D.+Nervous+System+(Neurons+and+Synapses)

Meagan- This unit has related to my profession the most I feel. As an OTA, I need to understand the central nervous system, CNS, and the peripheral nervous system, PNS. It is important to understand how the sensory and motor neurons travel from the tissues in our bodies to our brains and how they are interpreted. If we touch something hot, the sensory neurons transmit an electrical signal from our tissues to the brain. The brain then transmits a signal to that tissue saying "move your hand!" If these signals cannot be sent and understood, then the individual will not be able to function, and may leave their hand on the hot stove for a long time! In a way if these signals were not sent or understood, it reminds me of how some people have a left side neglect. If they were to touch something hot on their left side, their brain would not even realize it because the body does not recognize it even has a left side! I wonder if there is something doctors could do so they could know to remove their hand from the hot stove.
 * Application **

Kalli- The Central Nervous System is made up of the brain and spinal cord. If there is an issue between the brain and spinal cord, or the brain and neurons, the human body recognizes that connection failure as some sort of disability. OTAs need to make sure they have full understanding of the nervous system in order to plan out which kinds of therapy are going to most help the patient succeed in which tasks they accomplish. I believe patients should also gain knowledge of whichever condition they have in order to better understand which therapies are going to help them and why. Perhaps, if the patient better understands what is going on in their own body, the discouragement and insecurity during rehabilitation would diminish and the patient would have a better outlook on the therapy.

Christine- The nervous system and how it function is one of the first things we as nurses check during our initial assessment and our daily assessments. If there is a change in a mental status of a patient or a level of consciousness this is a very serious situation. In our assessment we are basically just checking to see if the central nervous system and the peripheral nervous system are doing their jobs. We might ask the patient simple questions like what day it is or if they can follow simple commands like following my finger with their eyes. If the patient is unconscious we might try to test them to see if the neurotransmitters are still sending signals by asking the patient to squeeze our hand. A big test for someone who is unconscious is to see if they can do something we take for granted everyday...to breathe!


 * Content **

Central Nervous System is composed of the Brain and Spinal Cord. These two are the control centers of the nervous system. The Peripheral Nervous System is composed of cranial and spinal nerves that make communication possible between the Central Nervous System, muscles, and glands.

The neurons are the functional cells and send electrical signals. Here are the major parts of the neuron:

1. cell body- consists of the nd ajor 2. Dendrite- is the part of the neuron the receives the stimuli 3. Axon- carries the stimulus away
 * often covered with a myelin sheath
 * __Axon hillock__ is usually located at the beginning of the axon and is where the action potential starts
 * __Axon terminals__ are where the neurotransmitters are released



http://www.google.com/imgres?q=a+neuron&hl=en&biw=1280&bih=601&gbv=2&tbm=isch&tbnid=hHsZ7cGB2FmFTM:&imgrefurl=http://disjointedthinking.jeffhughes.ca/2011/02/all-about-the-brain-part-1/&docid=--553sbpppbjTM&w=640&h=403&ei=QXuCTonBC8evsAKwhrmgDw&zoom=1&iact=hc&vpx=330&vpy=190&dur=518&hovh=98&hovw=156&tx=139&ty=85&page=1&tbnh=98&tbnw=156&start=0&ndsp=21&ved=1t:429,r:1,s:0

__**Events During an Action Potential **__

When the cell is at resting point it sits at -70 mV. This just means that the inside of the cell is more negatively charged in the inside of the cell than on the outside. When a stimulus occurs the neuron goes through a series of events to start an action potential.

1. Depolarization- This is when a stimulus causes a neuron to go from resting to not. As the stimulus triggers this event the Sodium channels are opened causing the Sodium to rush into the cell making it more positive. Once a cell reaches around -55 mV it will hit its threshold and will be able to fire an impulse. However if this threshold is not met then there will be no impulse. As more Sodium is rushed into the cell it is causing a positive feedback response in which there is further depolarization followed by more channels opening allowing more Sodium to rush in which in turns allows further depolarization. At some point the mV will reach around +30.

