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A stroke occurs when something disrupts the blood supply to part of the brain. Two types of strokes can occur (CDC, 2023). However, most strokes are ischemic strokes. An ischemic stroke occurs when blood clots or particles block the blood vessels in the brain (CDC, 2023). The brain controls our movements, stores our memories, and is the source of our thoughts, emotions, and language. The brain also controls many functions of the body, like breathing and digestion (CDC, 2023). In order to work correctly, the brain needs oxygen.
Arteries deliver oxygen-rich blood to all parts of the brain. If something happens to block the flow of blood, the lack of oxygen will cause brain cells to begin dying within minutes (Qin et al., 2022). During an ischemic stroke interrupted cerebral blood flow depletes the brain of oxygen and glucose, which leads to disrupted ATP synthesis and energy deficiency, as well as impaired ion homeostasis and acid-base imbalance, which will cause the cells directly affected by the lack of glucose and oxygen in the neuronal core die by necrosis (Qin et al., 2022).
The brain is particularly vulnerable to ischemia because complete interruption of blood flow to the brain for only five minutes triggers the death of vulnerable neurons in several brain regions, whereas 20–40 minutes of ischemia is required to kill cardiac myocytes or kidney cells(J et al., 2000). In part, the prominent vulnerability of brain tissue to ischemic damage reflects its high metabolic rate. Without a continuous supply of blood, ischemic strokes can result in death or permanent neurological deficits, including hemiplegia or paralysis of one side of the body, numbness, loss of sensory function and vibratory sensation, balance problems, decreased reflexes, visual field defects, and apraxia or the loss of ability to execute or carry out skilled movement and gestures despite having the physical ability and desire to perform them (Apraxia, 2023), due to neuronal damage of pathways of the central nervous system, including the cerebellum (Kessner et al., 2019).
For my project, I used drawing to illustrate an isometric stroke and its effects on the neurons within the brain. At the top of my drawing is a normal brain with regular blood flow. Next to that brain, I have depicted a close-up image of red blood cells moving unhindered throughout the artery. Next to this picture are two alive and active neurons with a close-up of the neurotransmitters transferring from one neuron to another. The image below depicts a brain during an isometric stroke. By drawing the surrounding brain tissue slightly gray, I illustrated the lack of oxygen due to decreased blood flow. Next to the affected brain is a close-up of the affected artery. In this close app, you can see the plaque buildup on the inside of the artery, as well as a blood clot, blocking the flow of red blood cells at that point. The disruption of blood supply causes surrounding neurons to receive an inefficient amount of oxygen and glucose, causing their axons to shorten and the affected neurons to die. I have illustrated this process by depicting two neurons that are unable to communicate through electric signals or transfer neurotransmitters next to the affected brain.
Reference:
Apraxia. (2023). National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/disorders/apraxia#:~:text=Apraxia%20is%20the%20loss%20of,and%20desire%20to%20perform%20them.
CDC. (2023, May 4). About Stroke. Centers for Disease Control and Prevention. https://www.cdc.gov/stroke/about.htm
J, L., Grabb, M. C., Zipfel, G. J., & Choi, D. W. (2000). Brain tissue responses to ischemia. Journal of Clinical Investigation, 106(6), 723–731. https://doi.org/10.1172/jci11003
Kessner, S. S., Schlemm, E., Cheng, B., Bingel, U., Fiehler, J., Gerloff, C., & Thomalla, G. (2019). Somatosensory Deficits After Ischemic Stroke. Stroke, 50(5), 1116–1123. https://doi.org/10.1161/strokeaha.118.023750
Qin, C., Yang, S., Chu, Y.-H., Zhang, H., Pang, X.-W., Chen, L., Zhou, L.-Q., Chen, M., Tian, D.-S., & Wang, W. (2022). Signaling pathways involved in ischemic stroke: molecular mechanisms and therapeutic interventions. Signal Transduction and Targeted Therapy, 7(1). https://doi.org/10.1038/s41392-022-01064-1