Dr.Dodson
9.19.96


Brachial plexus
nerves - very important in biology of the animal.
in order to make sense of nerves, you have to understand the muscles.
Understanding the nerves can help you integrate the muscles and muscle 
function.

There are 7 nerves of the brachial plexus.

[ship drawing :) - SS MARMU]

from cranial-caudal:

Suprascapular	-	short
Subscapular		-	short
Musculocutaneous - long
Axillary	-	short
Radial	-	long
Median	-	long
Ulnar	-	long

These nerves arise from the roots of the cranial nerves, C5-T2. Primarily 
C6,7,8 and T1 though.

Specific origins of the 7 nerves not that big of a deal. Really, just 
need to know where they go and what they do. 

THese nerves are identified by where they go.

These nerves have sensory and motor functions.

Short nerves:

The subscapular nerve attaches from the body wall to the subscapular 
muscle and can be seen on the medial side of that muscle. There are 
typically two points of insertion into the muscle. Has no sensory field.

suprascapular nerve, most cranial of brachial plexus nerves. Sends a 
branch to the supraspinatus and to the infraspinatus - motor nerve of 
those muscles

axillary nerve - goes to teres major, teres minor, and deltoids (goes 
into the deep surface of the deltoid. It is motor to these muscles, and 
has a small sensory field on the cranial aspect of the shoulder joint and 
somewhat distally. The sensory branch is called the cranial cutaneous 
antebrachial nerve.

Long nerves:

most cranially is the musculocutanous, innervating the biceps, 
coracobrachialis and distally the brachialis, all flexors of the elbow. 
Those are motor innervations. Then there is a sensory field of the medial 
cutaneous antebrachial nerve along the forearm. also sends branch to 
median nerve

median nerve innervates flexor carpi radialis, flexor carpi ulnaris, sup. 
dig. flexor and deep dig flexor. continues as sensory nerve to palmar 
surface of paw.
also innervates pronator teres.

ulnar nerve innervates ulnar head of f.c.ulnaris and ulnar head of deep 
dig flex.
sensory portion = caudal cutaneous antebrachial, sensory to lateral digit 
and lateral palmar and dorsal paw. this nerve = "funny bone". 

radial nerve: motor to triceps

most of the nerves tend to stay on the medial side in the course down the 
limb, but the radial nerve crosses to the lateral side mid-humerus, in 
order to innervate extensor carpi radialis, ulnaris lateralis, common 
digital extensor, and lateral digital extensor. also the supinator. Then 
the radial nerve remains  as a sensory branch to the entire dorsum of the 
paw, except for the 5th digit which is innervated by ulnar nerve as noted 
above. This is called lateral cutaneous antebrachial.

nerve probs can be diagnosed by testing motor and sensory capacity.

if you cut radial nerve proximally, the arm will be completely crippled, 
totally non-wt bearing. A proximal fx of humerus can cause complete 
radial paralysis and lack of sensation to lateral side of arm. a midshaft 
fx can cause damage such that extensors of carpi don't work, so animal 
will knuckle walk. If no sensation on dorsum of paw, this would confirm 
damage to radial nerve.