The chemical transmitter between sympathetic postganglionic fibers and the effector organs is:

Correct Answer: A

Rationale: Norepinephrine is the primary neurotransmitter released by sympathetic postganglionic fibers to effectors (e.g., smooth muscle). Acetylcholine is used at ganglia, adrenaline/epinephrine are adrenal medulla secretions.

Correct Answer: B

Rationale: α₂ autoreceptors on presynaptic terminals inhibit norepinephrine release (negative feedback). Other receptors (α₁, β₁, β₂) mediate effector responses.

Correct Answer: D

Rationale: The ANS regulates involuntary visceral functions, not conscious motor control (somatic nervous system). Other options are ANS roles.

Correct Answer: C

Rationale: The knee jerk is a monosynaptic spinal reflex with its center in the spinal cord (L2-L4), not conditioned or polysynaptic.

Correct Answer: D

Rationale: Impulse speed depends on fiber diameter, myelination (including Schwann cells in PNS), and physiological condition (e.g., ion channels). Length affects total time, not speed (m/s).