Final answer:
The effects of neurotransmitters from sympathetic or parasympathetic postganglionic neurons can be either stimulatory or inhibitory, varying based on the neurotransmitter released and the target organ's receptors.
Step-by-step explanation:
The correct option is C) The effects may be stimulatory or inhibitory depending on the neurotransmitter released and the receptors within effector organs.
In the autonomic nervous system, both the sympathetic and parasympathetic nervous systems can exert influence over different effectors in the body, often with opposing effects. The neurotransmitters released from postganglionic neurons in these systems can either stimulate or inhibit their target organs. The sympathetic nervous system generally prepares the body for 'fight-or-flight' responses, releasing neurotransmitters that lead to increased heart rate and energy mobilization. Conversely, the parasympathetic nervous system supports 'rest-and-digest' actions, such as slowing the heart rate and promoting digestion.
All preganglionic neurons in both systems release acetylcholine (ACh), which binds to nicotinic receptors on postganglionic neurons. However, these postganglionic neurons release different neurotransmitters. In the sympathetic nervous system, postganglionic neurons mostly release norepinephrine, which binds to adrenergic receptors on target cells, causing varied effects such as increased heart rate. Parasympathetic postganglionic neurons release ACh that binds to muscarinic receptors, which can cause effects such as decreased heart rate.
The misinformation in option D should be noted. It incorrectly states that parasympathetic neurons release norepinephrine, while sympathetic neurons release ACh on the target organ. This is the reverse of what actually happens.