Case 2 Flashcards
1
Q
What does the vertebral column develop from
A
The notochord and somites.
2
Q
Which primary germ layer do the somites develop from ?
A
The mesoderm
3
Q
What is the remnant of the notocord present in the vertebral column?
A
The nucleus pulposus at the center of every vertebral disc.
4
Q
What type of nerve does the dorsal root contain?
A
afferent sensory neurons.
5
Q
What type of nerve does the ventral root contain?
A
efferent motor neurons
6
Q
Where do spinal nerves leave the vertebrae?
A
Through the intervertebral foramen.
7
Q
What does a white ramus communicans connect
A
A sympathetic ganglion and its corresponding spinal nerve.
8
Q
what type of nerve fibers do white ramus communicans contain?
A
myelinated preganglionic sympathetic fibers.
9
Q
What type of nerve fiber do grey ramus communicans contain?
A
unmylinated post-ganglionic sympathetic fibers.
10
Q
What do grey ramus communicans originate from?
A
a sympathetic ganglion
11
Q
What does a whit ramus communicans originate from
A
a spinal nerve.
12
Q
Where are the white ramus communicates?
A
Each spinal nerve except for the cervical spinal nerves and those below L2
13
Q
Which type of ramus communicans is found below L2?
A
grey ramus communicates.
14
Q
What are the respective numbers of, cervical, thoracic, lumbar, sacral and coccygeal spinal nerves.
A
8, 12, 5, 5 and 1
15
Q
Roughly what level does the spinal cord end? How do the spinal nerves continue past this level?
A
The end at roughly the L2 level spinal nerves continue from this point via the cauda equina.
16
Q
What does a spinal nerve split into once it has passed through the intervertebral foramina what areas do the resultant structures innervate?
A
It splits into a dorsal and vetral ramus these innervate structures in front of and behind the vertebral column respectively.
17
Q
What information do ascending white matter tracts convey?
A
Sensory information to the brain.
18
Q
What information do descending white matter tracts convey?
A
Voluntary motor control
19
Q
Where do the primary afferents that carry sensory information terminate?
A
Different laminae of the grey matter of the spinal cord.
20
Q
How many laminae can the grey matter of the spinal cord be divided into.
A
10
21
Q
How many lamina can the dorsal horn of the spinal cord be divided into?
A
6
22
Q
What laminae constitute the superficial dorsal horn?
A
I & II.
23
Q
What is the alternate name for lamina II of the grey matter?
A
The substansia gelatinosa
24
Q
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?
A
Pain, Nociceptors.
25
What is used to define the different laminae of the grey matter of the spinal cord?
Cell size.
26
What is the other name for low-threshold cutaneous receptor?
Touch receptors.
27
What region of the grey matter receives input from touch receptors?
Laminae III through VI
28
Where does laminae III through VI receive information from?
Touch receptors
29
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)
30
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.
31
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.
32
What are the three main ascending tracts of the somatosensory system?
The dorsal column, the spinothalamic tract and the spinocerebellar tract.
33
What is the role of the dorsal column?
To convey information about discriminative touch (perception of pressure vibration and texture.
34
What kind of nerve fiber is the dorsal column mediated by?
A alpha and A beta fibers.
35
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
36
What type of nerve fiber i the spinothalamic system mediated by?
A delta and C fibers.
37
What is the role of the spinocerebellar tract?
to convey information regarding proprioception.
38
What type if nerve fiber is the spinocerebellar tract mediated by?
A alpha fibers.
39
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.
40
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.
41
Where does the first order neuron of the dorsal column synapse?
In the gracile or cuneate nucleus of the medulla depending on which fascicullis it traveled via.
42
What does the second order neuron of the dorsal column travel via?
The medial lemniscus pathway
43
Where does the second order neuron of the dorsal column synapse?
In the postereolateral nucleus of the thalmus.
44
Where does the third order neuron of the dorsal column synapse?
