Question

How are cranial nerves and spinal nerves similar? How are they different?

2. What components come together to form a spinal nerve? What’s the difference between a dorsal root, ventral root, dorsal primary Ramos,and ventral primary ramus? What type of fibers, sensory or motor, are found in each of these structures?

3. At what level is a spinal tap performed. From an embryological stand point why is this possible?

4. What is the embryological basis for most NTDs? Can they be diagnosed prenatally? Are there any means of prevention?

5. Prenatal ultrasound reveals an infant with an enlarged and expansion of both lateral ventricles. What is this condition called and what might have caused it?

6. What are the two parts of the ANS? Where are their respective preganglionic neurons located? What cells give rise embryologically to their postganglionic neurons?

Answer 1

1. Cranial nerves and spinal nerves both are associated with sensory ganglia and autonomic ganglia. Cranial nerves are more closely associated with parasympathic ganglia.

Cranial nerves directly emerged from brain whereas spinal nerves emerged from segments of spinal cord. Cranial nerves comprises 12 nerve pairs while spinal nerves comprises 31nerve pairs. Cranial nerves forms dorsal and ventral roots while spinal nerves do not.

2. Spinal nerves are formed by the union of dorsal and ventral roots thus all spinal nerves are composed of both sensory and motor fibre.

The dorsal roots contains a dorsal root ganglion containing the cell bodies of sensory neurons while ventral roots consists of axons from the lower motor neuron in the ventral horn of spinal cord. The dorsal and ventral rami consist nerves that provide visceral motor, somatic motor, sensory message or information with the dorsal ramus feeding the dorsal trunk while ventral ramus feeding the ventral trunk and limbs via venterolateral surface.

3. A spinal tap is performed in the lower back in the lumbar region. During lumbar puncture a needle is inserted between two lumbar vertebrae or bone to remove a sample of cerebrospinal fluid.

4. NTDs includes spina bifia and ancephaly are severe birth defects of CNS which origmiate during embroyic development. NTDs can be diagnosed prenataly by triple screen blood test. It can be prevented by taking vitamin supplement regularly.

Please do like the answer and if you have any query comment down