review question:

explain how

​ three homeostatic mechanisms operate. 

digest

​1. receptors detect change =stimulus
2. coordination center interprets change
3. effectors carry out response to change

baroreceptors detect the level of resistance in arterial walls

too much glucose in blood

3. blood calcium level:
​Calcium homeostasis relies on the release of hormones.
Hormones are circulating ligands that bind to specific receptors and trigger a response within the cells that exhibit those receptors.  
Blood calcium too high ->
Thyroid gland releases calcitonin which increases the uptake of calcium by bone reducing calcium in the blood
Blood calcium too low ->
Parathyroid glands release PTH which triggers bone to release of calcium 

vasoconstriction increases resistance = rise in blood pressure

dehydration...

review question:

describe the three components of
​homeostasis. 

4. Osmoregulation:
water concentration in blood is controlled by:
osmoreceptors in the hypothalamus ->
 send info to the pituitary ->
pituitary responds by secreting  ADH = anti-diuretic hormone 
ADH is made by the hypothalamus and stored in the pituitary gland.
ADH targets kidney tubules, more water is reabsorbed by kidney into blood.

  Higher water concentration means high blood volume blood pressure.
 concentration of solutes (Na, K, Cl, CO2) in your blood must be isotonic.
Osmotic sensors stimulate kidneys to reabsorb or release water. 
They also regulate thirst.

rest

vasodilation
decreases resistance = lowers blood pressure

calcium receptors detect changes in blood calcium concentration. 

2. blood pressure:
the hypothalamus 
​raises or lowers blood pressure by
adjusting the sympathetic nervous system.

while positive
​ feedback loops
​are less common

too little glucose in blood

fight 

can you think of an example of an effector?

acidosis =
pH too low=
​too much CO2

review question:

explain how a positive feedback loop differs from a negative feedback loop.

homeostasis
​is a self-regulating, dynamic process by which an organism strives to maintain internal equilibrium while adjusting to changing external conditions.

your hypothalamus is an area in your brain that regulates your  autonomic nervous system and pituitary gland.
it is "in charge" of:
body temperature, thirst, hunger, sleep, behavior/emotions

homeostatic mechanisms follow one of two patterns: 
1. ​negative feedback loop
2. positive feedback loop

alkalosis =
pH too high=
​too little CO2

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homeostasis

7. blood pH:
pH is regulated by CO2 concentrations...
as CO2 concentrations rise, blood pH declines​

some examples of homeostatic mechanisms

1. body temperature:
 thermoregulatory center of the hypothalamus functions as a thermostat
receives info from peripheral nerve receptors stimulated by external cold/heat
and internal receptors that monitor the temp of the blood circulating about the hypothalamus. The maximum body temperature a human can survive is 108°F. 

big picture...

most systems rely on
​negative feedback loops

 flight

                                      5. blood glucose concentration:
                 Insulin and glucagon work antagonistically to maintain  blood glucose levels.

When blood sugar level is elevated:
       beta cells of pancreas respond by secreting insulin. 
       cells increase glucose uptake and liver converts blood glucose to glycogen.  

​When blood sugar level is too low:
        alpha cells of pancreas respond by releasing glucagon.
        a. stimulating the liver to convert glycogen to glucose
        b. increasing the production of glucose from amino acids 
        c. stimulating fat tissue to release fats so they can be converted to glucose.