Parkinson’s Disease Pathophysiology

Parkinson’s Disease is part of a group of conditions which are broadly categorised as movement disorders. Hence, Parkinson’s disease is mainly due to the loss of the brain’s controls over voluntary movements.The death of nerve cells in the substantia nigra region of the brain is the main reason for the onset of Parkinson. These nerve cells are responsible for the secretion of dopamine. Dopamine is a neurotransmitter which relays signals from the substantia nigra to the basal ganglia regions in the striatum. This in turn allows us to control our balance, movement and coordination. Actually, it is normal for there to be a decline in the number of dopamine-secreting nerve cells in individuals. In the specific case of individuals with Parkinson’s, the decline is much more rapid. Among Parkinson’s sufferers, majority have contracted idiopathic Parkinson’s Disease. Unfortunately, this means that the we are still not able to accurately and decisively pinpoint the underlying cause of Parkinson’s disease. However, it is heartening to note that significant amount of research is being dedicated to investigate the identify the underlying causes of this debilitating illness.

Epilepsy

Long before the advances in medicine, people who were subject to having fits and seizures were not thought to have a medical condition, rather they were thought to have been possessed by some sort of third-party demon. However, since the remarkable breakthroughs in the dynamic and ever-changing medical field, doctors and research professionals have clarified that it’s due to a medical condition affecting the brain: epilepsy.

Although it is a neurological condition affecting the brain, it also has a physical effect, as the body is affected when a seizure occurs. Anyone can develop epilepsy: all ages, all races, and people of all social classes. However it is more distinguishably recognised in youngsters under the age of 20 years and in the elderly over the age of 65 years. The condition is usually only diagnosed after the person has experienced more than one seizure. These seizures take place when there is a sudden and irregular interruption in the way that the brain would normally work.

Epilepsy is a condition that varies from person to person, and affects them in different ways. There are over 40 different types of epilepsy so just knowing that somebody is epileptic, indicates very little about their epilepsy and the type of seizures they experience. For instance, some sufferers go blank for a few seconds or minutes, while others may walk around in confusion, whereas others tend to fall into convulsion where they fall to the ground and begin shaking involuntarily. The latter, is the more commonly recognised form of epilepsy, however the other types must not go ignored.

The potential causes of epilepsy are many and will vary between different people. Sometimes the reason behind the development of epilepsy can be found out, for example if somebody has suffered a traumatic head accident or undergone a stroke; however, there are other times when a person’s epilepsy and the seizures may start off randomly with no physical causes, and hence the actual cause of it becomes more difficult to uncover. The main causes of epilepsy can be divided into three groups. The first is when there is a known cause for the condition, such as trauma to the head, infections such as meningitis or a stroke as described above. In these cases, usually an MRI scan (Magnetic Resonance Imaging) can be used to detect the cause as it will most likely show up. The second group is when the epilepsy is likely to be due to genetics and the way the genes are made up, inherited from either one or even both the parents. The third and more ambiguous group is when the cause for a person’s epilepsy has not yet been found, despite there being various investigations already taken place.

Epilepsy is usually treated by the use of anti-epileptic drugs, otherwise known as AEDs. The sole aim of the anti-epileptic drugs are to stop seizures from occurring, but they do not cure the condition. In the majority of cases, anti-epileptic drugs are very effective and the seizures experienced can be controlled by taking these drugs. However, in very few cases the AEDs seem to have very little, if any, effect on the number of seizures that occur. In such circumstances, surgery may be an option. The surgery involves removing the part of the brain which is responsible for causing the seizures.

Metabolic Rate explained

  Couch potatoes are ‘as fit as hunter-gatherers,’ according to several media outlets, based on research undertaken by anthropologists from Hunter College, New York, and several other academic institutions in the US.

The study compared the number of calories members of an African tribe burned in a day to the average ‘burn rate’ of those from developed countries.  They then calculated the total energy expenditure and found it was about the same.

The study concentrated in particular on the metabolic rate of the African tribe and how it compared with westerners.

Metabolic rate is the total body energy expenditure per unit time. The normal metric unit of energy is the joule, but for metabolism the unit calorie is used. One calorie is the amount of heat energy needed to raise the temperature of one gram of water from 14.5C to 15.5C.

Therefore, basal metabolic rate (BMR) is the metabolic rate when a person is at mental and physical rest but not sleeping, at a comfortable temperature and has fasted at least 12hrs.

