Bio did ya know of the day. Been slacking on this. This will be a three parter ONE (dumbed down a bit) Movement of right arm (RA) / Higher functioning sends three basic signals. One signal is generated by the left side of brain. The signal in the motor cortex simply says what to move and where. This signal is an all or none signal. It just tells the muscle to contract (on off switch). The second is sent to the basal ganglia. The basal ganglia interprets the signal which creates its own series of signals. These create info on how hard and how fast. This feeds into the motor cortex. (Main neurotransmitter here is dopamine)(Dimmer switch) The third is a the summation of signals into the motor cortex, of which you can think of POSITIVE movement and the basal ganglia of which you can think of NEGATIVE movement. From the motor cortex it again enters the basal ganglia for fine motor movement. From there it crosses over at the lower brain stem to the opposite side. It arrived in the spinal column. Then to the brachial plexuses (a plexus is a group of nerves). It then interacts with the muscle (synapse). From here a series of further chemical reactions occurs. One of which is the release of ach (acetylcholine) onto the muscle fibers themselves. The amount of ach is directly proportional to the amount of dopamine released earlier by the motor cortex that was the summation of positive and negative impulses by the motor cortex and basal ganglia. The ach stimulates calcium channels to open, creating an influx of calcium. The calcium reacts with sodium (na) and potassium (k) channels. The difference between the sodium inside the cells and potassium outside the cells creates an electrical charge. Once this charge meets a certain voltage (mv) the muscle will contract. This entire reaction from the moment you decide to move until the muscle contracts can only be measured by extremely sensitive device....its that fast. - pretty cool huh?! TWO (I have patients ask me why a Parkinsons pt needs their med regimin adjusted so often) In part ONE we spoke of a summation of positive and negative neurotransmitters (ntm) that dictate how hard and fast your muscles move. Positive ntm are glutamate and negative ntm are GABA. The filter for movement is the basal ganglia. The BG is very complicated and not fully understood. We do know that there are many disorders that may originate here, such as Parkinsons(PK). Furthermore A lack of dopaminergic (D1) receptors is thought to be responsible. D1 is responsible for GABA, a negative movement NTM to be lacking. This causes glutamate, a positive NTM, to take over. This causes fast, jerky and unpredictable movements to take over the muscles. We try to increase dopamine levels, but dopamine doesnt cross the blood brain barrier....(figures!). Thus we give L-Dopa. L-Dopa is then hopefully converted to Dopamine....this is extremely unpredictable. Thus the medication regimen of a PK patient may need to be adjusted daily. THREE - reflexes. As seen in ONE, the process of muscle movement is complex (and also not fully understood. But very very fast. There are times when general muscle movement, which is mediated by neurotransmitters, is NOT fast enough. A reflex is simple. A receptor on the skin is triggered, an impulse is sent to the spinal column, an impulse is sent STRAIGHT from the spinal column to a group of muscle fibers, the muscle fibers contract fast and fully, unlike in step one. The entire process is mediated by SODIUM and sodium only. After a reflex is triggered, the exact location and what triggered it is related to the brain. A stimulus is also sent to the adrenal gland to immediately release adrenaline into the blood stream. It is thought that reflexes are 50x faster than general movement. Note that reflexes in PK patients are still preserved. This is important on differentiating between a pt with Parkinsons vs a tonic seizure :). The difference between general movement and reflex movement can save you from serious injury and death. Some other facts about reflexes. 1. Magnesium causes reflexes to be stimulated easier. High magnesium, such as in a pregnant woman with eclampsia will first be evident by hyper reflex ability. 2. A reflex can not be turned off. The brain can dull a reflex if it is determine that there is no threat....with that said, an opiate OD pt will not have the ability to dull repeated reflex stimulation. 3. In areas such as the patella there are nerves that actually sit in the skin. The force of something hitting them causes the chemical reaction...kind of like a trip wire. Thats it for tonight. Are you curios about something that occurs in the body but have never been able to understand it? Shoot me a message ! Until next time. I hope your basal ganglia has less glutamate and more GABA for a good nights rest! Next up will be anesthesia, whats going on when Im asleep?
Posted on: Tue, 03 Jun 2014 05:56:53 +0000
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