biology notes (B1-B11)

biology notes (B1-B11) - Biology- Herrara`s lecture Some...

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Biology- Herrara’s lecture Some definitions of physiology: 1) “It is the study of the normal functioning of a living organism and its component parts, including all its chemical and physical processes.” –Silverthorn, in Human Physiology 2) “Physiology is not a science or profession, but more a point of view”—Ralph Gerald Internal Environment: Different systems exist in the body: digestive (digests food to extract the nutrients from it and eliminates waste from the body), respiratory (supplies oxygen to the body and eliminates carbon dioxide as a waste product during exhalation), circulatory (central role because it transports the oxygenated blood all around the body), excretory system (filtering and processes the blood to maintain the composition of the body’s fluid and the skin (provides mechanical strength, barrier to infection, way of preventing water loss from the body and it separates the internal environment from the external. -In order for cells to maintain their integrity and to function properly, its essential that their immediate physical and chemical environment to be ideal for their life. -Homeostasis: Maintenance of the constancy of the internal environment. -Every physiological system mentioned above is homeostatic in some way. -Mechanism of homeostasis is negative feedback. Eg. Glucose homeostasis. Regulation of glucose concentration involves the pancreas, the liver and the cells of the body. After a meal, there is a rise in glucose concentrations, this provides a stimulus to beta cells in the pancreas, and this secretes the hormone insulin and causes the cells in the body to take up glucose. Liver cells synthesize glycogen which stores excess glucose. This then leads to a drop in blood glucose which returns the glucose concentration to the normal level. During fasting or not eating for a while, the blood glucose concentration decreases which provides a stimulus to the alpha cells in the pancreas which releases the hormone glucagons which releases glucose into the blood to bring the levels back up to normal. The Circulatory System -Central function of the circulatory system is to transport materials such as water, ions, nutrients, waste products and respiratory gases through an animal’s body. -Diffusion is adequate for the circulation only for very short distances. Protists or porous organisms can exist without a circulatory system. -2 general types of circulatory system: open and closed. These systems both have a heart that acts as a muscular pump, there is a fluid that circulates-blood, and there is a set of branching tubes called blood vessels through which the blood flows. The way this works
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is that through muscular contraction raises the hydrostatic pressure of the blood which creates a pressure gradient-pushes blood through the system. -The distinction between an open and closed system is whether or not the blood is always
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This note was uploaded on 02/27/2008 for the course BISC 220L taught by Professor Herrera,mcclure during the Spring '07 term at USC.

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biology notes (B1-B11) - Biology- Herrara`s lecture Some...

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