*** PLEXUS CUTS *** Flashcards
Mastery
What happens if I cut the C5 nerve
nerve?
muscles?
actions?
not affected, somewhat, and fully
**Radial(C5-T1)
**Median(c5-T1)
***Upper. and lower subscapular
***Dorsal scapular nerve
- Rhomboid major and minor: Scapular retraction.
- Levator scapulae: Scapular elevation.
Effect: Weak scapular retraction and elevation.
***Suprascapular nerve (C5, C6)
- Supraspinatus: Initial 15° of shoulder abduction.
- Infraspinatus: Lateral rotation of the arm.
Effect:
- Shoulder abduction initiation significantly weakened.
- Weak lateral rotation of the arm.
***Axillary nerve (C5, C6)
- Deltoid: Shoulder abduction (beyond 15°).
- Teres minor: Lateral rotation of the arm.
Effect:
- Severe loss of shoulder abduction.
- Some loss of lateral rotation (suprascapular also contributes).
***Musculocutaneous nerve (C5, C6, C7)
- Biceps brachii: Elbow flexion and forearm supination.
- Brachialis: Elbow flexion.
- Coracobrachialis: Shoulder flexion and adduction.
Effect:
Weak elbow flexion (C6 compensates somewhat).
Slight loss of supination.
***Long thoracic nerve (C5, C6, C7)
- Serratus anterior: Scapular protraction and stabilization.
Effect: Weak scapular protraction.
Nerve to subclavius (C5, C6)
***Lateral pectoral nerve (C5, C6, C7)
- Pectoralis major (clavicular head): Shoulder flexion and adduction.
Effect: Weakness in shoulder flexion and adduction.
What happens if I cut the C7 nerve
nerve?
muscles?
actions?
not affected, somewhat, and fully
***Radial nerve (C5, C6, C7, C8, T1)
- Triceps brachii (all heads): Elbow extension.
Effect:
Significant weakness in elbow extension.
Weak wrist extension and both radial/ulnar deviation.
Weak finger and thumb extension.
***Median nerve (C5-T1)
- Palmaris longus: Tenses palmar fascia and assists wrist flexion.
- Flexor carpi radialis: Wrist flexion and radial deviation.
- Flexor digitorum superficialis: Flexion of fingers 2-5 at PIP joints.
Effect:
Weakness in wrist flexion and radial deviation.
Reduced flexion at the PIP joints of fingers 2-5.
***Musculocutaneous nerve (C5, C6, C7)
- Biceps brachii: Elbow flexion and supination.
- Brachialis: Elbow flexion.
Effect:
Weak elbow flexion and supination (minimal, as C5/C6 contribute more).
***Thoracodorsal nerve (C6, C7, C8)
- Latissimus dorsi: Shoulder extension, adduction, and medial rotation.
Effect:
Weakness in shoulder extension, adduction, and medial rotation.
***Long thoracic nerve (C5, C6, C7)
- Serratus anterior: Scapular protraction and stabilization.
Effect: Weak scapular protraction, leading to scapular winging.
***Lateral pectoral nerve (C5, C6, C7)
- Pectoralis major (clavicular head): Shoulder flexion and adduction.
Effect: Weakness in shoulder flexion and adduction.
What happens if I cut the C6 nerve
nerve?
muscles?
actions?
not affected, somewhat, and fully
***Suprascapular nerve (C5, C6)
- Supraspinatus: Initial 15° of shoulder abduction.
- Infraspinatus: Lateral rotation of the arm.
Effect:
Shoulder abduction initiation somewhat weakened (C5 contributes).
Weak lateral rotation of the arm.
***Axillary nerve (C5, C6)
- Deltoid: Shoulder abduction beyond 15°.
- Teres minor: Lateral rotation of the arm.
Effect:
Severe loss of shoulder abduction.
Some loss of lateral rotation.
***Musculocutaneous nerve (C5, C6, C7)
- Biceps brachii: Elbow flexion and forearm supination.
- Brachialis: Elbow flexion.
- Coracobrachialis: Shoulder flexion and adduction.
Effect:
Significant weakness in elbow flexion and supination.
Slight loss of shoulder flexion and adduction.
***Radial nerve (C5, C6, C7, C8, T1)
Extensor carpi radialis longus: Wrist extension and radial deviation.
Effect:
Weak wrist extension and radial deviation.
Loss of elbow flexion in neutral grip (brachioradialis).
***Median nerve (C5-T1, minimal C5 contribution):
- Pronator teres: Forearm pronation.
- Flexor carpi radialis: Wrist flexion and radial deviation.
Effect:
Weak wrist flexion and radial deviation.
