Peripheral nerves & plexuses — table
Roots, course, branches and what each nerve supplies. 30 entries.
Organisation 5
| Nerve | Roots | Course | Branches | Supplies / function |
|---|---|---|---|---|
| Somatic nervous system | — | — | — | Voluntary and reflex contraction of skeletal muscle; Conscious perception of touch, pain, temperature and limb position; Provides the sensory and motor limbs of somatic reflexes |
| Autonomic nervous system | — | — | — | Regulates cardiac output and blood pressure (baroreceptor reflex); Controls airway calibre and secretions; Regulates gastrointestinal motility, secretion and sphincters |
| Sympathetic nervous system | — | — | — | Fight-or-flight mobilisation in exercise, stress and emergencies; Maintains vasomotor tone and blood pressure (baroreceptor reflex efferent limb); Thermoregulation: sweating, skin blood flow, piloerection |
| Parasympathetic nervous system | — | — | — | Rest and digest: promotes digestion, absorption and energy storage; Slows the heart (vagal tone sets the resting rate ≈60–80 bpm, below the intrinsic SA rate ≈100 bpm); Near response: miosis and accommodation |
| Enteric nervous system | — | — | — | Generates peristalsis, segmentation and the migrating motor complex; Controls epithelial secretion of water and electrolytes; Regulates local mucosal blood flow |
Spinal cord 1
| Nerve | Roots | Course | Branches | Supplies / function |
|---|---|---|---|---|
| Cauda equina | Dorsal and ventral roots of L2–L5, S1–S5 and Co1. | — | — | Carries motor fibres to the lower limbs, pelvic floor and sphincters.; Carries sensory fibres from the lower limbs, perineum (saddle area), bladder and rectum.;… |
Spinal nerves & reflexes 1
| Nerve | Roots | Course | Branches | Supplies / function |
|---|---|---|---|---|
| Spinal nerves | — | — | — | Carry all sensory and motor innervation of the body below the head, apart from the territory of the vagus.; Distribute sympathetic postganglionic fibres to skin and vessels via grey rami.;… |
Cranial nerves 1
| Nerve | Roots | Course | Branches | Supplies / function |
|---|---|---|---|---|
| Cranial nerves (overview) | — | — | — | Special senses: smell (I), vision (II), hearing and balance (VIII), taste (VII, IX, X); General sensation of the face, scalp, oral and nasal cavities, pharynx and larynx (mainly V, plus IX and X);… |
Cervical & brachial plexuses 3
| Nerve | Roots | Course | Branches | Supplies / function |
|---|---|---|---|---|
| Cervical plexus | Ventral rami of C1–C4. The phrenic nerve also takes C5. | — | Cutaneous (all emerging at Erb's point): • Lesser occipital (C2): scalp behind the ear. • Great auricular (C2–C3): skin over the parotid, the angle of the mandible and the auricle.… | Cutaneous sensation of the neck, posterior scalp, auricle and shoulder; Motor supply to the infrahyoid muscles (stabilising the hyoid for swallowing and speech); Motor and sensory supply of the diaphragm (phrenic nerve) |
| Phrenic nerve | C3, C4, C5 (mainly C4). | Lateral border of the anterior scalene → descends on its anterior surface (lateral to medial) deep to the prevertebral fascia → between the subclavian artery and vein → anterior to the lung root, between the fibrous pericardium… | — | Contraction of the diaphragm, the principal muscle of inspiration; Sensation from the central diaphragm, pericardium and mediastinal pleura; Motor limb of hiccups (singultus) |
| Brachial plexus | Ventral rami of C5, C6, C7, C8 and T1 (with possible contributions from C4 or T2). | — | From the roots: • Dorsal scapular (C5): rhomboids and levator scapulae. • Long thoracic (C5–C7): serratus anterior. • A contribution to the phrenic nerve (C5).… | Motor supply to all muscles of the upper limb and most of the shoulder girdle; Cutaneous sensation of almost the whole upper limb; Proprioception from the joints and muscles of the upper limb |
Upper-limb nerves 6
| Nerve | Roots | Course | Branches | Supplies / function |
|---|---|---|---|---|
| Musculocutaneous nerve | C5, C6, C7 (lateral cord). | Lateral cord → pierces coracobrachialis → descends between biceps (superficial) and brachialis (deep) → emerges lateral to the biceps tendon in the cubital fossa → lateral cutaneous nerve of the forearm. | — | Flexion of the elbow (biceps, brachialis); Powerful supination of the forearm (biceps); Flexion and adduction of the arm at the shoulder (coracobrachialis, biceps) |
| Axillary nerve | C5, C6 (posterior cord). | Posterior cord → anterior to subscapularis → below the shoulder joint capsule → quadrangular space (with the posterior circumflex humeral vessels) → anterior and posterior branches around the surgical neck of the humerus. | — | Abduction of the arm from about 15° to 90° (deltoid; supraspinatus starts abduction); Flexion and medial rotation (anterior deltoid); extension and lateral rotation (posterior deltoid);… |
