external image images?q=tbn:ANd9GcTBLwTxwljuq3P-5UMIt8dq06fdurQLAQBenL3rd1O_uAhBtG7v Homeostasis external image images?q=tbn:ANd9GcTBLwTxwljuq3P-5UMIt8dq06fdurQLAQBenL3rd1O_uAhBtG7v
Chapter Summary:
In chapter 1, we learned a lot about the history of Physiology, homeostasis and feedback control mechanisms, the primary tissues of the body and also about the organs and the organ systems that make up our bodies. Physiology is the study of how the body works and how it functions. In anatomy, we learned the "what" of the human body. Physiology teaches us the "how" of the human body. The homeostasis and feedback control section teaches us how the body uses feedback control to maintain a realative state of internal constancy. The primary tissues of the body section was a review from anatomy that covered muscle tissue, nervous tissue, epithelial tissue and connective tissue. The section on the organs and organ systems went over what composes an organ and how organs function within their systems.

History of Physiology:
According to our textbook, physiology is defined as "the study of biological function-of how the body works, from molecular mechanisms within the cells to the actions of tissues, organs and systems, and how the organism as a whole accomplishes particular tasks essential for life." Physiology is the study of how we work they way we do and why we work the way we do. Physiology uses the scientific method to obtain new information. The scientific method uses various steps to prove or disprove theories. First an educated guess know as a hypothesis is formed. The hypothesis is then tested many times over until a theory is formed. Theories must be based on reproducible data. Erasistratus is considered the father of physiology. He made an attempt to study the human function and apply physical laws to it. It was the French physiologist Claude Bernard who discovered that the body is in a constant state of change and remains fairly stable despite this. The term "Homeostasis" came into usage in the early 20th century from the American Physiologist Walther Cannon. Because of advances in technology, the majority of information obtained through physiology has been in the later years of the 20th century. As more technology is invented, more can be found out about the physiological processes of the human body.

Homeostasis and Feedback Control Mechanisms:
Homeostasis is defined as "the tendency of a system, especially the physiological system of higher animals, to maintain internal stability, owing the coordinated response of its parts to any situation or stimulus tending to disturb its normal condition or function." Basically homeostasis is the ability of the body to regulate itself to maintain a stable environment. The internal environment of the body is constantly changing and uses feedback mechanisms to regulate itself. Feedback mechanisms can be both positive and negative.
Positive feedback mechanisms are relatively rare in the human body. In a positive feedback mechanism, an increase in one effector action increases the action of another effector. An example of this is in the female reproductive cycle. When a woman goes into labor, the pituitary gland secretes oxytocin. The increase in oxytocin stimulates the contractions in the uterus. Increase in oxytocin=increase in uterine contractions.
Negative feedback loops run in a different way. In a negative feedback mechanism, the increase in the action of one effector decreases the action of another effector. It is a "push-pull" control mechanism. An example of a negative feedback mechanism is the decrease in blood flow to the organs that are deemed not needed during exercise. An increase in the need of blood flow to the active muscles signals a decrease in the blood flow to organs that are not vital in that moment.

Primary Tissues of the Body:
The primary tissues of the body are muscle tissue, nervous tissue and epithelial tissue. Below are pictures of each type of tissue.
Skeletal Muscle Tissue
Nervous Tissue
Epithelial Tissue

Fibrous Connective Tissue

Picture Source (Muscle) Picture Source (Nervous) Picture Source (Epithelial) Picture Source (Connective Tissue)
There are three kinds of muscle tissue. There is skeletal muscle (shown in above picture), cardiac muscle and smooth muscle. The skeletal muscle is the muscle that controls the movement of the skeletal system of the body. This includes the joints and limbs. Cardiac muscle tissue is found only in the heart and controls the beating of the heart and the pumping of blood into the vascular system. The smooth muscle is the muscle that is found in the digestive tract. This muscle is controlled by the autonomic nervous system and cannot be consciously controlled.

