Explanation: Hyperventilation → excessive CO2 exhalation → respiratory alkalosis (↓PaCO2, ↑pH).
A) Rapid influx of Na+ through fast voltage-gated channels B) Inward “funny current” (If) carried mainly by Na+ and K+ efflux decrease C) Exclusive T-type Ca2+ channel activation D) Na+/Ca2+ exchanger operating in reverse mode
Explanation: Hypotension reduces baroreceptor firing → increased sympathetic outflow to heart (β1 receptors) → increased HR. Vagal tone decreases, not increases.