Spinal Nerves and Distribution Flashcards
Uses of lumbar puncture?
To get a sample of CSF for microbiology/biochemistry/cytology
Measuring CSF pressure
Injecting treatments like anaesthetics/antibiotics/chemotherapy
What is contraindication?
Patients with raised intracranial pressure which can result in coning (progressive cerebral herniation)
Process of lumbar puncture
Patient lies in fetal position (on side with back and hips flexed)- spaces spinous processes
Needle inserted between L3 and L4 or L4 and L5
What are somites
Paired aggregation of paraxial mesoderm that can be divided into:
sclerotomes: vertebral column, rib cage and occipital bone
dermomyotomes: muscles and skin
What is a myotome?
A group of muscles innervated by the same spinal nerve
Where are cell bodies of motor neurons found?
Ventral side of neural tube
Where are cell bodies of sensory neurons found?
In dorsal root ganglia
What is a dermatome?
An area of skin supplied by a single spinal cord level
Clinical relevance of dermatomes
Shingles
Caused by varicella zoster virus
Rash develops in skin area supplied by the spinal nerve affected (within a dermatome)
What does a spinal nerve consist of?
Motor neurons innervating a group of muscles arising from the same somite
Sensory neurons that innervate an area of dermis
Sympathetic neurons to structures in the body wall T1-L2
Divisions of spinal nerve
Dorsal rami
Ventral rami
Dorsal rami
Carries motor neurons to erector spinae muscles/ intrinsic back muscles/ expaxial muscle
Carries sensory neurons from skin of back and vertebral joints
Carries sympathetic neurons to blood vessels and sweat glands
Ventral rami
Carries motor neurons to intercostal muscles
Carries sensory neurons from thoracic skin and pleura and vertebral joints
Carries sympathetic neurons to blood vessels and sweat glands
From plexuses which give rise to peripheral nerves
Reflex
Rapid, involuntary motor response to stimulus
- test for a specific myotome
Reflex arc
Receptor, sensory neuron, integration centre, motor neuron, effector
