Case 6 Flashcards
1
Q
What is the other name for the pyramidal motor system?
A
The corticospinal tract.
2
Q
What is the other name for the portion of the precentral gyrus that contains motor neurons?
A
The motor strip
3
Q
What kind of movement does the corticospinal tract deal with?
A
voluntary movement
4
Q
Where in the motor strip would neurons that control the muscles of the face be located?
A
Near the lateral fissure.
5
Q
Where in the motor strip would neurons that control the muscles of the leg be located?
A
near the longitudinal fissure or central sulcus
6
Q
Where do pyramidal first order neurons coalesce to form as they pass through the deep matter?
A
The internal capsule
7
Q
What do neurons of the internal capsule descend the midbrain through?
A
The cerebral peduncle
8
Q
What do neurons of the corticospinal tract that have passed through the cerebral peduncle condense to form?
A
The pyramids
9
Q
What tract deals with motor control of the fact? where do the first order neurons of this tract synapse?
A
corticobulbar tract, the first order neurons synapse at their relevant cranial nerve nuclei.
10
Q
Where in the midbrain is the coticobulbar tract?
A
it is located medially.
11
Q
What separates the medulla from the spinal chord?
A
the pyramidal decussation
12
Q
What proportion of fibers decussate at the distal part of the medulla what do the decussating and non-decussating fibers form?
A
about 75%-90% of the fibers decussate. Those that decussate form the lateral corticospinal tract those that don’t form the ventral corticospinal tract.
13
Q
What does the lateral corticospinal tract deal with?
A
motor neurons of limbs.
14
Q
What does the ventral corticospinal tract deal with?
A
axial motor neurons.
15
Q
Where do the first order neurons of the corticobulbar tract tract pass through the the internal capsule and cerebral peduncle?
A
They descend through the genu of the internal capsule and pass through the medial part of the cerebral peduncle.
16
Q
What are the functions of the extra pyramidal motor system?
A
dampening of erratic motion, maintenance of muscle tone and truncal stability.
17
Q
What are the three main constituents of the extrapyramidal motor system?
A
The subcortical nucleus, the substantia nigra and the red nucleus.
18
Q
What part of the extrapyramidal motor system is most affected in Parkinson’s?
A
The substasianigra
19
Q
What is the other name for the subcortical nucleus?
A
the basal ganglia.
20
Q
Name three structure contained within the subcortical nucleus/basal ganglia.
A
The caudate, putamen and globus pallidus
21
Q
Where is the red nucleus located?
A
immediately adjacent to the substansia nigra in the mid brain.
22
Q
What do nerve from the nuclei of the extrapyramidal system synapse with apart from one another?
A
The brainstem, cerebellum and pyramidal system.
23
Q
What is the main organ of the vestibular system?
A
The vestibular apparatus of the inner ear.
24
Q
What nuclei send information from the vestibular apparatus through the inferior cerebellar peduncle?
A
The superior and lateral vestibular nuclei
25
What lobe of the cerebellum receives information from the superior and lateral vestibular nuclei?
The flucculonodular lobe
26
What are the three major tracts of the vestibular system?
the lateral vestibulospinal, the vestibuloocular ans the vestibulocortical.
27
What are saccade eye movements?
small rapid eye movements that are made when scanning a visual scene.
28
What is the role of the lateral vestibulospinal tract?
maintenance of equilibrium (posture related)
29
What is the role of the vestibuloocular tract?
Control of saccadic eye movements.
30
What is the role of the vestibulocortical tract?
causes dizziness when stimulated.
31
What are the three lobes of the cerebellum?
Thee anterior, posterior and flocculonodular lobe
32
What is the cerebellum located inferior to?
The tentorium cerebella
33
What is the role of the flucculonodular lobe of the cerebellum?
maintenance of equilibrium
34
What is the role of the anterior lobe of the cerebellum?
Maintenance of muscle tone
35
What is the role of the posterior lobe of the cerebellum?
co-ordination, allows us to perform intricate tasks.
36
What are the four major cerebellar tracts?
spinocerebellar, vestibulospinal, corticopontocerebellar and dentatorubrothalamic
37
What does the spinocerebellar tract connect?
The spinal cord and cerebellum
38
What does the vestibulospinal tract connect?
the cerebellum and vestibular system
39
What does the corticopontocerebellar tract connect?
the cortex, pons and cerebellum
40
What does the dentatorubrothalamic tract connect?
