Examples of Homeostasis

Rise in Blood Glucose Concentration

Stimuluso Blood glucose concentration rises above normal.

Receptoro This stimulates the islets of Langerhans in pancreas.

Self-Regulatory Corrective Mechanismo The islets of Langerhans secrete insulin into the bloodstream.o The blood transports insulin to the liver and muscles.o Insulin increases the permeability of cell surface membrane to glucose

causing the cell to absorb glucose quickly.o Insulin also causes the liver and muscles to convert the excess glucose

into glycogen.o Glycogen is then stored in the liver and muscles.

Negative Feedbacko The blood glucose concentration decreases and so insulin production

decreases. Normal

o The blood glucose concentration returns to normal condition.

Fall in Blood Glucose Concentration

Stimuluso Blood glucose concentration falls below normal.

Receptoro This stimulates the islets of Langerhans in pancreas.

Self-Regulatory Corrective Mechanismo The islets of Langerhans secrete glucagon into the bloodstream.o The blood transports glucagon to the liver and muscles.o Glucagon causes the liver and muscles to convert the stored glycogen

back into glucose.o From the liver, glucose enters the bloodstream.

Negative Feedbacko The blood glucose concentration increases and so glucagon production

decreases. Normal

o The blood glucose concentration returns to normal condition.

Rise in Water Potential in Blood

Stimuluso Water potential in blood rises above normal.

Receptoro This stimulates the hypothalamus in brain.

Self-Regulatory Corrective Mechanismo The hypothalamus stimulates the pituitary gland to release more anti-

diuretic hormone (ADH) into the bloodstream.o When ADH reaches the kidney tubules, it causes more water to be

reabsorbed by the kidney tubules.

o Thus, less water is excreted causing a less but more concentrated urine to be produced and excreted.

Negative Feedbacko The water potential in blood decreases and so ADH secretion decreases.

Normalo The water potential in blood returns to normal.

Fall in Water Potential in Blood

Stimuluso Water potential in blood falls below normal.

Receptoro This stimulates the hypothalamus in brain.

Self-Regulatory Corrective Mechanismo The hypothalamus stimulates the pituitary gland to release less anti-

diuretic hormone (ADH) into the bloodstream.o When ADH reaches the kidney tubules, it causes less water to be

reabsorbed by the kidney tubules.o Thus, more water is excreted causing a more diluted urine to be produced

and excreted.

Negative Feedbacko The water potential in blood increases and so ADH secretion decreases.

Normalo The water potential in blood returns to normal.