| Radial nerve | C5, C6, C7, C8, T1 (posterior cord). | Axilla (behind the axillary artery) → triangular interval with the profunda brachii artery → radial groove of the humerus → pierces the lateral intermuscular septum → between brachialis and brachioradialis anterior to the lateral… | - Muscular: triceps (all heads), anconeus, brachioradialis, extensor carpi radialis longus, and a small part of brachialis.… | Extension of the elbow (triceps, anconeus); Extension of the wrist and digits; abduction and extension of the thumb; Supination (supinator) and elbow flexion in mid-pronation (brachioradialis) |
| Median nerve | C5 (variable), C6, C7, C8, T1 (lateral and medial cords). | Union of the lateral and medial roots anterior to the axillary artery → lateral to the brachial artery, crossing anteriorly at mid-arm to lie medial → cubital fossa (medial to the brachial artery, deep to the bicipital… | - Forearm muscular branches: pronator teres, flexor carpi radialis, palmaris longus and FDS. • Anterior interosseous nerve: flexor pollicis longus, the lateral half of FDP (index and middle fingers) and pronator… | Pronation of the forearm (pronator teres, pronator quadratus); Flexion of the wrist (FCR) and fingers (FDS; FDP to the index and middle fingers); Flexion of the thumb IP joint (FPL) |
| Ulnar nerve | C8, T1 (often C7) — medial cord. | Medial cord → medial to the axillary and brachial arteries → pierces the medial intermuscular septum → posterior to the medial epicondyle (cubital tunnel) → between the heads of FCU → on FDP under FCU, medial to the ulnar artery… | - Forearm: flexor carpi ulnaris and the medial half of FDP (ring and little fingers). • Cutaneous: the palmar cutaneous branch and the dorsal cutaneous branch, which arises proximal to the wrist and is spared in Guyon… | Ulnar deviation and flexion of the wrist (FCU); Flexion of the DIP joints of the ring and little fingers (FDP); Abduction and adduction of the fingers (interossei); MCP flexion with IP extension (lumbricals, interossei) |
| Long thoracic nerve | C5, C6, C7 (from the roots, before the trunks form). | Roots C5–C7 → through or behind the middle scalene → behind the brachial plexus and axillary artery → over the first rib → descends on the lateral surface of serratus anterior in the mid-axillary line. | — | Protraction of the scapula (serratus anterior); Upward rotation of the scapula, allowing elevation of the arm above the head (with trapezius); Holds the scapula against the chest wall |
Thoracic & autonomic nerves 2
| Nerve | Roots | Course | Branches | Supplies / function |
|---|---|---|---|---|
| Intercostal nerves | Ventral rami of T1–T11 (intercostal) and T12 (subcostal). | Intervertebral foramen → posterior intercostal space (between the pleura and the internal intercostal membrane) → costal groove between the internal and innermost intercostals (lowest of the VAN bundle) → lateral cutaneous branch… | Rami communicantes (to and from the sympathetic trunk), collateral branch, muscular branches, lateral cutaneous branch (the intercostobrachial nerve from T2), anterior cutaneous branch, and branches to the parietal pleura… | Motor control of the intercostal muscles for breathing (elevation and depression of the ribs, stiffening of the chest wall); Motor supply of the anterior abdominal wall (forced expiration, coughing, abdominal pressure);… |
| Splanchnic nerves | - Greater: T5–T9. • Lesser: T10–T11. • Least: T12. • Lumbar: L1–L2. • Sacral (sympathetic): from the sacral trunk. • Pelvic (parasympathetic): S2–S4. | — | - Cardiopulmonary splanchnics (postganglionic sympathetic, from the cervical and T1–T5 ganglia): cardiac and pulmonary plexuses. • Greater: coeliac ganglion and adrenal medulla.… | Sympathetic control of the gut (reduced motility and secretion, sphincter contraction, vasoconstriction of splanchnic vessels); Stimulation of adrenaline release from the adrenal medulla;… |
Lumbosacral plexus & lower-limb nerves 11
| Nerve | Roots | Course | Branches | Supplies / function |
|---|---|---|---|---|
| Lumbar plexus | Ventral rami of L1–L4 (± T12). | — | - Iliohypogastric (L1, ± T12): internal oblique and transversus abdominis; skin over the iliac crest and suprapubic region.… | Motor supply to hip flexors (iliopsoas), knee extensors (quadriceps) and hip adductors; Sensation of the lower abdomen, groin, anterior genitalia and most of the anterior and medial thigh, plus the medial leg and foot… |
| Femoral nerve | L2, L3, L4 (posterior divisions). | Lateral border of psoas → groove between psoas and iliacus (deep to the iliac fascia) → deep to the inguinal ligament, lateral to the femoral artery and outside the femoral sheath → femoral triangle → divides into anterior and… | - Muscular branches: iliacus, pectineus, sartorius, rectus femoris, vastus lateralis, vastus intermedius and vastus medialis. • Anterior cutaneous branches of the thigh (medial and intermediate cutaneous nerves).… | Extension of the knee (quadriceps), essential for standing, climbing stairs and rising from a chair; Hip flexion (iliacus, rectus femoris, sartorius, pectineus);… |