The dentate nucleus of the cerebellum, the red nucleus and the thalamus.
41
What two signals does the cerebellum compare what does it do if these do not match?
The cerebellum compares information from the brain motor control areas about the desired sequence of muscle contraction and the actual movement as depicted by peripheral sensory feedback. If they do not match instantaneous subconscious corrective signals are transmitted to the motor system to modulate the degree of contraction by muscles
42
What part of the brain learns if a movement does not occur as intended to make certain muscle contractions weaker or stronger?
The cerebellar circuit.
43
What three parts can the processing circuit of the cerebellar cortex be divided into?
input axons, processing interneurons and output neurons.
44
Mossy fibers from what regions terminate on granule cells in the cerebellar cortex?
the spinocerebellar tract, dorsal column nuclei and the postcerebellar tract
45
What do inputs from the inferior olivary nucleus enter the cerebellar circuit via what do they contact with?
They enter the cerebrum as parallel fibers and make contacts on purkinje fibers
46
Where in the cerebellar processing circuit do climbing fibers of the spinal chord and inputs from the inferior olivary nucleus send inputs to ?
purkinje fibers and the deep cerebellar nuclei.
47
What are the four kind of interneurons in the cerebellar processing circuit
Granule cells, golgi cells, stellae cells and basket cells
48
What is the role of granule cells in the cerebellar processing circuit?
They receive the most input to the cortex from the mossy fiber, they send axons up towards the cortical surface branching in parallel making connections with many cells types.
49
What is the role of golgi cells in the cerebellar processing pathway?
after they are stimulated by the granule cells they inhibit the granule cells in a negative feedback loop.
50
What is the role of the stellate and basket cells?
They are inhibitory cells that limit the output of purkinje cells the out put cells of the cerebellar processing tract.
51
what kind of projections do purkinje cells send to the deep cerebellar nuclei?
GABAinergic/inhibitory
52
What are the roles of the superior middle and inferior cerebellar peduncles.
The inferior and middle peduncles are primarily for inputs the superior is primarily for outputs from the deep cerebellar nuclei
53
where does the inferior peduncle arise from what purpose does it serve?
It arises from the medulla and provides the most input to the anterior lobe of the cerebellum.
54
Where does the middle peduncle arise from what is it's role.
It arises from the pontine nuclei of the pons and caries information from the motor cortex commissural fibers from one side of the cerebellum to the other via the pontine nuclei.
55
Where are the lower motor neurons of the ANS innervated smooth muscle?
The paravertebral and prevertebral sympathetic chain ganglai, the parasympathetic postganglionic ganglia near the organ or in the case of the enteric system the gut wall itself
56
What is the ANS involuntary innervation of smooth muscle controlled by?
The hypothalamus, brainstem, reticular formaton and spinal chord autonomic centers.
57
What is notable about the trigemnal nucleus?
It is very large stretching from the medulla all the way to the midbrain.
58
Via what and to what do sensory afferents of the trigemnal nerve enter the spinal chord.
via the trigemnal ganglion they enter the spinal cord in the midpons
59
What is the discriminative touch pathway for the face?
Large diameter fibers of touch enter the main sensory nucleus of the trigemnal nucleus they synapse here and decussate joining the medial leniscus pathway and following the same course as the dorsal column.
60
What is the course of the first order neuron of the pain and temperature system of the face?
They travel from their receptor through the trigemnal ganglion (where the cell body is located) and travel down the pons and medulla till it reaches the caudal medulla where it synapses.
61
What tract does the first order neuron of the facial pain and temperature tract travel down into the caudal medulla via? What nucleus do they travel within?
They travel in spinal tract V in the spinal nucleus of V.
62
What is the course of the second order neurons of the facial pain and temperature system take?
They decussate and join the spinothalamic tract traveling to thalamus.
63
What proprioceptive axons are contained within the trigemnal nerve?
Stretch and tendon receptors in the muscles of mastication.
64
What is unique about the propricoeptive axons of the face?
Their cell bodies are located in the CNS and they do no pass through the trigemnal ganglion?
65
The tract of which component of sensory innervation of the face does not pass through the trigemnal ganglion?
Proprioception.
66
What nucleus do the first order neurons of facial proprioception pass through?
The mesenphalic nucleus of the brainstem.
67
What does the mesenphalic nucleus resemble?
