Autonomic Nervous System: Functions, Divisions & Examples

Lesson Overview

• What Is the Autonomic Nervous System?
• How Is the Autonomic Nervous System Different From the Somatic Nervous System?
• What Are the Two Main Divisions of the Autonomic Nervous System?
• How Do Sympathetic and Parasympathetic Systems Affect Your Organs Differently?
• What Neurotransmitters Does the Autonomic Nervous System Use?
• What Are Some Common Misconceptions About the Ans?
• How Does Your Body Balance the Two Systems?

As Jake nervously stepped up to speak in front of his class, his heart pounded, and his breathing quickened. He wondered why he couldn't control these reactions. Understanding the Autonomic Nervous System helps explain these automatic bodily responses. This lesson clearly breaks down how your body manages stress and relaxation effortlessly.

What Is the Autonomic Nervous System?

Before diving deeper, let's first understand what the ANS is and what it does for your body.

The Autonomic Nervous System is a part of your nervous system responsible for controlling functions that you don't consciously manage. It handles vital bodily functions such as heartbeat, digestion, breathing, and pupil size. Unlike lifting your hand, these processes occur automatically.

Key Points:

• Manages involuntary body functions.
  
• Keeps your internal environment stable (homeostasis).
  
• Controls smooth muscle, cardiac muscle, and glands.

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Autonomic Nervous System Quiz

How Is the Autonomic Nervous System Different From the Somatic Nervous System?

Here, we clarify the main differences between the ANS and the system that controls voluntary actions.

• Autonomic Nervous System: Controls involuntary functions like heartbeat, digestion, and gland secretion.
  
• Somatic Nervous System: Controls voluntary movements like walking, writing, and jumping.
  

Quick Tip: Think of "somatic" as actions you do intentionally (like smiling), while "autonomic" actions happen automatically (like digesting).

What Are the Two Main Divisions of the Autonomic Nervous System?

Your ANS has two main branches: the Sympathetic Nervous System and the Parasympathetic Nervous System. Let's explore each one in detail.

What Does the Sympathetic Nervous System Do?

When you're faced with danger or stress, your sympathetic nervous system kicks into gear. Often called the "fight or flight" system, it prepares your body for immediate action.

Key effects:

• Heart rate and blood pressure increase.
  
• Airways expand, making breathing easier.
  
• Pupils dilate, improving vision.
  
• Digestive activities slow down, conserving energy for immediate use.
  
• Energy stores like glucose release into the bloodstream for quick use.
  

Mnemonic: Remember "Sympathetic = Stress," preparing you to respond quickly to emergencies.

What Does the Parasympathetic Nervous System Do?

When you're resting or relaxing after a meal, your parasympathetic nervous system becomes more active. Known as the "rest and digest" system, it supports body maintenance and energy conservation.

Key effects:

• Heart rate and blood pressure decrease.
  
• Breathing slows down, and airways constrict slightly.
  
• Pupils constrict for close, calm vision.
  
• Digestive activity increases significantly.
  
• Energy is conserved and stored.
  

Mnemonic: Think of "Parasympathetic = Peace," guiding your body into calmness and restoration.

How Do Sympathetic and Parasympathetic Systems Affect Your Organs Differently?

Let's compare how these two systems affect major organs and functions side-by-side:

What Neurotransmitters Does the Autonomic Nervous System Use?

Neurotransmitters are chemical messengers. Let's see which neurotransmitters your autonomic system uses:

• Acetylcholine (ACh): Released by both sympathetic and parasympathetic neurons initially, but parasympathetic neurons always release it to their target organs.
  
• Norepinephrine (NE): Released by most sympathetic neurons to their target organs, creating the fight-or-flight effects.
  

Key Points to Remember:

• Sympathetic: Preganglionic neurons use ACh; postganglionic neurons typically use NE.
  
• Parasympathetic: Both preganglionic and postganglionic neurons use ACh.
  

Quiz Tip: If a quiz asks, "Do sympathetic neurons use only acetylcholine?" The answer is "No," because they mostly use norepinephrine at the target organ.

What Are Some Common Misconceptions About the Ans?

Let's clear up some frequent student misunderstandings about the Autonomic Nervous System.

• Misconception 1: "Only one ANS branch is active at a time."
  Truth: Both sympathetic and parasympathetic systems are constantly active to varying degrees, maintaining balance.
  
• Misconception 2: "We can control the ANS consciously."
  Truth: Generally, ANS functions are automatic, although techniques like deep breathing can indirectly influence them.
  
• Misconception 3: "The sympathetic system uses only ACh."
  Truth: Sympathetic neurons primarily use norepinephrine at target organs, though acetylcholine is used initially.
  

How Does Your Body Balance the Two Systems?

Your brain continuously adjusts the balance between sympathetic and parasympathetic systems based on the situation:

• Brainstem and hypothalamus monitor internal and external signals.
  
• High stress or activity: Increases sympathetic, decreases parasympathetic.
  
• Rest or safety: Enhances parasympathetic activity, reduces sympathetic drive.

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Autonomic Nervous System MCQ Trivia: Quiz!