A/P Unit 2 Flashcards
1
Q
What are the 3 classifications of neuron fibers?
A
Types A, B and C
2
Q
Describe the differences between the 3 types of neuron fibers?
A
A is myelinated, B is lightly myelinated, C is non-myelinated. Type A is the largest, C is the smallest.
3
Q
What are the 4 sub categories of type A fibers?
A
A-Alpha fibers - The largest, fastest and myelinated
A-Beta fibers - A little smaller than A-alpha
A-Gamma fibers - smaller than A-beta
A-Delta - smallest myelinated neurons
4
Q
What type of neurons connect to skeletal muscles?
A
A-Alpha
5
Q
What type of fibers are generally pain fibers? What makes up the smaller percentage?
A
A-Delta as the primary, C-fibers as the smaller percentage
6
Q
What are the advantages of myelinazation?
A
Faster signal conductance, lower metabolic demands, greater ability to survive times of ischemia
7
Q
What are the maintenance cells in the CNS? The PNS?
A
CNS - Oligodendrocytes
PNS - Schwann cells
8
Q
What is the part of the neuron that functions as the “brakes.” What binds to it to elicit this response?
A
The axon hillock, and usually GABA
9
Q
Why does alcohol withdrawal cause seizures?
A
Because alcohol functions as a neuronal suppressant. Because the body as adapted to this, it no longer makes much GABA. Without GABA, if alcohol is abruptly taken away, there is nothing to suppress neuronal excitability and the whole system can go haywire (seizures).
10
Q
Describe Excitatory and Inhibitory post-synaptic potential
A
Most dendrite connections are excitatory connections, so another neuron is communicating with the receiving one to try and create an AP. If enough are communicating, they can cause depolarization. Inhibitory are the opposite; when they communicate, they are trying to repolarize or make the neuron more negative.
11
Q
What type of neuron is a decision making neuron?
A
Multi-polar
12
Q
How does a decision making neuron make a decision?
A
It makes decisions based on the charge difference created by neurons sending messages to the decision making neuron.
13
Q
What is pre-synaptic potential?
A
This is when a neurotransmitter released by the communicating neuron (not the decision maker) comes back to the communicating neuron and binds to stop further neurotransmitter release
14
Q
What is post-synaptic potential?
A
Classic neuronal communication; the communicator is sending a message through the synapse to the decision making neuron.
15
Q
What would make a neuron more + and -?
A
More + (or less -) open Na or Ca channels, close K channels.
More - (less +) open Cl or K channels, close Na channels
16
Q
What are the 4 types of glial cells?
A
Astrocytes, ependymal cells, oligodendrocytes, microglia
17
Q
What do astrocytes do?
A
Star like appearance, goal is to maintain constant conditions in the nervous system. Can buffer CSF. End feet support the BBB.
18
Q
Why does a drop in Na increase ICP?
A
Because the BBB is mostly impermeable to salt, so a difference in concentration gradient can drive water into the brain.
19
Q
What do Oligodendrocytes/Schwann cells do?
A
Maintain the myelin of the CNS/PNS
20
Q
What do ependymal cells do? Where are they located?
A
Produce CSF, and using cilia act as a secondary circulatory system (pump) to send CSF throughout the CNS system. They hang out in the 3rd/4th ventricles and the lateral ventricles.
21
Q
What do microglia do?
A
They act as scavengers of the CNS, break things down, almost function as a mini-immune system
22
Q
Where do most brain cancers originate from?
A
Glial cells, because of their ability to reproduce themselves. Neurons (for the most part) in the CNS can’t regenerate/make copies of themselves.
23
Q
What are the basic neuron types?
A
Multi-polar, Pseudo-unipolar and Bipolar
24
Q
Describe a multi-polar neuron, pseudo-unipolar and bipolar neuron
A
Multi-polar - Numerous dendrites, 1 myelinated axon. Decision making neuron.
Pseudo-unipolar - Long axon with soma off to the side. Typical setup for sensory neurons. Generally occur in a cluster (ganglia in the PNS, nuclei in the CNS)
Bipolar - one single axon, one dendrite. Reserved for special sense such as retina and photoreceptors
25
Describe the term "somatic"
Things we are aware of, sensations such as pain or pressure. This is also allows us to use our skeletal muscle to move.
