Question

complete each sentence by selecting the correct word in each blank.1. also known as the division, the parasympathetic nervous system has axons exiting the cns at the medulla oblongata.2. action potentials travel down the preganglionic nerve axons of the, towards the effector organs.3. these impulses arrive at the cardiac plexus where secretion of acetylcholine creates an action potential in the neuron.4. the impulse arrives relatively quickly at the heart, as parasympathetic postganglionic axons are compared to sympathetic postganglionic axons.5. action potentials arriving at the sinoatrial and atrioventricular nodes of the heart cause to be released.6. this parasympathetic neurotransmitter causes a in heart rate and contractility.

Explanation:

1. The parasympathetic nervous system is also called the craniosacral division as its preganglionic neurons originate from cranial nerves (like the vagus nerve) and sacral spinal cord segments.
2. Action potentials travel down the preganglionic nerve axons of the vagus nerve (a major cranial nerve in the parasympathetic system) towards effector organs.
3. In the parasympathetic system, after the preganglionic neuron (which releases acetylcholine at the ganglion), the impulse is passed to the postganglionic neuron.
4. Parasympathetic postganglionic axons are short compared to sympathetic postganglionic axons. Sympathetic postganglionic neurons are long as they have to travel from ganglia close to the spinal cord to target organs.
5. At the sinoatrial and atrioventricular nodes (pacemaker regions of the heart), the parasympathetic neurotransmitter acetylcholine is released.
6. Acetylcholine (the parasympathetic neurotransmitter) causes a decrease in heart rate and contractility. It slows down the firing of the sinoatrial node (pacemaker) and reduces the force of heart muscle contraction.

Answer:

1. craniosacral
2. vagus nerve
3. postganglionic
4. short
5. acetylcholine
6. decrease