Reduced pronation strength.
***Long thoracic nerve (C5, C6, C7)
- Serratus anterior: Scapular protraction and stabilization.
Effect: Weak scapular protraction, leading to scapular winging.
***Lateral pectoral nerve (C5, C6, C7)
- Pectoralis major (clavicular head): Shoulder flexion and adduction.
Effect: Weakness in shoulder flexion and adduction.
***Thoracodorsal nerve (C6, C7, C8)
- Latissimus dorsi: Shoulder extension, adduction, and medial rotation.
Effect: Weakness in shoulder extension and adduction.
Subscapular nerves (upper and lower) (C5, C6)
***Subscapularis: Medial rotation of the arm.
- Teres major (lower only): Shoulder adduction and medial rotation.
Effect: Weakness in medial rotation and adduction of the arm.
***Nerve to subclavius (C5, C6)
What happens if I cut the C8 nerve
nerve?
muscles?
actions?
not affected, somewhat, and fully
***Radial nerve (C5, C6, C7, C8, T1)
- Triceps Brachii
Effect:
- weakend extension of arm and forearm
***Median nerve (C5-T1)
- Flexor digitorum superficialis: Flexion of PIP joints of fingers 2-5.
- Flexor digitorum profundus (lateral half): Flexion of DIP joints of fingers 2-3.
- Flexor pollicis longus: Thumb flexion.
- Pronator quadratus: Forearm pronation.
Effect:
Weakness in PIP and DIP flexion of fingers 2-5.
Weak thumb flexion and opposition.
Impaired pronation.
***Ulnar nerve (C7, C8, T1)
- Flexor carpi ulnaris: Wrist flexion and ulnar deviation.
- Flexor digitorum profundus (medial half): Flexion of DIP joints of fingers 4-5.
Effect:
Weak wrist flexion and ulnar deviation.
Loss of fine motor control (e.g., finger abduction/adduction).
Weakness in DIP flexion of fingers 4-5.
Weakness in thumb adduction.
***Thoracodorsal nerve (C6, C7, C8)
- Latissimus dorsi: Shoulder extension, adduction, and medial rotation.
Effect:
Weakness in shoulder extension, adduction, and medial rotation.
***Medial pectoral nerve (C8, T1)
- Pectoralis major (sternal head): Shoulder adduction and medial rotation.
- Pectoralis minor: Scapular protraction and depression.
Effect:
Weakness in shoulder adduction and medial rotation.
Weak scapular protraction and depression.
What happens if I cut the T1 nerve
nerve?
muscles?
actions?
not affected, somewhat, and fully
***Median nerve (C5-T1)
- Pronator Teres
- FCR
- Palmaris Longus
- FCU
- FDP
Anterior Interosseous Nerve(c5-T1)
- Pronator Quadratus
- flexor policis longus
- flexor digitorum profundus
Effect:
- pronation
- flexion of hand, and radiocarpal
- flexion of MCP, DIP, PIP
***Ulnar nerve (C7, C8, T1)
- flexor digitorum profundus
- FCU
***Medial cutaneous nerve or arm and forearm ( c8-t1)
sensory only.
***Medial pectoral nerve (C8, T1)
- Pectoralis major (sternal head): Shoulder adduction and medial rotation.
- Pectoralis minor: Scapular protraction and depression.
Effect:
Weakness in scapular protraction and depression.
Slight loss of shoulder adduction and medial rotation.
what happens if I cut the anterior division of the superior trunk
nerve?
muscles?
actions?
not affected, somewhat, and fully
***Musculocutaneous nerve (C5-C7)
- Directly affected; no longer receives input from C5 and C6.
Median nerve (C5-T1)
- Partially affected; loses contributions from C5 and C6.
Lateral pectoral nerve (C5-C7)
- Directly affected; loses input entirely.
**Lateral pectoral nerve(c5-c7)
**Median Nerve C5-T1
Muscles Affected
Biceps brachii (via musculocutaneous nerve)
- Action: Elbow flexion, supination of forearm.
- Effect: Weakness in elbow flexion and supination.
Brachialis (via musculocutaneous nerve)
- Action: Primary elbow flexor.
- Effect: Severe weakness in elbow flexion.
Coracobrachialis (via musculocutaneous nerve)
- Action: Shoulder flexion, adduction.
- Effect: Weakness in shoulder flexion and adduction.
Pectoralis major (clavicular head) (via lateral pectoral nerve)
- Action: Shoulder flexion, adduction, and medial rotation.
- Effect: Weakness in shoulder flexion, adduction, and medial rotation.
