11-6-05, Nervous System continued

See the notes from last Friday on the nervous system and in particular the individual neuron cells that make up nervous tissues. Generate reinforcement of the nervous system. Ask somebody what we talked about on Friday.

Dendrites receive cellular messages. Axons send cellular messages. The axons are covered in the Myelin sheaths and they keep the electrical signals going in the direction that they were transmitted. The Schwann cell relays the charges of the electrical signals. The Schwann cells produce the Myelin sheaths and these Myelin sheaths are high in lipids and thus focus the message towards the target cells. It was all about the neural impulse. Sum up the lecture that we had from the other day. The action potential travels along the axon, and there is this reverse in polarity and that is the wave of action potential that goes all of the way down until there is the release of the neural transmitters.

Talk about neural transmitters. Nerve impulses are electrical action potentials that move down the axon from the cell body of one neuron. When the action potential, calcium ions flow inwards. The neurotransmitters at one point bind to the receptor of the ion channel receptor. The ion channel then opens and sodium ions are allowed to pass into the membrane. The action potential is passed to the next neuron. Enzymes degrade the neural transmitters. Ions will no longer be allowed to enter the dendrite.

There are multiple steps to this. Understand these steps. You can learn anything in some step-by-step fashion. What is the end result of that passage of the neural impulse? Well, there is an axon, and in the axon from the nerve body, there is this `action potential' which is changing the interior polarity from negative to positive by opening sodium-potassium gates and the sodium ions rush in. First of all, the first thing in the release of the neurotransmitters, is this particular step. This is the transformation of the electrical message to chemical message format. The messages have to go from one nerve cell to another, the electrical message (the action potential) is transformed into chemical messages, the neurotransmitters.

The first step in that transformation is instead of sodium gates being opened in the axon terminal, they are now calcium gates. The first step is the calcium gates open. The calcium gates are in the axon terminal. The calcium gates open, the calcium ions flow in. You have this influx of calcium ions. When these come in, it causes the vesicles to absorb the neuron transmitters.

What are neurotransmitters? Neurotransmitters are specific to synaptic gaps. Synaptic gaps are the spaces between the axons of one cell and the dendrite of another. The neurotransmitters that cross that gap are individual chemicals (probably enzymes) by the axon terminal. As the neurotransmitters flow in, then there are sacs of neurotransmitters with the interplay with vesicles and the Golgi apparatus.

The third step is that of the vesicles fuse with the cell membrane and release the neurotransmitters. The vesicles fuse with the cell membrane. Then they release the neurotransmitters. There are several different kinds of active transport: ionic pumps, removal or important of large particles. In this particular case, this vesicle transportation, these are fairly large particles. The membrane is the fluid mosaic and it absorbs and opens up the vesicle to the external environment to release the neurotransmitters. Now we have this flood of neurotransmitters in the synaptic gap.

The fourth step involves another type of active transport. Each of those neurotransmitters are bound to a receptor protein on the dendrite of the next cell in the chain. They are bound on the receptor proteins on the cell membrane of the dendrite on the next cell. This is the lock-and-key theory all over again. These neurotransmitters are specific to this synapse, and they are also specific to receptor proteins on the dendrite of the next cell.

When the receptor proteins bind to the neurotransmitters, they are specific, this is active transport, it causes a sodium-potassium channel to open in the dendrite. It changes the shape of the protein. You will see this in the videos. The shape of the receptor protein is changed and the ionic channel is opened. And what rushes in? This is the fifth step: the channel is opened to sodium ions. Caused by the neurotransmitters binding to the receptor proteins, the receptor proteins change shape and open up the channels, and then sodium ions rush in.

The sodium ions produce the action potential. The sixth step is the action potential. The action potential in the dendrite creates a new wave. Action potential is this wave that shoves the message across to the length of the membranes from the dendrites to the next axon terminal and so on. The action potential creates a new `wave'. Where does that wave go?

This wave goes to the axon terminal and then the entire process starts over. Neurotransmitters cross the synaptic gap and it starts again. Review the human anatomical nervous system.

Enzymes literally degrade the ion channels and the shape is closed. As the enzymes, which we know are neurotransmitters, as those enzymes denature, degrade is the term the video used, the sodium channels are caused to close, and when they close, it cuts off that particular nerve transmission and it sets it up for the next nerve transmission. Human nerve cells are one of the slowest to regenerate themselves because of the complexity of the nervous system processes.

A lot of our information concerning the ability of our nerves to regenerate comes from the Vietnam war. That's the war where the majority or large majority of injuries were head injuries. As a result of that, we had lots of research done on how to re-establish nerve connections, and one of the things that they found is that there is a connection between the right and left hemispheres of your brain, and by separating the Corpus c. in brain damaged people, you can teach the other side of the brain to take over some of the behaviors of the human body.

