The nervous system has been likened to the electrical cords of the body. YOu can think of the nervcous system as being comprised of: sensory input, integration, and motor output.
It is dviided into the CNS, central nervous system, and perihperial nervous system, PNS.
When a neuron is stimulated ? it fires an electrical signal that fires down it’s axon to other neurons. It is one signal, strength and speed. The frequency or speed can be better.
The nerve impulse is called the action potential ? . Voltage which is sometimes called electromotive foce, EMF, electric pressure, or electric tension. Voltage can cause currents to move ? Moving charges are called a current, basically that is the flow of electrictry from one point to another. Voltage is the electric potential difference betwen two places. There are two types of voltage: AC and DC.
The resting membrane potential is -70mW The axon? of the neuron has a naegative charge, while outside of that has a positive charge. Outside of a neuron there is sodium ions with a positive charge. Inside the cells there are potassium ions with a positive charge.
Inside the cell there are potassium ions which have a positive charge, but there is also bigger negatively charged proteins. Because there are more sodium ions outisde, than potassium ions sinde the cell has an overall negative charge.
For every two potassium ions it pumps into the cell, it pumps out three sodium ions. The difference is called an electrochemical gradient. The channels that these ions use to go in and outside the cell is called voltage gated channels.
There’s also ligand gated channels that only allow certain neuro transmitters in. There’s also mechanically gated channels. The electrical evebts in neurons is based on the movements of ions.
A small change in gradeitn energy is called a graded potential? The strength in the action potential is the same, what changes is the frequency. The speed is affected by whether there is a myelin sheath on the axon. Myelin sheets are formed by schwann cells wrapping themself around the axon in the PNS. Axon with a large rdiameter conduct more quickly as they offer less resistance.
As the cells don’t touch each other there are spaces in between the myelin called the ” nodes of ranvier”
In the CNS the mylineeation occurs by the ogliodendrocytes wrapping around the axon. This style of communication comes from the Latwin word for leaping called ” saltatory conduction”.
When there is a difference in charge between cells, we call this the “membrane potential”.
The action potential goes through the stages of resting state, depolarisation, repolarisation, and hyperpolarisation.
The neurons cell body, the dendrities extending out look like treee branches. The axon is like the communicator?
A process, or a part that projects out. Tjhe vast majrotiy of neurons are multipolar neurons. They have a cell body, dendrite and axon, but has multiple densrties ? A bipolar neuron has a sole axon, and only one dendrite. Axons are essentially the transmission lines of thenervous system, as bundles they make nerves. The longest axons in the body are those of the sciatic nerve ? that run from the spine to the foot.
In vertabrates the axons sheathed in myelin which is one of two types of glial cells. The peripheral nuerons are called Schwann cells, and the CNS are called oligodendrocytes.
There are unipolar neuronds ? that are found mainly in the sensory receptors.
The meeting point between two neurons is called the synapse. The synapse the communication junctions between the neurons allow the neurons to work together. Neurons like people need each other to carry out their biological tasks. Synapse comes from a Greek word that can mean conjunction, or to fasten, or to join. The term was first used by Michael Foster in his ” Textbook of physiology”. The term was suggested by Arthur Woollgar Verral as a term meaning connection between two elements. Foster has apparently originally struggled to reconcile a name for a
The brain has over 100 trillion synapses, up to 1000 trillion synapses by some estimates. There are two types of synapses both chemical and electrical. The chemical is slower, more precise, and more abundant, where as the electrical is more immediate, and me be less precise. The synpases commuhicate through gap junctions.
The chemical signals are called neurotransmitters. Even though the neurons never touch they communicate, there is a tiny gap called a synaptic cleft. These diffuse across the synaptic cleft. When neurons communicate they go from the presynaptic neuron to the presynaptic terminal, called th axon terminal ?
When the action potential travels along the axis of a neuron it reaches the pre synaptic terminal. This has synpatic vesicles which contain thousands of molecules of a neuro transmiters. On the post synaptic membrane of the target cell there are receptors.
There is a voltage gated ion channel called a voltage gated calcium channel. The voltage gated calcium channel play an important role in neuro transmitter release. It activates the calcium channels at the pre synaptic terminal.
In the embryo electrical synapses are more common than chemical ones, but they slowly get replaced through neural development.