Human Anatomy
Peripheral Nervous System
PNS
Part II
2 Components of PNS
1. 12 pr. of cranial nerves
2. 31 pr. of spinal nerves
2. Spinal Nerves
31 pair
Dermatome
• Each pair of spinal nerves monitors a
specific region of the body’s skin.
• This specific region of skin is a
dermatome.
Dermatome Map
Damage to a spinal nerve
will result in loss of
sensation to a specific
area of skin
shingles
Nerve Plexus
Network of
spinal nerves
A plexus produces
peripheral nerves
For instance….
The Brachial Plexus
Spinal n. plexus peripheral n.
Nerve Plexus
• There are four nerve plexuses.
1. Cervical (C1 – C5)
2. Brachial (C5 – T1)
3. Lumbar (T12 – L4)
4. Sacral (L4 – S4)
Study Hint for the
Plexus Nerves
• Make a table with 3 columns
• The headings for the 3 columns (L to R)
should be:
• Name
• Function
• Deficiency
1. Cervical Plexus
C1 – C5
1. Cervical Plexus
• Innervate swallowing muscles of larynx
• Skin of upper chest, shoulder, neck and ear
• Phrenic n.– innervates the diaphragm
• Phrenic n. is a peripheral n. having
contributions from 3 spinal nerves (C3-5).
1. Cervical Plexus
See Table 14.1
p. 366
Brachial Plexus
C5 – T1
2. Brachial Plexus
Peripheral n.
2. Brachial Plexus
• Innervates muscles and skin of upper
extremities
1. Axillary n. – deltoid and shoulder skin
2. Radial n. – posterior upper extremities
3. Musculocutaneous – anterior arm
4. & 5. Median and Ulnar – anterior
forearm and anterior hand
• Ring finger – dual innervation
2. Brachial Plexus
See Table 14.2 p. 367
2. Brachial Plexus
Regions easily damaged 1.
1. Upper
2. Lower
2.
Brachial Plexus Damage
• Crutch Palsy
• Crutches too long
• Damages radial nerve
• Wrist drop
Lumbar Plexus
Lumbar Plexus
T12 – L4
Lumbar Plexus
• Innervates muscles of anterior and medial thigh
• Innervates skin of anterior, medial and lateral
thigh
1. Femoral n. – anterior thigh muscles and skin
2. Obturator n. – medial thigh muscles and skin
See Table 14.3 p. 370
Lumbar Plexus
Sacral Plexus
Sacral Plexus
L4 – S4
Sacral Plexus
• Innervates posterior thigh and leg
1. Sciatic n. – posterior thigh
• In the popliteal fossa, the sciatic n.
divides into 2 nerves
2. Tibial n. – posterior leg
3. Common peroneal (fibular) n. – anterior
leg
4. Gluteal n. – gluteal region (g. maximus)
Sacral Plexus
See Table 14.3 p. 370