Neuron Doctrine and Levels of Analysis

Level of Analysis

• Molecular, Systems, Cellular, Behavioural, and Cognitive are the levels of analysis in the nervous system.

The Neuron Doctrine

• The neuron is the basic functional unit of the brain.
• Brain function and human behavior arise from the communication between different types of neurons.
• Neurons communicate using electrical and chemical signals.
• Understanding how neurons function is essential to understanding how the brain works.

The Typical Neuron

• A neuron is composed of soma, dendrites, and axon.
• Each compartment has specialized functions.
• The structure of neurons allows for unique functions compared to other non-neuronal cells.

The Cost of Ignorance: Nervous System Disorders

• Various disorders, such as Alzheimer's, Parkinson's, and Huntington's, are associated with nervous system dysfunction.

The Cytoskeleton

• The cytoskeleton is not static and constantly changes.
• It provides internal scaffolding of the neuronal membrane.
• The cytoskeleton consists of microtubules, microfilaments, and neurofilaments.

The Axon Terminal

• The axon terminal contains synaptic vesicles, abundant membrane proteins, and a large number of mitochondria.
• These differences distinguish the axon terminal from the axon.

The Axon

• Axons are responsible for relaying information from one neuron to the next.
• The axon consists of the axon hillock, axon proper, and axon terminal.
• The axon differs from the soma in terms of ER extension and protein composition.

The Synapse

• The synapse is the point of communication between neurons.
• The axon is referred to as the presynaptic location of the neuron.
• Synaptic transmission occurs through electrical-to-chemical-to-electrical transformation.

Types of Synapses

• Chemical synapses communicate with chemicals (neurotransmitters).
• Electrical synapses communicate with electricity.

Flow of Information between Neurons

• Afferent axons carry information toward a particular point.
• Efferent axons carry information away from a point.

The Soma

• The soma is the main body of the neuron.
• It contains the nucleus and other organelles, including the rough endoplasmic reticulum.

The Soma Organelles

• The rough endoplasmic reticulum is a major site for protein synthesis.
• The nucleus is responsible for gene expression, transcription, and RNA processing.
• The smooth endoplasmic reticulum and Golgi apparatus are involved in protein trafficking and regulation.

The Neuronal Membrane

• The neuronal membrane is a barrier that encloses the cytoplasm.
• It is approximately 5 nanometers thick.
• Protein concentration varies, and discrete membrane regions influence neuronal function.

Mitochondrion

• The mitochondrion is the site of cellular respiration.
• It houses the Krebs cycle and is the cell's energy source.

Dendrites

• Dendrites act as the "antennae" of neurons, receiving information relayed from axons.
• Dendrites are responsible for receiving and processing information sent from the axons of other neurons.
• They have numerous branches, forming a dendritic tree.
• The majority of synapses and receptors are located on dendrites.

Classification Based on the Number of Neurites

• Unipolar neurons have a single neurite.
• Bipolar neurons have two neurites.
• Multipolar neurons have more than two neurites.

Classification Based on Dendritic and Somatic Morphologies

• Stellate cells have a star-shaped morphology.
• Pyramidal cells have a pyramid-shaped morphology.
• Dendrites can be smooth or spiny.

Neurons Structure Correlates with Function

• The diversity of neurons within the brain allows for the multitude of brain functions.
• Examples of these functions include thought processes, motor activity, pain, and senses.