3-2 Arterial Circulation

Study Notes

Main Goal of Cardiovascular System

Maintain mean arterial pressure (MAP), influenced by cardiac output (CO) and total peripheral resistance (TPR).
CO is a product of stroke volume and heart rate.

Arterioles Function

Regulate blood pressure by adjusting resistance levels.
Constriction increases resistance, reduces downstream flow, and raises upstream pressure, impacting MAP.
Dilation decreases resistance, enhances downstream flow, and lowers upstream pressure.

Total Peripheral Resistance (TPR)

Represents the cumulative resistance from all arterioles.
Directly correlates with MAP; higher TPR equates to a higher MAP.

Local Control of Blood Flow

Flow auto-regulation occurs as tissues adjust blood flow based on metabolic needs.
Low flow results in decreased oxygen and increased CO2, prompting arterioles to dilate.
Active hyperemia occurs during increased metabolic activity (e.g., during muscle exertion), resulting in heightened blood flow.
Reactive hyperemia is seen after occlusion, leading to increased blood flow once the obstruction is removed.

Central Control Mechanisms

Baroreceptors located in the aortic arch and carotid bifurcation detect changes in MAP.
Elevated MAP leads to increased firing of baroreceptors, which reduces sympathetic tone and induces vasodilation.
Lower sympathetic tone results in decreased TPR and a subsequent drop in MAP.

Sympathetic vs Parasympathetic Effects

Sympathetic activation, particularly via epinephrine, causes vasoconstriction, raising TPR and MAP.
Parasympathetic activity, mediated by the vagus nerve, lowers heart rate and CO, contributing to decreased MAP.

Hormonal Regulation

Angiotensin II and anti-diuretic hormone (ADH) act as vasoconstrictors, elevating TPR and blood pressure.
Nitric oxide serves as a vasodilator, resulting in decreased TPR and MAP.

Summary of Local Vasodilators

Factors triggering vasodilation include reduced oxygen, increased CO2, potassium, and adenosine derived from ATP breakdown.
These signals aim to enhance blood flow to tissues in need.

Possible Test Concepts

Importance of arterioles in controlling MAP.
Understanding TPR mechanisms and their relation to blood pressure regulation.
Differences in local and central blood flow control, including baroreceptor reflex mechanisms.
Impacts of sympathetic and parasympathetic activation on vascular tone.
Key hormonal regulators involved in vasoconstriction and vasodilation.

Description

This quiz covers important concepts related to arterial circulation and the cardiovascular system. Focused on the maintenance of mean arterial pressure (MAP), it explores the role of arterioles in regulating blood pressure through resistance and flow dynamics. Test your knowledge on these critical physiological mechanisms.