Introduction to Neurons

Introduction to Neurons

• Neurons are the fundamental units of the nervous system.
• Their primary function is to transmit information throughout the body in the form of electrical and chemical signals.
• They communicate with each other at specialized junctions called synapses.

Different Types of Neurons

• Sensory Neurons (afferent neurons): Transmit sensory information from the peripheral organs (e.g., skin, muscles) to the central nervous system (CNS).
• Motor Neurons (efferent neurons): Transmit signals from the CNS to muscles and glands, triggering actions.
• Interneurons: Connect sensory and motor neurons within the CNS, processing information and relaying signals, crucial for complex reflexes and higher-level cognitive functions.

Structure of a Neuron

• Cell Body (Soma): Contains the nucleus and other organelles, maintaining the neuron's life.
• Dendrites: Branching extensions that receive signals from other neurons at synapses.
• Axon: A long, slender projection that transmits signals away from the cell body to other neurons, muscles, or glands.
  • Myelin Sheath: An insulating layer that wraps around some axons, increasing signal transmission speed.
  • Nodes of Ranvier: Gaps in the myelin sheath, where the action potential jumps, accelerating signal speed (saltatory conduction).
• Synaptic Terminals (Axon Terminals): The end of the axon, releasing neurotransmitters to communicate with the next cell.

Neurotransmitters

• Neurotransmitters are chemical messengers that transmit signals across synapses.
  • Diverse types of neurotransmitters exist, each with specific effects on target cells.
• Examples include dopamine, serotonin, norepinephrine, and GABA, each linked to different functions in the brain and body.
• The release and reception of neurotransmitters are crucial for regulating various bodily processes.

Glial Cells

• Glial Cells (or Glia): Provide support and protection for neurons.
• They outnumber neurons 10 to 50 times in the nervous system.
• Glial cells perform vital functions, including: maintaining the chemical environment around neurons, providing structural support, insulating axons, and facilitating signal transmission between neurons.

Types of Glial Cells

• Astrocytes: Star-shaped cells regulating the chemical environment surrounding neurons, providing nutrients, and removing waste products.
• Oligodendrocytes (CNS): Form myelin sheaths around axons in the central nervous system.
• Schwann Cells (PNS): Form myelin sheaths around axons in the peripheral nervous system.
• Microglia cells: Immune cells within the CNS, protecting against pathogens and removing cellular debris.

Differences Between Neuron Types

• Size and shape vary significantly between different neuron types.
• The length and complexity of axons vary depending on the specific function of the neuron.
• Location within the nervous system also varies depending on the specific function of the neuron.

Importance of Neuron Function

• Neurons are essential for all aspects of human function.
• Their communication allows body systems to coordinate responses to stimuli.
• This coordination is essential for processes like muscle movement, sensation (touch, taste), thought, emotion, memory, and reflexes.