Human Physiology- Chapter 1 summary
Human Physiology- Chapter 1 summary BIOL 2213
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This 4 page Class Notes was uploaded by Celine Notetaker on Wednesday January 20, 2016. The Class Notes belongs to BIOL 2213 at University of Arkansas taught by Dr. Hill in Fall 2014. Since its upload, it has received 45 views. For similar materials see Human Physiology in Biology at University of Arkansas.
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Date Created: 01/20/16
Chapter 1 – Homeostasis: A Framework of Human Physiology Section 1.1 1. Physiology: The study of how living organisms function 2. Pathophysiology: The study of disease states or physiology “gone wrong” Section 1.2 1. The level of organization in the body goes from cells to tissues to organs to organ systems to the organism. 2. 4 Different Tissue Types: a. Muscle Tissue i. There are 3 types of muscle cells and therefore 3 types of muscle tissues: skeletal, cardiac and smooth. They are all specialized to generate mechanical force. Contraction of skeletal muscle is under voluntary control while cardiac and smooth muscle contractions are involuntary. Smooth muscle often lines tubes in the body like the blood vessels or in the gastrointestinal tract. b. Nervous Tissue i. A neuron is a cell of the nervous system that is specialized to initiate, integrate, and conduct electrical impulses. A collection of neurons form nervous tissue, such as in the brain or the spinal cord. Neurons carry signals to and from parts of the body. Some neurons can be packed together with connective tissue to form nerves. c. Epithelial Tissue i. Epithelial cells are specialized for selective secretions, and the absorption of ions and organic molecules, and for protection. Epithelial tissue can form from any type of the various epithelial cells, which are named according to their shape. The type of epithelium that forms in a certain area reflects the function of that particular epithelium. All epithelium are attached to a basement membrane, which is an extracellular protein layer that anchors the epithelium. d. Connective Tissue i. This is the confusing type of tissue. They are made up of connectivetissue cells. There is loose connective tissue, dense connective tissue, bone, cartilage, adipose tissue, and blood. One important function of connective tissue is to form an extracellular matrix (ECM), a protein complex interspersed within the extracellular fluid. 3. The 11 organ systems in the body and their respective organs and functions can be studied on page 5, Table 11. Section 1.3 1. There are 2 body fluid compartments. There is extracellular fluid and intracellular fluid. Intracellular fluid is simply the fluid inside the cells. It makes up 67% of the total water inside the human body. Extracellular fluid, on the other hand, is made up of the fluid part of the blood, called plasma, and the fluid in between cells, called interstitial fluid. Plasma makes up 7% of the totalbody water and interstitial fluid makes up 26% of totalbody water. 2. As blood flows through capillaries, the plasma exchanges oxygen, nutrients, wastes, and other substances with the interstitial fluid. Therefore, concentrations of dissolved substances are almost identical in the plasma and interstitial fluid. The only exception is protein concentration, which always has a higher concentration in the plasma. Section 1.4 1. Homeostasis is a relatively stable condition of the internal environment that results from regulatory system actions. 2. Physiology variables that are regulated: + a. Blood pressure, plasma Na concentration, plasma glucose levels, plasma pH, plasma oxygen concentration, and body temperature Section 1.5 1. Mechanisms that mediate homeostatic responses are called homeostatic control systems. An example of this is when room temperature drops. The body loses heat and body temperature drops. The body then responds by constricting blood vessels, shivering, etc. to decrease heat loss and increase heat production to return the body temperature to a normal value. 2. Steady state is defined as a system in which a particular variable is not changing but in which energy must be added continuously to maintain a constant condition. a. The set point is the steady state value controlled by homeostatic control systems 3. Equilibrium is defined as a system in which a particular variable is not changing but no input of energy is required to maintain the constancy. 