Video Transcript
In the autonomic nervous system, which division’s nerves extend from the brain stem
and sacral regions of the spinal cord? (A) Sympathetic, (B) motor, (C) sensory, (D) parasympathetic, (E) somatic.
To answer this question, we must recall the subdivisions of the autonomic nervous
system and the origin of the nerves that help carry out the functions of each
subdivision. The autonomic nervous system is the subdivision of the motor division that regulates
involuntary and subconscious activities. This system is further subdivided into two parts: the sympathetic and parasympathetic
nervous systems.
The sympathetic nervous system is responsible for the body’s fight-or-flight
response. Activation of the sympathetic nervous system triggers several physiological changes
that prepare the body to confront or flee a dangerous situation, such as an
increased heart rate and breathing rate. To carry out these responses, the sympathetic nervous system sends out signals
through the thoracic and lumbar spinal nerves. The thoracic spinal nerves control the action of the heart, the airways, the sweat
glands, the liver, and the digestive system. The lumbar spinal nerves control the action of the adrenal glands and the urinary
system.
In contrast, the parasympathetic nervous system is responsible for relaxation,
resting, and feeding, which is known as the body’s rest-and-digest response. Activation of the parasympathetic nervous system triggers physiological changes that
prepares the body to rest or sleep, stimulates the digestive system, and regulates
blood pressure.
The parasympathetic nervous system is mainly composed of the cranial nerves and the
sacral spinal nerves. To achieve the rest phase of rest and digest, the cranial nerves stemming from the
brain stem stimulate the pupils, the heart, and our airways. To achieve the digest phase of rest and digest, the sacral spinal nerves stimulate
the liver, digestive system, and urinary system. So the nerve fibers of the parasympathetic nervous system extend from the brain stem
and the sacral regions of the spinal cord.
With this information, we can now answer the question. The division of the autonomic nervous system whose nerves extend from the brain stem
and sacral regions of the spinal cord is the parasympathetic nervous system.