Christopher Reeves, because of his fall from his horse, he used his money to fund neural research and we have had very big advances. Christopher Reeves had made amazing strides in his ability to manipulate nerve cells, but we are not there yet because they do not regenerate quickly enough.

As this century becomes yours, this is really neat that this is your century, you are going to establish the direction for your kids and grandchildren will control this entire century, you will have to look at research and the direction that research takes, and the dollars that you spend through your votes determines how you will do all of this, you have this huge responsibility in this particular century.

Talk about the anatomy of the human nervous system. That's what we really need to learn about. There are two basic channels in the human nervous system. There is the delivery system, which is called the peripheral nervous system. And there is the interpretation which is the central nervous system.

The central nervous system is composed of the brain and spinal cord. The peripheral nervous system is composed of sensory neurons and motor neurons. Sensory are the receptors. Motor are the performers.

The peripheral nervous system is a two-way street. One way is the sensory neurons taking information back to the spinal cord. The motor system is also there, taking interpretations back from the brain and spinal cord to the action of the muscles. Peripheral nervous system features are mainly voluntary muscles whereas the central nervous system is mainly for the involuntary muscles (double check this).

Afferent neurons transmit information toward the central nervous system. Efferent neurons transmit information away from the central nervous system. The peripheral nervous system consists of any neurons that are not part of the brain or spiral cord.

The afferent neurons are the sensory neurons. The efferent neurons are the motor neurons. The video just described a reflex arch. A reflex arch is a developed neuron pathway. This is one of thousands of reflex arches, it's just one of them, it's one particular neuron pathway. These allow us to actually understand what actually happens when we have those action potentials taking place.

Nerve messages are developed through learning (and Ragsdale and Puckett need to talk about this), anyway, babies are born with two `instincts'. Instincts are engrained neuron pathways. A baby dog or puppy has neuron pathways built into its DNA that causes it to bark. It will eventually bark. It is not learned. Baby fish, when they are born, instinctively do some things. They have instinctive behaviors already built in. Human beings do not have many built-in responses until somebody tells Ragsdale differently.

All humans have this instinctive ability to nurse and to attain nourishment from their mother. They also have another instinctive behavior. If you start to drop them then they will instantly start to react with some instinctive behavior.

The rest of what we do is learned, and this is what learned behavior is. Put photograph of the brain. The learned behavior has this whole system of neural pathways that are executing. At this moment, you are responding to my words through electrochemical signals, if you already know this, this information is running along that neuron pathway, and if there is new information, it produces “spider webs”, it produces new axons that are attaching to new dendrites and it all has this information passing around and so on.

Understand synaptogenesis. You are building up your reflex arches. There are two types of children. You can tell a small child that it is hot, and the child will respond in one of two ways. That reflex arch is going to learn and create itself because you tell it is hot, and that child when it runs up against a hot surface will pull his hand away and say, “it's hot”, just by you telling them. That's a reflex arch. The other type of child has to have that reflex arch reinforced. Ragsdale has a 35 year-old son, at least two, and he had also lost part of his finger before in another power saw accident, and his nerves never regenerated.

A reflex arch is this automatic neuron pathway that does not go to the brain. It does not go to the brain. It turns around in the spinal cord. It is a learned, automatic or `programmed' response. Somebody, somewhere has to program that information. Once you program the arch, once you make the response, that programs it, once you tell the child (or some of them at least), that's programming it, reinforcement and so on.

Dorsal root carries sensory neurons, and the other ones carry the muscle neuron messages. Dorsal root carries input. Ventral root carries output. Of course, the reflex arches are then going to be established in the body of the spinal cord.

There are two kinds of nerve tissue. There is gray tissue and there is white tissue. Which one has Myelin sheath? Gray tissue is indicative of interpretation. The white tissue is indicative of transmission. The white one then has the Myelin sheath.

Understand the sections of the human brain. It is hard to understand how those nerve messages are transmitted if you do not understand neurons. Neurons indicate a bundle of nerve cells and particular pathways. Think about that bundle like transatlantic cable. Making a call on the old land-lines followed one specific electrical pathway bundled up with many other lines.

The landline has interference and due to electrical storms the signals can jump across. Sometimes you can get a `twitch', or even a muscle twitch in your leg. Those are crossover signals that jump across those particular cables. That's what's happening on occasion. As your sensory apparati and are stimulated, there are four of those, maybe five or six, six different senses: touch, pain, temperature, light, sound, chemical and not just olfactory. There is another chemical input—taste. There are two areas of chemical sensing: in your nose and the taste buds on the tongue. Touch is also pressure.

Pressure is interesting depending on where you are in the human body because the pain sensors are located much differently than anywhere else.