Skip to main content
Ch. 19 The Cardiovascular System: Blood Vessels
Hoehn - Marieb Human Anatomy & Physiology, 12th edition
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732Not the one you use?Change textbook
Chapter 19, Problem 2

Total peripheral resistance:
a. is inversely proportional to the length of the vascular bed
b. increases in anemia
c. decreases in polycythemia
d. is inversely related to the diameter of the arterioles

Verified step by step guidance
1
Step 1: Understand the concept of total peripheral resistance (TPR). TPR is the resistance to blood flow offered by all of the systemic vasculature, primarily influenced by the diameter and length of blood vessels, and blood viscosity.
Step 2: Recall that TPR is directly proportional to the length of the vascular bed, meaning that as the length increases, resistance increases. Therefore, it is not inversely proportional to length.
Step 3: Consider the effect of anemia and polycythemia on blood viscosity. Anemia decreases blood viscosity, which tends to decrease TPR, while polycythemia increases blood viscosity, which tends to increase TPR.
Step 4: Recognize that vessel diameter, especially of arterioles, has a strong inverse relationship with resistance. According to Poiseuille's law, resistance is inversely proportional to the fourth power of the vessel radius (or diameter), so smaller diameter means higher resistance.
Step 5: Use these principles to evaluate each option: (a) is incorrect because TPR is directly proportional to length; (b) is incorrect because anemia decreases viscosity and thus TPR; (c) is incorrect because polycythemia increases viscosity and TPR; (d) is correct because TPR is inversely related to arteriole diameter.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
1m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Total Peripheral Resistance (TPR)

TPR refers to the overall resistance to blood flow offered by the systemic blood vessels, primarily arterioles. It is a key determinant of blood pressure and is influenced by vessel diameter, blood viscosity, and vessel length.
Recommended video:
3:33
Peripheral Nervous System

Relationship Between Vessel Diameter and Resistance

Resistance to blood flow is inversely related to the fourth power of the vessel radius, meaning small changes in arteriole diameter greatly affect TPR. Narrower arterioles increase resistance, while wider arterioles decrease it.
Recommended video:
6:40
Relationship Between Blood Flow, Pressure, & Resistance

Effect of Blood Viscosity on Resistance

Blood viscosity, influenced by factors like hematocrit, affects TPR. Anemia (low red blood cells) decreases viscosity and resistance, while polycythemia (high red blood cells) increases viscosity and resistance.
Recommended video:
8:32
Altering Resistance in Blood Vessels