This article is incomplete.
The peripheral nervous system is the part of the nervous system that resides outside of the brain and spinal cord.
There are 12 sets of nerves that connect directly to the brain, known as cranial nerves.
There are 31 sets of nerves that connect to the spinal cord.
Also known as: Cranial Nerve I (1)
Sensory nerve only.
Also known as: Cranial Nerve II (2)
Sensory nerve only.
Also known as: Cranial Nerve III (3)
Also known as: Cranial Nerve IV (4)
Also known as: Cranial Nerve V (5)
Also known as: Cranial Nerve VI (6)
Also known as: Cranial Nerve VII (7)
Also known as: Cranial Nerve VIII (8)
Sensory nerve only.
Also known as: Cranial Nerve IX (9)
| Muscle | Location | Function |
|---|---|---|
| Stylopharyngeus | Head | Swallowing, by elevating the larynx, elevating and dilating pharynx |
Also known as: Cranial Nerve X (10)
| Muscle | Location | Function |
|---|---|---|
| Cricothyroid | Head | Increasing pitch of voice, by tensioning and elongating the vocal cords |
| Levator veli palatini | Head | Swallowing, by elevating the soft palate of the mouth |
| Salpingopharyngeus | Head | Swallowing, by relaxing the pharyngeal walls to allow them to lower |
| Palatopharyngeus | Head | Swallowing, by raising the pharynx |
| Palatoglossus | Head | Raising rear of tongue |
| Others: this list is incomplete | ||
Also known as: Cranial Nerve XI (11)
| Muscle | Location | Function |
|---|---|---|
| Sternocleidomastoid | Neck: front left, front right | Rotating the head in opposition to the muscle being activated; activating both flexes the neck, i.e. tilts the head toward the chest |
| Trapezius | Trapezoid shape: formed by top of neck, right shoulder, mid-back, and left shoulder | Shrugging the shoulders, drawing shoulder blades together, extending the neck |
Also known as: Cranial Nerve XII (12)
| Muscle | Location | Function |
|---|---|---|
| All tongue muscles except for palatoglossus | Head | Tongue functions related to speaking, chewing, and swallowing |
Spinal nerves are mixed nerves (sensory and motor) located in the spine. They are categorized based on the region of the spine with which they emerge.
| Table: spinal nerves by region | |
|---|---|
| Region/Classification | Nerves |
| Cervical nerves | C1 - C8 |
| Thoracic nerves | T1 - T12 |
| Lumbar nerves | L1 - L5 |
| Sacral nerves | S1 - S5 |
| Coccygeal nerve | Co (self) |
| Count: 31 | |
C1 innervates several muscles directly. C1 does not supply other nerves, however, it does connect to the hypoglossal nerve (12th cranial nerve).
| Table: Muscles innervated by C1 | |
|---|---|
| Muscle | Notes |
| Longus capitis muscle | Innervated by C1, C2, C3, C4 |
| Rectus capitis anterior muscle | |
| Rectus capitis lateralis muscle | |
| Rectus capitis posterior major muscle | |
| Geniohyoid muscle | Through hypoglossal nerve |
| Thyrohyoid muscle | |
| Omohyoid | Through Ansa cervicalis: neural loop which connects C1, C2, C3, and sometimes C4 |
| Sternohyoid | |
| Table: Muscles innervated by C2 | |
|---|---|
| Muscle | Notes |
| Longus capitis muscle | Innervated by C1, C2, C3, C4 |
| Rectus capitis anterior muscle | |
| Rectus capitis lateralis muscle | |
| Rectus capitis posterior major muscle | |
| Omohyoid | Through Ansa cervicalis: neural loop which connects C1, C2, C3, and sometimes C4 |
| Sternohyoid | |
| Table: spinal nerves by region | |||
|---|---|---|---|
| Region/Classification | Nerve | Anterior division | Posterior division |
| Cervical nerves | C1 | ||
| C2 | |||
| C3 | |||
| C4 | |||
| C5 | |||
| C6 | |||
| C7 | |||
| C8 | |||
| Thoracic nerves | T1 | ||
| T2 | |||
| T3 | |||
| T4 | |||
| T5 | |||
| T6 | |||
| T7 | |||
| T8 | |||
| T9 | |||
| T10 | |||
| T11 | |||
| T12 | |||
| Lumbar nerves | L1 | ||
| L2 | |||
| L3 | |||
| L4 | |||
| L5 | |||
| Sacral nerves | S1 | ||
| S2 | |||
| S3 | |||
| S4 | |||
| S5 | |||
| Coccygeal nerve | Self | ||
| Nerve Branch | Muscle | Location | Function |
|---|---|---|---|
| Intercostal nerves | Intercostal muscles | Between ribs | Draws ribs closer together; decreases thoracic volume |
| Phrenic nerve |
Thoracic diaphragm a.k.a. Diaphragm |
Thoracic cavity below the lungs | |
| Table: muscles innervated by the median nerve | ||
|---|---|---|
| Muscle | Location | Function |
| Pronator teres | Forearm | Pronates the hand, i.e. rotates the hand from looking at one's palm, to looking at the back instead |
| Flexor carpi radialis | Forearm | Flexion and radial abduction of the hand, i.e. shortening the distance between the palm of the hand and the inside of the elbow |
