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Dear PARKINSN friends, In response to the question by Warren Whitney, I'd like to share some views on his father's experience with the "system", fall and all! 1. Failure to maintain sufficient blood pressure in the brain is often the cause of a fall in PD sufferers. The best known mechanism for arterial pressure control is called a baroreceptor reflex. During changes of body posture, the pressure receptors (baroreceptors) located in the walls of the major systemic arteries transmit signals to the Central Nervous System, iliciting a strong sympathetic response. Example: If a person sits or stands up after having been lying down, the arterial pressure in the head and upper body tends to fall. The baroreceptors in the walls of the carotid sinus and aorta detect the loss of pressure, and elicit an immediate response. Constriction of blood vessels throughout the body, and an increase in cardiac output and strength of contraction, results in minimizing the decrease of pressure in the head and upper body. As is the case with other muscle action, these responses take longer in PD sufferers. It is thus important to be carefull in changing posture, rather accomplish the change of posture in steps. Obviously, complicating factors such as congestive heart failure (even mild forms) diminish the ability of the body to cope with the change of posture. Levidopa also enter sympathetic neurons and may interfere with the normal function of the sympathetic nervous system, in the majority of patients causing low blood pressure. An important feature is that the blood pressure is normal while sitting or lying down, but low while standing (pooling of blood in the legs). 2. As a person caring for a PD patient, one has to be extremely cognitive and sensitive in distinguishing between the inability to communicate and dementia. Often, ignorant or insensitive people mistake the inability to communicate for dementia, leaving the patient disheartened, dejected and depressed, ultimately leading to an unwillingness to attempt communication. Often, overworked and hurried medical personnel unknowingly elicit this response. Finally, I'd like to stress that neurons, even more so than any other cell in the body, need a constant supply of blood to function properly. If blood flow to the brain is impaired, either by low blood pressure, fever, etc., lapses of memory may occur. This is true for any individual, not merely PD sufferers. This also goes for any knock to the head. Hans ===================================================================== Hans van Zyl | Cell Physiology Group | [log in to unmask] Irene Animal Production Institute | Tel: (27) 12 672 9261 Private Bag X2 | Fax: (27) 12 665 1604 IRENE 1675, South Africa | =====================================================================