26
What type of nerve ending do pain receptors have?
Free nerve endings
27
Describe how Pacinian and Meissner's corpuscles work
Imagine a circle, when pressure is applied it flattens out. When flattened out, the sodium channels are "pulled wider" to allow Na to rush in. This increases the rate of AP firing and tells the CNS that pressure is occurring at this site.
28
Describe how baroreceptors work
Similarly to pressure sensors, if pressure increases/decreases in the Aorta or carotid, this will increase/decrease the firing rate of APs to let the CNS know about the change in pressure. If pressure remains high/low, over a 48 hour period the the baroreceptors can become adapted to this change, and make it the new baseline.
29
What type of nerve ending exhibits reverse adaptation? Describe reverse adaptation?
Free nerve endings. If you experience pain, and keep experiencing it, you will become more sensitive to it, or sensitize.
30
Describe how tactile hairs work
Think a cats whiskers. Sensors are wrapped around it that respond to an external stimulus, such as whiskers rubbing against a door, or a fly landing on my arm.
31
Describe how the golgi tendon apparatus works
Located in the tendons of muscles. Tells the CNS if the tendons are under strain, if strain is high, it will protect the tendon by relaxing the muscles around the tendon.
32
Describe how the muscle spindle stretch sensor works
Fibers are wound around skeletal muscle that are distorted when muscle contracts. This distortion creates APs to confirm to the CNS that the muscles are doing what they have been ordered to do. Simplified; it sense the tension in the muscles.
33
What is rostral and caudal?
Think bird, beak and feather (directionality). The forward and front is the beak (rostral) and the lower and to the rear is caudal.
34
What is the telencephalon?
The out part of the brain, the cerebral cortex.
35
What is the diencephalon?
The deep inner structures of the brain, mainly the thalami (thalamus, hypothalamus, epithalamus).
36
What do the thalami help control?
Body temp, infection control
37
What is the mesencephalon?
The midbrain, or top of the brainstem
38
What are the component parts of the brainstem?
Midbrain, pons, medulla oblongata (in order).
39
Where does higher order thinking occur?
Cerebral cortex
40
Where do automatic functions occur in the brain?
The diencephalon and brain stem
41
What are the 4 lobes?
Frontal, parietal, occipital, and temporal
42
What is the primary function of the frontal lobe?
Conscious thinking, personality, decision making
43
Where is the location of the motor cortex?
Back of the frontal lobe in front of the cerebral sulcus
44
What is the primary function of the parietal lobe?
This is where sensations/sensory information is processed.
45
What separates the frontal and parietal lobes?
The central sulcus, this is a major landmark of the brain
46
What is the primary function of the occipital lobe?
Processing visual input, thinking about what we see. No good anatomical marker to differentiate the parietal from occipital lobes.
47
What is the primary function of the temporal lobe?
Handles auditory sensation, some limbic function as well (limbic is dealing with emotions)
48
What is the landmark that separates the temporal and occipital lobes?
The temporo-lateral fissure. Also called the temporal fissure.
49
What separates the brain hemispheres?
The longitudinal fissure
50
What allows the hemispheres to communicate with each other?
The corpus callosum
51
Describe the location of the olfactory bulbs
One for each hemisphere, runs on the inferior side of the frontal lobe. Neurons extend out from here, one for each nostril
52
What is the other name for the pituitary gland? Describe its location and constituent parts.
The hypophysis, and inferior part of the brain, near the back of the frontal lobe. Made of the anterior and posterior glands (hypophysis and neurohypophysis)
53
Describe the location of the optic nerves
Start next to the anterior mesencephalon (brain stem) and in front of the hypophysis.
54
Where does vision get routed back to the occipital lobe?
The optic chiasm, which is very close to the origin of the optic nerves, and curls around the hypophysis
55
Describe the anatomical location of the cerebellum
Tail end at the bottom, meaning the caudal position.
56
What is the anatomical location of the motor cortex? And its basic function?
Pre-central gyrus, and to send efferent signals to the skeletal muscle
57
What function does the post-central gyrus perform?
