Lecture 6: Nervous System, Brachial Plexus

Question 1

Nervous system organization

CNS consists of __________ & _____________

PNS consists of __________ & _____________

ANS consists of ____________ & __________

Answer 1

Brain &spinal cord

Cranial nerves & Spinal nerves

Sympathetic & parasympathetic

Question 2

CNS characteristics

Answer 2

Brain and spinal cord

Arise directly from neural tube

Question 3

PNS characteristics

Answer 3

Carries info b/w CNS and external/internal environment

Afferent (sensory) pathway - info to CNS
Efferent (motor) pathway - away from the CNS

Question 4

PNS components

Answer 4

Cranial nerves (12 pairs) 
Spinal nerves (31 pairs) 
Sensory receptors in the skin, tendons, & skeletal m
Motor end plates b/w motor neurons & skeletal m fibers

Question 5

ANS

Sometimes considered a subdivision of PNS

Answer 5

Entirely motor; Innervates sm m & glands
Sympathetic (thoracolumbar) fight of flight
Parasympathetic (craniosacral) feed & breed

Question 6

Nucleus

Answer 6

Aggregation of dendrites and nerve cell bodies in CNS

Question 7

Ganglion

Answer 7

Aggregation of dendrites and nerve cell bodies in the PNS

Question 8

Nerve

Answer 8

Bundle of fibers (axons) in PNS

Question 9

Tract

Answer 9

Bundle of fibers (axons) in CNS

Question 10

Commissure

Answer 10

Tract in the CNS that crosses from one side to the other

Question 11

White matter

Answer 11

Areas of myelinated axons

Question 12

Gray matter

Answer 12

Areas of unmyelinated axons, cell bodies, and dendrites

Question 13

Spinal nerve branches

Answer 13

Dorsal primary ramus
Ventral primary ramus
Ramus recurrent 
White ramus communicans (myelinated)
Gray ramus communicans (unmyelinated)

Question 14

ANS

Answer 14

Paravertebral ganglion
Splanchnic nerve (supplies viscera)
Prevertebral ganglion

Question 15

Axillary Sheath Contents and Fxn

Answer 15

Axillary a.
Axillary v.
Brachial plexus- lateral, medial, and posterior cords

Protection

Question 16

What are the 5 spinal cord levels of the brachial plexus?

What are the direct branches from the rami?

Answer 16

Ventral rami of C5-T1

Dorsal scapular nerve - C5 —> rhomboid m.

Long thoracic nerve - C5-7 —> serratus anterior m.

Question 17

What are the trunks of the brachial plexus and what nerves supply them?

Answer 17

Superior (upper); C5 & C6
Middle; C7
Inferior; C8 & T1

Question 18

What are the direct branches from the superior trunk?

Answer 18

• Suprascapular nerve; C5, C6 —> supraspinatus & infraspinatus m
• Nerve to subclavius

Question 19

What are the two divisions of the brachial plexus? And what cords to they form?

Answer 19

Anterior division - responsible for anterior UE (flexors); Lateral & medial cords

Posterior division - responsible for the posterior UE (extensors); posterior cord

Question 20

Lateral Cord

Answer 20

From anterior divisions of upper & middle trunks.

Direct branches: lateral pectoral n. (C5-C7)—> clavicular head of pec major m.

Terminal nerves: musculocutaneous (C5-7)—>biceps, brachialis, coracobrachialis & lateral root of median nerve (C5-7)

Question 21

Medial Cord

Answer 21

From anterior divisions of lower trunk

Direct branches:
1) medial pectoral n. (C8-T1) —> external head of pec major m. & pectoralis minor
2) medial cutaneous nerve to arm (T1) (brachium)
3) medial cutaneous nerve to forearm
Terminal branches:
1) Ulnar n. (C8-T1)—> flexors
2) medial root of median nerve (C8-T1)

Question 22

Posterior Cord

Answer 22

From pos. Divisions of all trunks

Direct branches:
1) Upper subscapular n. (C5-6)—> subscapularis m.
2)thoracodorsal n. (C6-7)—> latissimus dorsi m.
3) Lower subscapular n. (C5-6) —> subscapularis & teres major m.
Terminal branches:
1) axillary n. (C5-6); motor (deltoid & teres minor), sensory (skin of deltoid & upper lateral cutaneous n.)
2) Radial n. (C5-T1); motor (post. Arm/forearm & brachioradialis, sensory (back of arm, forearm, hand)