- part of PNS - emerge from spinal cord - 31 pairs - exit vertebral canal via intervertebral foramen - named for related vertebrae

- ventral roots and dorsal roots emerge from the spinal cord - roots join to form spinal nerves - ventral roots contain motor axons only (motor neuron cell bodies are in ventral horn) - dorsal roots contain sensory axons only (sensory axon cell bodies are in the dorsal root ganglion)

- spinal nerves exit through intervertebral foramen - after that, split into ventral and dorsal rami - rami contain sensory and motor neurons - ventral rami form most named nerves and plexuses - dorsal rami innervate small strip of the back

- a network of nerves formed by adjacent VENTRAL rami - most ventral rami contribute to a plexus - T2-T12 nerves do not, and instead continue as the intercostal nerves - each muscle in a limb receives its nerve supply from more than one spinal nerve (damage to one spinal nerve can't completely paralyze a limb) Somatic Nerve Plexuses 1. Cervical plexus (C1-C4) 2. Brachial plexus (C5-T1) 3. Lumbar plexus (L1-L4) 4. Sacral plexus (L4-S4) Lumbosacral plexus - combined (L1-S4) named for the lumbar and sacral plexuses as they are connected

- C1-C4 nerves - Innervates many muscles of the hyoid to aid in moving the larynx - C3-C4 spinal nerves contribute to phrenic nerve

- C3-C5 - innervates the respiratory diaphragm

- partly in neck, partly in axilla - gives rise to most nerves of the upper limb - mixing of ventral rami of C5-T1 Main components - roots (ventral rami) - trunks - divisions - cords - branches

- sensory innervation: skin of medial hand, medial side of digit 4, all of digit 5 - motor innervation: flexors and intrinsic hand muscles - "funny bone"

- sensory innervation: skin of lateral palm and digits 1-3 and lateral side of digit 4 - motor innervation: anterior compartment of forearm (with ulnar), intrinsic muscles of thumb

Lab 9 Flashcards by Riley Cissell

Spinal Nerves

part of PNS
emerge from spinal cord
31 pairs
exit vertebral canal via intervertebral foramen
named for related vertebrae

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Spinal nerve numbers per section

8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal

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Spinal Nerve names and locations

C1-C7 exit above the vertebra of the same name
no C8 vertebra, but there is a C8 spinal nerve - emerges inferior to C7 vertebra
that causes a shift
Nerves T1-Co1 exit below the vertebra of the same name

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Spinal Cord Grey Matter

skinny posterior arms of “H” are dorsal horns
thicker anterior arms are ventral horns

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Roots

ventral roots and dorsal roots emerge from the spinal cord
roots join to form spinal nerves
ventral roots contain motor axons only (motor neuron cell bodies are in ventral horn)
dorsal roots contain sensory axons only (sensory axon cell bodies are in the dorsal root ganglion)

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Rami

spinal nerves exit through intervertebral foramen
after that, split into ventral and dorsal rami
rami contain sensory and motor neurons
ventral rami form most named nerves and plexuses
dorsal rami innervate small strip of the back

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Nerve Plexuses

a network of nerves formed by adjacent VENTRAL rami
most ventral rami contribute to a plexus
T2-T12 nerves do not, and instead continue as the intercostal nerves
each muscle in a limb receives its nerve supply from more than one spinal nerve (damage to one spinal nerve can’t completely paralyze a limb)

Somatic Nerve Plexuses
1. Cervical plexus (C1-C4)
2. Brachial plexus (C5-T1)
3. Lumbar plexus (L1-L4)
4. Sacral plexus (L4-S4)

Lumbosacral plexus - combined (L1-S4) named for the lumbar and sacral plexuses as they are connected

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Cervical Plexus

C1-C4 nerves
Innervates many muscles of the hyoid to aid in moving the larynx
C3-C4 spinal nerves contribute to phrenic nerve

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Phrenic nerve

C3-C5
innervates the respiratory diaphragm

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Brachial Plexus

partly in neck, partly in axilla
gives rise to most nerves of the upper limb
mixing of ventral rami of C5-T1

Main components
- roots (ventral rami)
- trunks
- divisions
- cords
- branches

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Terminal branches of Brachial plexus

Musculocutaneous
axillary
median
radial
ulnar

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Musculocutaneous Nerve

sensory innervation: skin of lateral forearm
motor innervation: anterior compartment of arm (coracobrachialis, biceps, 1/2 brachialis)

