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Tissue
- -stable association of differentiated cells
- -humans have over 200 types
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Organ
-body structure that integrates different tissues and carries out a specific function
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Desmosomes
- -adhering junctions that "spot-rivet" cells in random places
- -anchor cells together in tissues
- -can stretch a lot
- -used in cell to cell communication
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Tight Junctions
- -also known as occluding junctions
- -form a tight waterproof junction between cells
- -major proteins claudins and occludins
- -anchor the actin portion of the cytoskeleton together
- -can have tight or leaky junctions
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Blood-Brain Barrier
- -separation of circulating blood from the brain extracellular fluid
- -made up of tight junctions around the capillaries that do not exist in normal circulation
- -allow diffusion of small hydrophobic molecules only
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Gap Junctions
- -communicating junctions made up of connexons
- -directly connects the cytoplasm of the cells
- -similar to plasmodesmata in plants
- -highly expressed in the heart to allow rapid transport of electrical signals to allow the heart to beat in a paced interval
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Membrane Nanotubes
- -aka cytonemes
- -long, thin tubes that connect animal cells over long distances(100um)
- -transfer of nucleic acid between cells
- -can carry vesicles and organelles
- -can also spread toxins (HIV, prions etc)
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Extracellular Matrix
- -provides essential structural support
- -made up of polysaccharide gels and elastic proteins
- -fill any and all spaces between cells
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Collagen and Elastic Glycoproteins
-can be calcified to form shells, bones and spicules
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Plasma
- -make up about 55% of total blood volume
- -mostly water, but contains dissolved proteins and clotting factors
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Serum
- -the component of blood that is neither a blood cell nor a clotting factor
- -it is the plasma with the fibrinogens(clotting factors) removed
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Movement of Water
- -fluid moves easily in and out of cells, osmosis
- -swollen and shrunken cells are more vulnerable
- -hypertonic=more solute than compared(water will flow in)
- -hypotonic=less solute than compared(water will flow out)
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Homeostasis
- -process where the body's internal environment is kept stable
- -37°C
- -pH 7.365
- -blood glucose 5mmol/L
- -concentration of water vs electrolytes
- -blood pressure 120/80 mm Hg
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Homeostatic Regulation
- -mainly by secretion of hormones
- -by Hypothalamus, pituitary, pancreas, thyroid and parathyroid, adrenals
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Regulation of Blood Glucose
- -insulin secreted by β cells of pancreas
- -when glucose levels are high, it is converted to glycogen
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Glucagon
- -secreted by the α-cells of the pancreas and signals glycogenlysis , the conversion of non carbohydrate carbon sources to glucose(gluconeogenesis)
- -prevents hypoglycaemia
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Regulators
-maintain parameters at a constant level over wide ambient environmental changes
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Conformers
- -allow the environment to determine parameters
- -endothermic animals(warm blooded)
- -ectothermic animals(cold blooded)
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Avoiders
-change their location in the environment
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Endotherm
- -organism that produces internal heat
- -warm blooded animals
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Ectotherm
- -rely on environmental sources of heat
- -cold blooded animals
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Homeotherm
- -organism that maintains a stable internal temp regardless of external influence
- -often higher temp than immediate environment
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Poikilotherm
- -organism who's internal temp varies widely depending on the environment
- -lots of fish and reptiles
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Homeostatic Control Mechanisms
- -four interdependent components
- -set point=normal value for variable
- -sensor/receptor=monitors the variable
- -integrator=compares signal to set point
- -effector=compensates for any deviations from set point
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Negative Feedback
- -upon signal reception, change occurs to depress the deviation
- -signal says decrease in body temp, response to increase temp (shivering)
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Positive Feedback
- -accelerate or enhance output from stimulus
- -push levels out of normal range into a supra physiological response
- -oxytocin release during childbirth to enhance contractions
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Feedforward Regulation
- -learned behaviour to prepare for a change before it occurs
- -speeds up response and therefor minimizes deviations from the set point
- -ex. horse trained to get ready for a race, Pavlov's dogs
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