Nervous System Overview

Nervous System consists of:

• Central Nervous System (CNS)

  • Brain

  • Spinal cord

• Peripheral Nervous System (PNS)

  • Cranial nerves

  • Spinal nerves

Central Nervous System (CNS)

Brain: white matter surrounded by grey matter.

3 main parts of the Brain :

• cerebrum

• brainstem

• cerebellum

White matter: mainly nerve fibres with their myelin sheaths

Grey matter: mainly nerve cell bodies and branching dendrites

Spinal cord: gray matter surrounded by white matter.

Peripheral Nervous System (PNS)

• Somatic Nervous System

  • skeletal muscle

• Autonomic Nervous System

  • glands, smooth muscles, cardiac muscles

  • Parasympathetic Nervous System: (discrete activation)

  • Sympathetic Nervous System: (diffuse activation)

12 pairs of cranial nerves:

• olfactory (CN I)

• optic (CN II)

• oculomotor (CN III)

• trochlear (CN IV)

• trigeminal (CN V)

• abducent (or abducens; CN VI)

• facial (CN VII)

• vestibulocochlear (CN VIII)

• glossopharyngeal (CN IX)

• vagus (CN X)

• accessory (CN XI)

• hypoglossal (CN XII)

31 pairs of spinal nerves:

• 8 cervical nerve pairs (C1-C8)

• 12 thoracic nerve pairs (T1-T12)

• 5 lumbar nerve pairs (L1-L5)

• 5 sacral (S1-S5)

• 1 coccygeal nerve pair

Types of Neurons:

Afferent (sensory neurons): nerve fibers responsible for bringing sensory information from different parts of the body to the CNS.

• cell bodies are located just outside of the spinal cord in the dorsal root ganglion

Interneurons: central nodes of neural circuits, enabling communication between sensory or motor neurons and the CNS.

Efferent nerves: nerves that carry nerve impulses away from the CNS.

• cell bodies located in the ventral horn of the spinal cord

Somatic vs Autonomic Nervous System