The somatosensory cortex of the postcentral gyrus.
45
What are the four brodmann's areas of the somatosenrsory cortex?
1, 2, 3a and 3b
46
How much of the input from ventroposterior thalmus do bradmann's areas 1&2 and 3a&3b receive respectively?
30% and 70%
47
What type of input does area 3b of the somatosensory cortex receive?
Cutaneous input.
48
What type of information does area 3a of the somatosensory cortex receive?
Proprioceptors in muscles.
49
What type of input does area 2 of the somatosensory cortex receive? what is it though to be important for?
Proprioceptors in joints. It is thought to be important for stereogenesis.
50
What type of input does area 1 of the somatosensory cortex receive? What is it thought to be important for?
input from rapidly adapting cutaneous mechanoreceptors. It is thought to be important for texture discrimination.
51
What are the four types of nerve endings that are though to be important for fine touch and proprioception?
Meiseners corpusles, Pacinian corpusles, Ruffini endings and Merkel endings.
52
What is the specialty of the meisener corpuscle?
Detection of vibrations between 10 and 50Hz
53
What is the specialty of the pacinian corpuscle?
Detection of vibrations around 250 Hz. They are far more sensitive to changes in pressure rather than consistent force. They are thought to be very important in the detection of pressure.
54
What is the specialty of a ruffini ending?
Stretch reception, it responds better to sustained pressure.
55
What is the specialty of a merkel ending
Detection of low frequency vibration 5-15 Hz
56
Where are the cell bodies of the first order neurons of the spinothalamic tract?
The dorsal root ganglion.
57
How far does the typical first order neuron of the spinothalmic tract ascend before synapsing with its second order neuron?
1-2 levels.
58
Through what section of the white matter does a first order neuron of the spinothalamic pathway ascend the spinal cord?
Lissauer's fascicullis.
59
Where does the first order neuron of the spinothalamic pathway synapse?
A cell body in the dorsal horn of the grey matter.
60
Where are the cell bodies of the second order neurons of the spinothalamic tract located?
In the dorsal horn in the substatia gelatinosa or the nucleus proprius.
61
What does the second order neuron of the spinothalamic tract decussate?
The anterior white commisure.
62
Via what does the second order neuron of the spinothalamic pathway ascend the spinal cord?
the lateral lemniscus
63
What is the lateral lemniscus continuous with once it reaches the medulla?
The medial lemniscus.
64
Where does the second order neuron of the spinothalmic pathway synapse?
The ventroposterior nucleus of the thalmus
65
What are the two subparts that the spinothalamic tract can be divided into?
The anterior (paleo) and the lateral (neo)
66
Where do the cell bodies of the anterior region of the spinothalamic tract originate from?
laminae VII of the spinal chord grey matter.
67
What type of sensation is the anterior section of the spinothalamic tract associated with?
crude or sensual touch, itch tickle and pressure.
68
What type of sensation is the lateral part of the spinothalamic tract associated with?
"fast pain"
69
Which pathways deal with unconscious and conscious proprioception respectively?
The spinalcerebellar tract and dorsal column.
70
What path do the first order neurons of the spinocerebellar tract take?
The first order neurons travel though the dorsal column then after a few segments leave the white matter and synapse in the Clarke's nucleus.
71
Where do the firs order neurons of the spinocerebellar tract synapse?
Clarks nucleus.
72
What is the course of the second order neuron of the spinocerebellar tract?
It ascends the spinal cord to the cerebellum without decussating it then enters the cerebellum via the inferior cerebellar peduncle and terminates on purkinje cells.
73
Where do purkinje relay information to in the spinocerebellar tract?
The deep cerebellar nuclei and from there to the motor areas of the thalmus, brainstem and basal ganglia.
74
What is the other name for acute pain what are its two main functions?
Noiceptive pain, its two main functions are to protect the body from damage and homeostasis informing the body when activity is putting excessive strain on the body.
75
What is the main function of prolonged pain when does it cease?
