1. The neuron is the basic unit of the nervous system and is composed of three main parts: the cell body, dendrites, and axon. The cell body contains the nucleus and other organelles that are responsible for the metabolic functions of the neuron. Dendrites are branching extensions that receive incoming signals from other neurons and transmit them to the cell body. The axon is a long, slender projection that carries outgoing electrical impulses away from the cell body.
Electrical impulse conduction in a neuron begins with the dendrites receiving signals from neighboring neurons. These signals, in the form of neurotransmitters, bind to specific receptors on the dendrites and generate postsynaptic potentials. If the summation of these potentials reaches a certain threshold, an action potential is initiated at the axon hillock. This action potential then travels down the axon towards the axon terminals, where it triggers the release of neurotransmitters into the synapse. The net result of this electrical impulse conduction is the communication between neurons.
For example, in a sensory neuron, when a person touches a hot surface, specialized receptors in the skin detect the temperature change and generate a signal. This signal is then transmitted through the dendrites to the cell body and axon, which carries the electrical impulse to the brain. At the termination of the impulse, the brain receives and interprets the signal as a sensation of heat, prompting a reflex response to remove the hand from the hot surface.
2. The subcortical structures are located beneath the cerebral cortex and include the thalamus, hypothalamus, basal ganglia, and limbic system. The hippocampus, which is part of the limbic system, plays a role in learning and memory. The basal ganglia, specifically the ventral tegmental area and substantia nigra, are involved in addiction.
The two key neurotransmitters located in the nigra striatal region of the brain that play a major role in motor control are dopamine and gamma-aminobutyric acid (GABA). Dopamine is involved in reward, motivation, and movement, while GABA is the main inhibitory neurotransmitter in the brain.
3. Glia cells, also known as neuroglia, function in the central nervous system to support and protect neurons. They play a crucial role in maintaining the overall health and well-being of the nervous system. Some examples of glia cells include astrocytes, oligodendrocytes, and microglia.
Astrocytes provide structural support to neurons and help regulate the chemical environment in the brain. They also contribute to the formation of the blood-brain barrier, which protects the brain from harmful substances.
Oligodendrocytes produce myelin, a fatty substance that wraps around axons and enhances the speed and efficiency of electrical impulse conduction.
Microglia are the immune cells of the central nervous system and function to remove waste products and foreign substances from the brain.
4. The synapse is the junction between two neurons where communication occurs. It consists of the presynaptic neuron, which releases neurotransmitters, and the postsynaptic neuron, which receives the neurotransmitters.
Communication between neurons at the synapse occurs in a specific direction. The presynaptic neuron releases neurotransmitters into the synaptic cleft. These neurotransmitters then bind to receptors on the postsynaptic neuron, generating an electrical signal. This communication can be either excitatory, where the neurotransmitters depolarize the postsynaptic neuron and increase the likelihood of an action potential, or inhibitory, where the neurotransmitters hyperpolarize the postsynaptic neuron and decrease the likelihood of an action potential.
5. Neuroplasticity refers to the brain’s ability to adapt and change in response to experiences and learning. It involves the creation of new connections between neurons or the strengthening of existing connections. Neuroplasticity is a vital mechanism for learning and memory formation.
For example, in the case of stroke-induced paralysis, neuroplasticity allows the brain to reorganize itself and compensate for the lost function. The unaffected areas of the brain can take over the function of the damaged areas, allowing the individual to regain some motor control through rehabilitation and therapy. Similarly, learning a new skill, such as playing an instrument, involves the formation of new connections between neurons in the brain, leading to improved coordination and proficiency over time.