Spinal Nerves and their Distribution Flashcards
What could you inject into the vertebral canal via lumbar puncture?
Anaesthetics, antibiotics and chemotherapeutic agents.
What is coning?
Herniation of the brain.
When should you not do a lumbar puncture?
When a patient has raised intracranial pressure.
Why might you need to access the vertebral canal?
Sample CSF for blood or organisms and measure pressure of CSF.
Why is access safest in the lumbar region?
Spinal cord ends at L1/L2 so cauda equina unlikely to be damaged.
Which way do hypaxial muscles form?
Ventrally.
Which way do epaxial muscles form?
Dorsally.
Where does the subarachnoid space extend to?
S2.
Where does the lumbar cistern extend?
From disc between L1 and L2 to the lower border of S2.
What surrounds the cauda equina?
The lumbar cistern.
How should the patient lie when doing a lumbar puncture?
In the fetal position to space the spinous processes.
Where is the needle inserted in a lumbar puncture?
Between L3 and L4 or L4 and L5.
What are somites?
Paired aggregations of paraxial mesoderm.
How are somites arranged?
Sequentially along each side of the neural tube.
What part of the somite gives rise to musculoskeletal elements?
Dermatomyotome
Where are cell bodies of neurons located?
Anteriorly in the neural tube.
What is the function of somatic motor efferents?
Carry impulses from the CNS to skeletal muscle and stimulate muscle contraction.
What does the dermatomyotome of each somite give rise to?
Individual skeletal muscle.
What follows the development of the skeletal muscle from the dermatomyotome?
Spinal nerves from adjacent somites.
How does the skeletal muscle correspond to the somatic motor fibres?
The muscle receives the fibre from the spinal cord segment adjacent to their somite.
Where do the cell bodies lie?
In the dorsal root ganglia.
Where do the dorsal root ganglia develop from?
The neural crest.
What does the dermis send?
Somatic sensory fibres to the spinal cord segment adjacent to its corresponding somite.
What gives rise to the dermis of skin?
The dermatomyotome.
What is a dermatome?
An area of skin innervated by a single spinal segment.
What causes shingles?
Varicella zoster virus.
Where does chickenpox go after initial infection?
The virus lies dormant in a dorsal root ganglion.
How is shingles related to the spinal nerves?
The rash develops in the skin area supplied by the spinal nerve affected.
What are the horns of the gray matter?
Dorsal horn, lateral horn and ventral horn.
What are the columns of the white matter?
Dorsal column, lateral column and anterior column.
What does a pair of spinal nerves consist of?
Axons of: motor neurons, sensory neurons and sympathetic neurons.
What are the function of motor neurons in the spinal nerves?
They innervate a group of muscles arising from the same somite (myotome).
What are the functions of sensory neurons in the spinal nerves?
They innervate a defined area of skin (dermatome).
What are the functions of the sympathetic neurons of the in the spinal nerves?
They go to structures on the body wall that control body temperature.
What is the end of the spinal cord called?
Conus medullaris.
What happens when the cells of the neural crest invaginate?
They form the neural groove.
What are epaxial muscles supplied by?
Dorsal rami.
What are the hypaxial muscles supplied by?
Ventral rami.
What type of neuron emerges from the anterior horn of the spinal cord?
Afferent motor neuron.
What type of neuron develops out of the lateral horn of the spinal cord?
Efferent sympathetic neuron.
What happens to the sympathetic neuron in the ganglion?
They synapse onto a postganglionic neuron.
What develops from the neural crest cells?
Sensory nerve cell bodies.
Which part of the rami are used for communicating?
Ramis communicans.
Where do dorsal rami of the thoracic spinal nerves carry motor neurones?
To erector spinae muscles.
Where do dorsal rami of the thoracic spinal nerves carry sensory neurones?
From the skin of the back and from vertebral joints.
Where do dorsal rami of the thoracic spinal nerves carry sympathetic neurones?
To blood vessels and sweat glands of the skin.
Where do the ventral rami of the thoracic spinal nerves carry motor neurones?
To intercostal muscles.
Where do the ventral rami of the thoracic spinal nerves carry sensory neurones?
From thoracic skin and pleura and vertebral joints.
Where do the ventral rami of the thoracic spinal nerves carry sympathetic neurones?
To blood vessels and sweat glands of the skin.
What is involved in a reflex arc?
Receptor, sensory neuron, integration centre, motor neuron and effector.
What is a reflex?
A rapid, involuntary motor response to a stimulus.
What is a spinal reflex?
Somatic spinal reflexes provides information on integrity of the reflex pathway and degree of excitability.
Where does the axon of the motor neuron lie?
In the ventral root.
Where does the axon of the sensory neuron lie?
In the dorsal root.
Which spinal vertebrae have lateral horns?
T1-L2.
What is altered sensation called?
Paraesthesia.
What is a symptom of paraesthesia?
Nerve irritation can cause pins and needles.
What does nerve compression cause?
Muscle weakness, loss of sensation and reflexes.
