Anatomy and Physiology

1. Anatomy and Physiology 9.5 – Brain Disorders and Studies

2. Warm Up 01.29.07 • What are the functions of cerebrum?

3. Brain Disorders – Destruction of Brain Tissue • Injury or disease can destroy neurons • A common example of the destruction of neurons is from a cerebrovascular accident (CVA) or stroke. • A CVA is a hemorrhage from or cessation of blood flow through cerebral blood vessels • The oxygen flow to the brain is disrupted and neurons cease functioning and eventually die

4. Brain Disorders - CVA • The symptoms of a stroke depend on the portion of the brain affected by the CVA • If the motor control part of the brain is affected, the individual can no longer voluntarily move • Because the paths of motor neurons in the cerebrum cross over in the brainstem, it affects the side of the body opposite from the side of the brain with the CVA

5. Hemiplegia • Hemi means “half” • Plegia means “paralysis” • So hemiplegia is paralysis (loss of voluntary muscle control) of one whole side of the body • As is common with a CVA

6. Cerebral Palsy • One of the most common crippling diseases, appears during childhood • Involves permanent, nonprogressive damage to motor control areas of the brain • Either present at birth or occurs shortly after birth and remains throughout life

7. Cerebral Palsy (cont’d) • Causes of brain damage: • Prenatal infections or maternal disease • Mechanical trauma to the head before, during or after birth • Nerve-damaging poisons • Reduced oxygen supply

8. Manifestation of Brain Damage • Spastic paralysis • Characterized by involuntary contractions of affected muscles • Hemiplegia if it affects one side of the body • Paraplegia if it affects both legs • Triplegia if it affects both legs and one arm • Quadriplegia if it affects all four extremities.

9. Degenerative Disease • Degeneration can progress to adversely affect memory, attention span, intellectual capacity, personality and motor control • General term for this = dementia

10. Alzheimer’s Disease • Has characteristic lesions that develop in the cortex during the middle to late adult years • We do not know what causes the formation of these lesions • Maybe a genetic basis or environmental factors may play a role • Effective treatment is difficult because the cause is unknown

11. Huntington Disease • A genetic disease characterized by chorea (involuntary, purposeless movements) that eventually turns into severe dementia and death • Initial symptoms appear between 30 and 40 years and death usually by 55 • The gene for this disease has been located and there are available tests

12. Moral Questions from Genetic Tests • If you could learn early in life if you have HD, would you want to know? • If you could learn if your unborn child would have HD, would you want to know?

13. Seizure Disorders • Characterized by seizures (sudden bursts of abnormal neuron activity that result in sudden changes in brain function) • Can be mild (subtle changes in consciousness) to quite severe (jerky, involuntary muscle contraction called convulsions or even unconsciousness)

14. Epilepsy • Recurring or chronic seizure episodes make up the condition called epilepsy • Epilepsy can be traced to specific causes (trauma, chemical imbalances, turmos) but most is idiopathic • Epileptics are treated with meds that block neurotransmitters in affected areas of the brain

15. Electroencephalogram (EEG) • Graphic representation of brain activity • A normal EEG shows a chaotic rise and fall of the electrical activity in different parts of the brain as wavy lines (brain waves) • A seizure is an explosive increase in the size and frequency of these waves • See Figure 9-14 on page 283

16. Brain Studies • X-Ray photography – traditional radiography, can reveal tumors or injuries but shows no soft tissue detail • Computed Tomography (CT) – Scanning the head with a revolving x-ray generator, constructs an image that appears as a “slice” of brain on a screen, can detect hemorrhages, tumors and other lesions

17. Brain Studies • Positron Emission Tomography (PET) • Variation of CT in which a radioactive substance is introduced into the blood supply of the brain and shows up as a bright spot on the image • Determines functional characteristics of specific parts of the brain (see page 281)

18. Brain Studies • Single Photon Emission Computed Tomography (SPECT) • Similar to PET, but more stable substances are used and visualizes blood flow patterns in the brain, making it useful in diagnosing CVAs & brain tumors • Ultrasonography • High frequency sound waves (ultrasound) are reflected off of anatomical structures to form images similar to radar, usually used to diagnose hydrocephalus or brain tumors in infants

19. Brain Studies • Magnetic Resonance Imaging (MRI) • AKA: Nuclear magnetic resonance (NMR) • Canning method that doesn’t use harmful radiation • The magnetic field surrounding the head induces the brain tissue to emit radio waves used by the computer to produce a sectional image • Produces sharper images than the CT or ultrasound so is used to detect small brain lesions

20. Brain Studies • Evoked Potential (EP) Test • Similar to the EEG, but the brain waves observed are caused by specific stimuli (e.g. flash of light or a sudden sound) • This information is analyzed by a computer that generates a graphic image of the brain and displays it on a video screen (a brain electric activity map) • Changes in color represent changes in brain activity