Parasympathetic nervous system

Definition

The parasympathetic nervous system is a division of the autonomic nervous system responsible for promoting the 'rest and digest' response in the body. This system works to conserve energy, slowing down the heart rate and increasing intestinal and gland activity, while relaxing sphincter muscles in the gastrointestinal tract. It plays a critical role in maintaining homeostasis by counterbalancing the effects of the sympathetic nervous system.

5 Must Know Facts For Your Next Test

1. The parasympathetic nervous system is activated during restful states, leading to physiological changes such as decreased heart rate and increased digestion.
2. It uses acetylcholine as its primary neurotransmitter to transmit signals between neurons and target organs.
3. This system has a calming effect on the body, helping to promote relaxation and recovery after periods of stress.
4. The parasympathetic response helps to restore energy levels after physical activity and supports overall wellness by enhancing metabolic processes.
5. Key functions regulated by this system include salivation, lacrimation (tear production), urination, digestion, and defecation, often referred to as the SLUDD functions.

Review Questions

• How does the parasympathetic nervous system interact with the sympathetic nervous system to maintain homeostasis?
  • The parasympathetic nervous system and sympathetic nervous system work together to maintain homeostasis through a balance of their opposing actions. While the sympathetic nervous system prepares the body for stressful situations by initiating 'fight or flight' responses, the parasympathetic system promotes a 'rest and digest' state that counteracts those effects. This interplay ensures that bodily functions such as heart rate and digestion are adjusted according to situational demands, allowing for optimal functioning during both stress and relaxation.
• Discuss how the activation of the parasympathetic nervous system influences digestive processes.
  • Activation of the parasympathetic nervous system significantly enhances digestive processes by increasing blood flow to the digestive organs and stimulating peristalsis, which is the movement of food through the gastrointestinal tract. The release of acetylcholine leads to increased secretion of digestive enzymes and saliva, facilitating better breakdown and absorption of nutrients. Additionally, it relaxes sphincter muscles, allowing for smoother passage of food, thus optimizing nutrient uptake and overall digestion.
• Evaluate the role of the vagus nerve in regulating parasympathetic functions throughout the body.
  • The vagus nerve is crucial for regulating many parasympathetic functions throughout the body, impacting heart rate, digestion, and even emotional responses. By transmitting signals from the brain to various organs, including the heart and stomach, it helps facilitate a state of calmness and promotes recovery from stress. Evaluating its role reveals that stimulation of the vagus nerve can lead to significant health benefits, such as reduced anxiety levels and improved gut health, emphasizing its importance in overall autonomic regulation and homeostasis.

Related terms

Sympathetic Nervous System: The division of the autonomic nervous system that prepares the body for 'fight or flight' responses during stressful situations.

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

Vagus Nerve: The longest cranial nerve, which plays a major role in controlling parasympathetic functions such as heart rate and digestive processes.