Chapter 1 Homeostasis and Feedback Systems Six levels of structural organization Chemical level atoms to molecules Cellular level molecules are organized into cells Tissue level groups of similar cells work together Organ level two or more tissues become an organ System level related organs with common functions Organismal level all of the cells tissues and organ system become a human Homeostasis the maintenance of relatively constant conditions inside the body although conditions within the body are stable this is a result of many dynamic processes that constantly adjust internal activities to match changing needs balance equilibrium Homeostasis Control Mechanism Body Fluids volume and composition of the various fluids within our body are carefully regulated can be divided into intracellular fluid the fluid inside our cells and extracellular fluid all other body fluids other than the ones inside our cells extracellular can be divided into different categories according to location Interstitial fluid the fluid between cells and tissues Plasma the fluid component of blood Lymph the fluid in our lymphatic vessels Cerebrospinal Fluid CSF the fluid within the CNS Synovial Fluid the fluid within most joints Feedback Systems 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 1 Receptor detects changes in controlled conditions 2 Control Center decides the type and amount of response required 3 Effector reacts to signals from the control center and produces the required response o EXAMPLE OF NEGATIVE FEEDBACK SYSTEM Blood Pressure Regulation Three essential components 1 Baroreceptors detect changes in blood pressure and communicate with the brain 2 The brain interprets information and sends signals to the heart and blood vessels 3 Heart and blood vessels alter their activities based on signals from the brain Resulting in the blood pressure being restored to normal Positive Feedback Systems are important in specific situations when a very rapid or very strong effect is desired Unlike negative feedback here the response is the same as that caused by the initial change A stimulus causes a response that reinforces the effect of the stimulus A positive feedback cycle must be stopped or limited by some event or condition outside of the cycle Chapter 3 Diffusion osmosis membrane transports resting potential and protein synthesis Cells are made of three main parts 1 The plasma membrane flexible outer surface of the cell that separates the intracellular fluid from the extracellular fluid It is the major means of communication cells use to communicate with other cells and the outside environment 2 The cytoplasm numerous organelles surrounded by the cytosol the intracellular fluid 3 The nucleus large organelle that contains the cells chromosomes The plasma membrane a bilayer of phospholipids provides a structural foundation a variety of membrane proteins interact with the lipids all lipids and many proteins are able to move freely Phospholipid bilayers are effective barriers for polar and charged molecules and ions They are most abundant Cholesterol and glycolipids are other two types of lipids Molecules that are soluble in fats cross through the phospholipid bilayer ones that aren t through proteins The phospholipid bilayer has a head that is hydrophilic soluble in water and 2 tails that are hydrophobic Integral Proteins Transmembrane proteins a type of integral proteins from one side of lipid bilayer membrane to the other Ion Channel allows specific ion to move through the water filled pore Most plasma membranes include specific channels for several common ions Carrier channel Carries specific substances across membrane by changing shape Receptor Recognizes specific ligand and alters cell s function in some way Peripheral Proteins on the surface of the membrane that are not embedded in the lipid bilayer They attach loosely to integral proteins Active vs Passive Processes Passive Processes Spontaneous no energy required in the passive processes Chemicals move based on their kinetic energy Higher to lower concentration downhill Examples simple diffusion facilitated diffusion osmosis Occurs if lipid soluble small and assisted by carrier molecule Active Processes Used stored energy Energy input is required for chemicals to move Lower to higher concentration uphill Examples primary and secondary active transport endocytosis Passive Transport Diffusion The rate of diffusion depends on several things such as concentration gradient temperature temp increase effects diffusion mass of diffusing ion molecule membrane surface area longer distance slower movement and diffusion distance In order to diffuse there must be a difference in concentration Net diffusion stops when concentration is equal homeostasis and equilibrium is met There has to be a difference in concentration gradient High to Low o Simple diffusion non polar molecules and lipid soluble substances move directly through the lipid bilayer dependent on the concentration gradient No energy required and no proteins needed Examples lipids fats triglycerides gases oxygen and carbon dioxide higher on the inside of the cell and diffuses out Integral proteins help with facilitated diffusion There are two types of Facilitated diffusion depending on the size of the molecule channels smaller and carrier larger o Ion channel facilitated diffusion water soluble integral proteins needed moves through water filled protein channels Examples used for ions or electrolytes sodium potassium calcium and chloride for sodium from high to low diffusion but can be active transport if sodium moves from low to high o Carrier mediated facilitated diffusion polar molecules are transported this way it is water soluble and uses integral proteins binding to protein carriers in the membrane and ferried across for bigger molecules Examples glucose and amino acids KNOW WHICH EXAMPLES GO TO WHICH FORM OF DIFFUSION but know that they can also be active transport depending on what direction they move in or out of the cell Osmosis Movement of water instead of solutes water moves in response to differences in solute concentrations and water always moves toward the higher solute level Water follows solutes the solutes don t change water just diffuses to more solutes OSMOLARITY total concentration of a solute in a
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