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Chapter 1

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York University
Kinesiology & Health Science
KINE 2011
Roy Parteno

Human Physiology: 2. Homeostasis refers to the dynamic mechanisms that detect and respond to deviations in physiological variables from their “set point” values by initiating effector responses that restore the variables to the optimal physiological range. Scientific DEF: Homeostasis A state of reasonable stable balance between the physiological variables such as blood pressure, body temperature blood borne factors (O2, glucose, Na+) Homeostasis is a dynamic process (e.g. glucose between meals) (diabetes) not static Range of variation is limited - and balance always sought Cells: - Pg 2 - The process of transforming an unspecialized cell into a specialized cell is called cell differentiation - Cells migrate to new locations during development and form selective adhesions with other cells to produce multicellular structures - 4 categories emerge from 200 kinds of cells - Pg 3 - Muscle cells are specialized to generate the mechanical forcers that produce movement - Nerve cells are specialized to initiate and conduct electrical signals, often over long distances. They can control other cells - Epithelial cells are specialized for the selective secretion and absorption of ions and organic molecules and for protection - Basement membrane forms the boundaries between compartments and act as barriers which regulate the exchange of molecules - Connective tissue cells connect, anchor and support the structures of the body Tissues - Tissue is an whole/total of a single type of specialized cells - Muscle tissue, nerve tissue, epithelial tissue, and connective tissue - The extracellular matrix provides a scaffold for cellular attachments and it transmits information in the form of chemical messengers Organs - Composed of 4 tissues Body Fluids Pg. 5 - The fluid present in the blood is called extracellular fluids - The fluid which lies around and between cells in called interstitial fluid which is 75-80% of the extracellular fluid - Plasma (20-25% of extracellular fluids)exchanges oxygen, nutrients and waste with the interstitial fluid Homeostasis: Pg. 6 - Most cells come in contact with the Interstitial fluid, which was found to be in a state of flux (constant change) with water and solutes such as ions, gases which move back and forth through it between the cell interiors and the blood in nearby capillaries. Exchanges. Figure 1-2 - Homeostasis was defined as a state of reasonably stable balance between physiological variables such as those just described. (blood pressure, body temperature, oxygen, glucose and sodium) - Homeostasis is a dynamic, not a static General Characteristics of Homeostatic Control Systems Pg 7 - The activity of cells, tissues and organs must be regulated and integrated with each other si that any changes in the extracellular fluid initiates a reaction to correct the change - A steady state is a system in which a particular variable is not changing, but energy must be added continuously to maintain a constant condition. - Equilibrium is a particular variable which is not changing but no input of energy is required to maintain constancy. - The steady temperature is known as the set point - Stability of an internal environment variable is achieved by the balancing of inputs and outputs - In response to figure 1-4 about body temperature: The first homeostatic response is that the blood vessels to the skin become constricted (narrowed), reducing the amount of warm blood flowing through the skin - A person may curl up to reduce surface area of the skin available for heat loss - Shivering produces heat Feedback Systems Pg 8 - Negative feedback system is an increase or decrease in the variab
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