Lecture Notes: Understanding Stress and the Sympathetic Nervous System

Introduction

• Scenario: Awaking to a smoke alarm emphasizes body’s stress response.
  • Immediate physiological responses: increased heart rate, rapid breathing, sweating.
• Purpose of Stress:
  • Stress is not always negative; useful in survival situations (e.g., escaping danger).
  • Managed by the sympathetic nervous system (SNS).

Sympathetic Nervous System Mechanics

• Function: Activates body’s response to stress, shutting down non-essential functions to focus energy on immediate survival.
• Process:
  • Signals travel from the brain via spinal cord to ganglia.
  • Neurotransmitter Acetylcholine (ACH): Released at ganglia to boost signals.
  • Norepinephrine: Released from postganglionic neurons to effectors (e.g., muscles), increases blood flow and muscle activity.

Neurotransmitters and Hormones

• Neurotransmitters:
  • Chemicals released by neurons for communication across synapses.
• Hormones:
  • Secreted by glands, travel through bloodstream, affecting various organs.
• Dual Role of Norepinephrine:
  • Functions as both neurotransmitter and hormone depending on context.
  • As neurotransmitter: Travels across synapses to effectors.
  • As hormone: Released by adrenal glands for widespread bodily response.

Receptors and Responses

• Receptor Types:
  • Alpha Receptors: Found on smooth muscles; restrict blood flow (e.g., to digestive tract).
  • Beta Receptors: Cause muscles to relax, increase blood flow to skeletal muscles (e.g., legs for movement).
• Role in Stress:
  • Facilitates blood distribution according to priority (e.g., muscles over digestion).

Implications of Chronic Stress

• Frequent Activation:
  • Chronic activation (e.g., stress from daily life) can lead to health issues like high blood pressure, digestive problems.
• Need for Balance:
  • Importance of the parasympathetic nervous system for relaxation and recovery.

Conclusion

• Understanding the sympathetic nervous system provides insights into stress management.
• Future discussions will focus on the parasympathetic nervous system.

Acknowledgments

• Thanks to contributors and the production team for supporting educational content.