Nervous tissue is found in the brain, neurons and in the nerves of the body. Nervous tissue is made up of 3 parts: The cell body, dendrites and axons. The cell body is responsible for the metabolic action of the cell and also contains the neuron. The dendrites are the branched units of the cell that receive messages from other cells of the body. The nerve cell also contains the axon. The axon is the tail extension of the nerve cell that is responsible for conducting the nervous impulses of the cell. The axon can be short or very long.

Epithelial tissue is the tissue that forms membranes to cover other tissues throughout the body. The skin is an example of epithelial tissue. The lining of the blood vessels and lining of organs are also composed of epithelial tissue. Epithelial tissue can exist as a single layer of cells called simple epithelia, a multi-layered epithelia are called stratified epithelia. Epithelial tissues are also classified by their shapes. Squamous epithelia is a flat irregular shape, cuboidal epithelia exists in a cube shaped and columnar epithelia are in tall narrow columns. Each shape can exist in any different layer type.

Connective tissue is divided into many different categories. The primary types are Connective tissue proper, cartilage, bone and blood. Connective tissue proper consists of loose connective tissue and dense connective tissue. Loose connective tissue provides room for nerves, blood vessels and other tissues. The dermis of the skin is an example of loose connective tissue. Dense connective tissue has protein fibers that are packed tightly together. Cartilage is an example of dense connective tissue. The bones in the body have layers of material that is calcified and surround blood vessels. Bones are a living structure because of the vascular system that runs through them. Blood is classified as a connective tissue because the majority of the blood composition is in the blood plasma which is an extra cellular fluid.


Picture Source (Bone) Picture Source (Blood)

Application to Nursing:
Nurses need to adapt their plan of care to their patient's changing condition. One thing that is watched closely in many patients is their level of blood sugars. Blood sugar levels change in every patient constantly. Eating, activity, insulin production and energy expenditure from necessary body processes all affect blood glucose levels. The body is trying to maintain a level of homeostasis by reacting to changes in blood sugar levels. In patients that are diabetic or suspected of being diabetic, blood sugar levels are checked at specific intervals throughout the day. Doctors commonly use a Sliding Scale Insulin order so the nurse knows how much insulin to give the patient based on their blood sugar levels. Below is an example of sliding scale insulin. The nurse must have a good understanding of how the body tries to maintain homeostasis by changing insulin and blood glucose levels before administering any insulin to the patient. By understanding this action, the nurse can make decisions that will benefit the patient and reduce the possibility of causing harm to the patient.
Insulin Sliding Scale Example:
BG 150-199: 2 unit bolus Insulin (regular or RA)
BG 200-249: 3 units bolus Insulin
BG 250-299: 5 units bolus Insulin
BG 300-349: 7 units bolus Insulin
BG Over 350: 8 units bolus Insulin
Insulin Chart Source

Essential Question:
"Describe negative feedback and how insulin is controlled by a negative feedback inhibition. Why is it essential that insulin and other molecules be regulated?"Negative feedback is a control mechanism used by the body. In a negative feedback loop, a stimulus is detected by a sensor, the sensor sends that information to an integrating center and the integrating center sends the appropriate information to an effector. The effector then makes an action happen. The action can be a hormone secretion, and increase or decrease in muscle action, or even a change in heart rate. During a negative feedback action, the increase of one effector action inhibits another effector action. For insulin regulation, an increase in glucose levels is the stimulus. Cells detect this change in blood glucose and the information is sent to the brain which is the integrating center. The brain then sends a message to the pancreas to increase insulin levels which will result in the lowering of blood glucose levels. The pancreas secretion of the insulin is the effector in this case. The human body has to maintain a certain level of stability at all times. The body is in a constant state of change in an attempt to maintain this stability. Many health problems and health complications can arise if molecules are not in proper regulation or are at the incorrect levels in the blood. If insulin is not maintained at the proper levels or not regulated properly, conditions like diabetes can arise. Diabetes can cause things like blindness and organ failure if not controlled properly. Insulin and other molecules must be regulated in the body because if they are not, many problems can arise that will affect the health and well-being of the individual.

Homeostasis definition: http://dictionary.reference.com/browse/homeostasis