It occurs when injury has occurs its main purpose is to prevent further damage to the affected area and assist healing. It subsides when healing has occurred.
76
What is the other name for chronic pain how does it differ from the other types of pain?
Neuropathic pain. It is different as it results from dysfunction or damage to the nervous system itself it is notably more difficult to treat.
77
What is a polymodal receptor?
A receptor sensitive to more than one kind of stimulus.
78
What type of fiber typically transmits fast pain?
A delta.
79
What type of fiber typically transmits slow pain
C fbers
80
What type of pain is usually described as bright sharp or stabbing what type of fiber transmits it?
Fast pain, A delta fibers.
81
What type of pain is usually described as dull, throbbing nagging or aching what type of fibers transmit this?
Slow pain, C fibers.
82
What accounts for the lack of localisation in visceral and muscular pain when compared to cutaneous pain?
The lower innervation density
83
What are the three ascending pathways of the anterolateral pain system?
The spinothalamic, spinoparabrachial and spinoreticular tracts.
84
What are the roles of the spinothalmic tract and the combined efforts of the spinoreticular and spinobarabrachial tracts respectively?
sensory discriminative aspect and the homeostatic and affective aspects respectively.
85
Are C fibers myelinated?
No
86
What type of stimuli does lamina I receive?
Only painful
87
What type of input does lamina IV receive?
Low threshold afferents stimulated by sensual touch etc.
88
What is lamina V particularly useful for why is this? How can the brain determine whether a stimulus from lamina V is painful?
Lamina V receives stimuli from both noiceptors and low threshold afferents making it very good at locating a stimulus the brain uses whether signals are also being sent fro lamina I to determine whether the stimulus is painful.
89
What is another common cause of compression of an isolated nerve root apart from a herniated intervertebral disc?
Bone changes due to rheumatoid or osteoarthritis.
90
What proportion of sufferers of prolapsed disc will improve without need for treatment?
90%
91
What three types of drugs are typically given to someone suffering from sciatica?
pain killers, anti-inflamatory and muscle relaxant drugs.
92
What is the name for the operation for a prolapsed disc?
disectomy or laminectomy
93
What is the typical treatment for sciatica?
bed rest along with analgesia surgery if these are ineffective.
94
Which two discs are most commonly prolapsed in sciatica, what nerve roots are effected?
discs L4-L5 and L5-S1 are most commonly effected the nerve roots L5 and S1 are effected.
95
What can be effected in sciatica when it is particularly severe that is observable in a clinical exam?
Knee and ankle jerk reflexes.
96
What receptors are effected by TENS machines what does TENS stand for?
Opioid receptors. Transcutaneous Electrical Nerve Stimulator.
97
What are the four ways high frequency TENS devices reduce pain?
Activation of delta opioid receptors both supraspinally and in the medulla, reduces the excitation of central neurons that carry noiceptive information, modulates the release of neurotransmitters increasing the release of inhibitory ones (e.g. GABA) and decreasing excitatory ones (e.g. glutamate) and activates muscarinic receptors producing an analgesic effect.
98
How do low frequency TENS devices reduce pain?
Activation of mew opioid receptors in the spinal cord and supraspinally, causes the release of serotonin, the release of GABA and the activation of muscarinic receptors. The last two effects cause a reduction in excitability of Nociceptive neurons in the spinal cord.
99
What is the summary of Gate control Theory?
The idea that the perception of pain is not directly caused by the signals of noiceptive fibres but it is also modulated by non nociceptive fibers (A beta fibers) That inhibit nociceptive signals when they are stimulated.
100
What type of nerve fiber is thought to have an inhibitory effect on pain in gate control theory?
A beta fibers.
101
What effect does stimulation of the periaqueductal grey matter surrounding the third ventricle how does it do this?
it has analgesic effects by activating descending pathways that both directly and indirectly inhibiting noiceptors in the lamina of the spinal cord.
