Case 2 Flashcards
What does the vertebral column develop from
The notochord and somites.
Which primary germ layer do the somites develop from ?
The mesoderm
What is the remnant of the notocord present in the vertebral column?
The nucleus pulposus at the center of every vertebral disc.
What type of nerve does the dorsal root contain?
afferent sensory neurons.
What type of nerve does the ventral root contain?
efferent motor neurons
Where do spinal nerves leave the vertebrae?
Through the intervertebral foramen.
What does a white ramus communicans connect
A sympathetic ganglion and its corresponding spinal nerve.
what type of nerve fibers do white ramus communicans contain?
myelinated preganglionic sympathetic fibers.
What type of nerve fiber do grey ramus communicans contain?
unmylinated post-ganglionic sympathetic fibers.
What do grey ramus communicans originate from?
a sympathetic ganglion
What does a whit ramus communicans originate from
a spinal nerve.
Where are the white ramus communicates?
Each spinal nerve except for the cervical spinal nerves and those below L2
Which type of ramus communicans is found below L2?
grey ramus communicates.
What are the respective numbers of, cervical, thoracic, lumbar, sacral and coccygeal spinal nerves.
8, 12, 5, 5 and 1
Roughly what level does the spinal cord end? How do the spinal nerves continue past this level?
The end at roughly the L2 level spinal nerves continue from this point via the cauda equina.
What does a spinal nerve split into once it has passed through the intervertebral foramina what areas do the resultant structures innervate?
It splits into a dorsal and vetral ramus these innervate structures in front of and behind the vertebral column respectively.
What information do ascending white matter tracts convey?
Sensory information to the brain.
What information do descending white matter tracts convey?
Voluntary motor control
Where do the primary afferents that carry sensory information terminate?
Different laminae of the grey matter of the spinal cord.
How many laminae can the grey matter of the spinal cord be divided into.
10
How many lamina can the dorsal horn of the spinal cord be divided into?
6
What laminae constitute the superficial dorsal horn?
I & II.
What is the alternate name for lamina II of the grey matter?
The substansia gelatinosa
What type of sensation is the superficial dorsal horn/ lamina I & II though to be in control of? What type of receptor does it receive information from?
Pain, Nociceptors.
What is used to define the different laminae of the grey matter of the spinal cord?
Cell size.
What is the other name for low-threshold cutaneous receptor?
Touch receptors.
What region of the grey matter receives input from touch receptors?
Laminae III through VI
Where does laminae III through VI receive information from?
Touch receptors
What do laminae VII through IX of the grey matter contain?
The cell bodies of motor neurons, interneurones and the primary afferents from muscles and joints (proprioceptive afferents)
In the spinal cord where roughly are the motor neurons that innervate extensor muscles relative to those that innervate flexors?
extensors are usually more ventral.
What is meant when it is said that there is a topographical representation of the periphery in the medio-latero plane in the grey matter of the spinal cord?
That areas proximal to the spinal cord tend to have the cell bodies of the neurons that innervate them more medial in the spinal cord than more distal areas.
What are the three main ascending tracts of the somatosensory system?
The dorsal column, the spinothalamic tract and the spinocerebellar tract.
What is the role of the dorsal column?
To convey information about discriminative touch (perception of pressure vibration and texture.
What kind of nerve fiber is the dorsal column mediated by?
A alpha and A beta fibers.
What is the role of the spinothalamic tract?
To transmit information regarding pain and temperature as well as the sensations of itch, tickle and touch
What type of nerve fiber i the spinothalamic system mediated by?
A delta and C fibers.
What is the role of the spinocerebellar tract?
to convey information regarding proprioception.
What type if nerve fiber is the spinocerebellar tract mediated by?
A alpha fibers.
What do the three main ascending pathways all have in common?
They all have four neurons and they all decussate (cross over to the contralateral side). In each of the three pathways it is the second order neuron that decussates.
Describe the course of the dorsal-medial lemniscus pathway how does it vary between the upper and lower limbs
What is known as the dorsal column contains two pathways the fascicullis gracilis and the more lateral fascicullis cuneatus. Afferent neurons are arranged somatotopically so afferents from the lower lower limb and trunk travel via the fascicullis gracilis and afferents from the upper limb travel via the gracilis cuneatus. They in the first order neuron ipsilaterally til they reach the medulla more specifically the cuneate and gracile nuclei depending on which fascicullis they traveled via here they synapse with their second order neuron which decussates and travels via the medial lemniscus to the ventral postereolateral nucleus of the thalmus where it synapses with its third order neuron and from that travels to the primary somatosensory cortex in the post central gyrus. Some of this information is sent to areas such as the posterior parietal association cortex.