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Ulnar Nerve

sensory innervation: skin of medial hand, medial side of digit 4, all of digit 5
motor innervation: flexors and intrinsic hand muscles
“funny bone”

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Median Nerve

sensory innervation: skin of lateral palm and digits 1-3 and lateral side of digit 4
motor innervation: anterior compartment of forearm (with ulnar), intrinsic muscles of thumb

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Carpal tunnel syndrome

compression of the median nerve inside the carpal tunnel where it transits with many tendons from the forearm
numbness tingling in the palm and first 3 or 4 digits
weakness in the hand/thumb

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Axillary Nerve

sensory innervation: shoulder joint and skin on part of deltoid
motor innervation: teres minor and deltoid

Radial Nerve

sensory innervation: skin over dorso0lateral arm, forearm, and hand
motor innervation: posterior compartment of arm and forearm (extensors, triceps)

Wrist drop

unable to extend wrist against gravity
can be the result of pressure to radial nerve from atypical upper limb positioning (crutches, arm hung over a chair)

Lumbosacral Plexus (L1-S4) Terminal branches

Lumbar Plexus
- Femoral
- Obturator

Sacral
- superior gluteal
- inferior gluteal
- Sciatic: common peroneal and tibial
- Pudendal

Femoral Nerve

sensory innervation: skin of antero-medial thigh, skin of medial leg and foot
motor innervation: muscles of anterior thigh, thigh flexors and leg extensors (iliopsoas, Sartorius, rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius)

Obturator Nerve

sensory innervation: skin of medial thigh
motor innervation: muscles of medial thigh, adductors (adductor longus, gracilis, adductor magnus, and adductor brevis)

Superior Gluteal Nerve

motor innervation: gluteus Medius and minimums, thigh abduction

Inferior Gluteal Nerve

motor innervation: gluteus maximus, thigh extension

Pudendal Nerve

sensory innervation: skin of external genitalia
motor innervation: levator ani, muscles of the perineum, external anal sphincter

Sciatic Nerve

- 2 divisions: common fibular and tibial - innervate posterior thigh and leg - compression by the piriformis muscle can result in widespread lower limb pain and weakness

Tibial Nerve

- sensory innervation: skin of postero-lateral leg, skin of sole of foot (subdivides into plantar nerves) - motor innervation: muscles of posterior thigh, muscles of posterior leg (adductor magnus, bicep femoris, hamstrings, gastrocnemius, soleus, and digital flexors)

Common Fibular Nerve

- sensory innervation: skin of anterior and lateral leg, skin on dorsum of foot - motor innervation: muscles of anterior leg (deep fibular), muscles of lateral leg (superficial fibular) (tibialis anterior) - also innervates bicep femoris with the tibial nerve

Foot Drop

- unable to dorsiflex foot and keep toes off the ground - can result from trauma to the neck of the fibula, where common fibular nerve transits

Autonomic Nervous System

- general visceral motor system of the PNS - involuntary control: regulates smooth and cardiac muscles and glands - regulates heart rate, blood pressure, breathing, body temp, secretions, digestion, homeostasis - controls all the 'routine" functions of physiological systems

Divisions of ANS

Sympathetic - thoracolumbar (T1-L2) - "fight or flight" - increase heart rate - decrease digestion/secretion - emergencies, exercise, excitement Parasympathetic - craniosacral (brainstem and S2-S4) - "rest and digest" - decrease heart rate - increase digestion - normal, everyday functioning

Parasympathetic Structures

Cranial Nerves - come directly from the brain and/or leave through foramen in the skull - not all cranial nerves carry parasympathetic fibers - innervate ciliary muscles and glans of head and neck, digestive tract up to about the splenic flexure, heart, bronchial tree - CN III, CN VII, CN IX, CN x Pelvic Splanchnic Nerves - come from spinal cord and initially travel with spinal nerves (S2-S4) - innervates hindgut and pelvic organs

Sympathetic Structures

- sympathetic chain/trunk: series of paravertebral ganglia on each side of the vertebral column - ventral rami from T1-T12 connect lateral horn grey matter via rami communicans to sympathetic chain ganglia - fibers can ascend of descend in the chain to reach areas above T1 (head/neck) and below L2 (pelvis) - fibers to organs leave the ganglia and travel on splanchnic nerves Splanchnic Nerves - nerves traveling to organs from the sympathetic chain