chapter 15 notes

chapter 15 notes - CHAPTER 15 Neurological disorders Tumors...

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CHAPTER 15: Neurological disorders Tumors: = a mass of cells whose growth is uncontrolled and that serves no useful function. Malignant = cancerous; not encapsulated, no distinct border btw it and surrounding tissue. Benign = non-cancerous; encapsulated, distinct border, can be cut out, won't metastasize. Metastasis: process by which cells break off a tumor, travel through vascular system, +grow. Tumors infiltrate brain tissue by 2 means: 1. compression: even a benign tumor, by occupying space/ pushing against the brain can directly destroy brain tissue or block flow of cerebrospinal fluid/ cause hydrocephalus. 2. infiltration: as a malignant tumor grows, it invades surrounding region and destroys cells in its path. Tumors do not arise from nerve cells, which do not divide; they arise from other cells found in brain or from metastases originating elsewhere in the body. Most serious types are metastases and gliomas → derived from forms of glial cells. Types of brain tumors: Gliomas → glioblastoma multiformae (poorly differentiated glial cells) astrocytoma (astrocytes) ependymoma (ependymal cells that line ventricles) medulloblastoma (cells in roof of 4 th ventricle) oligodendrocytoma (oligodendrocytes) Meningioma → cells of the meninges (encapsulated and benign) Pituitary adenoma → hormone-secreting cells of pituitary gland Neurinoma → Schwann cells or cells of connective tissue covering cranial nerves Metastatic carcinoma → depends on nature of primary tumor Angioma → cells of blood vessels Pinealoma → cells of pineal gland Seizure disorders: ~2.5 million people in the US have a seizure disorder; most important disorder after stroke. Convulsion: a violent sequence of uncontrollable muscular movements caused by a seizure; occurs if the excessive activity of cerebral neurons happens in the motor system neurons. Partial seizures : begin at a focus (source of irritation, e.g a scarred region or site of developmental abnormality); remains localized, not generalizing to rest of brain. Simple partial seizures: often cause changes, but not loss, of consciousness Complex partial seizures: lead to loss of consciousness (more severe/ worse locations) Generalized seizures : involve most of brain, sometimes origin cannot be discovered. Grand mal : a generalized, tonic-clonic seizure → convulsions; involves motor systems. Tonic phase: 1 st phase of grand mal; all skeletal muscles are contracted; unconsciousness Clonic phase: rhythmic jerking movements, eye rolling, autonomic activity, sleep after. Neural firing begins at focus at time of aura (sensation preceding seizure), then spreads to surrounding regions and then to contralateral cortex (via corpus callosum), the basal ganglia, thalamus, +various nuclei of brain stem reticular formation → symptoms begin.
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