Circulatory System Principles Flashcards

Questions and Answers

How is Bernoulli's principle applied to the circulatory system?

The total energy in the vascular system is a balance between potential energy and kinetic energy. Therefore, if blood velocity goes up, there must be a pressure decrease.

In the human circulatory system, when do viscous and inertial losses occur?

Viscous losses occur as the layers of blood rub against each other moving through the vessel, and inertial losses occur whenever blood is forced to change direction or velocity.

Why does the velocity of the blood decrease as the blood travels from the aorta to the arterioles?

Velocity is inversely related to total cross-sectional area, and the total cross-sectional area of blood vessels increases from the aorta to the arterioles.

According to Poiseuille's law, how is volume flow impacted by changes in vessel radius?

Volume flow is directly related to radius to the fourth power; as radius increases, volume flow increases but at a much higher rate. Signup and view all the answers

Why is hydraulic filtering necessary in the circulatory system?

Hydraulic filtering converts the intermittent output of the heart to a steady flow through the capillaries. Signup and view all the answers

How does capacitance in the arterial system change with age?

Capacitance decreases with age as the vessel walls become rigid. Signup and view all the answers

What are the main factors that control peripheral circulation?

Peripheral circulation is controlled centrally by the nervous system and locally by conditions at the tissue bed. Signup and view all the answers

How does a critical stenosis affect pressure and flow?

As stenosis increases to a critical level, pressure and flow will decrease. Signup and view all the answers

How can the ICA and ECA be safely differentiated?

ECA is typically medial and has branches beyond bifurcation; temporal tap will affect ECA sound wave. Signup and view all the answers

What is the primary criterion for determining an ICA stenosis? Once the primary threshold has been exceeded, what is the secondary criterion to further categorize diagnosis?

PSV >125 cm/sec indicates >50% stenosis; EDV >140 cm/sec indicates >80% stenosis. Signup and view all the answers

What did NASCET determine to be the best criteria for determining a >70% stenosis?

No detectable patent lumen on grayscale imaging and no flow with PW Doppler, color Doppler, or power Doppler. Signup and view all the answers

How is stenosis determined in extracranial vessels other than the ICA?

A focal velocity increase in PSV twice that of a normal proximal site, the presence of poststenotic turbulence, and distal waveform changes. Signup and view all the answers

How can pseudoaneurysm be differentiated from an enlarged lymph node?

Pseudoaneurysms have a neck connecting to the native vessel with a to-and-fro flow pattern; lymph nodes show a low-resistance arterial pattern. Signup and view all the answers

In addition to US findings, what should the vascular technologist pay attention to when assessing a patient suspected of an uncommon vascular pathology?

Patient history plays a very important role in determining which pathology the technologist should consider. Signup and view all the answers

With TCD, why is spectral broadening unavoidable?

The sample gate is relatively large compared to the size of the artery evaluated. Signup and view all the answers

What are the main quantitative values used for diagnostic purposes in a transcranial exam?

The mean velocities and the pulsatility index. Signup and view all the answers

Study Notes

Bernoulli's Principle in Circulatory System

Total energy in the vascular system balances between potential and kinetic energy.
Increased blood velocity leads to a decrease in pressure.

Viscous and Inertial Losses

Viscous losses occur from friction as blood layers slide against each other.
Inertial losses arise when blood changes direction or velocity; depend on blood density and velocity.
Energy losses due to viscosity are greater than those from inertia in blood vessels.

Blood Velocity and Vessel Cross-Section

Blood velocity decreases from the aorta to arterioles due to an increase in total cross-sectional area.

Poiseuille's Law on Vessel Radius

Volume flow correlates directly with the vessel radius to the fourth power.
Doubling the radius increases volume flow by a factor of 16.

Hydraulic Filtering's Role

Ensures a steady flow from the heart to capillaries for effective nutrient and waste exchange.

Arterial capacitance decreases with age due to rigid vessel walls.
Increased vessel stiffness results in higher systolic and pulse pressure.

Control of Peripheral Circulation

Peripheral circulation is regulated by the nervous system and local tissue conditions.
Arterioles play a pivotal role in managing blood flow to specific organs or regions.

Effects of Critical Stenosis

Increases in stenosis lead to decreases in pressure and flow, especially in low-resistance systems.

Differentiating ICA and ECA

ECA is usually positioned medial and has branches past bifurcation; characterized by a temporal tap affecting sound waves.

Determining ICA Stenosis

Primary criterion for >50% stenosis is PSV >125 cm/sec; EDV >140 cm/sec indicates >80% stenosis as a secondary criterion.

NASCET Criteria for >70% Stenosis

Identified absence of a detectable patent lumen and no flow on grayscale imaging and Doppler assessments.

Stenosis Assessment in Extracranial Vessels

Detected through a focal velocity increase in PSV >2 times the normal proximal site and poststenotic turbulence.

Differentiating Pseudoaneurysm from Lymph Node

Pseudoaneurysms connect to a vessel via a neck, showing to-and-fro flow and a swirling "yin-yang" pattern.
Lymph nodes demonstrate a low-resistance flow pattern and apparent venous flow.

Importance of Patient History in Assessment

Patient history is crucial for determining potential uncommon vascular pathologies during evaluation.

TCD and Spectral Broadening

Spectral broadening in TCD is unavoidable due to the larger sample gate size compared to the artery being evaluated.

Quantitative Values in Transcranial Exam

Mean velocities and pulsatility index are the primary quantitative measures for diagnostic purposes in a transcranial exam.

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Description

Explore key principles related to Bernoulli's principle and energy balance in the circulatory system with these flashcards. Ideal for students studying cardiovascular physiology, this quiz will enhance your understanding of blood flow dynamics and energy losses in vessels.