Biology of Behavior Part 2

Neuron Overview

  • Neurons are the fundamental cells of the nervous system, found in both the central (CNS) and peripheral (PNS) nervous systems.

  • They communicate through electrochemical signals:

    • Electrical signals occur within a neuron.

    • Chemical signals occur between neurons.

Neuron Structure

Cell Body

  • Acts as the neuron's life-support center.

  • Contains:

    • Cytoplasm

    • Nucleus (houses DNA and RNA)

    • Organelles essential for cellular functions.

Dendrites

  • Branch-like structures extending from the cell body.

  • Function:

    • Receive incoming messages from other neurons.

Axon

  • The longest part of the neuron that sends messages away from the cell body.

  • Unique characteristics:

    • Only one axon per neuron, but can be quite long.

    • Encased in a myelin sheath, which:

      • Insulates the axon.

      • Maintains the speed of signal transmission.

Axon Terminals

  • Located at the end of the axon.

  • Stores chemical messengers known as neurotransmitters (e.g., dopamine, serotonin).

  • Responsible for releasing neurotransmitters into the synapse.

Synapse and Neurotransmission

  • Synapse: The space between neurons where communication occurs.

  • Neurotransmitters (NTs): Chemical messengers released from axon terminals into the synapse.

  • Action Potential: The electrical signal that travels down the axon to the axon terminal.

Receptors

  • Binding sites on the dendrites of receiving neurons.

  • Function using a lock-and-key analogy:

    • Neurotransmitters (keys) bind to specific receptors (locks).

    • This can open or close ion channels, generating a new action potential in the receiving neuron.

Neurotransmitter Recycling

  • Reuptake: The process by which neurotransmitters are reabsorbed into the axon terminal after they have performed their function.

  • Ensures neurotransmitters are recycled for future use.

Neurotransmitter Types

Dopamine

  • Known as the "pleasure chemical"; important for voluntary movement.

  • Parkinson's disease: Associated with reduced dopamine levels, leading to movement issues.

Acetylcholine

  • Critical for cognition, memory, and muscle movement.

  • Involved in Alzheimer's disease due to reduced levels, causing memory loss.

Serotonin

  • Found throughout the brain; regulates mood, sleep, and appetite.

  • Represents a complex system with many receptor types.

Endorphins

  • Natural pain relievers produced by the brain, sometimes referred to as "natural morphine".

  • Functions to alleviate pain and enhance mood.