Spinal Nerves

Question 1

What is the brachial plexus?

Answer 1

A large nervous system structure that is formed from the ventral rami of spinal nerves C₅-C₈ and T₁.

• innervates muscles of upper limbs, neck and shoulders
• result of injury: causes weakness or paralysis of upper limbs

Question 2

What is the advantage of forming nerves from a mix of many spinal nerves rather than from individual spinal nerves?

Answer 2

If a spinal nerve is damaged, you wouldn’t lose total innervation to a limb or limb region.

Question 3

Which major nerve arises from the Posterior Cord?

Answer 3

Radial & Axillary Nerve

Question 4

What major nerve arises from the Lateral Cord?

Answer 4

Musculocutaneous

Question 5

What major nerve arises from the Medial Cord?

Answer 5

Ulnar Nerve

Question 6

What major nerve is formed from branches of the lateral and medial cords?

Answer 6

Median nerve

Question 7

What are the five roots of the brachial plexus?

Answer 7

Ventral Rami C₅-T₁

Question 8

The five roots unite to form?

Answer 8

Upper, Middle, and Lower Trunks

Question 9

The three trunks bifurcate to form?

Answer 9

Anterior and Posterior Division

Question 10

Anterior and Posterior Divisions give rise to?

Answer 10

Three large fiber bundles:

Lateral, Medial and Posterior Cords

Question 11

Give Location, Areas Innervated and the Result of Injury for Musculocutaneous Nerve:

Answer 11

Location: From Lateral Cord

Areas innervated: innervates flexor muscles in anterior arm (biceps, brachialis & coracobrachialis)

Result of Injury: weakness or loss of elbow flexion

Question 12

Give Location, Areas Innervated and the Result of Injury for Median Nerve:

Answer 12

Location: from a branch of lateral and medial cord

Areas innervated: innervates flexor muscles of forearm, the first two fingers, pronates forearm, flexes wrist & fingers & opposes thumb.

Result of Injury: Loss of pincer grasp

Question 13

Give Location, Areas Innervated and the Result of Injury for Ulnar Nerve:

Answer 13

Location: From Medial Cord

Areas innervated: innervates some flexor muscles in forearm and intrinsic hand muscles; also adducts and abducts medial fingers

Result of Injury: Clawhand (last two fingers become hyperextended)

Question 14

Give Location, Areas Innervated and the Result of Injury for Radial nerve:

Answer 14

Location: From Posterior Cord

Areas innervated: innervates extensors of forearm & hand (elbow extension, supination of forearm, extension of wrist & fingers & abduction of thumb); extends forearm (triceps, brachioradialis)

Result of Injury: Wristdrop (unable to extend hand at wrist)

Question 15

Give Location, and Areas Innervated for Axillary Nerve:

Answer 15

Location: From Posterior Cord

Areas innervated: innervates deltoid & teres minor muscles

Question 16

What areas does Medial Pectoral innervate?

Answer 16

Medial Pectoral: innervates pectoralis minor and pectoralis major

Question 17

What area does Thoracodorsal nerve innervate?

Answer 17

Latissimus Dorsi

Question 18

What area does Long Thoracic nerve innervate?

Answer 18

Serratus Anterior

Question 19

What area does Lateral Pectoral nerve innervate?

Answer 19

Pectoralis Major

Question 20

What area does Subscapular nerve innervate?

Answer 20

Teres major & subscapularis

Question 21

What area does Suprascapular nerve innervate?

Answer 21

Supraspinatus & Infraspinatus

Question 22

What are the roots and areas it innervates for the Cervical Plexus?

Answer 22

From ventral rami of C₁-C₄

It innervates muscles of neck, shoulder & skin on back of the head, on neck and shoulders.

Question 23

What nerve from the cervical plexus innervates the diaphragm for breathing?

What are its spinal roots?

Answer 23

Phrenic Nerve

Ventral Rami: C₃-C₅

Question 24

Dorsal Rami

Answer 24

Innervate the deep muscles of the back for motor control and skin for sensory input.

Question 25

Ventral Rami

Answer 25

Form Nerve Plexuses

Question 26

Nerve Plexuses

Answer 26

Interlacing nerve networks that occur in the cervical, brachial, lumbar and sacral regions and primarily serve the limbs.

Question 27

Intercostal Nerves

Answer 27

Ventral rami T₂-T₁₂ do not form nerve plexuses. It innervates muscles for breathing

Question 28

How is the Brachial Plexus Organized?

Answer 28

Roots (Ventral Rami) C₅-T₁ ► Trunks (Upper, Middle, Lower) ►Divisions (Anterior, Posterior of each Trunk) ► Cords (Lateral, Medial, Posterior) ► Peripheral Nerves