Chapter 1 An Introduction to the Human Body EXAM Homeostasis the existence and maintenance of a relatively constant PET3322 environment within the body Examples of stable conditions are blood glucose body temperature and blood pressure Small amounts of fluid surround each body cell and for a cell to function normally the volume temperature and chemical content of this fluid must remain within a narrow range Ex Body temperature increases in a hot environment or decreases Our bodies cannot stay perfectly stable however they fluctuate very little in a cold environment around the set point The organ system helps keep the body s internal environment relatively constant Body fluids carefully regulated Fluids include cells Volume and composition of various fluids within our bodies are o Intracellular fluid fluid inside our cells Extracellular fluid all body fluids other than the ones inside our o Interstitial fluid fluid between cells in tissues o Plasma the fluid component of blood o Lymph the fluid in our lymphatic vessels o Cerebrospinal fluid csf the fluid within the cns o Synovial fluid fluid within most joints Negative Feedback most of the body is regulated by this and it maintains homeostasis Negative feedback systems act to stabilize the body in the face of changing external and internal conditions These systems cause an opposite response to the initial change and so are self limiting Three essential components Baroreceptors detect changes in blood pressure and communicate Brain interprets info and sends signals to the heart and blood Heart and blood vessels alter their activities based on signals from with the brain vessels the brain Three components to negative feedback 1 Receptor detects changes in controlled conditions 2 Control center receives information about the changes from the receptor and decides the type and mount of response required 3 Effector reacts to signals from control center and produces the required response Ex Maintaining normal blood pressure o 1 Receptors that monitor blood pressure are located within large blood vessels near the heart and head o 2 A control center in the brain receives signals sent through nerves from the receptors The control center evaluates information and sends signals through nerves to the heart o 3 The heart is the effector and the heart rate increases or decreases in response to signals from the brain o If the blood pressure increases slightly receptors detect that change and send the info to the control center in the brain The control center causes the heart rate to decrease lowering the blood pressure OPPOSITE o If the blood pressure decreases slightly receptors detect that change and send the info to the control center in the brain The control center causes the heart rate to increase which elevates the blood pressure o of the stimulus Positive Feedback a stimulus causes a response that reinforces the effect Ex During blood loss a chemical responsible for blood clot formation is thrombin The body stimulates production of even more thrombin The body goes back to homeostasis Ex Birth near the end of the pregnancy the baby s larger size stretches the uterus Two main principles 1 Many disease states result from the failure of negative feedback mechanisms to maintain homeostasis 2 Some positive feedback mechanisms can be detrimental instead of helpful o ex of detrimental positive feedback mechanism inadequate delivery of blood to cardiac heart muscle o Contraction of cardiac muscle generates blood pressure and the heart pumps blood to itself through system of blood vessels on the outside of the heart Blood pressure must be maintained to ensure adequate delivery of blood to the cardiac muscle o Following extreme blood loss blood pressure decreases to the point that the delivery of blood to cardiac muscle is inadequate As a result the cardiac muscle does not function normally o The heart pumps less blood which causes the blood pressure to drop even further a deviation further from the setpoint The additional decrease in blood pressure further reduces blood delivery to cardiac muscle and the heart pumps even less blood Which again decreases the blood pressure This can make the heart stop beating and result in death CH 3 CELL BIOLOGY 06 02 2015 Plasma membrane the flexible outer surface of the cell Cytoplasm contains numerous organelles surrounded by cytosol Nucleus large organelle that contains the cells chromosomes Plasma Membrane Intracellular substances inside the cell Extracellular substances outside the cell Membrane potential an electrical charge difference across the plasma membrane which is a result of the cell s regulating of ion movement into and out of the cell Outside of membrane s positively charged compared to the inside of the membrane because of gathering ions along outside and inside Glycocalyx collection of glycolipids glycoproteins and carbohydrates on the outer surface of the plasma membrane Membrane lipids phospholipids form a lipid bilayer a double layer of phospholipid molecules because they have a polar charged head and a nonpolar uncharged tail Hydrophilic water loving heads are exposed to aqueous extracellular and Hydrophobic water fearing tails face on another in the interior of the intercellular fluids of the cell plasma membrane Fluid mosaic model plasma membrane is neither rigid nor static in structure but is highly flexible and can change its shape and composition though time Cholesterol major lipid in the plasma membrane and is interspersed among the phospholipids The amount determines fluid nature of the membrane Fluid nature provides allows o Distribution of molecules within the membrane o Phospholipids automatically reassembled if membrane is damaged o Membranes can fuse with each other Membrane permeability phospholipid bilayers Small and or non polar molecules are able to pass easily through The permeability of membranes to ions polar molecules depends on the number of specific transport proteins How quick the ions and molecules cross membranes depends on o Concentration gradient of ion molecule PRIMARY o Electron gradients that can speed or slow the movement of ions SECONDARY Membrane proteins Integral membrane proteins penetrate deeply into the lipid bilayer in many cases extending from one surface to the other and can form channels through the membrane Peripheral membrane proteins attached to either the inner or the outer surfaces of the lipid bilayer Channel proteins one or more integral
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