A dorsal root ganglion that has been forced into the CNS.
68
Where do the facial proprioceptive neurons synapse in the spinal chord? Why is this?
The motor nucleus near to the mesenphalic nucleus, they synapse here so they can initiate the tendon reflexes for the muscles of mastication.
69
What are the two main muscles of mastication?
The masseter and the temporalis.
70
What nucleus do the motor neurons travelling through the trigemnal nerve arise from?
The motor nucleus of V
71
How do the motor fibers of the trigemnal nerve leave the spinal chord?
they leave through the midpons and bypass the trigemnal ganglion.
72
Where does somatosensory information from the face and rest of the body go to respectively before being transmitted to the primary somatosensory cortex of the brain?
Faces goes to the ventroposterior medial nucleus of the thalamus and the body goes to the ventroposterior lateral nucleus.
73
The primary somatosensory cortex is arranged somatotopic fashion which parts of the body are located medially and what parts laterally?
legs are represented medially at the top of the head the face is represented laterally.
74
What does dielectric mean?
An electrical insulator that can be polarized by an applied electrical field.
75
What proportion of myelin is protein and what is lipid?
80% lipid and 20% protein.
76
Name two of the proteins that make up myelin.
myelin basic protein (MBP) and myelin oligodendrocyte protein.
77
what is the name of the process by which schwan cells increase the speed of the propagation of impulses?
saltatory conduction
78
Briefly describe the process of saltatory conduction.
The cytoplasm/axoplasm of the axon is electrically conductive, myelin stops charge from leaking through the membrane but allows the voltage at he sequential node of ranvier to be raised enough for action potential initiation thus allowing the action potential to hop from node to node rather than flowing as a wave.
79
What happens when a nerve is demylinated?
conduction of the nerve is impaired or sometimes losts, the nerve will sometimes wither and die
80
What inflamatory mediator is thought to be upregulated leading to the death of the myelin?
Tumor necrosis factor
81
What are the two stages of remylination?
Recruitment of oligodendrocyte progenitor cells by proliferation and migration where necessary, and the differentiation of the oligodendrocyte progenitor cells forming oligodendrocytes which then engage the demylinated axons.
82
What regulates the remylination process, what do they control specifically?
various growth factors and other extra cellular factors that control the differenciation of the OPC into myelin forming oligodendrocytes.
83
What constitutes the brainstem?
The medulla, pons and mid brain
84
At what level is the brainstem continuous with the cerebellum
The foramen magnum
85
What is the reticular formation?
a complex hetrogenous matrix of nerves in the brain stem which many individually identified nuclei exist within
86
What vitamin is thought to reduce the risk of MS what does this relate to in terms of factors that effect its prevalence.
Vitamin D, levels of this vitamin correlate closely with sunlight exposure so is thought to be related to the fact that MS is much less common in the tropics than colder climates.
87
what is the difference in the prevalence of MS in people who spend their first 15 years of life in cold climates and those who spend these years in tropic climates?
1 in 2000 for cold regions 1 in 10000 for the tropics
88
What is fibrous gliosis
A reactive change of glial cells in response to CNS damage making them more fibrous.
89
Where does fibrous gliosis effect in in MS?
The CNS primarily in the white matter particularly the optic nerves and periventricular areas. Tracts in the pons midbrain and cerebellum are also effected as well as grey matter tracts in the the cerebellum and spinal cord though to a much smaller degree.
90
What are the four types of multiple sclerosis based on prognosis?
relapsing remitting, primary progressive, secondary progressive, progressive relapsing
91
MS typically is characterized by several CNS defects with remissions and recurring exacerbations how frequent are these exacerbations?
about three a year though they vary greatly from person to person
92
What characterizes relapsing remitting MS?
the exacerbations alternate with remissions when the partial or full recovery occurs the symptoms are stable, The remissions themselves can last for years and can spontaneous or be trigger by infections such as influenza.
93
What characterizes primary progressive MS
The disease gradually progresses without remissions though there may be plateaus where the disease does not progress. This presentation of MS does not have any clear exacerbations.
94
What characterizes secondary progressive MS?
This pattern starts with alternating relapses and remissions but this progression is followed up by a gradual progression of the disease
95
What characterizes Progressive relapsing MS?
The disease progresses gradually but is punctuated by sudden clear relapses.
96
What is the rarest presentation of MS?
Progressive relapsing.
