Parasympathetic Nervous System

Definition

The parasympathetic nervous system is one of the two main divisions of the autonomic nervous system, responsible for the body's rest-and-digest functions. It works in opposition to the sympathetic nervous system, promoting activities that conserve and restore energy.

5 Must Know Facts For Your Next Test

1. The parasympathetic nervous system originates from the brainstem and the sacral region of the spinal cord.
2. It is responsible for conserving and restoring energy by slowing the heart rate, increasing digestive and glandular activity, and promoting relaxation.
3. Parasympathetic nerves release the neurotransmitter acetylcholine, which binds to muscarinic receptors on target organs.
4. Activation of the parasympathetic system counteracts the effects of the sympathetic system, allowing the body to rest, digest, and recover.
5. Disruption of the parasympathetic nervous system can lead to conditions like irritable bowel syndrome, sexual dysfunction, and urinary incontinence.

Review Questions

• Describe the primary functions of the parasympathetic nervous system and how they differ from the sympathetic nervous system.
  • The parasympathetic nervous system is responsible for the body's rest-and-digest functions, promoting activities that conserve and restore energy. This includes slowing the heart rate, increasing digestive and glandular activity, and stimulating relaxation. In contrast, the sympathetic nervous system prepares the body for action, increasing heart rate, blood pressure, and energy expenditure. The two systems work in opposition, with the parasympathetic system counteracting the effects of the sympathetic system to allow the body to rest, digest, and recover.
• Explain the role of the neurotransmitter acetylcholine in the parasympathetic nervous system and how it differs from the neurotransmitters used by the sympathetic nervous system.
  • The parasympathetic nervous system primarily uses the neurotransmitter acetylcholine to stimulate its rest-and-digest responses. Acetylcholine binds to muscarinic receptors on target organs, triggering physiological changes such as slowing the heart rate, increasing digestive activity, and promoting relaxation. This is in contrast to the sympathetic nervous system, which primarily uses the neurotransmitters norepinephrine and epinephrine to elicit its fight-or-flight responses, such as increasing heart rate, blood pressure, and energy expenditure. The distinct neurotransmitters used by the two divisions of the autonomic nervous system contribute to their opposing effects on the body's physiological functions.
• Analyze the potential consequences of a disruption or imbalance in the parasympathetic nervous system and how it might affect an individual's overall health and well-being.
  • Disruption or imbalance in the parasympathetic nervous system can have significant consequences for an individual's health and well-being. Since the parasympathetic system is responsible for conserving and restoring energy through functions like slowing the heart rate, increasing digestive activity, and promoting relaxation, a dysfunction in this system can lead to a variety of issues. For example, it can contribute to conditions like irritable bowel syndrome, sexual dysfunction, and urinary incontinence by impairing the proper regulation of these bodily functions. Additionally, a parasympathetic imbalance may disrupt the body's ability to rest, recover, and maintain homeostasis, potentially leading to chronic stress, anxiety, and other health problems. Understanding the crucial role of the parasympathetic nervous system in overall physiological balance is essential for identifying and addressing any disruptions or imbalances that may arise.

Related terms

Autonomic Nervous System: The part of the nervous system that controls involuntary bodily functions, including heart rate, blood pressure, digestion, and respiration.

Sympathetic Nervous System: The division of the autonomic nervous system that prepares the body for action, increasing heart rate, blood pressure, and energy expenditure.

Acetylcholine: The primary neurotransmitter released by parasympathetic nerves, which stimulates rest-and-digest responses in the body.