Define electrolyte and homeostasis. Provide examples of electrolytes and describe the main types of homeostatic control mechanisms.

Here are the answers to questions Q4, Q5, and Q6 from your physiology test.

Q4:

1. An electrolyte is a substance that, when dissolved in a solvent (like water), produces ions and can conduct electricity.

   • The main types are strong electrolytes (which dissociate completely in solution, e.g., NaCl) and weak electrolytes (which dissociate only partially, e.g., acetic acid).

2. Examples of electrolytes:

   • Extracellular Cations:
     • Sodium ($\text{Na}^+$)
     • Calcium ($\text{Ca}^{2+}$)
   • Extracellular Anions:
     • Chloride ($$\text{Cl}^-$)
     • Bicarbonate ($$HCO_3^-$)
   • Intracellular Cations:
     • Potassium ($\text{K}^+$)
     • Magnesium ($\text{Mg}^{2+}$)
   • Intracellular Anions:
     • Phosphate ($\text{HPO}_4^{2-}$)
     • Proteins (negatively charged)

Q5:

1. Homeostasis is the ability of the body to maintain a stable internal environment despite changes in external conditions. It involves a dynamic equilibrium of physiological processes.

2. The main types of homeostatic control mechanisms are negative feedback and positive feedback.

   • Negative feedback is the most common type, where the response counteracts the initial stimulus to return the variable to its set point.
     • Example: Regulation of body temperature. If body temperature rises, mechanisms like sweating are activated to cool the body down. If it falls, shivering generates heat to warm the body.
     • Example: Regulation of blood glucose levels. When blood glucose rises, insulin is released to lower it; when it falls, glucagon is released to raise it.

Q6:

1. Blood is a specialized connective tissue composed of plasma (a liquid matrix) and formed elements (red blood cells, white blood cells, and platelets). It circulates throughout the body, delivering oxygen and nutrients to cells, transporting waste products away, and playing a crucial role in immunity and hormone transport.