Sympathetic Response to Hypotension

Introduction

• Hypotension: Falling blood volume and blood pressure.
• Sympathetic Nervous System (SNS): Part of the autonomic nervous system responsible for the fight-or-flight response.
• Goal: Preserve blood pressure during hypotension.

Receptor Types and Their Effects

Alpha-1 Receptors

• Location:
  • Smooth muscle of blood vessels around skin, abdominal organs, digestive tract, kidneys.
• Effect:
  • Vasoconstriction, leading to increased total peripheral resistance.
  • Increases blood pressure by "squeezing the pipes."

Beta-1 Receptors

• General: Think "Beta 1, 1 heart."

Heart

• SA Node:
  • Effect: Chronotropic response (increases heart rate).
  • SA node sends more action potentials to contract the heart.
• AV Node:
  • Effect: Dromotropic response (increases electrical conduction speed).
  • Increases conduction velocity through the AV node, leading to quicker heart contractions.
• Myocardium:
  • Effect: Inotropic response (increases contractility of heart muscle).
  • Leads to increased stroke volume; more blood is pumped per heart contraction.

Kidneys

• Location: Juxtaglomerular cells (near the nephron filter).
• Effect:
  • Release of renin, starting the RAF system.
  • Helps increase blood pressure by reabsorbing fluid from kidneys.

Conclusion

• SNS Role: The sympathetic nervous system effectively responds to hypotension by utilizing different receptors and physiological mechanisms to preserve and increase blood pressure.
• Study Tip: Understanding the role of each receptor and its location is crucial for grasping how the body reacts to hypotension.