Anatomy of the Nervous System

· Central nervous system (CNS)· Brain· Spinal cord

· Peripheral nervous system (PNS)· Nerve outside the brain and spinal cord

The 12 pairs of cranial nerves

Spinal Nerves 31 pairs

Spinal Nerves

Dorsal ramus

Ventral ramus

The segmental innervation of anterior surface of trunk

PNS Throughout Life

• Embryonic muscles migrate to new locations

• Some skin dermatomes become displaced

• Muscles and skin always retain their original nerve supply

Spinal nerve plexus

The Cervical Plexus

• Deep in the neck under the sternocleidomastoid muscle.

• Formed by ventral rami of first 4 cervical nerves (C1 – C4)

• Most are cutaneous nerves• Phrenic nerve – major nerve

The Cervical Plexus

(C5 -T1)

Brachial plexus main branches

• Axillary:shoulder (Deltoid)

• Musculocutaneous:Flexors in arm

• Radial: Extensors in arm and forearm

• Median:Flexors in forearm

• Ulnar:Flexors in forearm and hand

Lumbar Plexus

The Lumbar Plexus

Sacral Plexus

The Sacral Plexus

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Innervation of the Skin: Dermatomes

• Dermatome – an area of skin

• Innervated by cutaneous branches of a single spinal nerve

• Upper limb – skin is supplied by nerves of the brachial plexus

• Lower limb:Lumbar nerves – anterior surfaceSacral nerves – posterior surface

PosteriorMap of

Dermatomes

Anterior

Autonomic Nervous System

• General visceral motor part of the PNS

• Has 2 divisions (with opposite effects):- Parasympathetic: ‘housekeeping’ activities (rest and digest)- Sympathetic: extreme situations (fight or flight)

Sympathetic

Sympathetic

Sympathetic

Sympathetic

Parasympathetic

Parasympathetic