FYI
potassium is absorbed from food in your small intestine. 
if your potassium levels are too low, your body may make less insulin which
​may lead to an increase in blood glucose and type 2 diabetes.
Why?...
The depolarization of their membranes of the beta cells of your pancreas triggers these cells to release insulin. This depolarization involves the movement of K+ across the membrane. So there needs to be a gradient of potassium across the membrane. Low K+ levels prevent this gradient from being maintained. We'll learn about how membranes propagate electric charges via ion transfer later this semester. Where can you get dietary potassium?
As with all things healthy...eat right ;)
ideas...greens, berries, potatoes, citrus, peanuts, bananas, avocados and wheat germ 

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

review question:

describe three homeostatic mechanisms. 

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

calcium receptors detect changes in blood calcium concentration. 

some examples of homeostatic mechanisms

while positive
​ feedback loops
​are less common

fight 

can you think of an example of an effector?

review question:

describe the three components of
​homeostasis. 

6. Potassium (K) concentration:
Potassium homeostasis is maintained primarily by your kidneys with the help of your adrenal gland and your pancreas.
​ The adrenal gland produces a hormone called aldosterone.
In your kidneys, there are aldosterone receptors. 
Aldosterone increases sodium and water reabsorption raising blood pressure.
Potassium (K+) is excreted to balance the sodium (Na+) being absorbed.

big picture...

most systems rely on
​negative feedback loops

review question:

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

 flight

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, regulating their permeability.

  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.

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

                                      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 conversion of glycogen in liver to glucose = glycogenolysis
        b. accelerating the synthesis of glucose from amino acid molecules = gluconeogenesis.
        c. stimulating adipose tissue to release fats into the bloodstream so they can be converted                to glucose...lipids broken down into glycerol/fatty acids then converted to glucose.

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

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

homeostasis

receptors detect the greater resistance in arterial walls

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 

7. blood pH:
pH is regulated by CO2 concentrations...

circulation and respiration hand in hand

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.