Definition

Definition:
Stroke is a serious medical disease characterized by sudden onset of weakness , numbness , difficult speech , loss of speech , vision problem and any other manifestation of sudden interruption of blood flow to the specific area of brain.
Explanation:
stroke cause due to a blood clot formed in blood vessel and reduce blood flow to brain. Due to it brain tissue become damaged or die. The stroke also known as brain attack. Brain attack occurs when something blocks blood supply to the part of brain or when the blood vessel in the brain bursts. In this case, parts of the brain become damaged or die. The brain attack cause lasting brain damage, long-term disability, or even death. Brain controls many vital function in our body such as movement, store information and the source of thought, emotion and circulation. Brain also controls many other function of body such as breathing, digestion, etc. To work properly your brain needs oxygen, energy and nutrients. Brain makes up only 2% of human body weight, it uses 20% of the total oxygen when human breathe. Carotid arteries and vertebral arteries deliver oxygen-rich blood to all parts of your brain.
Types of stroke:
There are two types of stroke
1) Ischemic stroke
2) Hemorrhagic stroke

1) Ischemic stroke:
An ischemic stroke occurs when blood clots or other particles block the blood vessels to the brain. Fatty accumulation are called plaque also cause blockages by building up in the blood vessels. Most strokes are ischemic stroke which are about 87%

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2) Hemorrhagic stroke:
A hemorrhagic stroke happens when an artery in the brain flow blood out of blood vessel or ruptures. The leaking blood puts too much pressure on brain cells, which damages them. Both type of stroke cause brain cell death.
There are two types of hemorrhagic strokes
a) Intracereberal hemorrhage : Intracerebral hemorrhage is very common type of brain stroke. It occurs when an artery in the brain bursts and fill the surrounding tissue with blood.
b) Subarachnoid hemorrhage: Subarachnoid hemorrhage is a less common type of hemorrhagic brain attack. It cause due to bleeding in the area between the brain and the thin tissues that cover it.

Pathophysiology:
A stroke cause when the blood flow to an area of the brain is disturbed, resulting in some exetent of permanent neurological damage. The two major categories of stroke are ischemic due lack of blood and hence oxygen to an area of the brain and hemorrhagic stroke due to bleeding from a burst or going out of blood from blood vessel in the brain.
Pathophysiology of ischemic stroke: The common pathway for ischemic stroke lack of enough blood flow the brain tissue due to narrow or blockage of arteries leading to the brain or within brain. When blood flow to the brain stop occurs then ischemic cascade is initiated. This is a series of biochemical reaction in brain and other aerobic tissue which usually go for three to four hour and but can last for day even after normal blood flow can return.
Important steps:
1) Without adequate blood flow to brain there is low oxygen or no oxygen so brain cell lost their ability to produce energy especially adenosine tri phosphate ATP.
2) Due to low supply brain cell start anaerobic respiration which produce less amount of ATP and release lactic acid by product.
3) Lactic acid is irritant which is the potential to destroy normal brain cell by disturbing acid base balance in brain.
4) ATP dependent ion transport pump fail causing the cell membrane to depolarize leading to large influx of ca** and efflux of potassium.
5) Calcium level increase in inside cell and trigger the release of excitatory aminoacid neurotransmitter glutamate
6) Glutamate stimulate AMPA receptors and calcium permeable NMDA
7) High level of calcium inside the cell more excites the cell and activates protease, lipase enzyme and produce free radical.
8) Cell membrane is broken by phospholipase enzyme and allow more ion and harmful substance to move inside the cell
9) Due to it mitochondria break down and release toxin and apoptotic factor in the cell.
10) Cell start apoptosis
11) If cell die due to necrosis it release toxic chemical and glutamate into the around environment. Toxic poison overexcite nearby neuron and glutamate.
12) The loss of vascular structure integrity results in breakdown of protective blood brain barrier and contributes cerebral edema which can cause secondary progression of brain injury.

Pathophysiology of hemorrhagic stroke:
Hemorrhagic stroke are due to rupture of blood vessel leading to compression of brain tissue from an expending hematoma. This can damage and injure the brain tissue. In addition the pressure may lead to loss of blood supply to the effect area of brain with resulting infraction and the blood released by the brain hemorrhage appear to have direct toxic effect on brain tissue and vasculature.

Sign and Symptoms:
? Sudden numbness or weakness in face, arm or leg especially on one side of body
? Sudden confusion, difficulty understanding speech or trouble speaking
? Sudden trouble seeing in one or both eye
? Sudden trouble walking, dizziness or loss of balance, or lack of coordination
? Sudden severe headache with no cause

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