There are many factors that can affect metabolic rate including:

•             Sleep, as metabolic rate decreases during sleep.

•             It decreases with age. After 20 years, it reduces about 2% every decade; this is because there’s a strong link between exercise volume and your metabolic rate. In other words, the more exercise you do, the higher your metabolic rate.

Second, metabolic rate is also linked to total calorie intake. This means that the more you eat, the higher your metabolic rate. And as people get older they tend to eat less, hence they usually have a lower metabolic rate.

•             Gender. (Women have less than men at any size) Women naturally have a lower BMR, due to breast and gluteal tissue which is higher in fat than in men, due to natural processes such as child birth.

•             Fasting. This is because when fasting humans must   maintain blood glucose above 2mM otherwise the brain will stop working- unconsciousness. This is done for example as fatty acids are released from adipose tissue. The fatty acids are used as fuels by most tissues in preference to glucose.

 

However the presence of or an increase in any of these factors can cause an increase in metabolic rate:

•             Height, weight and body surface area contribute a lot to BMR, as the greater the surface area the greater you’re BMR, tall and thin people tend to have high BMR.

•             Pregnancy, menstruation, lactation

•             Growth

·                Infection or other diseases

·                Exercise

·                Hormones (such as leptin and thyroid hormone.)

·                Muscular Activity

The thyroid hormones are the most important determinant of metabolic rate, for people of all ages, size and sex. Thyroid hormones increases oxygen consumption and heat production of most body tissues excluding the brain. This is called the calorigenic effect, the ability to increase metabolic rate. If there too many thyroid hormones for a long time, for example with those with hyperthyroidism, a lot of effects other than the calorigenic effect will take place. For example, the increased metabolism will cause an increase in hunger and food intake.  Whereas a lack of thyroid hormones can result in mental and physical lethargy and delayed reflexes.

However, the factor that increases metabolic rate most is altered skeletal muscle activity. Small increases in muscle contraction can affect metabolic rate and strenuous exercise dramatically, and can potentially cause an increase in energy expenditure by fifteen times.  This is why during sleep the metabolic rate is extremely low because there is less skeletal activity.

Ultrasound Scan Objective

I would like to start by saying that I am sorry for having disappeared for the past couple of months due to exams and UCAS, but hopefully I can write more often now .

On my recent work experience at BRI I was fortunate to be able to shadow a sonographer and so thought I’d share my experience.

Ultrasound is a form of energy using high frequency soundwaves to produce an image. During my time in ultrasound many abdominal cases and a madible case was seen. These involved gall stones, mass, focal lesions and lymph node in the mandible.

A gel medium was required in order to improve transmission of soundwaves. The speed of this sound varies depending on the medium density and compressibilty. Without the gel the soundwaves would have to travel through different densities; through air and then through soft tissue.

Even though ultrasound does not give off radiation, it still may not be as safe. The bioeffects of ultrasound are heating and cavitation. The beam is attenuated as it passes through tissue therefore energy is lost. This energy is absorbed and converted into heat. This can cause over heating of any microbubbles which may be present within organs. Changes in pressure of the beam may cause the microbubbles to oscillate in size and cause tissue damage. However, ultrasound has not yet been proven to be unsafe.

Ultrasound soundwaves cannot pass through bone so only the outer surfaces of bones will be shown, and what is within the bony structures will not be shown. Another limitation is large body habitus and if there is more gas than bone present. Because of these limitations other modalities such as CT, general X-RAY and MRI have to be used.

idoctor says hello!

Well where do I begin…. this is my first post on the blog so I just want to say a little hello an introduce myself to those who read this blog and other writers. A lot like many of you I am an aspiring medic. I applied last year with one interview which was unsuccessful so without a doubt will be trying again for 2013. Received my a level grades 2 weeks ago, big smilees 🙂 🙂 🙂 which also showed me how much I want to study medicine. Being quite an academic person I have always been told that I can do whatever i want and that ‘the world is my oyster’. easier said than done 😉 well ill keep it short and simple… hoping to try new things during my gap year, and blogging being one of them, i thought this would be a great way to write about things that interest me whilst trying something new. I’ll try to post every week and talk about different topics in the medicine world that I find most interesting and most important and i’ll also keep you upto date on my application to medicine ..take two 😉