Endocrine Homeostasis

Question 1

Claude Bernard

Answer 1

• French physiologist of the 19^th century
• The first to conceptualize how the various systems in the body deal with external influences
• “the stability of the composition of extracellular fluids”

Question 2

Walter Cannon

Answer 2

• Coined the term homeostasis in 1932
• Described the stability of steady state living systems displaced from equilibrium by the investiture of energy
• Homeostasis is also known as Dynamic Constancy

Question 3

Glucose Homeostasis

Answer 3

• Normal blood glucose concentration is 70-100 mg/dl
• There are several influences that can cause deviation for this set point
• Carbohydrate ingestion increases glucose
• Aerobic exercise decreases glucose

Question 4

Pathway for Blood Glucose Homeostasis

Answer 4

• Increased blood glucose
  
  • β cells in the pancreas sense increased blood glucose and secrete insulin
  • Insulin converts glucose to glycogen to be stored in liver and skeletal muscle
• Decreased blood glucose
  
  • α cells in the pancreas sense a decrease in blood glucose and secrete glucagon
  • glucagon breaks down glycogen stores to produce glucose

Question 5

Calcium Homeostasis

Answer 5

• Normal concentration in the blood and ECF is 10 mg/dl
  
  • Does not change drastically because body cannot handle large blood calcium changes
• There are several causes of deviation from the set point including
  
  • Dietary intake of calcium
  • Tissue removal of calcium
    
    • Bone, kidney, intestine

Question 6

Pathway for Calcium Homeostasis

Answer 6

• Increased blood calcium
  
  • Parafollicular cells in the Thyroid sense and increase in blood calcium and release calcitonin
  • Calcitonin stores calcium in bone to decrease blood calcium
• Decreased blood calcium
  
  • Parathyroid gland senses decrease in blood calcium and releases PTH
  • PTH releases calcium from bone

Question 7

Sodium Homeostasis

Answer 7

• Normal concentration of sodium in the blood and ECF is 142 mEq/l
• Influences that cause deviation from set point
  
  • Dietary intake of sodium
  • Sodium loss in sweat and urine

Question 8

Pathway for Sodium Homeostasis

Answer 8

• Juxtaglomerular Cells in the kidney sense a decrease in sodium and secrete Renin
• Renin is a peptidase that cleaves plasma andiotensinogen to form Angiotensin I
• Angiotensin Converting Enzyme (ACE) converts Angiotensin I to Angiotensin II
• Angiotensin II goes to the adrenal cortex and causes a release of aldosterone
• Aldosterone increases sodium and water retention

*Sodium is the most important osmolite in plasma

Question 9

Fluid Balance Homeostasis