| Obturator nerve | L2, L3, L4 (anterior divisions). | Medial border of psoas → behind the common iliac vessels, lateral to the internal iliac vessels and ureter → lateral pelvic wall (on obturator internus) → obturator canal (with the obturator vessels) → anterior and posterior… | - Anterior division: adductor longus, adductor brevis, gracilis, (pectineus), hip joint, and the cutaneous branch to the medial thigh.… | Adduction of the thigh (crossing the legs, stabilising the pelvis in gait); Assists medial or lateral rotation and flexion of the hip; Sensation of the medial thigh and the hip and knee joints |
| Sacral plexus | L4, L5 (lumbosacral trunk), S1, S2, S3, S4. | — | - Superior gluteal (L4–S1): above piriformis; gluteus medius, gluteus minimus and tensor fasciae latae. • Inferior gluteal (L5–S2): below piriformis; gluteus maximus. • Sciatic (L4–S3).… | Hip extension (gluteus maximus), abduction and pelvic stabilisation (gluteus medius and minimus), and lateral rotation (short rotators); Knee flexion (hamstrings) and all movements of the ankle and foot (via the sciatic nerve);… |
| Superior gluteal nerve | L4, L5, S1. | Sacral plexus → greater sciatic foramen above piriformis (with the superior gluteal vessels) → between gluteus medius and minimus → ends in tensor fasciae latae. | — | Abduction and medial rotation of the hip; Stabilisation of the pelvis on the stance leg during walking (preventing contralateral pelvic drop) |
| Sciatic nerve | L4, L5, S1, S2, S3. | Sacral plexus → greater sciatic foramen below piriformis → descends deep to gluteus maximus, midway between the greater trochanter and the ischial tuberosity, over the short rotators → posterior thigh on adductor magnus, deep to… | - Tibial division: semitendinosus, semimembranosus, long head of biceps femoris, and the hamstring (ischial) part of adductor magnus. • Common fibular division: the short head of biceps femoris.… | Flexion of the knee and extension of the hip (hamstrings); Through the tibial and fibular nerves, all movements of the ankle, foot and toes; Sensation of the lateral and posterior leg and the foot (via branches) |
| Tibial nerve | L4, L5, S1, S2, S3 (anterior divisions). | Apex of the popliteal fossa → through the fossa superficial to the popliteal vessels → deep to the soleal arch → posterior compartment with the posterior tibial vessels (on tibialis posterior) → behind the medial malleolus under… | - Muscular: gastrocnemius, soleus, plantaris, popliteus, tibialis posterior, flexor digitorum longus and flexor hallucis longus.… | Plantarflexion of the ankle (gastrocnemius, soleus), for push-off in walking and standing on tiptoe; Inversion of the foot (tibialis posterior); Flexion of the toes; intrinsic foot muscle support of the arches |
| Common fibular nerve | L4, L5, S1, S2 (posterior divisions). | Apex of the popliteal fossa → along the medial border of biceps femoris and its tendon → superficial to the lateral head of gastrocnemius → posterior to the fibular head → winds around the fibular neck (subcutaneous) → enters… | - Lateral sural cutaneous nerve. • Sural communicating branch. • Articular branches to the knee (including the recurrent articular nerve). • Terminal branches: the superficial fibular and deep fibular nerves.… | Dorsiflexion of the ankle and extension of the toes (via the deep fibular nerve), which clears the foot during swing phase; Eversion of the foot (via the superficial fibular nerve);… |
| Deep fibular nerve | L4, L5, S1 (mainly L5). | Fibular neck → through EDL → interosseous membrane with the anterior tibial artery → deep to the extensor retinaculum (between the EHL and EDL tendons) → medial and lateral terminal branches on the dorsum of the foot. | — | Dorsiflexion of the ankle (tibialis anterior), clearing the toes during the swing phase; Extension of the toes, including the great toe (EHL, EDL, EDB, EHB); Inversion assistance (tibialis anterior) |
| Superficial fibular nerve | L4, L5, S1. | Fibular neck → lateral compartment between fibularis longus and brevis → pierces the deep fascia in the distal third of the leg → medial and intermediate dorsal cutaneous nerves over the dorsum of the foot. | — | Eversion of the foot (fibularis longus and brevis); Support of the lateral and transverse arches (fibularis longus); Sensation of the dorsum of the foot |
| Pudendal nerve | S2, S3, S4. | Sacral plexus → greater sciatic foramen (infrapiriform) → crosses posterior to the sacrospinous ligament at the ischial spine → lesser sciatic foramen → pudendal (Alcock) canal → inferior rectal, perineal and dorsal nerves. | - Inferior rectal nerve: the external anal sphincter, the lower anal canal and the perianal skin. • Perineal nerve: bulbospongiosus, ischiocavernosus, the superficial and deep transverse perineal muscles, the **external… | Voluntary control of urinary and faecal continence (external urethral and anal sphincters); Sensation of the perineum and external genitalia;… |