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2013
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Maintaining specific parameters of the internal environment
It’s important to maintain because all parameters (pH, ion concentration, oxygen and CO2 levels, temperature) need to stay at an optimal steady state
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Insulin is an effector, as it’s activity reduces the amount of glucose in the blood
Optimal concentration of glucose in the blood is the set point.
The actual level of glucose in the blood is the feedback information
Insulin is an effector signal in that when it binds to receptors on target cells, it changes the activity of these effectors in that they increase their rate of glucose absorption. – This reduces the glucose level in the blood, removing the stimulus that caused insulin secretion by the pancreas – this is negative feedback
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Positive feedback The increase in pepsin formation leads
to more pepsin formation Rather than returning the system to a
setpoint, the process amplifies the conversion of pepsinogen to pepsin.
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Negative Feedback It is a drinking response to low bp When low bp causes sensory neurons to
provide feedback information that bp has decreased, reflexes are activated to restore optimal bp
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Positive feedback Clumping of platelets reduces the loss of
blood from an injured vessel Clumped platelets at an injury site
release a chemical signal that further enhances clumping of more platelets, helping to seal the leak in the injured vessel and reduce the loss of precious blood
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Temperature equilibrates to the increasing environmental temperature
Forces the animal to slow its biochemical reactions
Internal temperature remains constant due to metabolism
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Lipid soluble – so they can pass thru phospholipid membranes of cells
Don’t dissolve well in watery blood plasma, so they circulate to carrier proteins
Water soluble – so they are easily transported in the blood
They can’t cross membranes easily (due to size) but the receptor proteins for these signals are on the plasma membranes of target cells
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“downregulation” reduces an organism’s sensitivity to the hormone
So in Type II diabetes, chronically high levels of the hormone insulin (usually caused by excessive carb intake) downregulate production of insulin receptors throughout the body
Cells become less sensitive to the hormone insulin
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a. FALSE – Hypothyroid goiter results when there is not enough circulating thyroxine to turn off thyroid-stimulating hormone or TSH production
b. TRUE – The levels of TSH are high in people with hypothyroid goiter because there is not enough thyroid hormone cirulating to turn off TSH production in the anterior pituitary gland
c. TRUE – The levels of TRH are abnormally high for the same reason as give in part b
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Ingestion of excessive amounts of foods high in Ca will cause calcium levels in the bloodstream to rise
This inhibits the secretion of parathyroid hormone (PTH)
Therefore the PTH levels of “Uncle” will be low relative to a person with a more normal diet
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a. Ib. Ac. Id. Ie. Af. A
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Proteins that bind specifically to antigenic sites of molecules/cells that are identified by the immune system as “nonself”
Specific for a certain pathgen
Can bind small peptides to cell surfaces so that antigens can be recognized
Can bind a variety of potential peptide targets
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Similar in that they are both types of WBC’s that originate in the bone marrow
Part of the natural immune system
Each represents one of the 2 major classes of WBC’s
Different in that phagocytes are non-specific destroying invading microorganisms by phagocytosis where lymphocytes are specific to one antigen
Phagocytes are involved in innate and adaptive. Lymphocytes are only involved in adaptive
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The skin presents a physical barrier that bacteria can rarely penetrate.
Saltiness and acid on skin does not promote bacterial growth
Numerous bacteria and fungi that normally reside on skin compete with pathogens for space and nutrients
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Saliva prevents infection by bacteria because it contains lysozymes – enzyme that cleaves bacterial cell walls
If it gets into nasal passage, mucus provides line of defense.
If it get swallowed, peristalsis and cilia movement helps move it to the acidic stomach
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Stomach – hostile environment for bacteriaGastric juice is deadly for bacteria
HCl and proteases
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Old people have been exposed to more pathogens in their lifespan
Immune systems “remember” that pathogen
Older people thus have more antibodies
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Both possess special membrane receptors that bind to antigens on cell surface
Response is differentT helper cell binding results in activation of
adaptive immune responseCytotoxic T cell binding results in the death
of the cell carrying the antigen
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Pathogen – cold virus
Innate immune system
Physical barrier – skin
No infection – pathogen does not enter bodyh
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Pathogens in seawater swallowed Innate immune system First line of defense – digestive system
mucus and gastric juices Some pathogens are destroyed Some pathogens survive and invade Second line of defense – phagocytes, natural
killer cells, MHC, interferons, inflammation Rise in internal body temperature Pathogens destroyed Body temperature returns to normal
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Project to central nervous system
Information coded from them affects what happens next in the central nervous system
Project OUT of the central nervous system
Information coded from them effect change in the periphery, such as muscle contraction or gland secretion
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Sodium potassium pump uses the energy of ATP hydrolysis to actively expel Na+ out of the cell and K+ comes into the cell
This causes the concentration of Na+ to be higher outside the cell and the K+ concentration to be higher inside the cytoplasm
creates a concentration gradient for both ions
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