Neurons

Neurons

• Definition: Neurons are highly specialized cells that store information and carry messages within the nervous system and between other body systems.

Structure of Neurons

• Parts of a Neuron:

  • Cell Body: Contains the nucleus and organelles necessary for the neuron's function.

  • Dendrites:

    • Branchlike extensions of the cytoplasm and cell membrane.

    • Receive messages from neighboring cells.

    • A neuron can have multiple dendrites, each capable of many branches.

  • Axon:

    • A long extension that carries electrical messages away from the cell body.

    • Each neuron has only one axon.

Types of Neurons

• Sensory Neurons: Detect stimuli and transmit signals to the brain and spinal cord.

• Interneurons:

  • Receive signals from sensory neurons.

  • Relay information within the brain and spinal cord

  • Process information and pass signals to motor neurons.

• Motor Neurons: Transmit messages from the nervous system to other tissues, including muscles.

Support Cells

• Schwann Cells: Specialized support cells that cover axons and aid in signal transmission.

Myelin Sheath

• A collection of Schwann cells that insulate neurons' axons, enhancing the speed and efficiency of signal transmission.

Signal Transmission in Neurons

• Mechanism:

  • Neurons transmit information as electrical and chemical impulses.

  • Stimulation of a neuron produces an electrical impulse traveling within the neuron.

  • Before moving to the next cell, the electrical impulse transforms into a chemical signal.

Resting Potential

• Rest State: A neuron at rest maintains a charge difference across its membrane, preparing it for impulse transmission.

• Charge Characteristics:

  • Inside the neuron is more negatively charged than outside.

  • This charge difference is known as resting potential.

• Ionic Concentration:

  • Sodium Ions (Na+): More present outside the cell than inside.

  • Potassium Ions (K+): More present inside the cell than outside.

Sodium-Potassium Pump

• A protein in the membrane that uses energy to transport Na+ ions out and K+ ions into the neuron, maintaining the resting potential.

Action Potential

• Definition: An electrical impulse that moves down the axon following stimulation, caused by a portion of the inner membrane becoming positively charged.

Transmission Between Neurons

• Synapse: The tiny gap between neurons.

• Neurotransmitters:

  • Chemical signals released into the synapse from vesicles in the axon terminal when the impulse reaches there.

  • Bind to receptor proteins on adjacent neurons, inducing action potential in the next neuron.

Comparison of Signal Transmission

• Within Neurons: Signal transmission is electrical.

• Between Neurons: Signal transmission is chemical.