Lecture Notes: Classification of Neurons and Neurodevelopment

Classification of Neurons

Structural Classification
- Unipolar Cells
  - Primarily found in the embryo
  - Consists of a soma and a process
- Pseudo-unipolar Cells
  - Located in the dorsal root ganglia (spinal ganglia)
  - Two processes, one stem to the soma
  - Peripheral process (acts as dendrite) is myelinated
- Bipolar Cells
  - Consist of a dendrite and axon
  - Found in retina, olfactory epithelium, and auditory ganglion
- Multipolar Cells
  - Most numerous type
  - Example: Anterior horn cell
Functional Classification
- Motor Neurons
  - Example: Anterior horn cell
- Sensory Neurons
  - Example: Dorsal root ganglia (spinal ganglia)
- Interneurons
  - Connect motor and sensory neurons
Chemical Classification
- Cholinergic Neurons
  - Transmitter: Acetylcholine
- Adrenergic Neurons
  - Transmitter: Adrenaline
- GABAergic Neurons
  - Transmitter: GABA (Gamma-Aminobutyric Acid)

Groups of Neurons

Inside the CNS
- Called Nuclei (plural)
- Example: Dorsal motor nucleus of the 10th cranial nerve (Vagus nerve)
Outside the CNS
- Called Ganglia (plural)

Development of the Nervous System

Neural Tube
- Forms the central nervous system (CNS)
- Develops into the brain and spinal cord
Divisions of the Neural Tube
- Forebrain (Prosencephalon)
  - Divides into Telencephalon and Diencephalon
- Midbrain (Mesencephalon)
  - Remains as Mesencephalon
- Hindbrain (Rhombencephalon)
  - Divides into Metencephalon and Myelencephalon

Derivatives of Brain Divisions

Myelencephalon
- Forms the Medulla Oblongata
- Functions: Cardiovascular and respiratory centers
- Cranial nerves 8-12
- Contains the 4th ventricle
Metencephalon
- Forms the Cerebellum and Pons
- Cerebellum: Balance, coordination, fine movement learning (e.g., pianist)
- Pons: Bridge connecting cerebral cortex to cerebellar cortex
Mesencephalon
- Contains quadrigeminal bodies (Superior and Inferior colliculi)
- Superior Colliculi: Visual motion
- Inferior Colliculi: Auditory pathway
- Ventral surface: Cerebral peduncles

Important Structures and Functions

Substantia Nigra
- Associated with Parkinson’s disease

Key Terminology and Concepts

Cerebral Aqueduct: Smallest part of the central canal in the brain
Developmental Pathologies
- Anencephaly: Absence of a major portion of the brain, skull, and scalp

Visual and Structural References

Corpora Quadrigemina: Located on the dorsal surface of Midbrain (Mesencephalon)
Cerebral Peduncles: Located on the ventral surface of Midbrain
Ventricles
- 4th Ventricle: Located within the Medulla

These notes provide an overview of neuron classification and structure, as well as foundational concepts in neurodevelopment and key brain structures. Additional details and diagrams may be useful for a deeper understanding.

Overview of Neuron Classification and Development