Neuronas

Neurons are specialized cells responsible for receiving, processing, and transmitting information, enabling communication. They share basic cellular structures but have unique compositions and protein synthesis based on their DNA.

Besides neurons, other cells like astrocytes, microglia, and oligodendrocytes support neuronal function. Oligodendrocytes myelinate axons, creating insulation that enhances signal transmission.

Key neuronal characteristics include excitability (responding to stimuli with electrical changes), conductivity (propagating electrical changes), and secretion of neurotransmitters. Neurons typically don't reproduce, with most lasting a lifetime.

Neurons use electrical mechanisms internally for communication and chemical mechanisms to communicate with other neurons. The soma contains the nucleus, dendrites receive information, and axons transmit signals through terminal buttons.

Neurons are either presynaptic (emitting neurotransmitters) or postsynaptic (receiving neurotransmitters). Electrical phenomena occur throughout the neuron's structure, with chemical events at the synapse.

The cell membrane, made of proteins, carbohydrates, and phospholipids, regulates substance passage. It maintains cell integrity while allowing selective exchange with the environment via various transport mechanisms.

The neuron maintains different electrical charges inside and outside the membrane. The interior is typically more negative. Ion channels regulate the flow of charged particles, influencing the membrane's polarity.

Electrical phenomena are potentials, either local or action. A neuron sums local potentials at dendrites. If this sum surpasses a threshold at the axon hillock, an action potential is triggered, propagating down the axon as a nerve impulse.

Excitatory neurotransmitters open sodium channels, causing depolarization (making the inside less negative). Inhibitory neurotransmitters open chloride channels, causing hyperpolarization (making the inside more negative).

The neuron exists in different states with the resting potential (polarized), excitatory signals drive it to a depolarized state. It briefly has a positive charge and then repolarizes returns to negative state and it propagates the signal along the axon.

Myelin, produced by Schwann cells and oligodendrocytes, insulates axons, improving the speed of nerve impulse transmission by allowing the signal to jump between Nodes of Ranvier.

Synapses are mostly chemical, involving a presynaptic neuron, a postsynaptic neuron and a gap between them. Neurotransmitters are manufactured in the soma vesicles transport the neurotransmitters down the axon to the terminal.

When an electrical impulse reaches the axon terminal, calcium channels open, causing vesicles to fuse with the membrane and release neurotransmitters into the synaptic cleft. These neurotransmitters bind to receptors on the postsynaptic dendrite.

The binding of neurotransmitters to specific receptors, like a lock and key, dictates the effect. Excitatory signals trigger sodium channel opening, while inhibitory signals trigger chloride channel opening, restarting the cycle.

Neurotransmitters trigger rapid excitation or inhibition, while neuromodulators have slower, longer-lasting effects, often modulating the effects of neurotransmitters. Psychopharmaceuticals often work by affecting neurotransmitter and neuromodulator activity.

The receptor determines the outcome depending if it's excitatory or inhibitory. The neurotransmitters can provoke fast and transient responses or start extended chemical reactions inside of the cell.

In the example shown, Glutamate will create always the membrane depolarization for excitatory functions. GABA will create always the membrane negativity for inhibitory functions.

Acetylcholine for muscular and cognitive process, Dopamine for movement and behavior reinforcement, control. The neurotransmitter affects different functions.

Neuroplasticity is the brain capability to modify itself as a result of the experience of the environment.