Human Anatomy
Introduction to the Nervous System
Nervous system overview for MBBS: central and peripheral divisions, neuron and glia, ganglia and nuclei, and autonomic outflow, mapped to NMC codes AN7.1 to AN7.8.
MedNext Academy | 3 min read
Introduction to the Nervous System
Nervous system overview for MBBS: central and peripheral divisions, neuron and glia, ganglia and nuclei, and autonomic outflow, mapped to NMC codes AN7.1 to AN7.8.
This chapter gives the framework for the whole of neuroanatomy, dividing the nervous system into central and peripheral, and somatic and autonomic parts. It introduces the neuron, the supporting glia, and the basic vocabulary of ganglia, nuclei and tracts used throughout later study.
High-yield: Introduction to the Nervous System
- The nervous system is divided anatomically into the central nervous system and the peripheral nervous system.
- The central nervous system comprises the brain and spinal cord; the peripheral part comprises the cranial and spinal nerves and ganglia.
- Functionally the nervous system is divided into somatic and autonomic components.
- The neuron is the structural and functional unit, with a cell body, dendrites and an axon.
- Grey matter contains nerve cell bodies while white matter contains myelinated axons.
- A ganglion is a collection of nerve cell bodies outside the central nervous system.
- A nucleus is a collection of nerve cell bodies within the central nervous system.
- There are twelve pairs of cranial nerves and thirty-one pairs of spinal nerves.
- Each spinal nerve arises by a dorsal sensory root and a ventral motor root that join at the intervertebral foramen.
- The autonomic system has a sympathetic thoracolumbar outflow and a parasympathetic craniosacral outflow.
- Sympathetic preganglionic fibres are short and postganglionic fibres are long, the reverse of the parasympathetic pattern.
- Neuroglia support and insulate neurons and include astrocytes, oligodendrocytes, microglia and ependymal cells.
- Peripheral nerve fibres are myelinated by Schwann cells and central fibres by oligodendrocytes.
- A synapse is the junction where one neuron communicates with the next, usually by a chemical transmitter.
Divisions of the nervous system
- **Central nervous system:** Brain and spinal cord; contains grey matter (cell bodies) and white matter (tracts).
- **Peripheral nervous system:** Twelve cranial and thirty-one spinal nerves with their ganglia.
- **Somatic:** Serves skin, skeletal muscle and joints under voluntary control.
- **Autonomic:** Serves smooth muscle, cardiac muscle and glands; sympathetic and parasympathetic parts.
NMC competencies in this chapter
- **AN7.1:** Divisions of the nervous system
- **AN7.2:** Structure of a neuron and types of neurons
- **AN7.3:** Types of neuroglia
- **AN7.4:** Grey and white matter, ganglia and nuclei
- **AN7.5:** Cranial and spinal nerves in outline
- **AN7.6:** Somatic and autonomic nervous systems
- **AN7.7:** Sympathetic and parasympathetic outflow
- **AN7.8:** Applied anatomy of the nervous system
Frequently Asked Questions
How is the nervous system divided?
Anatomically it splits into the central nervous system, the brain and spinal cord, and the peripheral nervous system, the cranial and spinal nerves. Functionally it splits into somatic and autonomic parts.
What is the difference between a ganglion and a nucleus?
A ganglion is a collection of nerve cell bodies outside the central nervous system, while a nucleus is a collection of nerve cell bodies within the central nervous system.
How do the sympathetic and parasympathetic outflows differ?
The sympathetic outflow is thoracolumbar with short preganglionic and long postganglionic fibres, whereas the parasympathetic outflow is craniosacral with long preganglionic and short postganglionic fibres.
What are neuroglia?
Neuroglia are the supporting cells of the nervous system. They include astrocytes, oligodendrocytes, microglia and ependymal cells centrally, and Schwann cells peripherally, which myelinate axons.
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