| Palmaris longus | Forearm | Vestigial; 14% of the human population lacks this muscle |
| Flexor digitorum superficialis | Forearm | Flexion of the four main digits in the hand at the middle knuckles, i.e. one of the muscles activated when holding a bucket by the handle |
|
Flexor digitorum profundus (also innervated by ulnar nerve) |
Forearm | Flexion of the four main digits in the hand at the knuckles near the fingertips, i.e. one of the muscles activated when holding a bucket by the handle |
| Flexor pollicis longus | Forearm | Flexes the knuckle of the thumb, unless the thumb is fixed, in which case it flexes the wrist |
| Pronator quadratus | Forearm | Works with the pronator teres to pronate the hand, i.e. rotates the hand from looking at one's palm, to looking at the back instead |
| First lumbrical | Hand | Flexes the palm of the hand, while straightening the index finger |
| Second lumbrical | Hand | Flexes the palm of the hand, while straightening the middle finger |
| Abductor pollicis brevis | Hand: Thenar eminence (mound at the base of the thumb) | Abduction of the thumb, i.e., with the palm lying flat facing upward, raises the thumb toward the sky |
|
Flexor pollicis brevis (also innervated by ulnar nerve) |
Flexes the thumb at the first knuckle | |
|
Opponens pollicis (innervated by ulnar nerve in 20% of population) |
Cups the palm, i.e. brings the base of the thumb closer to the base of the smallest finger | |
| Table: muscles innervated by the radial nerve | |||
|---|---|---|---|
| Muscle | Location | Function | |
|
Triceps brachii (also innervated by axillary nerve) |
Posterior of proximal upper limb, i.e. back of upper arm | Extends the elbow, i.e. straightens the arm | |
| Anconeus | Posterior of elbow | Minor role in extending the elbow, i.e. straightens the arm | |
| Brachioradialis | Forearm | Flexes the forearm at the elbow | |
| Extensor carpi radialis longus | Forearm | Abducts the hand at the wrist, i.e. draws the base of the thumb closer to the inside of the elbow | |
| Extensor carpi radialis brevis | Forearm | Extends and abducts the wrist joint, i.e. draws the base of the fingers closer to the outside of the elbow, such as when twisting the throttle on a motorcycle | |
| Supinator | Forearm | Supinates the forearm, i.e. rotates the right forearm clockwise, or the left forearm counterclockwise | |
| Extensor digitorum | Forearm | Extends the phalanges (fingers), the wrist, and the elbow | |
| Extensor digiti minimi | Forearm | Extends the wrist, and the little finger | |
| Extensor carpi ulnaris | Forearm | Extends the wrist, and eventually the elbow | |
| Abductor pollicis longus | Forearm | Abducts, rotates, and extends the thumb | |
| Extensor pollicis brevis | Forearm | Extends and abducts the thumb | |
| Extensor pollicis longus | Forearm | Extends the terminal phalanx of the thumb, i.e. the muscle used to give a thumbs-up | |
| Extensor indicis | Forearm | Extends the index finger, then extends the wrist | |
| Table: muscles innervated by the ulnar nerve | |||
|---|---|---|---|
| Muscle | Location | Function | |
| Flexor carpi ulnaris | Forearm | Flexes and duct, the wrist joint, i.e. shortens the distance between the base of the smallest finger and the elbow | |
|
Flexor digitorum profundus (also innervated by median nerve) |
Forearm | Flexion of the four main digits in the hand at the knuckles near the fingertips, i.e. one of the muscles activated when holding a bucket by the handle | |
| Opponens digiti minimi | Hand | Draws the base of smallest finger closer to the base of the thumb | |
| Abductor digiti minimi | Hand | Abducts the smallest finger, i.e. curls the smallest finger | |
| Flexor digiti minimi brevis | Hand | Abducts the smallest finger, i.e. curls the smallest finger | |
|
Dorsal interossei (first, second, third, fourth) |
Hand | Abducts the index, middle, and ring fingers. First dorsal assists with thumb adduction, plays a role in pinch strength | |
| Palmar interossei | Hand | Adducts fingers toward the middle finger, i.e. squishes all fingers against each other | |
| Adductor Pollicis | Hand | Draws the thumb closer to the index finger | |
|
Flexor pollicis brevis (also innervated by median nerve) |
Hand: Thenar eminence (mound at the base of the thumb) | Flexes the thumb at the first knuckle | |
| Palmaris brevis | Hand | Tenses the skin at the base of the palm | |
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| Nerve Branch | Muscle | Location | Function |
|---|---|---|---|