Which of the following is NOT a similarity between the somatic motor neurons and autonomic neurons? Both Question 4 options: 1) are the part of the PNS that sends signals from the CNS to the effectors/target cells 2) can stimulate muscle contraction 3) would have signals blocked with cholinergic nicotinic antagonists 4) synapse at ganglions outside of the CNS

The correct answer is 4) "synapse at ganglions outside of the CNS".

Here's why:

1. Both somatic motor neurons and autonomic neurons are indeed part of the Peripheral Nervous System (PNS) that sends signals from the Central Nervous System (CNS) to the effectors/target cells.

2. Both types of neurons can stimulate muscle contraction. Somatic motor neurons stimulate skeletal muscle contraction, while autonomic neurons can stimulate or inhibit smooth and cardiac muscle contraction.

3. Both types of neurons would have signals blocked with cholinergic nicotinic antagonists. These are drugs that block the action of acetylcholine, a neurotransmitter that both somatic motor neurons and autonomic neurons use to send signals.

4. However, not both types of neurons synapse at ganglions outside of the CNS. This is a characteristic of autonomic neurons, not somatic motor neurons. Somatic motor neurons have their cell bodies in the CNS and send a single axon to the skeletal muscle it innervates, without any synapses in between. On the other hand, autonomic neurons have a two-neuron chain - the first neuron (preganglionic neuron) has its cell body in the CNS and synapses with the second neuron (postganglionic neuron) in a ganglion outside the CNS. The postganglionic neuron then sends signals to the effector organ.