4. Feedback Systems a. Negative Feedback: a system in which an increase or decrease in the variable being regulated brings about responses that tend to move the variable in the direction opposite the direction of the original change b. Positive Feedback: a system in which an initial disturbance sets off a chain of events that increases the disturbance even further c. Feedforward System: an anticipatory action that anticipates changes in regulated variables such as internal body temperature or energy availability, improves the speed of the body’s homeostatic responses, and minimizes fluctuations in the level of the variable being regulated (it reduces the amount of deviation from the set point) Section 1.6 1. A reflex is a specific, involuntary, unpremeditated, unlearned response to a particular stimulus. a. On the other hand, a learned/acquired reflex is a behavior that appears to be stereotypical and automatic but which in fact results from considerable conscious effort to be learned 2. A reflex arc is the pathway mediating a reflex. The first component is the stimulus, which is a detectable change in the internal or external environment, such as a change in temperature. A receptor detects the change. The stimulus acts upon the receptor in such a way that the receptor produces a signal that is relayed to an integrating center by an afferent pathway. The integrating center receives signals from many receptors, which respond to different types of stimuli. Thus, the output of an integrating center reflects the net effect of the total afferent input. The output of the integrating center is sent by an efferent pathway to an effector, whose change in activity constitutes the overall response of the system. When the response causes a decrease in the magnitude of the stimulus, then we have a negative feedback system, a typical homeostatic control system. 3. Nerves are common afferent or efferent pathways. The major effectors of biological control systems are muscles and glands. Muscles are effectors attached to nerves that receive efferent signals from various integrating centers. Glands are effectors that produce hormones, chemical messengers that circulate throughout the body. 4. In addition to reflexes, local homeostatic responses are important for homeostasis. The responses are initiated by a change in the stimulus (from the internal or external environment), just like reflexes. However, the stimulus causes a direct alteration of cell activity with the net effect of counteracting the stimulus. Unlike a reflex, the entire sequence occurs only in the area of the stimulus. a. Example: When a cell becomes metabolically active, it secretes substances into the interstitial fluid that dilates blood vessels so that there is a higher rate of exchange of nutrients, oxygen, and waste in that particular area. Section 1.7 1. Chemical messengers are chemicals that aid in intercellular communication. There are 3 categories of chemical messengers: a. Hormones i. Hormone secreting cells release hormones to communicate with target cells. The blood acts as a delivery system. The glands responsible for secreting hormones are the endocrine glands. b. Neurotransmitters i. Chemical messengers that are released from the endings of neurons onto other neurons, muscle cells, or gland cells. These chemicals diffuse through extracellular fluid separating the neuron from the target cell, and are therefore not released into the blood, like hormones. c. Paracrine substances i. These are involved in local homeostatic responses. Paracrine substances are released by cells into the extracellular fluid once a stimulus has been detected. Paracrine substances diffuse to neighboring cells. Autocrine substances are substances produced by the cell to be reused by the same cell. Section 1.8 2. Adaptation denotes a characteristic that favors survival in specific environments. 3. Acclimatization is the improved functioning of an already existing homeostatic system. 4. Biological rhythms add an anticipatory component to homeostatic control systems and a feedforward system can operate with no detectors. A Circadian rhythm is a 24 hour biological rhythm that can be the waking and sleeping cycle, body temperature, hormone concentrations in the blood, and the excretion of ions in urine. 5. Definitions: a. Phase Shift – a resetting of the circadian clock due to altered environmental cues b. Pacemaker – neurons that set a rhythm of biological clocks independent of external cues; any neuron or muscle cell that has an inherent autorhythmicity, and determines activity pattern of other cells Section 1.9 1. Pool – the readily available quantity of a chemical substance in the body. It is often identical to the amount present in the extracellular fluid. c. Negative balance – loss exceeds gain, so that the total amount of the substance in the body is decreasing d. Positive Balance – gain exceeds loss, so that the total amount of the substance in the body is increasing e. Stable Balance – gain equals loss 6. Sources of gain in the body are air, food, and synthesis in the body. Sources of loss are metabolism and excretion from body via the lungs, GI tracts, kidneys, skin, or vagina. Sources that are reversible (forms of both gain and loss)
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