临床医学英语教学课件：Unit 4Parkinson’s Disease

1、Unit 4Parkinsons DiseaseImportant Combining Forms1. idio-: self, spontaneous2. lev(o)-: left3. dys-: bad, diseased4. kinesi(o)-: movement The Basics of Parkinsons DiseaseWhat Is Parkinsons Disease?Parkinsons disease, which mostly afflicts older people, results from gradual degeneration of nerve cell

2、s in the portion of the midbrain that controls body movements. The first signs are likely to be barely noticeable - a feeling of weakness or stiffness in one limb, perhaps, or a fine trembling of one hand when it is at rest (activity causes the tremor to disappear). Eventually, the shaking worsens a

3、nd spreads, muscles tend to stiffen, and balance and coordination deteriorate. Depression and other mental or emotional problems are common.Usually the disorder begins between the ages of 50 and 65, striking about 1% of the population in that age group; it is slightly more common in men than in wome

4、n. Medication can treat its symptoms, and the disorder is not directly life-threatening.What Causes Parkinsons Disease? Bodily movements are regulated by a portion of the brain called the basal ganglia, whose cells require a proper balance of two substances called dopamine and acetylcholine, both in

5、volved in the transmission of nerve impulses. In Parkinsons, cells that produce dopamine begin to degenerate, throwing off the balance of these two neurotransmitters. Researchers believe that genetics sometimes plays a role in the cellular breakdown. In rare instances, Parkinsons disease may be caus

6、ed by a viral infection or by exposure to environmental toxins such as pesticides, carbon monoxide, or the metal manganese. But in the great majority of Parkinsons cases, the cause is unknown.HistorySymptoms of Parkinsons disease have been known and treated since medieval times, most notably by Aver

7、roes. However, it was not formally recognized and its symptoms were not documented until 1817 in An Essay on the Shaking Palsy by the British physician James Parkinson. Parkinsons disease was then known as paralysis agitans, the term Parkinsons disease being coined later by Jean-Martin Charcot. The

8、underlying biochemical changes in the brain were identified in the 1950s due largely to the work of Swedish scientist Arvid Carlsson, who later went on to win a Nobel Prize. L-dopa entered clinical practice in 1967, and the first large study reporting improvements in patients with Parkinsons disease

9、 resulting from treatment with L-dopa was published in 1968.Parkinsons disease (also known as Parkinson disease or PD) is a degenerative disorder of the central nervous system that often impairs the sufferers motor skills, speech, and other functions.Parkinsons disease belongs to a group of conditio

10、ns called movement disorders. It is characterized by muscle rigidity, tremor, a slowing of physical movement (bradykinesia) and, in extreme cases, a loss of physical movement (akinesia). The primary symptoms are the results of decreased stimulation of the motor cortex by the basal ganglia, normally

11、caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level cognitive dysfunction and subtle language problems. PD is both chronic and progressive.Substantia nigra and Parkinsons diseaseParkinsons

12、disease is a slowly progressive disorder that affects movement, muscle control, and balance.Part of the disease process develops as cells are destroyed in certain parts of the brain stem, particularly the crescent-shaped cell mass known as the substantia nigra. Nerve cells in the substantia nigra se

13、nd out fibers to tissue located in both sides of the brain. There the cells release essential neurotransmitters that help control movement and coordination. The NeuronWhen sufficient neurotransmitters cross synapses and bind receptors on the neuronal cell body and dendrites, the neuron sends an elec

14、trical signal down its axon to synaptic terminals, which in turn release neurotransmitters into the synapse that affects the following neuron. The brain neurons that die in Parkinsons Disease release the transmitter dopamine. Oligodendrocytes supply the axon with an insulating myelin sheath.Neuronal

15、 Pathways that Degenerate in Parkinsons Disease.Signals that control body movements travel along neurons that project from the substantia nigra to the caudate nucleus and putamen (collectively called the striatum). These nigro-striatal neurons release dopamine at their stargets in the striatum. In P

16、arkinsons patients, dopamine neurons in the nigro-striatal pathway degenerate for unknown reasons.The boxer Muhammad Ali and the actor Michael J. Fox suffer from Parkinsons disease. Both have supported efforts to find a cure.levodopaMost patients suffering from Parkinsons Disease are treated with a

17、drug called levodopa, which the brain converts into dopamine. It initially helps most patients, but unfortunately, side effects of the drug increase over time and its effectiveness wanes. This leaves Parkinsons patients and their doctors fighting a long, uphill battle to balance medication with side

18、 effects to maintain function. In the end, many patients are utterly helpless.Structures in the brain related to Parkinsons disease. Basal ganglia affect normal movement and walking; the substantia nigra produces the neurotransmitter dopamine, and the globus pallidus affects movement, balance and wa

19、lking. The thalamus is a relay station for brain impulses, and the cerebellum affects muscle coordination.Parkinsons disease is a progressive motor disorder resulting from the selective death of a very tiny group of neurons in the brain called the substantia nigra. These neurons may be few in number

20、, but they do something very important. They secrete a neurotransmitter called dopamine into a part of the brain called the basal ganglia.The basal ganglia works kind of like a switch that is involved in choosing to initiate motion. When you brain is considering initiating motion, a signal goes to t

21、he basal ganglia. The basal ganglia make a computation, and then a signal is sent back either encouraging or discouraging the activation of that motion. The computation is performed by the ratio of the activity through two parallel pathways. A message from one nerve cell to another is transmitted wi

22、th the help of different chemical transmitters. This occurs at specific points of contact, synapses, between the nerve cells. The chemical transmitter dopamine is formed from the precursors tyrosine and L-dopa and is stored in vesicles in the nerve endings. When a nerve impulse causes the vesicles t

23、o empty, dopamine receptors in the membrane of the receiving cell are influenced such that the message is carried further into the cell. In the treatment of Parkinsons disease, the drug L-dopa is given, and is converted to dopamine in the brain. This compensates for the patients lack of dopamine. Cr

24、oss-section of the human brain showing the substantia nigra, the region affected by Parkinsons disease. Difficult Words in the Text1. gait: n. A particular way or manner of moving on foot: a person who ran with a clumsy, hobbling gait. 步法，步态2. Parkinsonism: n. (a) Any of a group of nervous disorders

25、 similar to Parkinsons disease, marked by muscular rigidity, tremor, and impaired motor control and often having a specific cause, such as the use of certain drugs or frequent exposure to toxic chemicals. Also called Parkinsons syndrome. 帕金森综合征(b) Parkinsons disease. 帕金森病3. incidence: n.(a) The act

26、or an instance of happening; occurrence.(b) Extent or frequency of occurrence: a high incidence of malaria in the tropics. Incidence is a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate with a denominator.Incidence proportion (also known as cumulative incidence) is the number of new cases within a specified time period divide