Neurons -

Topics to be Covered

  • Neuroglia (CNS and PNS)

  • Neurons (types and functions)

  • Action Potentials

  • Electrochemical gradients

  • Myelin and its effect on nerve impulse speed

  • Excitation vs Inhibition

  • Neurotransmitters

CNS and PNS Cells

  • Distinct types of neurons and neuroglia in both CNS and PNS

  • Functions include:

    • Myelin production

    • Immune response

    • Conducting nerve impulses

    • Sensory and motor functions

CNS Anatomy Basics

  • Brain Regions: Cerebrum, Cerebellum

  • Ventricles: CSF-filled cavities

  • Central canal in spinal cord also filled with CSF

CNS Neuroglia

  • Oligodendrocytes: Myelin-producing cells in CNS

  • Ependymal Cells: Line ventricles, produce CSF

  • Astrocytes: Most abundant, maintain the blood-brain barrier, support, and clean brain

  • Microglia: Immune defense cells

PNS Neuroglia

  • Schwann Cells: Myelin-producing cells in PNS

  • Satellite Cells: Support cells in PNS

Neurons

  • Structural Classification:

    • Multipolar: Most common in CNS

    • Bipolar: Rare, found in sensory organs

    • Unipolar: Common in PNS, e.g., dorsal root ganglion

  • Functional Classification:

    • Multipolar Neurons: Interneurons and motor neurons

    • Bipolar Neurons: Sensory neurons for special senses

    • Unipolar Neurons: Primarily sensory neurons

Action Potentials

  • Voltage-Gated Ion Channels: Open for specific ions

  • Na+/K+ Pump: Pumps 3 Na+ out, 2 K+ in

  • Phases of Action Potential:

    • Depolarization: Na+ channels open, Na+ enters

    • Repolarization: K+ channels open, K+ exits

    • Hyperpolarization: After repolarization, membrane potential becomes extremely negative

Myelin and Nerve Conduction

  • Myelin insulates nerve fibers to speed impulses

  • Saltatory conduction: AP hops from node to node in myelinated fibers

Excitation vs Inhibition in Nervous System

  • Excitation: Starts a process (turning ON)

  • Inhibition: Ends a process (turning OFF)

Selected Neurotransmitters

  • Excitatory Neurotransmitters:

    • Nicotinic Acetylcholine, Glutamate

  • Inhibitory Neurotransmitters:

    • GABA, Serotonin, Endorphins

  • Mixed Effects: Muscarinic Acetylcholine, Dopamine, Histamine, Norepinephrine

Importance of Neurotransmitter Relationships

  • Balancing excitatory and inhibitory neurotransmitters is crucial for proper brain function

  • Glutamate and GABA examples of interdependent regulatory roles

    • Imbalances linked to conditions such as anxiety and hyperactivity.