Peripheral Nervous System Flashcards
Components of the PNS
- Cranial Nerves
- Spinal Nerves
- Autonomic Nervous System (Sympathetic and Parasympathetic)
- Enteric
Spinal Nerve System
- Segmental Dorsal Rami – deep axial muscles/posterior skin along spinal column
- Segmental Ventral Rami – limbs and body wall
– Cervical Plexus
– Brachial Plexus
– Intercostal nerves
– Lumbosacral Plexus
Segmental Dorsi Rami
Some have names, some don’t
Subocciptal Nerve (C1)
Greater Occipital Nerve (C2)
Third Occipital Nerve (C3)
C4 – T12 Dorsal Rami
L1-L3 Superior Cluneal Nerves
L4, L5 Dorsal Rami
S1-S3 Middle Cluneal Nerves
S4 – Cx2 Dorsal Rami
- primarily innervate posterior skin and deep spine muscles, and facet joints
C1- intervation may present as: Cranial facial pain, headaches
How to identify type of vertebrae
- Angle of the capsule of the articular process
- Look at the nerves in the spinal cord
Dorsal: Nerve goes to facet joint and muscle (multifidus) in image
Cervical Plexus
- C1 – C5
- Ansa Cervicalis (C1 – C3)
- Cutaneous Nerves (C2 – C4)
- Phrenic Nerve (C3-C5); Diaphram
Specific twigs that send little twigs out to muscles
Ansa Cervicalis: thyroid muscles
Brachial Plexus
C5-T1
RTDCB - MARMU
Splits into 3 anterior and 3 posterior division
Anterior Dividion of BP will innervate
Developmentally Ventral Structures
Posterior Division of BP will innervate
Developmentally Dorsal Structures
The three cords are names based off position to Axillary A.
The Divisions Join to form Three Cords – named for relation to axillary artery – lateral, posterior, medial
Lateral Cord
From Anterior Divisions (to ventral structures, mostly flexors!)
Lateral Pectoral Nerve (C5-C8)
Musculocutaneous Nerve (C5-C7)
Lateral Root to the Median Nerve (C6 & C7)
Median Nerve C6-T1
Medial Cord
From Anterior Divisions (also to ventral structures, mostly flexors)
Medial Pectoral Nerve (C7 – T1)
Medial Brachial Cutaneous Nerve (C8 & T1)
Medial Antebrachial Cutaneous Nerve (C8 & T1)
Medial Root to the Median Nerve (C8 & T1)
Ulnar Nerve (C8 & T1)
Median Nerve C6-T1
Posterior Cord
From Posterior Divisions (to dorsal structures, mostly extensors)
Upper Subscapular Nerve (C5 & C6)
Thoracodorsal Nerve (C6, C7 & C8)
Lower Subscapular Nerve (C5 & C6)
Axillary Nerve (C5 & C6)
Radial Nerve (C5, C6, C7 & C8)
Injuries above the plexus
Dermatome/Myotome Charts
Injuries below, use
peripheral distribution charts
Injury occuring in the middle of the plexus present as
random; individual situation
Upper Arm Compartmentalization - Anterior Arm
Flexes Shoulder and Elbow
Anterior Divisions
Musculocutaneous Nerve
C5, C6, C7
Upper Arm Compartmentalization - Posterior Arm
Extends Elbow
Posterior Divisions
Radial Nerve
C7 & C8
UA Compart - Anterior Forearm
Flexes Wrist and Fingers
Anterior Divisions
Median Nerve (Mostly)
C6, C7 & C8
UA Compart - Posterior Forearm
Extends Wrist and Fingers
Posterior Divisions
Posterior Interosseous Nerve (Mostly)
C7 & C8
UL Compart - Intrinsic Hand
Abducts/Adducts Fingers
Anterior Divisions
Ulnar Nerve (Mostly)
C8 & T1
Lumbar Plexus
- Subcostal Nerve – T12
- Iliohypogastric Nerve – L1
- Ilioinguinal Nerve – L1
- Genitofemoral Nerve – L1 & L2
- Lateral Femoral Cutaneous Nerve – L2 & L3
- Femoral Nerve – L2, L3, L4 (Posterior Divisions)
- Obturator Nerve – L2, L3, L4 (Anterior Divisions)
- Lumbosacral Trunk – L4 & L5
T12-L5
LFC: Commonly gets compressed with pregnancy, obesity, and tight clothes
Sacral Plexus
- Superior Gluteal Nerve – L4, L5, S1 (Posterior Divisions)
- Nerve to Quadratus Femoris – L4, L5, S1 (Anterior Divisions)
- Inferior Gluteal Nerve – L5, S1, S2 (Posterior Divisions)
- Nerve to Obturator Internus – L5, S1, S2 (Anterior Divisions)
