The Nervous System and Strokes

by Robert Tallitsch, PhD | September 1, 2022

Nervous System and Strokes Brain Builder

Video introduction to the nervous system and explanation of the Cincinnati Prehospital Stroke Scale! Share this video with your class!

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Written by: Robert Tallitsch, PhD

According to 2020 statistics, the Centers for Disease Control states that 1 in 6 deaths from cardiovascular disease was due to a stroke. In addition, in 2020 almost 800,000 people in the United States had a stroke. Of those strokes, 87% were diagnosed as an ischemic stroke, where a blood vessel supplying the brain with blood is either blocked or the blood vessel burst. Both of these conditions deprive an area of the brain with oxygenated blood.

Quick treatment for a stroke is essential. In this Brain Builder we will briefly discuss the nervous system and its components. Then we will discuss the blood vessels supplying the brain with blood, followed by a discussion of strokes and the Cincinnati Prehospital Stroke Scale.

An Introduction to the Nervous System

The nervous system, which includes all of the nervous tissue of the body, is composed of two subdivisions: the central nervous system (CNS) and the peripheral nervous system (PNS).

The CNS is composed of the brain and spinal cord, and is responsible for the coordinating, integrating, and processing of the sensory input and motor output. The CNS is also the location of “higher” functions, such as emotion, intelligence, learning, and memory.

The PNS contains all of the nervous tissue outside of the CNS. The PNS is subdivided into afferent and efferent divisions. The afferent division carries sensory information from the periphery to the CNS, and the efferent division carries motor information from the CNS to the peripheral effector organs.

The entire nervous system is composed of only two cell types: glial cells and neurons. Glial cells help maintain the intracellular environment of the nervous system, provide a supporting network to the nervous system, and act as phagocytic cells within the nervous system. There are more glial cells than neurons, and glial cells retain the ability to divide.

There are three types of glial cells within the CNS, and two types of glial cells within the PNS. Microglia, astrocytes, and oligodendrocytes are found within the CNS, while satellite cells and Schwann cells (also known as neurolemmocytes) are found within the PNS.

Neurons communicate with each other by structures termed synapses. In addition, neurons communicate with other structures (such as a muscle or a gland) at junctions termed neuroeffector junctions.

The brain is composed of three basic subdivisions:

Cerebral hemispheres
Cerebellum
Brain stem, which is subdivided into the

Diencephalon
Mesencephalon (midbrain)
Metencephalon (pons)
Myelencephalon (medulla)

For a more detailed explanation of the brain’s anatomy check out our Brain Builder on the Brain and Alzheimer’s Disease.

Vasculature of the Brain

The brain receives its blood supply from two arterial systems: the right and left vertebral arteries and the right and left internal carotid arteries.

The right and left vertebral arteries are branches of the right and left subclavian arteries. These two arteries enter the cranium through the foramen magnum of the skull. Upon entering the cranium they ascend on the anterolateral aspects of the medulla. The right and left posterior vertebral arteries unite at the anterior aspect of the pons, forming the basilar artery.

The right and left internal carotid arteries enter the cranium by the right and left carotid canals. The internal carotid arteries ultimately divide to form the anterior and middle cerebral arteries.

The cerebral arterial circle (also termed the circle of Willis) is a circle of vessels on the base of the brain that is formed by the union of the four vessels (right and left carotid arteries and right and left vertebral arteries) supplying the brain with blood.

The interconnections between the large branches of the vertebral and internal carotid arteries by the cerebral arterial circle form an extensive collateral circulation in the brain. Such a collateral circulation minimizes the effects of an occlusion of one vessel upon the brain as a whole. However, the interconnections between smaller branches off of the cerebral arterial circle might not be sufficient to prevent an infarct (also termed a stroke) of some part of the brain.

Brain Infarcts (Strokes)

Deprivation of the blood supply to a part of the brain could, if the interruption lasts for more than a few minutes, result in an inadequate supply of oxygen and glucose to the brain. This interruption typically results in an infarct of brain tissue, also termed a stroke. A stroke often results in either a temporary or permanent loss of sensory and/or motor function within some portion of the brain.

Cincinnati Prehospital Stroke Scale

Early recognition of a stroke is essential, and most clinical treatment decisions should be made within the first few hours after the onset of symptoms of a stroke. As stated in a research study by A. De Luca et al. (2019), the Cincinnati Prehospital Stroke Scale (CPSS) is a standardized and easy to use stroke screening tool. The CPSS tests three signs for a possible stroke.

Speech: Individual exhibits slurred speech, utilizes incorrect words in a sentence, or is unable to speak.
Facial droop: Individual is unable to smile normally, or if one side of the face doesn’t move as well as the opposite side or seems to droop.
Arm drift: Individual is asked to hold both arms straight out in front of them with the palms up and eyes closed for approximately 10 seconds. If both arms move equally or not at all the individual is believed to be normal. However, if one arm does not move, or one arm drifts downward compared to the other the individual is suspected of having a stroke.

A thorough understanding of the CPSS, even by a non-medical person, can be valuable in assisting an individual that may be undergoing or has recently undergone a stroke. Minimizing the time between the onset of a stroke and the initiation of medical treatment is essential, and a thorough understanding of the CPSS is one step in that process.

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Reference

De Luca, A. et al. (2019) The role of the Cincinnati Prehospital Stroke Scale in the emergency department: evidence from a systematic review and meta-analysis. Open Access Emerg Med 11:147-159.