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Hello everyone, we start a new unit today, a passionate unit, a unit that will take you to your brain, to your spinal cord, to your different glands of your body.

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We start unit number 7, Nervous and Endocrine Systems.

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Living things have three basic functions, nutrition, interaction and reproduction.

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We are going to study one of them.

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The interaction function.

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Point one.

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Interaction.

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Function which enables people to perceive changes and stimuli that occur both inside their bodies and in their environment.

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To interpret or process them and generate coordinated responses in order to survive.

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When we have something that hurts, imagine for example that we get our hand close to a flame.

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That flame is going to hurt us, and our brain tells our hands that we need to take it back

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if we don't want to get a big burn on our hands.

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How does that happen? By the interaction process.

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what are the different elements involved in that action in that situation on one

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hand we have first of all the stimuli we have some stimuli for example that flame

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is a stimuli the light that we can perceive with our eyes or if we feel hot

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on cold these are stimuli we receive it in our body through the receptors

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receptors are usually the senses our scene our sight our nose with our

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smell our taste in our mouth we receive those stimuli in those receptors then

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those receptors send the information to the organs that are going to coordinate all that information

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centers of coordination this coordination center could be the brain could be the spinal cord

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and these centers are going to take action how are they going to do they are going to use the

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effectors effectors could be the muscles could be a some glands okay so defectors are going to

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perform an action they're going to perform a response this response could be for example

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to take our hand out of the flame so we don't get hurt these actions can be divided into three

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different things. On one hand the stimuli and receptors are part of perception, the

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coordination center is part of integration and the factor and response

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are part of the action. Perception, integration and action. To help with this

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process of interaction we have two systems that we are going to study in

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this unit on one hand the nervous system and on the other hand the endocrine system

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both of them they are going to coordinate to perform all this function now we are going to

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copy some definitions of stimuli receptors and effector get ready stimulus physical or chemical

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change that takes place outside or inside the body and triggers a response in it receptor

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specialist cells which perceive stimuli and send information they detect to the coordination

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centers for processing effector part of the body that produces a response to a detected stimulus

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We get into the nervous system. We are going to the basic unit of it, the neurons, the Spanish neurona.

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We are going to see the different parts of the neurons, the type of them and how they connect with each other.

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Neurons have different parts that we need to know because each of them has a different function of sending the nerve impulse.

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First of all, this is a unique cell, okay?

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What I draw here is one single cell.

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If we go on our spinal cord, on our brain,

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we can see hundreds, millions of them in very little space.

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Maybe you remember from the tissues that we saw in the laboratory,

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one of them was the brain, and you could see a lot of neurons there.

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What are different parts of the neurons? Neurons have basically the cell body, which is what

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other cells we look at, we are more familiar with, we have the cell membrane, we have the nucleus,

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also inside the cell we still have mitochondria, the plasmic reticulum, we have back walls,

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we have everything which is in a normal cell. Cell body, which in Spanish is cuerpo neuronal,

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is the part that is going to receive the impulse from the previous cells this is going to be

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through the dendrites dendrites are ramifications that they are going to receive the impulse from

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another neuron then the impulse goes through the axon this could be really really long

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this is only one cell okay and the longest action on our body is a from our our spinal cord down

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to our foot and this could be more than a meter long so imagine one cell which is more than a

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meter long and that part the long part is the action ending up in action terminal which is

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the place where it's going to contact with the next neuron in between in the axon usually we

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have other cells surrounding the axon this is these are other cells okay these cells are the

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myelin sheath by nasdaq these myelin sheets are very important to continue with the speed of the

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nerve impulse there is an illness which is the multiple sclerosis sclerosis multiply in which

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people who has this illness they do not have the myelin sheath they have a problem and their immune

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system fight against the myelin sheath thinking that there's something wrong for the body

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these people they cannot coordinate properly they cannot coordinate properly because the

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immune system attack the myelin sheath so they are really really important to continue with the speed

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of the nerve impulse. We have drawn one type of neuron but there are very different types

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we're going to divide them 2.1 types. We can divide the neurons depending on the structure

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they have depending on the different numbers of dendrites and how long is the axon.

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In the unipolar neuron, we only have one axon. We do not have dendrites. They are only inside

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our ears for hearing. These are the only neurons that we have with this shape. No dendrites and

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one axon the most typical neuron that we have drawn before is the multipolar neuron which are

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very very common all around our nervous system in our brain our spinal cord on our name

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of on our nerves they are very common bipolar neurons are typical neurons that appear

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in the senses for example the touch or the eyes have this type of neurons which have one dendrite

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and one axon and more or less they are the same length we can also divide the neurons depending

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on the function that they perform sensory neurons are responsible that the receptor that are going

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to receive the stimuli will take the information to the center which could be the brain or the

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spinal cord. Neurons which has the function of connecting this center that we said to the

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effector which is going to move are the motor neurons and the neurons which are responsible

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for the connection between one neuron and the others are the interneurons.

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That's all for today, class

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Remember to connect your neurons to think

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to fill everything on your notebook

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and see you next day