What is the Difference Between Nerves and Blood Vessels

The main difference between nerves and blood vessels is that nerves are cable-like bundles of nerve fibers, serving as the pathway for the electrochemical impulses, whereas blood vessels are tube-like structures carrying blood. Furthermore, nerves belong to the peripheral nervous system, while blood vessels belong to the circulatory system.  

Nerves and blood vessels are two types of tubular structures that occur in the body. Generally, they are responsible for moving things from one to another place in the body. 

Key Areas Covered 

1. What are Nerves
     – Definition, Structure, Importance
2. What are Blood Vessels
     – Definition, Structure, Importance
3. What are the Similarities Between Nerves and Blood Vessels
     – Outline of Common Features
4. What is the Difference Between Nerves and Blood Vessels
     – Comparison of Key Differences

Key Terms 

Blood, Blood Vessels, Circulatory System, Nerves, Nerve Impulses, Peripheral Nervous System

What are Nerves 

Nerves are the components of the peripheral nervous system. Generally, they are made up of bundles of axons of neurons. The main function of nerves is to carry nerve impulses or action potentials in the form of electrochemical signals in and out of the central nervous system (CNS). Furthermore, the two types of cellular components of nerves are axons of neurons and Schwann cells. Here, the main function of Schwann cells is to synthesize myelin, insulating axons. And, this insulation speeds up the transmission of nerve impulses. In addition to these, a connective tissue layer called endoneurium wraps around each axon. Another connective tissue layer called perineurium wraps around a group of axon bundles of the nerve. Finally, epineurium is the outermost connective tissue layer, which covers the entire nerve.

Figure 1: The Structure of a Spinal Nerve

Furthermore, based on the direction of the transmission of nerve impulses, there are three types of nerves. They are sensory, motor, and mixed nerves. Generally, sensory nerves or afferent nerves carry impulses from sensory organs to the CNS. In contrast, motor nerves or efferent nerves carry impulses from the CNS to the effector organs. On the other hand, mixed nerves consist of both afferent and efferent nerves, conducting both sensory and motor impulses in the same bundle. However, there is another classification of nerves based on their origin. They are spinal nerves and cranial nerves. Usually, spinal nerves arise from the spinal cord, while cranial nerves arise from different parts of the brain. 

What are Blood Vessels 

Blood vessels are the tubular structures of the circulatory system, carrying blood throughout the body. Generally, blood is the circulating liquid which serves as the transporting medium for nutrients, oxygen, and metabolic wastes to their corresponding destinations of the body. There are three types of blood vessels in the circulatory system. They are arteries, veins, and capillaries. Basically, arteries convey oxygenated blood from the heart to all parts of the body. Also, they branch off into small arterioles. On the other hand, veins carry oxygen-depleted blood towards the heart. They begin from their small branches called venules. Blood capillaries are the smallest blood vessels, which connect arterioles to the venules. The exchange of nutrients, oxygen, and carbon dioxide between blood and extracellular fluid occurs through the walls of the capillaries.

Figure 2: Types of Blood Vessels

Moreover, the structure of both arteries and veins are composed of three layers: inner, middle, and outer layers. Here, the inner layer of them or the tunica intima is thin and is made up of simple squamous epithelium. The middle layer or the tunica media is the thickest layer in arteries made up of vascular smooth muscles. In contrast, the outer layer or the tunica adventitia is the thickest layer in veins made up of connective tissue. However, capillaries are made up of a single layer of endothelial cells. Furthermore, the autonomic nervous system is responsible for the regulation of blood flow through blood vessels. 

Similarities Between Nerves and Blood Vessels 

• Nerves and blood vessels are two types of tubular structures that occur in the animal body. 
• They are responsible for carrying their corresponding entities from one to another end of the body. 
• Their passage is unidirectional. 
• They are in different types based on the function. 
• A connective tissue layer surrounds both nerves and blood vessels. 

Difference Between Nerves and Blood Vessels 

Definition 

Nerves refer to the whitish fibers or bundles of fibers in the body, transmitting impulses in and out of the central nervous system while blood vessels refer to the tubular structures carrying blood through the tissues and organs. 

Structure 

Nerves are made up of axons of the neurons of the peripheral nervous system while blood vessels are made up of three layers; inner, middle, and outer layers.  

Color 

Most nerves are white in color, and some are yellow while arteries are red and veins appear in blue color under the pale color skin. 

Solid or Hollow Structures 

Nerves are solid structures, while blood vessels are hollow structures. 

Cells 

Moreover, nerves are composed of nerve cells and Schwann cells, while blood vessels are composed of endothelial cells and smooth muscle cells. 

Belong to 

Furthermore, nerves belong to the peripheral nervous system, while blood vessels belong to the circulatory system. 

Types 

The three types of nerves are sensory, motor, and mixed nerves, while the three types of blood vessels are arteries, veins, and capillaries. 

Network 

Nerves do not form a network while blood vessels form a network by making interconnections between different types of blood vessels. 

Branching 

While nerves are not branched structures, blood vessels are branched. 

Ends 

While nerves terminate at the CNS or effector organs, arteries and veins become smaller and interconnected through capillaries at their distal end from the heart. 

Function 

Moreover, nerves carry action potentials in the form of electrochemical signals in and out of the central nervous system while blood vessels carry blood throughout the body. 

Role 

Nerves help in the coordination of functions of the body in response to internal or external stimuli while blood vessels transport nutrients, oxygen, and metabolic wastes to their corresponding destinations of the body. 

Conclusion 

Nerves are the components of the peripheral nervous system, conducting nerve impulses in and out of the CNS. They are mainly composed of axons of nerve cells and supporting Schwann cells. Also, the three types of nerves are sensory, motor, and mixed nerves. In contrast, blood vessels are the components of the circulatory system, carrying blood away and towards the heart. However, the three types of blood vessels are arteries, veins, and capillaries. On the other hand, they are responsible for transporting nutrients, oxygen, and metabolic wastes to their corresponding destinations. Therefore, the main difference between nerves and blood vessels is their structure and function. 

References:

1. “Nerve.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., Available Here.
2. “Blood vessel.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., Available Here.

Image Courtesy:

1. “1319 Nerve StructureN” By OpenStax College – Anatomy & Physiology, Connexions Web site. (CC BY 3.0) via Commons Wikimedia   
2. “Blood vessels (retouched) -en” By File:Blood vessels-en.svg (CC BY-SA 3.0) via Commons Wikimedia