Muscle Types and Renal Function

Types of Muscle Fibers

• Red Muscle Fibers

  • Smaller size compared to white muscle fibers.
  • Contain many mitochondria, blood vessels, and lipids.
  • Classified as slow-twitch fibers; capable of sustained activities for prolonged periods.
  • Rely heavily on aerobic respiration (uses oxygen).
  • Examples include the breast muscles of ducks and geese, which require endurance for migratory flights.

• White Muscle Fibers

  • Larger size than red fibers and contain abundant glycogen.
  • Classified as fast-twitch fibers; adapted for quick, short bursts of activity.
  • More efficient in anaerobic respiration, allowing them to function with less oxygen.
  • Associated with rapid, brief movements, such as those of a chicken.

Muscle Physiology

• Calcium's Role: Essential for muscle contraction and the release of acetylcholine at the neuromuscular junction.
• Milk Fever in Cows:
  • Occurs when calcium levels in the blood drop, leading to muscle weakness and paralysis.
  • Symptoms include an S-shaped neck, inability to stand, and potential coma.
  • Treatment includes administering calcium via mouth or direct injection.

Renal System Overview

• Kidneys:

  • Latin origin renal, meaning 'kidney'.
  • Maintain osmolarity (~300 milliosmolar) for acid-base balance and waste elimination.
  • Regulate water retention, especially in terrestrial birds and mammals.

• Endocrine Functions:

  • Produce erythropoietin, stimulating red blood cell production in the bone marrow.
  • Regulate antidiuretic hormone (ADH), which decreases urine output and promotes water reabsorption.

Hormonal Regulation

• Erythropoietin:

  • Promotes the production of red blood cells, crucial for oxygen transport.
  • Acknowledged for misuse in sports as a performance enhancer by increasing red blood cell count.
  • Excessive erythropoietin can lead to complications, such as blood clotting and risk of death.

• ADH and Aldosterone:

  • ADH: Released from the posterior pituitary, increases water reabsorption in kidneys.
  • Aldosterone: Retains sodium and regulates potassium levels, essential for muscle function.

Kidney Anatomy and Function

• Kidneys are located retroperitoneally, outside the peritoneal cavity, and are responsible for filtering blood.

• They receive 20-25% of the cardiac output and consume a significant amount of oxygen (77-20% of total bodily oxygen).

• Blood Flow Dynamics:

  • The renal cortex receives around 80% of arterial blood, while 15% supplies the medullary region.

Importance of the Kidneys

• Kidneys play a vital role in maintaining homeostasis by regulating blood pressure, red blood cell production, and waste removal.
• Kidney transplantation is feasible due to the organ's functionality, wherein one healthy kidney can suffice for survival, emphasizing their efficiency and importance in the body.