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Lecture 3

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University of Toronto Scarborough

Lecture 3 Vascular System Brain Disorders - blood carries oxygen and sugars => oxygen is most critical bc person can only stay alive ~3 min w/o oxygen => brain has a very high metabolic rate, so cannot stay alive w/o oxygen even for very short periods => first organ to be damaged from a problem like a heart attack Types of problems: 1. Cerebrovascular accident (CVA, stroke): severe interruption of blood supply to the brain => results in ischemia (not enough blood/not enough oxygen); blood will be missing glucose/o2 => produces dead/dying tissue/severely damaged tissue – infarct 2. Encephalomalecia: very slow reduction in blood supply, due to long term blockage of arteries due to plaque/obstruction => softening of the brain tissue – some tissue death, but tissue as a whole hasn’t completely died; may see swelling of tissue => incomplete tissue death, some cells may be dying, others healthy 3. Transient ischemic attack: temporary (comes and goes) restriction of blood flow, involving musculature of a particular blood vessel => may occur during severe/migraine headaches => vessels constrict, reduction in vision/blurriness in a particular part of the visual field => do not cause brain damage – not sufficiently severe Causes of blood flow disruption: 1. Blockage: thrombosis: blockage that is locally formed; can form at any one site in the brain, eg blood clot => cause CVA embolism: blockage that breaks off from a plaque in a remote location away from the brain and travel until it lodges and blocks an artery in the brain => cause CVA arteriosclerosis: general clogging of the arteries, occurs more in elderly individuals; if clogged in the brain can cause encephalomalecia 2. Cerebral haemorrhage: - burst of blood vessels, results to a loss of blood supply from the cardiovascular system and bleeds into the brain tissue - can be life threatening, most often associated w high blood pressure => critical that blood pressure is controlled - bleeding into the brain it will kill the brain tissue where its bleeding 3. Subdural hematoma: - bleeding into the space bw the skull and the brain, bleeding underneath the dura - not bleeding inside the brain itself, but outside the brain into the area of the meninges - doesn’t kill the brain tissue directly, and if caught in time => puts pressure on the brain - pressure can be relieved w/o incurring permanent brain damage - black is lateral ventricle, should be one on the other side, but the hematoma (white) pushed the brain (grey) so far over that it took over the second lateral ventricle 4. Angioma: - collection/mass of enlarged abnormal blood vessels - congenital defect – during development, blood vessels tangled/crossed in a small area of the brain => can shunt blood in the wrong direction, not always a problem 1 - these blood vessels are inherently weak, if high blood pressure then they can burst leading to cerebral haemorrhage, etc, can lead to a stroke - if noticed in time, can be corrected surgically 5. Aneurysm: - vascular dilation, expanded blood vessel caused by localized problems in elasticity - if the bubble pops can lead to cerebral haemorrhage or hematoma - can lead to stroke Closed head injuries: - next major problem after blood supply problems - blow to the head that causes an injury to the brain but doesn’t open the brain up - most often due to automobile accidents or trauma to the head – motor vehicle, sports accidents => brain slammed against the front of the skull – damage the frontal lobes and the front part of temporal lobes - contracoup (countercoup) event – need to be aware that person can be injured not just on the side of the direct damage, but also on the opposite side due to recoil Brain tumours: - caused by cancer => mass of growing tissue independent of the surrounding tissue - gliomas most common – cancer of the glial cells => 45% of all brain tumours, range from benign to highly malignant - meningiomas – tumours formed in the meninges (not in the brain), u
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