Biological Psychology – Lecture 2: Neurons: Types and Functions

Biological Psychology – Lecture 2: Neurons: Types and Functions

Overview of Neurons

Neurons are the fundamental units of the nervous system and play crucial roles in receiving, processing, and transmitting information. Each neuron is structured to perform specific functions, which can be broken down into various processes:

  1. Information Reception: Neurons receive information through structures known as dendrites.
  2. Processing: The information is processed within the soma (cell body) of the neuron.
  3. Transmission: Finally, processed information is transmitted through the axon to other neurons, muscles, or glands via terminal buttons.

Neuron Classification

Neurons can be categorized based on their morphology or shape and structure, which is influenced by the number of neuronal processes.

  • Processes Defined: Processes encompass both dendrites and axons.
Morphological Classification
Golgi Types (Based on Axon Length)

Neurons can be classified into two Golgi types, primarily focusing on the axon length:

  1. Golgi Type 1 Neurons

    • Characteristics:
      • Possess long axons that project to distant areas in the body.
    • Function: These neurons are particularly significant for long-distance communication.
    • Example: Motor neurons which convey signals from the brain/spinal cord to muscles.

  2. Golgi Type 2 Neurons

    • Characteristics:
      • Have short axons that project locally, typically confined to a specific area.
    • Function: Responsible for local communication within the nervous system.
    • Example: Interneurons that connect various neurons within the brain and spinal cord.

Types of Neurons: Functional Definitions

Neurons can also be categorized based on their functions, which relate to sensory input, integration (processing), and motor output.

  1. Sensation (Input)

    • Neurons are responsible for collecting information from various sensory modalities, including:
      • Touch
      • Smell
      • Sight
      • Sound
    • Sensory information is transmitted through sensory receptors.

  2. Integration (Thinking / Processing)

    • Involves the brains and spinal cord processing and interpreting sensory information.
    • Different signals are combined, leading to a decision about the appropriate response to stimuli.

  3. Action (Output)

    • Neurons send signals to effectors which include:
      • Muscles:
      • Skeletal
      • Smooth
      • Cardiac
      • Glands:
      • sweat glands
      • blushing mechanisms
Functional Classification

The functions of neurons can be summarized into three main categories, each defined by their direction of information flow within the Central Nervous System (CNS):

  1. Sensory Neurons (Afferent Neurons)

    • Function: Carry information towards the CNS, from sensory receptors to the brain and spinal cord.
    • Examples of Sensory Input: Touch, pain, temperature, vision.
    • Structural Characteristics: Typically unipolar or bipolar in structure.

  2. Interneurons

    • Location: Found exclusively in the brain and spinal cord.
    • Function: Connect sensory neurons to motor neurons.
    • Role in Processing: Responsible for the integration and processing of information.
    • Structural Characteristics: Usually multipolar in design.

  3. Motor Neurons (Efferent Neurons)

    • Function: Carry information away from the CNS, sending commands from the brain or spinal cord to effectors (muscles and glands).
    • Structural Characteristics: Typically multipolar.

Functions of Neurons

1. Sensation
  • Neurons detect stimuli from the external environment and internal body states.
  • Examples of Stimuli Detected: Pain signals indicating potential danger or tissue damage.
  • Signal Transmission:
    • Pain signals are sent to the spinal cord, producing fast reflex responses (e.g., immediate withdrawal responses).
    • Information is also relayed to the brain, where sensation is processed consciously, resulting in emotional responses (e.g., fear) or controlled actions.
2. Integration
  • The process involves interpreting and combining sensory information.
  • Mediated by: Interneurons.
  • Objective: Enable the brain to:
    • Identify the stimulus accurately.
    • Evaluate its importance based on context and experiences.
    • Decide an appropriate response.
3. Action
  • Refers to the output responses generated by the nervous system.
  • Mechanism: Motor neurons transmit signals from the CNS to effectors, resulting in action.
  • Example:
    • Withdrawal reflex: The spinal cord triggers muscle contraction to swiftly remove a hand from a painful stimulus, demonstrating an immediate physiological response to harm.