Voluntary and Involuntary Control of the Body
The peripheral nervous system is divided into sections that control
voluntary and involuntary functions. Somatic nerves control voluntary
actions, those that you are aware of and consciously decide to do, such
as picking up a pencil or holding your breath. Autonomic nerves control
involuntary actions.
Autonomic nerves are further divided into two categories: sympathetic
and parasympathetic. Sympathetic nerves are responsible for the 'fight
or flight' response, in which a person must be prepared to confront or
flee a dangerous situation. To prepare the body for 'fight or flight,'
the sympathetic nervous system causes the heart to beat faster,
respiration to increase, and muscles to tense. It also de-emphasizes
functions like digestion, which can occur after the danger has passed.
Parasympathetic nerves do the opposite, prompting a 'rest and digest'
response in safe situations, such as when a person is meditating or
relaxing. The 'rest and digest' response conserves bodily energy by
slowing the heart rate and respiration and prioritizing tasks such as
digestion. In this phase, the body is better able to maintain
homeostasis, perform repairs, and return to normal after a stressful
event.
Click or tap on a description, then on the appropriate category to place
it.
Activates energy stored in liver for quick access to glucose
Airway muscles tighten to reduce lung workload
Pancreas releases insulin to produce glucose for energy
Perspiration is activated to compensate for increased internal
temperature
Heart rate decreases to conserve energy
Pupils enlarge to allow light in and improve long-distance vision
Mouth produces saliva to aid digestion and reduce mouth dryness
Blood vessels constrict to speed the flow of blood through the body
Prioritizing seeing things farther away enables a person to better react
in a dangerous situation.
The speedy flow of blood through the body provides increased oxygen to
cells in danger.
Quick access to usable energy is important for 'fight or flight.'
The body must still maintain homeostasis when in danger, so perspiration
lowers increasing body temperature.
As the goal is reducing workload, this is a parasympathetic response.
This is a part of digestion, turning food into energy-rich glucose.
This reduces energy as part of 'rest and digest.'
The production of saliva is de-emphasized in the sympathetic responses,
but emphasized in parasympathetic.