Reading Notes_ Unit 1 PDF

- Physiology is the study of the normal functioning of a living organism and its component parts, including all its chemical and physical processes. - - atoms of elements link together to form molecules. Collections of molecules in living organisms form cells, the smallest unit of struc...

- Physiology is the study of the normal functioning of a living organism and its component parts, including all its chemical and physical processes. - - atoms of elements link together to form molecules. Collections of molecules in living organisms form cells, the smallest unit of structure capable of carrying out all life processes. - Collections of cells that carry out related functions are called tissues - Tissues form structural and functional units known as organs - groups of organs integrate their functions to create organ systems - The integumentary system composed of the skin, forms a protective boundary that separates the body’s internal environment from the external environment (the outside world). - The musculoskeletal system support and body movement. - Four systems exchange materials between the internal and external environments. - The respiratory (pulmonary) system exchanges gases; the digestive (gastrointestinal) system takes up nutrients and water and eliminates wastes; the urinary (renal) system removes excess water and waste material; and the reproductive system produces eggs or sperm. - The remaining four systems extend throughout the body. - The circulatory (cardiovascular) system distributes materials by pumping blood through vessels. The nervous and endocrine systems coordinate body functions. - immune system, which includes but is not limited to the anatomical structures known as the lymphatic system. The specialized cells of the immune system are scattered throughout the body. They protect the internal environment from foreign substances by intercepting material that enters through the intestines and lungs or through a break in the skin. In addition, immune tissues are closely associated with the circulatory system. - The function of a physiological system or event is the “why” of the system or event - In contrast, most physiologists study physiological processes, or mechanisms—the “how” of a system. - The mechanistic approach to physiology examines process. - Although function and mechanism seem to be two sides of the same coin, it is possible to study mechanisms, particularly at the cellular and subcellular level, without understanding their function in the life of the organism. - We focus on themes most related to physiology: structure-function relationships, biological energy use, information flow within an organism, and homeostasis and the control systems that maintain it. - The integration of structure and function extends across all levels of organization, from the molecular level to the intact body. This theme subdivides into two major ideas: molecular interactions and compartmentation. - The ability of individual molecules to bind to or react with other molecules is essential for biological function. - The ability of individual molecules to bind to or react with other molecules is essential for biological function. - Compartmentation is the division of space into separate compartments. Compartments allow a cell, a tissue, or an organ to specialize and isolate functions.  - Growth, reproduction, movement, homeostasis—these and all other processes that take place in an organism require the continuous input of energy. - Information flow in living systems ranges from the transfer of information stored in DNA from generation to generation (genetics) to the flow of information within the body of a single organism. - In the human body, information flow between cells coordinates function. Cell-to-cell communication uses chemical signals, electrical signals, or a combination of both. Information may go from one cell to its neighbors (local communication) or from one part of the body to another (long-distance communication) - Organisms that survive in challenging habitats cope with external variability by keeping their internal environment relatively stable, an ability known as homeostasis - Homeostasis provides stability in functions such as body temperature, heart rate, and blood pressure - If the body fails to maintain homeostasis of the critical variables, If the body fails to maintain homeostasis of the critical variables - In both internally and externally caused diseases, when homeostasis is disturbed, the body attempts to compensate - If the compensation is successful, homeostasis is restored. If compensation fails, illness or disease may result. - For multicellular animals, it is the watery internal environment that surrounds the cells, a “sea within” the body called the extracellular fluid (ECF) - Extracellular fluid serves as the transition between an organism’s external environment and the intracellular fluid (ICF) inside cells - When physiologists talk about homeostasis, they are speaking of the stability of the body’s internal environment—in other words, the stability of the extracellular fluid compartment (ECF). - Steady state is not the same as equilibrium - Equilibrium implies that the composition of the body compartments is identical. - To maintain homeostasis, the human body monitors certain key functions, such as blood pressure and blood glucose concentration, that must stay within a particular operating range if the body is to remain healthy. - The simplest form of control is local control, which is restricted to the tissue or cell involved - In local control, a relatively isolated change occurs in a tissue. A nearby cell or group of cells senses the change in their immediate vicinity and responds, usually by releasing a chemical. The response is restricted to the region where the change took place—hence the term local control. - Changes that are widespread throughout the body, or systemic in nature, require more complex control systems to maintain homeostasis.  - Changes that are widespread throughout the body, or systemic in nature, require more complex control systems to maintain homeostasis. - A physiological reflex can be broken down into two parts: a response loop and a feedback loop - a response loop has three primary components: an input signal, an integrating center to integrate the signal, and an output signal. - Response Loops Begin with a Stimulus - Feedback Loops Modulate the Response Loop - Negative Feedback Loops Are Homeostatic - For most reflexes, feedback loops are homeostatic—that is, designed to keep the system at or near a setpoint so that the regulated variable is relatively stable - A pathway in which the response opposes or removes the signal is known as negative feedback - Negative feedback loops stabilize the regulated variable and thus aid the system in maintaining homeostasis. - Negative feedback loops can restore the normal state but cannot prevent the initial disturbance - In a positive feedback loop, the response reinforces the stimulus rather than decreasing or removing it. In positive feedback, the response sends the regulated variable even farther from its normal value. This initiates a vicious cycle of ever-increasing response and sends the system temporarily out of control - Because positive feedback escalates the response, this type of feedback requires some intervention or event outside the loop to stop the respons - Feedforward Control Allows the Body to Anticipate Change - Negative feedback loops can stabilize a function and maintain it within a normal range but are unable to prevent the change that triggered the reflex in the first place. - These anticipatory responses are called feedforward control - In physiological systems, the setpoints for many regulated variables are different from person to person, or may change for the same individual over a period of time. Factors that influence an individual’s setpoint for a given variable include normal biological rhythms, inheritance, and the conditions to which the person has become accustomed. - The adaptation of physiological processes to a given set of environmental conditions is known as acclimatization when it occurs naturally. Summary: - The human body has 10 physiological organ systems: integumentary, musculoskeletal, respiratory, digestive, urinary, immune, circulatory, nervous, endocrine, and reproductive. - The function of a physiological system or event is the “why” of the system. The mechanism by which events occur is the “how” of a system. The teleological approach to physiology explains why events happen; the mechanistic approach explains how they happen. - The function of a physiological system or event is the “why” of the system. The mechanism by which events occur is the “how” of a system. The teleological approach to physiology explains why events happen; the mechanistic approach explains how they happen. - Homeostasis is the maintenance of a relatively constant internal environment. Variables that are regulated to maintain homeostasis include temperature, pH, ion concentrations, oxygen, and water. - Failure to maintain homeostasis may result in illness or disease. - The law of mass balance says that if the amount of a substance in the body is to remain constant, any input must be offset by an equal loss. - Regulated variables have a setpoint and a normal range. - The simplest homeostatic control takes place at the tissue or cell level and is known as local control. - The simplest homeostatic control takes place at the tissue or cell level and is known as local control. - Reflex pathways can be broken down into response loops and feedback loops. - A response loop begins when a stimulus is sensed by a sensor. The sensor is linked by the input signal to the integrating center that decides what action to take. The output signal travels from the integrating center to a target that carries out the appropriate response. - In negative feedback, the response opposes or removes the original stimulus, which in turn stops the response loop. - In positive feedback loops, the response reinforces the stimulus rather than decreasing or removing it. This destabilizes the system until some intervention or event outside the loop stops the response. - In negative feedback, the response opposes or removes the original stimulus, which in turn stops the response loop. - Feedforward control allows the body to predict that a change is about to occur and start the response loop in anticipation of the change.