Which statement about the autonomic nervous system is true?...

Which statement about the autonomic nervous system is true? $a .$ The sympathetic division is afferent, and the parasympathetic division is efferent. b. The transmitter norepinephrine is always excitatory, and acetylcholine is always inhibitory. $c .$ Each pathway in the autonomic nervous system includes two neurons, and the neurotransmitter of the first neuron is acetylcholine. $d .$ The cell bodies of many sympathetic preganglionic neurons are in the brain stem. $e .$ The cell bodies of most parasympathetic postganglionic neurons are in or near the thoracic and lumbar spinal cord.

Which statement about the autonomic nervous system is true?
$a .$ The sympathetic division is afferent, and the parasympathetic division is efferent.
b. The transmitter norepinephrine is always excitatory, and acetylcholine is always inhibitory.
$c .$ Each pathway in the autonomic nervous system includes two neurons, and the neurotransmitter of the first neuron is acetylcholine.
$d .$ The cell bodies of many sympathetic preganglionic neurons are in the brain stem.
$e .$ The cell bodies of most parasympathetic postganglionic neurons are in or near the thoracic and lumbar spinal cord.

Key Concepts

Preganglionic and Postganglionic Neurons

Both divisions of the autonomic nervous system are generally organized into a two-neuron chain that comprises a preganglionic neuron and a postganglionic neuron. The preganglionic neuron, which originates in the central nervous system, typically utilizes acetylcholine as its neurotransmitter. The postganglionic neuron, located in peripheral ganglia, then conveys the signal to target organs using neurotransmitters that vary between divisions.

Parasympathetic Division

The parasympathetic division acts in contrast to the sympathetic division and is often described as controlling the 'rest and digest' functions of the body. It promotes conservation of energy by slowing heart rate, stimulating digestion, and supporting overall maintenance activities. Its preganglionic neurons are predominantly found in the cranial nerve nuclei of the brain stem and in the sacral region of the spinal cord.

Neurotransmitters

Neurotransmitters play a critical role in autonomic signal transmission. In both the sympathetic and parasympathetic divisions, acetylcholine is the neurotransmitter used by preganglionic neurons. However, postganglionic neurons differ between divisions: sympathetic postganglionic neurons generally use norepinephrine (with some exceptions) and parasympathetic postganglionic neurons continue to use acetylcholine. The actions of these neurotransmitters can be excitatory or inhibitory depending on the receptor types present on the target tissues.

Autonomic Nervous System

The autonomic nervous system (ANS) is a subdivision of the peripheral nervous system that regulates involuntary physiological functions such as heart rate, digestion, respiratory rate, pupillary response, and more. It operates largely below the level of conscious control and manages the body's internal environment through a balance between two major divisions.

Sympathetic Division

The sympathetic division is one half of the autonomic nervous system and is commonly associated with the 'fight or flight' response. It typically prepares the body for stressful or emergency situations by accelerating heart rate, dilating pupils, and redirecting blood flow towards muscles. The cell bodies of most sympathetic preganglionic neurons reside in the thoracic and lumbar regions of the spinal cord.

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