Autonomic Nervous System

Definition

The autonomic nervous system (ANS) is a component of the peripheral nervous system that regulates involuntary physiological functions, including heart rate, blood pressure, respiration, and digestion. It operates largely below the level of consciousness and is crucial for maintaining homeostasis within the body by controlling smooth muscles, cardiac muscles, and glands. The ANS is further divided into the sympathetic and parasympathetic systems, which work together to balance the body's responses to stress and relaxation.

5 Must Know Facts For Your Next Test

1. The autonomic nervous system is divided into two main branches: the sympathetic and parasympathetic nervous systems, which have opposing functions.
2. The sympathetic nervous system is activated in response to stress, increasing heart rate and redirecting blood flow to essential organs for a quick response.
3. The parasympathetic nervous system promotes relaxation by decreasing heart rate and enhancing digestive processes when the body is at rest.
4. The autonomic nervous system operates without conscious control, allowing it to manage essential life-sustaining functions automatically.
5. Neurotransmitters like acetylcholine and norepinephrine play critical roles in transmitting signals within the autonomic nervous system, influencing its various effects on target organs.

Review Questions

• How do the sympathetic and parasympathetic divisions of the autonomic nervous system interact to maintain homeostasis?
  • The sympathetic and parasympathetic divisions of the autonomic nervous system work in opposition to maintain homeostasis within the body. The sympathetic division activates bodily functions in response to stress or danger, preparing the body for a 'fight or flight' reaction by increasing heart rate and energy availability. Conversely, when the stressor is removed, the parasympathetic division promotes calming effects by slowing heart rate and enhancing digestion. This balance ensures that the body can react appropriately to various situations while maintaining stable internal conditions.
• What are some physiological effects of sympathetic activation in the autonomic nervous system?
  • When the sympathetic division is activated, several physiological changes occur to prepare the body for rapid action. These effects include an increase in heart rate and blood pressure, dilation of airways for improved oxygen intake, and redistribution of blood flow away from non-essential organs toward muscles and vital organs like the heart and brain. This coordinated response enhances physical performance during stressful situations but also requires subsequent activation of the parasympathetic division to return bodily functions to normal.
• Evaluate how dysfunctions in the autonomic nervous system can lead to health issues, providing examples.
  • Dysfunctions in the autonomic nervous system can lead to various health problems that significantly impact quality of life. For example, excessive sympathetic activation can result in chronic stress-related disorders such as hypertension or anxiety disorders due to persistent elevated heart rate and blood pressure. On the other hand, an underactive parasympathetic response may lead to digestive issues like irritable bowel syndrome or gastroparesis due to inadequate regulation of digestive processes. These dysfunctions illustrate how critical proper autonomic functioning is for maintaining overall health.

Related terms

Sympathetic Nervous System: A division of the autonomic nervous system that prepares the body for stressful or emergency situations, often referred to as the 'fight or flight' response.

Parasympathetic Nervous System: The other division of the autonomic nervous system that promotes the 'rest and digest' activities, helping to conserve energy and restore the body to a state of calm.

Homeostasis: The physiological process through which the body maintains stable internal conditions despite external changes, heavily regulated by the autonomic nervous system.