CBNS-2

What is Neuroscience and Goals

  • Definition: Neuroscience is the study of all aspects of nervous systems and is synonymous with neurobiology.

  • Goals:

    • Achieve a comprehensive understanding of nervous system functions from molecular to behavioral levels.

    • Decipher relationships between various subdisciplines of neuroscience.

    • Uncover general principles by observing similarities in neuron function and anatomy across species.

Basic Anatomy of the Nervous System

  • Divisions:

    • Central Nervous System (CNS): Comprises the brain and spinal cord, which are protected by bone.

    • Peripheral Nervous System (PNS): Consists of somatic and autonomic nervous systems.

      • Somatic Nervous System: Controls voluntary movements, connects to skin, joints, and skeletal muscles.

      • Autonomic Nervous System: Manages involuntary functions (breathing, heart rate, digestion), innervates glands, smooth muscle, and cardiac muscle; further divided into sympathetic & parasympathetic systems.

        • Sympathetic Nervous System: Increases heart rate.

        • Parasympathetic Nervous System: Decreases heart rate.

Levels of Organization in the Brain

  • Gray and White Matter:

    • Gray Matter: Composed mainly of cell bodies.

    • White Matter: Composed primarily of axons, appears white due to myelin.

  • Cytoarchitecture: Categorization of the brain based on the types of cells in different regions (e.g., hippocampus has granule cells).

  • Brodmann Maps: Created by Korbinian Brodmann in 1900, these maps categorize the brain according to varied cell types found in distinct areas.

Classes of Cells in the Brain

  • Main Classes:

    • Neurons: Specialized cells designed for information reception, integration, and transmission.

    • Glia: Support neurons, outnumbering them by a factor of ten.

Glia & Functions of Glia

  • Definition: Glia, meaning "glue" in Greek, are non-neuronal cells crucial for supporting neuronal functions.

  • Types of Glia:

    • Oligodendrocytes: Produce myelin in the CNS.

    • Schwann Cells: Generate myelin in the PNS.

    • Astrocytes: Help regulate the chemical environment around neurons (potassium concentration, neurotransmitter uptake, providing metabolic support).

    • Microglia: Act as immune cells, defending against infection and clearing debris.

Anatomy of Neurons

  • Structure:

    • Soma: Contains nucleus and organelles.

    • Nucleus: Encloses chromosomes and DNA.

    • Dendrites: Receive signals from other neurons, forming a dendritic tree.

    • Axon Hillock: Tapered region where the axon begins.

    • Axon: Transmits signals, may branch into axon collaterals.

    • Myelin: Insulating sheath that speeds signal transmission.

    • Node of Ranvier: Gaps in the myelin sheath exposing the axon membrane.

Functional Zones of Neurons

  • Input Zone: Soma and dendrites, where signals are received and potential changes occur (postsynaptic potentials).

  • Integration Zone: Axon hillock, where incoming signals converge to determine action potential initiation.

  • Conduction Zone: Axon, where action potentials travel using voltage-gated channels.

  • Output Zone: Terminal bouton, where neurotransmitters are released at the synapse, triggered by calcium ion influx.

Neuronal Diversity

  • Neurons show vast diversity (approximately 1,000 classes), but their structure and functional zones are conserved among vertebrates.

  • The complexity of the human brain arises from the number of neurons and intricate connections, rather than more complex neurons.