A middle-aged woman has been diagnosed with a vitamin D deficiency. How does this deficiency affect her musculoskeletal system?

A. Enteric nervous system: The Enteric nervous system is a mesh-like system of neurons that governs the function of the gastrointestinal tract (the "brain of the gut"). It manages digestion, not the systemic stress response.

B. Central nervous system: While the brain (specifically the hypothalamus and amygdala) perceives the threat, the execution of the physiological "fight or flight" changes (racing heart, dilated pupils) is carried out by the autonomic nerves.

C. Peripheral nervous system: Similar to Question 45, this is a broad anatomical term. While the stress response nerves are located in the periphery, the specific functional system is the Autonomic Nervous System.

D. Autonomic nervous system: The Autonomic Nervous System has two main branches: the Sympathetic and the Parasympathetic. The Sympathetic division is directly responsible for the "fight or flight" response, mobilizing the body's energy during stress.

Question: 47 of 48

A middle-aged woman has been diagnosed with a vitamin D deficiency. How does this deficiency affect her musculoskeletal system?

1. Reduced calcium absorption leading to weak bones
2. Increased muscle mass
3. Enhanced collagen production
4. Hypercalcemia due to excess calcium

Correct answer: A

A. Reduced calcium absorption leading to weak bones: The primary physiological role of Vitamin D is to facilitate the absorption of calcium in the intestines. Without sufficient Vitamin D, the body cannot absorb enough calcium from the diet. To maintain blood calcium levels, the body will then leech calcium from the bones, leading to lower bone density (osteopenia/osteoporosis) and increased fracture risk.

B. Increased muscle mass: Vitamin D deficiency is actually associated with muscle weakness and pain (proximal myopathy), not an increase in muscle mass.

C. Enhanced collagen production: Vitamin D is not a primary driver of collagen synthesis; Vitamin C is the key nutrient for collagen production.

D. Hypercalcemia due to excess calcium: A deficiency in Vitamin D leads to hypocalcemia (low calcium levels) because the gut cannot absorb it efficiently. Hypercalcemia would be a sign of Vitamin D toxicity (overdose) or hyperparathyroidism.