Sympathetic stimulation

Definition

Sympathetic stimulation refers to the activation of the sympathetic nervous system, which prepares the body for 'fight or flight' responses during stressful situations. This process influences various physiological functions, including heart rate and blood pressure, by releasing neurotransmitters like norepinephrine that affect the electrical conduction system of the heart, ultimately increasing cardiac output and preparing the body for rapid action.

5 Must Know Facts For Your Next Test

1. Sympathetic stimulation leads to an increase in heart rate by influencing the sinoatrial (SA) node, the heart's natural pacemaker.
2. During sympathetic activation, there is an increase in the conduction velocity through the atrioventricular (AV) node, allowing for faster electrical impulses throughout the heart.
3. Sympathetic stimulation enhances myocardial contractility, meaning that the heart muscle contracts more forcefully, which contributes to increased stroke volume.
4. The fight or flight response initiated by sympathetic stimulation also redirects blood flow away from non-essential organs towards muscles and vital organs like the heart and brain.
5. Overall, sympathetic stimulation is crucial for maintaining cardiovascular stability during times of stress or emergency, ensuring adequate blood supply to essential body systems.

Review Questions

• How does sympathetic stimulation affect heart rate and electrical conduction within the heart?
  • Sympathetic stimulation significantly increases heart rate by accelerating the pacemaker activity of the sinoatrial (SA) node. It also enhances conduction velocity through the atrioventricular (AV) node, facilitating quicker transmission of electrical impulses. This results in a more rapid heartbeat and improved coordination of contractions throughout the heart muscle.
• Discuss the physiological mechanisms by which sympathetic stimulation increases cardiac output during stressful situations.
  • Sympathetic stimulation increases cardiac output primarily by elevating both heart rate and stroke volume. Norepinephrine is released from sympathetic nerve endings, leading to increased contractility of the heart muscle. Additionally, as blood vessels constrict due to sympathetic activation, more blood is pumped with each contraction, thereby maximizing cardiac output to prepare the body for immediate physical action.
• Evaluate the role of sympathetic stimulation in coordinating cardiovascular responses during physical exertion or emergencies.
  • During physical exertion or emergencies, sympathetic stimulation plays a critical role in coordinating cardiovascular responses by rapidly increasing heart rate and blood pressure. This response ensures that vital organs receive enough oxygen-rich blood while redirecting resources away from less critical areas. By enhancing myocardial contractility and increasing cardiac output, sympathetic stimulation enables the body to meet heightened metabolic demands efficiently, thus supporting survival in high-stress situations.

Related terms

Parasympathetic Nervous System: The part of the autonomic nervous system that conserves energy and promotes 'rest and digest' functions, counteracting the effects of sympathetic stimulation.

Norepinephrine: A neurotransmitter released by the sympathetic nervous system that increases heart rate and contractility, enhancing cardiac performance during sympathetic stimulation.

Cardiac Output: The volume of blood the heart pumps per minute, which is influenced by heart rate and stroke volume, and is increased during sympathetic stimulation.