Neurophysiology Drawings

In class we have been learning about the nervous system. Down below is a drawing of a neuron and all the parts labeled. Neurons are cells that transmit signals via action potentials. Located around neurons are supporting cells. The body of a neuron contains the nucleus and has no centrioles. The axon, which is the site for propagation of axon potentials covered in Myelin Sheath, arises in the axon hillock. At the top of the neuron, above the nucleus, are dendrites. Dendrites attract electrical signals and send them to the bottom of the axon. For a signal to be sent down to the bottom, you got to have a really big one or two that come at the exact same time. It all depends on the size and the timing. 

Located at the end of the axon is the axonal terminal, which is branched terminus of the axon. The axon is what transfers or emits the action potentials. An action potential is all or nothing electrical discharge. They produce and release neurotransmitters at the synapse. Synapse is the area of impulse transmission between axons (communication between axons). Movement can be sent towards the axonal terminal are sent away from it. The longest axon can be up to 1 M long. 

Myelin Sheath protects the axon. It is a whitish, fatty sheath that can be found along most axons. This sheath insulates fibers electrically. With this present, the speed of impulse transmission increases. There are gaps that are located in the sheath that allow for the propagation of impulses known as nodes of ranvier. Myelin sheath is formed by schwann cells and both myelinated and unmyelinated cells are present. 

                                                    

Down below is a picture of a protein membrane channel (doors). There are many different types of channels that all help out in a certain way. A potassium channel and sodium channel are two of the channels.There is voltage gated sodium channel and a voltage gated potassium channel. When the sodium channel opens and sodium rushes in, the voltage rises due to more positive charges going inside. The voltage or charge then triggers the potassium channel and the potassium, which is negative, starts flowing out causing the voltage to decrease and eventually even out. There is also a na+ and a K+ pump. Some channels only allow potassium and some only allow sodium.

                                                

Action potential is what is shown in the picture below. An action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. The channeled gates open and close really fast (micro seconds) to try and even out the charge as fast as possible. The potassium gate opens at 50- because the sodium is flowing in causing the voltage to rise and the potassium helps bring it back down and eventually even it out.

                             

The picture down below represents synaptic potential. This is when the charge is different on the inside and outside of the neuron. The outside is positive and the inside is negative. These channels are polarized due to more negatives located on the inside. When sodium rushes in (voltage rises), positives start to fill the inside causing depolarization to happen. When potassium starts to rush out (voltage drops), depolarization happens. Eventually the charge evens out again.

Resting potential is when there is the same amount of positives on the outside as there are negatives in the inside. You can stab the membrane with a pipet to measure the voltage. Sodium enters with calcium.