Fluid & Electrolyte Balance
, Lecture 19 Introduction
• Fluid & Electrolyte Homeostasis
• Regulation of Blood Pressure and Volume
• Water Balance
– Vasopressin (ADH) and Aquaporins
• Countercurrent Exchange
• Sodium Balance
– Aldosterone and ANP
– Renin-Angiotensin System (RAS)
• Potassium Balance
• Acid-Base Balance
– Mechanisms to maintain pH homeostasis
– Acidosis and Alkalosis
, Fluid & Electrolyte Homeostasis
• The human body is in a state of constant flux.
• Over the course of a day, we ingest about 2 L of fluid that contains 6-15 g
of NaCl.
• In addition, we take in varying amounts of other electrolytes, including K+,
H+, Ca2+, HCO3-, and HPO42-.
• The body’s task is to maintain mass balance: what comes in must be
excreted if the body does not need it.
• Although physiological mechanisms that maintain fluid and electrolyte
balance are important, behavioral mechanisms also play an essential role.
- Thirst is critical because drinking is the only normal way to replace lost
water.
- Salt appetite is a behavior that leads people and animals to seek and
ingest salt.
, Fluid & Electrolyte Homeostasis
Na+ and water ECF volume and osmolarity
K+ Cardiac and muscle function
Ca2+ Exocytosis, muscle contractions, and other
functions
–
H+ and HCO3 pH balance
Body must maintain mass Excretion routes: kidney, feces, sweat, and
balance lungs
, Lecture 19 Introduction
• Fluid & Electrolyte Homeostasis
• Regulation of Blood Pressure and Volume
• Water Balance
– Vasopressin (ADH) and Aquaporins
• Countercurrent Exchange
• Sodium Balance
– Aldosterone and ANP
– Renin-Angiotensin System (RAS)
• Potassium Balance
• Acid-Base Balance
– Mechanisms to maintain pH homeostasis
– Acidosis and Alkalosis
, Fluid & Electrolyte Homeostasis
• The human body is in a state of constant flux.
• Over the course of a day, we ingest about 2 L of fluid that contains 6-15 g
of NaCl.
• In addition, we take in varying amounts of other electrolytes, including K+,
H+, Ca2+, HCO3-, and HPO42-.
• The body’s task is to maintain mass balance: what comes in must be
excreted if the body does not need it.
• Although physiological mechanisms that maintain fluid and electrolyte
balance are important, behavioral mechanisms also play an essential role.
- Thirst is critical because drinking is the only normal way to replace lost
water.
- Salt appetite is a behavior that leads people and animals to seek and
ingest salt.
, Fluid & Electrolyte Homeostasis
Na+ and water ECF volume and osmolarity
K+ Cardiac and muscle function
Ca2+ Exocytosis, muscle contractions, and other
functions
–
H+ and HCO3 pH balance
Body must maintain mass Excretion routes: kidney, feces, sweat, and
balance lungs
