Nerves

The optic nerve begins at the back of the eye at the optic disc, also known as the blind spot. This is where the ganglion cell axons converge to form the optic nerve, which carries visual information from the retina to the brain for processing.

Serotonin is not a neuron, it is a neurotransmitter. It relays information between neurons, with serotonin producing a calming, happy feeling. Lack of serotonin can cause depression, but an over abundance of serotonin can cause psychosis.

The sense of touch is used when handling something. It allows us to feel the texture, weight, temperature, and shape of objects.

The opening across which one neuron communicates with another neuron is called a synapse. At the synapse, chemical signals called neurotransmitters are released from the presynaptic neuron, which then bind to receptors on the postsynaptic neuron to transmit the signal.

Myelin sheath. This is the insulating sheath which covers most of the axon, between the Axon Hillock and Collateral branches of the Neuron.

phototransduction, where light energy is converted into electrical signals by photoreceptor cells in the retina. This process is essential for vision as it allows the brain to interpret visual information from the environment.

a pair of homologous chromosomes during meiosis. This pairing is called synapsis and allows for genetic recombination to occur between the maternal and paternal chromosomes, contributing to genetic diversity in offspring.

Hyperpolarization means that the membrane potential becames more negative than the resting potential. This means that it is more difficult for an action potential to be triggered at the postsynaptic membrane. This occurs at inhibitory synapses.

Hyperpolarization can be achieved by increasing the permeability of the membrane to potassium or chloride ions. If potassium permeability is increased more potassium ions will leave the cell, down their concentration gradient; if chloride permeability increases chloride ions will enter the cell down their concentration gradient. Both movements will make the inside of the cell more negative ie they will cause hyperpolarization.

Myelin sheath, comprised of glial cells wrapped around an axon one after another (oligodendrocytes in the CNS, schwann cells in the PNS).

The primitive types of artificial neurons include perceptrons, sigmoid neurons, and threshold neurons. These neurons serve as the building blocks for artificial neural networks and can be interconnected to perform various computational tasks.

The period of repolarization of a neuron corresponds to the time when potassium ions move out of the neuron, allowing the cell to return to its resting potential. This phase follows the peak of the action potential when sodium channels close and potassium channels open, leading to membrane potential restoration. Repolarization is essential for the neuron to be able to generate subsequent action potentials.

Neurons communicate through electrochemical signals, known as action potentials, that allow them to relay information to other neurons. When a neuron stimulates another neuron, it triggers the release of neurotransmitters that can excite or inhibit the activity of the receiving neuron, influencing its firing potential. This communication is key in coordinating various functions in the brain and nervous system.

Neurons are classified into different types based on their structure as follows: multipolar neurons with many dendrites and a single axon, bipolar neurons with one dendrite and one axon, and unipolar neurons with a single process extending from the cell body that branches into dendrites and an axon.

The main symptom of upper motor neuron syndrome is spasticity, which is characterized by increased muscle tone and exaggerated reflexes. Other common symptoms include muscle weakness, difficulty with fine motor skills, and impaired voluntary movement.

Neurons are supported by various types of glial cells, which provide structural support, insulation, and nourishment. Glial cells also help regulate the chemical environment surrounding neurons and play a crucial role in the repair and maintenance of the nervous system.

A mirror neuron is a type of neuron found in the brain that fires (i.e. activates) under two conditions: if an animal/person does a certain action (for example, wipe its face) or if the animal/person sees another animal/person do that action. These are individual neurons (or groups) that fire for a specific action, whether the action is seen or done. This is considered significant in social psychology, as it may (partially) neurologically explain why people are prone to imitate simple behaviors.

The trigger zone of a neuron includes the axon hillock, where graded potentials are summed together to determine if an action potential will be initiated. It is the region where voltage-gated sodium channels are concentrated and play a crucial role in generating an action potential. If the depolarization at the trigger zone reaches a certain threshold, an action potential will be generated and propagated down the axon.

Inside a resting neuron, there is a higher concentration of potassium ions compared to sodium ions. This creates a negative resting membrane potential that is essential for conducting nerve impulses. Additionally, there are large concentrations of negatively charged proteins within the neuron that contribute to the overall negative charge inside the cell.

The irregular fibrous (dense) connective tissue is covering most of the organs of our body: Fasciae (muscle, tendons, and below the skin), periosteum (bone), deep layer of dermis (our entire body), pericardium (heart and its valves), perichondrium (cartilage), joint capsules (joints), membrane capsules of liver, kidney, and lymph nodes, tunica albuginea (testicle), etcetera.

Connector neurons are specialized bipolar or multipolar neurons of the central nervous system. Connector neurons are also known as interneurons and connect sensory neurons.

Neurons with two processes are classified as bipolar neurons. These neurons have one dendrite and one axon extending from their cell body. Bipolar neurons are commonly found in specialized sensory pathways like the visual and olfactory systems.

No, dead neurons in the cortex are not typically replaced by new neurons. The brain has limited capacity for neurogenesis, especially in the cortex. Dead neurons are usually not replaced, but the brain can adapt and reorganize to compensate for lost function through processes like synaptic plasticity.

Neurons are organized at the molecular level with structures like receptors and ion channels, which facilitate their communication. At the cellular level, neurons interact through neurotransmitters and signaling pathways. At the network level, neurons form circuits and synapses that allow for complex information processing and transmission.

Sensory neurons are called afferent neurons because they carry information from sensory receptors to the central nervous system. "Afferent" means to carry inward, referring to the direction of information flow towards the central nervous system.

The length of a nerve can vary widely depending on its location and function. Some nerves in the body can be as short as a few millimeters, while others, such as the sciatic nerve in the leg, can be over three feet long.