing to operate properly or shutting down completely.