The sympathetic and parasympathetic nervous systems operate in tandem, producing antagonistic effects to maintain homeostasis. Their contrasting influences on various bodily organs include:
- **Pupils:** The sympathetic system dilates pupils, while the parasympathetic system constricts them.
- **Salivation:** Sympathetic activity inhibits salivation, whereas parasympathetic activity stimulates it.
- **Heart Rate:** The sympathetic division increases heart rate, but the parasympathetic division slows it down.
- **Bronchi:** The sympathetic nervous system dilates bronchi, in contrast to the parasympathetic system which constricts them.
- **Digestion:** Sympathetic activation inhibits digestion, while parasympathetic activation stimulates it.
- **Liver and Bile:** The sympathetic system stimulates the breakdown of glycogen; the parasympathetic system stimulates bile secretion.
- **Adrenal Gland:** Adrenaline and noradrenaline secretion is stimulated by the sympathetic system.
- **Bladder:** Contraction of the bladder is inhibited by the sympathetic system, whereas it is caused to contract by the parasympathetic system.

Opposing Functions of the Sympathetic and Parasympathetic Systems

The sympathetic and parasympathetic divisions of the autonomic nervous system have complementary functions. The sympathetic system prepares the body for stress-related 'fight-or-flight' activities, while the parasympathetic system is responsible for returning the body to routine 'rest-and-digest' operations. They work in tandem to maintain the body's internal balance.

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* Sympathetic nervous system
* Parasympathetic nervous system

Subdivisions of the Autonomic Nervous System

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

The sympathetic nervous system is a division of the autonomic nervous system that becomes activated in response to stressful or high-arousal situations. This activation triggers the 'fight-or-flight' response, a set of physiological changes that were evolutionarily adaptive for ancestors, enhancing their chances of survival when facing threats.

The Sympathetic Nervous System

A part of the autonomic nervous system that controls rest among other routine functions. It is also associated with returning the body to a relaxed state.

The Parasympathetic Nervous System

Comparison of the Sympathetic and Parasympathetic Nervous Systems

The sympathetic and parasympathetic systems operate with complementary functions, working together in tandem to maintain the body's homeostasis, which is a state of internal equilibrium where biological conditions are kept at optimal levels.

The Sympathetic and Parasympathetic Nervous Systems' Role in Homeostasis

A student is about to give a major presentation in front of a large audience. Moments before stepping on stage, they notice their heart is racing, their breathing has become quick and shallow, and their palms are sweaty. Which of the two major subdivisions of the body's involuntary internal regulation system is most active in this situation, and why do these specific physiological changes occur?

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