2013

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

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

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.

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

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

Temperature equilibrates to the increasing environmental temperature

Forces the animal to slow its biochemical reactions

Internal temperature remains constant due to metabolism

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

“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

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

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

a. Ib. Ac. Id. Ie. Af. A

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

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

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

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

Stomach – hostile environment for bacteriaGastric juice is deadly for bacteria

HCl and proteases

Old people have been exposed to more pathogens in their lifespan

Immune systems “remember” that pathogen

Older people thus have more antibodies

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

Pathogen – cold virus

Innate immune system

Physical barrier – skin

No infection – pathogen does not enter bodyh

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

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

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