Quiz 1 - Spinal Cord, Cervical, Brachial, Lumbar & Sacral Flashcards
Three regions in the central nervous system
Spinal
Brain stem and cerebellar
Cerebrum
Spinal Region
Cross-section of the spinal cord reveals gray matter, forming a shape similar to the letter H surrounded by white matter
Gray matter contains:
Neuronal cell bodies & synapses
White matter contains:
Myelinated axons
Dorsal horn has ____ ? And ventral horn has ____?
Sensory and motor
Rootlets
Small bundles of nerve fibers (axons) attached to each side of the spinal cord
Merge to form roots (dorsal and ventral)
Posterior (dorsal) root ganglion (somatic and visceral)
Sensory neuronal cell bodies
Anterior (ventral) root
Motor/efferent fibers (somatic and visceral)
Two parts in the Peripheral nervous system (PNS)
Motor (efferent) division: goes out of the PNS
Sensory (afferent) division: goes into the PNS
Break down of Motor (efferent) division
Somatic nervous system
Autonomic nervous system (ANS)
Somatic Nervous System
Motor innervation of all skeletal muscles
Autonomic Nervous System
Motor innervation of smooth muscle, cardiac muscle, and glands
Autonomic nervous system broken down into:
Sympathies division (fight or flight)
Parasympathetic division (rest & digest)
Rootlets
Small bundles of nerve fibers (axons) attached to each side of the spinal cord
Merge to form roots (dorsal and ventral)
Posterior (dorsal) root
Sensory / afferent fibers (somatic and visceral)
Posterior (dorsal) root ganglion (spinal ganglion)
Sensory neuronal cell bodies
Anterior (ventral) root
Motor / efferent fibers (somatic and visceral)
Spinal Nerve
Posterior and anterior roots merge to form a spinal nerve
Spinal nerve exits vertebral column through intervertebral or sacral foramina than branches into:
- Posterior (dorsal) ramus
- Anterior (ventral) ramus
- Rami communicantes (communicating branches)
Posterior (dorsal) ramus
Supplies motor and sensory fibers to the back region
Anterior (ventral) ramus
Supplies motor and sensory fibers to antero-lateral trunk and limbs
Thoracic region
Remain distinct and innervate a narrow strip forming the intercostal nerves that reach targets without networking with other spinal nerves (DO NOT form plexuses)
Non-thoracic regions
Ventral rami converge to form networks called plexuses (bundle of rami)
Rami communicantes (communicating branches)
2 branches that connect to sympathetic trunk:
1. Gray ramus communicans
2. White ramus communicans (only in T1-L2)
Spinal Nerves
31 paired nerves
- 8 cervical (C1-C8) *there are only 7 cervical vertebrae
- 12 thoracic (T1-T12)
- 5 lumbar (L1-L5)
- 5 sacral (S1-S5)
- 1 coccygeal (Co)
Cervical nerves numbered by vertebra below level they emerge EXCEPT:
C1 spinal nerve (aka suboccipital nerve) emerges ABOVE C1 vertebra
C8 exits below C7
Spinal cord ends around vertebral level _____ as the _____.
L1/L2
Conus medullaris
Thoracic, lumbar, and sacral nerves numbered by vertebra ____
ABOVE level they emerge
Ex: what is the vertebra that travels below T8 and T9?
- T8
Spinal roots continually as the ______.
Cauda equina (horse tail)
Plexuses
Composed of afferent and efferent fibers that arise from the merging of the anterior rami of spinal nerves
- cervical (C1-C4)
- brachial (C5 - T1)
- lumbar (L1-L4)
- sacral (L4-S4)
- coccygeal (S5-Co)
C1-C3 roots anastomose to form a loop called
Ansa cervicalis
Ansa Cervicalis is made up of the:
Innervation 3 of the 4 infrahyoid muscles (“strap muscles”): the sternothyroid, sternohyiod and omohyoid
What nerve roots make up the phrenic nerve and where does it innervate?
C3, C4, C5 (technically part of the brachial plexus)
Innervation diaphragm
Hypoglossal nerve (CNXII) and where does it innervate?
Not part of cervical plexus but contributes fibers to Ansa cervicalis
Innervates tongue muscles
Spinal accessory nerve (CN XI) and where does it innervate?
Medulla to C6
Fibers ascend spinal cord and emerge from jugular foramen
Innervates trapezius (C3, C4) — elevates shoulders
Innervates sternocleidomastoid (C2-C4) — turns head
Branches of nerve roots that innervate neck muscles:
Longs capitis, longs colli, scalenes, levator scapulae, recuts capitis, longus capitis
Cutaneous nerves carry _______
Sensory information from skin
Lesser occipital nerve
Innervates the skin and the scalp posterior to the auricle
Great auricular nerve
Innervates skin near concha auricle (outer ear) and external acoustic meats (ear canal)
Transverse cervical nerve
Innervates anterior region of neck
supraclavicular nerves
Innervate the skin above and below the clavicle
Cervical Plexus
Ventral rami of C1-C4
Emerge beneath sternocleidomastoid muscle
Innervates neck and head
Brachial Plexus
Ventral rami of C5-T1
Located between anterior and middle scalene muscles in neck
Supraclavicular part in posterior triangle of neck
Infraclavicular part in axilla
Innervates muscles, joints, skin of upper limb
Brachial plexus contains:
Ventral rami (roots)
Trunks
Divisions
Cords
Terminal nerves
Ventral Rami (Roots)
C5 - T1
Trunks
Superior (C5 & C6)
Middle (C7)
Inferior (C8 & T1)
Divisions
Each trunk has anterior and posterior division
Posterior divisions combine to form posterior cord
Cords
Named relative to axillary artery
Lateral
Posterior
Medial
Terminal nerves
Musculocutaneous
Median
Radial
Ulnar
Lumbar Plexus
T12 - L5 ventral rami
Formed within psoas major muscle
Motor and sensory innervation to pelvic girdle and lower limb
Lumbar roots split to form anterior and posterior divisions in general:
Anterior supplies pelvis and medial thigh
Posterior supplies anterior thigh
Sacral Plexus
L4-S4
- L4, L5 via lumbosacral trunk (technically located in lumbar plexus)
Rami split into anterior and posterior divisions
Sacral plexus splits into
Leg, foot, gluteal and pelvic regions
Anterior of piriformis muscle and posterior to internal iliac artery and vein
Sacral spinal nerves split into
Anterior and posterior rami prior to emerging from anterior and posterior sacral foramina respectively
Sciatic nerve
L4-S3
Contains common fibulae and tibial divisions
- both travel together but remain separate in thigh
- innervate posterior thigh muscles (hamstring)
Sciatic nerve — divisions split at
Popliteal fossa
Common fibular
Lateral and anterior compartments of the leg and dorsum of foot
Tibial
Posterior compartment of leg and plantar side of foot
Example Question: What is the vertebra that travels between T8 and T9?
T8
Example Question: What is the vertebra that travels between C4 and C5?
C5
Example Question: What are the spinal roots of the cervical plexus?
C1 - C4
Example Question: The posterior cord has what divisions associated with it?
3 divisions
