By nerve region.
Start with the root. Follow the movement. Connect it to the muscle and the peripheral nerve.
Explore motor patterns through myotomes and skin sensation through dermatomes. This first guide starts with myotomes, organized by spinal nerve-root level.
Myotomes · movement by spinal level
Open a level to see an example muscle and its named nerve pathway.
Myotome
A muscle group associated with a spinal nerve root. It describes a motor relationship.
Peripheral nerve
A named nerve carrying fibers from multiple spinal levels to muscles and other tissues.
Dermatome
A skin region associated with a spinal root. Sensory maps are different from the movement guide below.
Upper limb
Cervical and upper thoracic roots · C5–T1
C5Bend the elbowView muscle & nerve relationship
Example muscle: Biceps brachii
Peripheral pathway: Musculocutaneous nerve
This is a reference action for the highlighted root level. The muscle receives overlapping input from neighboring roots.
C6Extend the wristView muscle & nerve relationship
Example muscle: Extensor carpi radialis longus and brevis
Peripheral pathway: Radial nerve and its branches
This is a reference action for the highlighted root level. The muscle receives overlapping input from neighboring roots.
C7Straighten the elbowView muscle & nerve relationship
Example muscle: Triceps brachii
Peripheral pathway: Radial nerve
This is a reference action for the highlighted root level. The muscle receives overlapping input from neighboring roots.
C8Bend the middle finger’s tip jointView muscle & nerve relationship
Example muscle: Flexor digitorum profundus, middle-finger portion
Peripheral pathway: Median nerve via its anterior interosseous branch; ulnar contribution to the middle-finger portion is common
This is a reference action for the highlighted root level. The muscle receives overlapping input from neighboring roots.
T1Move the little finger outwardView muscle & nerve relationship
Example muscle: Abductor digiti minimi
Peripheral pathway: Ulnar nerve, deep branch
This is a reference action for the highlighted root level. The muscle receives overlapping input from neighboring roots.
Lower limb
Lumbar and sacral roots · L2–S1
L2Flex the hipView muscle & nerve relationship
Example muscle: Iliopsoas
Peripheral pathway: Psoas: direct lumbar plexus branches; iliacus: femoral nerve
This is a reference action for the highlighted root level. The muscle receives overlapping input from neighboring roots.
L3Straighten the kneeView muscle & nerve relationship
Example muscle: Quadriceps femoris
Peripheral pathway: Femoral nerve
This is a reference action for the highlighted root level. The muscle receives overlapping input from neighboring roots.
L4Lift the front of the footView muscle & nerve relationship
Example muscle: Tibialis anterior
Peripheral pathway: Deep fibular (peroneal) nerve
This is a reference action for the highlighted root level. The muscle receives overlapping input from neighboring roots.
L5Lift the great toeView muscle & nerve relationship
Example muscle: Extensor hallucis longus
Peripheral pathway: Deep fibular (peroneal) nerve
This is a reference action for the highlighted root level. The muscle receives overlapping input from neighboring roots.
S1Point the foot downwardView muscle & nerve relationship
Example muscle: Gastrocnemius and soleus
Peripheral pathway: Tibial nerve
This is a reference action for the highlighted root level. The muscle receives overlapping input from neighboring roots.
Reference actions follow the International Standards for Neurological Classification of Spinal Cord Injury. This educational guide is not the ISNCSCI assessment or a substitute for its standardized examination.
Use the map, then look more closely.
Movement, sensation, symptoms, and the wider examination help put a pattern in context. A change in strength or comfort alone does not identify a nerve lesion. Palpation and a movement retest do not establish which nerve or root is involved.
Dermatomes · skin sensation by spinal level
FORTHCOMING
Dermatomes describe areas of skin associated with spinal nerve roots. This separate section will focus on sensory patterns, keeping them distinct from the movement relationships above. Dermatome territories overlap and vary between people and reference maps.
From roots to peripheral nerves
This page begins with spinal-root groupings. A future layer can follow named nerves through the upper and lower limbs, with muscle relationships shown separately from skin sensation.
Anatomy references
Muscle and nerve relationships: UAMS upper-limb anatomy · UAMS lower-limb anatomy · Iliopsoas anatomy · Deep fibular nerve anatomy · Finger-flexor innervation variability.
Educational reference. Individual anatomy and clinical findings vary.