2. Repolarization- This is when the neuron goes back to resting potential. First the membrane potential reaches +30 mV which triggers the Sodium channels to activate. At the same time Potassium gates are opened allowing Potassium to flow out. This would make the cell go from a positive charge back to a negative charge. Once the membrane potential drops below the threshold the Potassium channels are closed.

3. Refractory Period- A neuron must pass through this phase before it can go through a second stimuli. During the resting time the cell negatively is usually less than -70mV This allows the neuron to restore. The Sodium/Potassium pump restores the ions by pumping 3 Sodium out .of the cell and pumping 2 Potassium into the cell.

Information came from our notes

media type="youtube" key="7EyhsOewnH4" height="315" width="420" http://www.youtube.com/watch?v=7EyhsOewnH4

__<span style="font-family: 'Comic Sans MS',cursive; font-size: 120%;">Multiple Sclerosis __

The myelin sheath is the membrane that covers the axon to insulate it as well as it accelerates the electrical signal transmission. In Multiple Sclerosis (MS) the bodies immune system attacks the myelin sheath and sometimes the nerve itself causing complications.When the body attacks this membrane it often leaves scar tissue which causes the impulse to traveling along the membrane to be come distorted. Some symptoms of MS include: Other symptoms that are less common include: speech disorders, swallowing issues, headache, hearing loss, seizures, tremor, breathing problems, and itching
 * fatigue
 * numbness
 * balance or coordination problems
 * bladder dysfunction
 * vision changes
 * dizziness
 * pain
 * cognitive issues
 * emotional change
 * Spasticity- stiffness of muscles and muscle spasms

Every patient is different and may have a different severity of the disease. There is no cure for MS. However, there are resources that can help with the symptoms and flare-ups. Often medications are taken to relieve the symptoms often in the form of a shot. Corticosteroids are given to relieve inflammation when needed and often therapy is recommended.

http://www.nationalmssociety.org/about-multiple-sclerosis/what-we-know-about-ms/treatments/index.aspx

__** Essential Ques **** tions **__


 * 1. Describe how the dendrite or cell body of the postsynaptic neuron is stimulated to send an impulse from the axon hillock to the rest of the neuron. **


 * This occurs when there is a release of a excitatory neurotransmitter from the presynaptic neuron. This allows the ligand-gated channels to open in the dendrites and cell body. After this there is a inward diffusion of Sodium causing depolarization and then a short period of conduction of EPSP. This allows the sodium and potassium voltage-gated channels to open in the axon hillock and finally the impulse is sent down the axon because of the process of the action potential. **


 * 2. Describe the sequence of events that occur to get an action potential to stimulate the release of neurotransmitters from the presynapic axon. What happens when the neuron is inhibited? **


 * When a neuron is at resting membrane potential it has a mV of -70. This just means that the voltage of the neuron in the inside of a cell is at negative 70. For an action potential to occur, a stimulus has to trigger an event to open the ligand-gated channels causing depolarization. As the ligand channels open Sodium enters the cell. During this time the inside of the cell must reach a threshold of -55mV for the impulse to occur. __If this threshold is not met there will be no impulse.__ As more Sodium enters the cell it causes further depolarization which allows more channels to open in which in turn causes further depolarization. This is an example of positive feedback. Once a neuron reaches a +30 mV the it will start repolarization. During this time the Sodium channels are deactivated and the Potassium channels are fully opened. This allows Potassium to flow out of the cell and the membrane to go back to resting potential. Once the membrane drops below the resting potential the Potassium channels close. The Sodium/Potassium pump is used to restore the membrane potential and ion concentration gradients. During this time 3 Sodium will be pumped out of the cell, while 2 Potassium will be pumped into the cell. **
 * When an action potential depolarizes the membrane it also opens Calcium ligand-gated channels. This allows the Calcium to diffuse down the concentration gradient which in turn allows the release of chemical neurotransmitters. A chemical neurotransmitter is stored in synaptic vesicles and when the Calcium is releases it stimulate exocytosis of the vesicles to allow the transmission of the neurotransmitter. The greater the stimulus the more Calcium ligand-gated channels will be opened and therefore more vesicles will undergo exocytosis to release the neurotransmitter into the synaptic cleft. **