- Partially Innervated via Affected Nerves
Flexor carpi radialis (via median nerve)
- Action: Wrist flexion and radial deviation.
- Effect: Minor weakness in wrist flexion.
Pronator teres (via median nerve)
- Action: Forearm pronation, weak elbow flexion.
- Effect: Minor weakness in pronation.
Flexor digitorum superficialis (via median nerve)
- Action: Flexion of PIP joints (fingers 2-5).
- Effect: Minor weakness in finger flexion.
what happens if I cut the lateral cord
nerve?
muscles?
actions?
not affected, somewhat, and fully
***Musculocutaneous nerve
- Innervates: Biceps brachii, brachialis, coracobrachialis.
Effect: Severe weakness in elbow flexion and forearm supination.
***Median nerve (partial)
Flexor carpi radialis, pronator teres, FDS, and thenar muscles.
Effect: Weakness in wrist flexion, pronation, and thumb movements (opposition, abduction).
***Lateral pectoral nerve
Innervates: Pectoralis major (clavicular head).
Effect: Weakness in shoulder flexion, adduction, and medial rotation.
what happens if i cut the inferior trunk
nerve?
muscles?
actions?
not affected, somewhat, and fully
***Ulnar nerve
Flexor carpi ulnaris and medial half of FDP.
Effect: Severe weakness in hand fine motor control, grip strength, and wrist flexion/ulnar deviation.
***Median nerve (partial)
Innervates (C8-T1 contribution):
Effect: Weakness in thumb opposition, flexion, and abduction, as well as precision grip.
***Med. Pectoral nerve
***Radial
***Thoracodorsal
Medial cutaneous nerves of arm and forearm
Sensory innervation to medial arm and forearm.
Effect: Loss of sensation on the medial side of the arm and forearm.
Medial pectoral nerve
Innervates: Pectoralis major (sternal head) and pectoralis minor.
Effect: Weakness in scapular protraction/depression and slight loss of shoulder adduction/medial rotation.
what happens if i cut the posterior cord
nerve?
muscles?
actions?
not affected, somewhat, and fully
***Axillary nerve (C5-C6)
Muscles innervated:
Deltoid: Shoulder abduction, flexion, extension.
Teres minor: Lateral rotation and stabilization of the shoulder.
Effect: Loss of shoulder abduction (15–90°), weakness in lateral rotation.
***Radial nerve (C5-T1)
Muscles innervated:
Triceps brachii: Elbow extension.
Brachioradialis: Elbow flexion in neutral grip.
Extensor muscles of the forearm (extensor carpi radialis longus/brevis, extensor digitorum, etc.): Wrist and finger extension.
Effect: Complete loss of elbow extension, wrist drop (loss of wrist extension), and finger extension.
***Upper subscapular nerve (C5-C6)
Muscle innervated:
Subscapularis (upper portion): Medial rotation and adduction of the shoulder.
Effect: Weakness in medial rotation of the shoulder.
***Lower subscapular nerve (C5-C6)
Muscles innervated:
Subscapularis (lower portion): Medial rotation and adduction of the shoulder.
Teres major: Shoulder extension, adduction, and medial rotation.
Effect: Weakness in shoulder adduction, extension, and medial rotation.
***Thoracodorsal nerve (C6-C8)
Muscle innervated:
Latissimus dorsi: Shoulder extension, adduction, and medial rotation.
Effect: Weakness in shoulder extension and adduction.
what happens if i cut the Medial cord
nerve?
muscles?
actions?
not affected, somewhat, and fully
***Ulnar nerve (C8-T1)
Intrinsic hand muscles: Interossei, lumbricals (4th-5th fingers), hypothenar muscles, adductor pollicis.
Forearm: Flexor carpi ulnaris, medial half of flexor digitorum profundus (4th-5th fingers).
Effect: Severe loss of grip strength, fine motor control, and wrist flexion/ulnar deviation.
***Median nerve (partial) (C8-T1 contribution)
Thenar muscles: Opponens pollicis, abductor pollicis brevis, flexor pollicis brevis.
Lumbricals (2nd-3rd fingers).
Effect: Weakness in thumb opposition, abduction, and flexion. Precision grip is impaired.
***Medial pectoral nerve (C8-T1)
Pectoralis major (sternal head) and pectoralis minor.
Effect: Weakness in shoulder adduction, medial rotation, and scapular protraction/depression.
***Medial cutaneous nerve of the arm (T1)
Sensory only: Medial skin of the upper arm.
Effect: Loss of sensation on the medial arm.
***Medial cutaneous nerve of the forearm (C8-T1)
Sensory only: Medial skin of the forearm.
Effect: Loss of sensation on the medial forearm
