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BIOL 2130: FINAL EXAM
Homeostasis
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Dynamic state of equilibrium in which internal conditions vary, but always within relatively narrow limits.
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The body is in homeostasis when...
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it's needs are adequately met, and it is functioning smoothly.
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Homeostatic Control Mechanisms
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Regardless of the factor or event being regulated - variable - all homeostatic control mechanisms are processes involving at least three components.
1. Receptor.
2. Control Center.
3. Effector.
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Receptor |
type of sensor that monitors the environment, and responds to changes called stimuli, by sending information (INPUT) to the second component.
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Control center
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The input flows from the receptor to the control center along the afferent pathway. The control center determines the set point (level or range at which a variable is to be maintained). The control center also analyzes the received input and determines the appropriate response. Information (OUTPUT) then flows from the control center to third component effector along the efferent pathway.
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Effector
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provides the means for the control center's response (OUTPUT) to the stimulus. Results of the response then feed back to the influence effect of the stimulus, either reducing it (negative feedback) so the whole control process is shut off, or enhancing it (positive feedback) so that the whole process continues at even a faster rate.
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Stimulus |
produces change in the variable.
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Receptor
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detects the change.
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Input |
information sent along afferent pathway to control center.
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Output.
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information sent along efferent pathway to effector.
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Response |
Response of the effector feeds back to reduce the effect of stimulus and returns variable to homeostatic level.
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Negative Feedback Mechanisms
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-most homeostatic control mechanisms.
-output shuts off the original effect of the stimulus or reduces it's intensity.
-opposite direction of initial response to stimulus.
-ex. thermostat system
-ex. glucose levels in blood. |
All negative feedback systems have the same goal to:
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prevent sudden severe changes within the body.
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Positive Feedback Mechanisms
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-the result or response enhances the original stimulus so the response is accelerated.
-same direction of initial response.
-typically set up series of events that are self perpetuating, and that one initiated, have an amplifying or waterfall effect.
-ex enhancement of labor contractions due to oxytocin.
-ex blood clotting.
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The Cell's three major components.
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1. Plasma Membrane.
2. Cytoplasm.
3. Nucleus.
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Plasma Membrane
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bilayer of upmost importance. cell's surface, outer limiting membrane.
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Cytoplasm
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churning sea of organelles and fluid maintaining cellular function.
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Mitochondria
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Power plants
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Ribosomes
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sites of protein synthesis.
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Endoplasmic Reticulim
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-Rough- ribosomes manufacture all proteins secreted from cells. Its also the cells membrane factory.
-Smooth-
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Golgi Apparatus
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traffic director for cellular proteins. Major function is to modify, concentrate, and package the proteins and lipids made at the ROUGH Endoplasmic Reticulum.
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Lysosomes
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digest almost all kinds of biological molecules. They work best is acidic conditions.
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Nucles
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"Brain" of cell - control center.
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Fluid Mosaic Model
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double bilayer of lipid molecules that defines and separates the boundaries between intracellular (within) and extracellular (outside) areas. |
Bilayer of Lipid Molecules.
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has hydrophobic (fear of water) and hydrophilic (water loving) regions.
-aggregates of far cells due to polarity and chemical charges allow for polar heads to face extracellular region and intracellular region. |
Membrane Proteins
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1. Integral
2. Peripheral
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Integral Proteins
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-firmly inserted into lipid bilayer (has hydrophobic and hydrophilic regions)
-about 1/2 of the membrane weigh in the cell.
-important in cellular function.
-exterior and interior ONLY.
-most are transmembrane (involved in transport) which has channels and carriers for transport. |
Peripheral Proteins.
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-lipids attach loosely only to integral proteins and are easily removed without disrupting the membrane.
-some peripheral proteins are enzymes
-others are motor proteins involved in mechanical functions (changing cell shape during cell division and muscle contraction)
-most glycocalyx which are glycoproteins - fuzzy, sticky, carbohydrate rich area at cell surface.
-assists cell in differentiating itself from other cells.
-ex. sperm recognizes ovum by it's unique glycocalyx. |
Membrane Specializations
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-Microvilli.
-Tight Junctions.
-Demosomes.
-Gap Junctions. |
Microvilli |
-extensions of membrane into extracellular space.
-increases surface area of cell. |
Tight Junctions. |
protein fusion between proteins on two separate cells allowing for a strong bond that creates an impermeable junction between cells.
-ex intestinal cell. |
Demosomes |
anchoring of cells together for flexibility and resistance to tension. |
Gap Junctions
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slightly looser connection than above connections allowing certain substances to pass between cells. |
Membrane Transport Types
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1. Active.
2. Passive. |
Passive Processes.
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substances cross the membrane without any energy. Input from the cell.
-diffusion.
-osmosis.
-facilitated diffusion. |
Simple Diffusion
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-CONCENTRATION GRADIENTS:
-movement from area of higher concentration to lower concentration/
-substances diffuse directly through the lipid bilayer. ex- oxygen, carbon dioxide, fat-soluable vitamins.
-OSMOSIS:
-type of diffusion dealing with diffusion of a solvent.
-best solvent known is WATER. |
Active Processes.
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-main difference between active and passive is that active uses ENERGY (ATP)
-substances or molecules may be too large or unable to use the concentration gradient to pass alone and need active support to get across. |
Primary vs. Secondary Active Transport.
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-Primary uses ATP - energy comes directly from hydrolysis of ATP.
-Secondary- happens indirectly by energy stored in ionic gradients created by operation of primary active transport pumps.
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