- Posterior Femoral Cutaneous Nerve – S1, S2, S3
- Pudendal Nerve – S2, S3, S4
- Pelvic Parasympathetics – S2, S3, S4
- Sciatic Nerve (Tibial and Fibular Nerve Combined)
– Common Fibular Nerve – L4, L5, S1, S2 (Posterior Divisions)
– Tibial Nerve – L4, L5, S1, S2, S3 (Anterior Divisions)
Muscles and Nerve Innervation - Lumbosacral
Developmental in the LE has rotation so…
what started out as dorsal is now anterior…i.e. the posterior divisions of the plexus innervate anterior compartments
LL Comp - Anterior Thigh
Flexes Thigh and Extends Leg
Posterior Divisions
Femoral Nerve
L2, L3, L4
LL Comp - Medial Thigh
Adducts and Flexes Thigh
Anterior Divisions
Obturator Nerve
L2, L3, L4
LL Comp - Posterior Thigh
Extends Thigh and Flexes Leg
Anterior Divisions
Tibial Nerve
L4, L5, S1
LL Comp - Ant Lower Leg
Dorsiflexes Foot
Posterior Divisions
Deep Fibular Nerve
L4, L5, S1, S2
LL Comp - Lateral Lower Leg
Everts Foot
Posterior Divisions
Superficial Fibular Nerve
L5, S1, S2
LL Comp - Posterior Lower Leg
Plantarflexes Foot
Anterior Divisions
Tibial Nerve
S1, S2
Anterior Interossi N. is
a terminal branch of the median nerve and is only motor innervation and is in the hand.
The PNS’s major function is..
Signal transduction
What forms the basis for neurodynamic assessment and treatment?
The idea that the system is continuous, and nerves like space, movement, and blood flow
Effectors =
muscles and glands
Receptors =
Energy biotransducers, they take energy from the environment, and transduce them to signals
Receptors: Adaptation, afferent, proprioceptove function
Receptive Fields for sensation
Vary depending on location in body.
Finger: Good at localizing, lots of sensory nerves
Low Back: Not good, less overlap of sensory nerves.
Why does the nervous system need to expand?
- Demand on length of nerves changes depending on position.
- Ex: spinal canal is 7-10 cm longer in flexion vs extension.
- Nerves are not elastic, they slide, fold, and twist
Peripheral nerve structure
- Peripheral nerves are sheathed, have a blood supply (Vasa Nervosum) and innervation (Nervi Nervosum)
- Sheath provides protection and nutrition
- Nerves are bloodthirsty!!
- Cells also depend on axoplasmic flow for functional processes – movement of organelles, proteins, etc. (similar to cytoplasm)
- Flow is movement dependent
- Movement = blood and axoplasmic flow
Peripheral nerves need:
Space, movement and blood
Missing one of these will result in them being symptomatic (pins and needles, weakness, etc.)
peripheral nerve lesions (compression)
- Often see sensory changes before motor
- Susceptible to compression in tight spaces or near hard surfaces
Pressure and spine
- Intervertebral foramen: nerves exit the spine from here; Common place of compressure
- Cervical: exit above veretbrae; Ex: C6 nerve root exist C5-C6
- Thoracic: Extremely rare.
- Lumbar: Spinal Cord ends at L1-L2, therefore peripheral nerves branch and go through spinal cord to exit. Ex: L3 N, exists below L3 Vertebrae at the top of the foramen. With a lesion there L3 N has no issues but L4 could be compressed.
- Cervical Ex: In the spinal cord tumor in at C7, leads to hyperreflexia in the legs as it is an UMN lesion. Also leads to myotome and dermatome issues for levels of C7 and below.
- Same situation but in lumbar: L3 lesion, L3 is able to leave myotome and dermatome good. L4-S4 myotome and dermatome affected.
Below L1-L2 injury would be…
peripheral nerve injury
LL Comp - Dorsal Foot
Supports Foot, Extends Toes
Posterior Divisions
Deep Fibular Nerve
S1, S2
Plantar Foot
Supports Foot, Flexes Toes
Anterior Divisions
Medial & Lateral Plantar Nerves
From Tibial Nerve
S2, S3