It is the sensory portion of the parietal lobe
58
Describe Broca's location and function
Frontal lobe, and is involved with word formation and thought processing about speech
59
Describe Wernicke's location and function
Language comprehension and temporal lobe
60
What is the pre-central gyrus? The post-central gyrus?
The motor cortex (frontal lobe location) and sensory processing (parietal lobe)
61
Describe the limbic system location and function
In the temporal lobe, and governs response to pain, general emotions, depression
62
Where are the cell bodies concentrated in the spinal cord?
The grey matter
63
Where are reflexes housed in the spinal cord?
Grey matter
64
Describe the 3d traveling orientation of information going through the spinal cord
It comes in the horizontal plane to the ventral/dorsal horns, and the vertical plane via the spinal columns
65
Basic function of the grey matter
Decision making
66
Basic function of white matter
Signal transduction (transferring information)
67
Describe the 2 major spine landmarks
The anterior median fissure (front) and the posterior median fissure (back)
68
What is the meeting point for the left/right sides of the column for white and grey matter (in that order)?
The anterior white commissure, and the lamina ten (lamina X)
69
What is the small opening in the lamina X? What is its function?
The central canal, it is lined with ciliated cells to help push/pump CSF down the cord
70
Describe how to identify the horns
First identify the anterior median fissure. Generally, the larger horns will be the ventral horns, and closer to the fissure, then then horns above them (and generally smaller) will be the dorsal horns
71
Describe the lateral horns
Small arrowhead shaped projections halfway between the ventral and dorsal horns. Not always present.
72
Describe the direction the horns send information
The ventral horns are taking messages from the CNS to the periphery, making it an efferent pathway. The dorsal horns are taking information from the periphery and sending it to the CNS (this could just be the spinal cord or the brain), making it an afferent pathway.
73
Describe the short version of the type of information handled by each of the horns
Sensory information is handled by in the back by the dorsal horns, motor information in the front by the ventral horns
74
What would occur with ischemia to the anterior spinal cord?
This would affect the ventral horns, so motor movement. Maybe even paralysis
75
What would occur with ischemia to the posterior spinal cord?
This would affect the dorsal horns, so sensory deficiences
76
What are the small superficial arteries in the spinal cord called?
Coronal arteries
77
Describe basic location of the 3 main spinal cord arteries
1 in the anterior median fissure, 2 on the back adjacent to the posterior median fissure
78
What is the name of the blood vessels that go into the spinal cord?
Sulcal arteries/veins
79
Describe the major veins of the spinal cord
The anterior spinal vein runs in the anterior median fissure, the other runs in the posterior median fissure
80
Describe the progression of nerve fibers coming in/out of the spinal cord
Rootlet -> root -> nerve -> ganglion
81
What type of information would posterior rootlets be handling?
Sensory information going to the dorsal horns
82
What type of information would anterior rootlets be handling?
Motor information coming from the ventral horns going out to the muscle
83
Where do the sympathetic ganglion go?
They run parallel to the cord/spine
84
Where are the ascending spinal columns/tracts? Where is this information going?
The posterior spine (in between the dorsal horns) and the antero-lateral cord (the left/right sides of the outer cord) and is information going up to the brain
85
What type of information ascends in the posterior column?
Basic senses
86
What type of information ascends the antero-lateral columns?
Pain
87
Where are the descending columns located?
In between the ventral/dorsal horns, slightly above where you could potentially find the lateral horns and more medial than the lateral ascending columns, and the anterior spine
88
Describe C-spinal nerve location, number and nomenclature
8 pairs, 16 total. C1 nerve comes out on top of its own vertebrae, C2 - 8 come out just below the prior vertebrae. So, nerve C2 comes out on the bottom of C1, this continues for nerves C2 - 8. *IMPORTANT* there are 7 cervical vertebrae, C1 nerve is on top of C1 vertebrae, C2 nerve comes out from the bottom of the C1 vertebrae.
89
Describe T-spinal nerve location, number and nomenclature
12 pairs, 24 total. They come out from the bottom of their respective vertebrae. So the T1 nerve comes out from the bottom of the T1 vertebrae, this continues through T12.
90
Describe L-spinal nerve location, number and nomenclature
5 pairs, 10 total. The same as T-spine nomenclature, the L1 nerves come out from the bottom of the L1 vertebrae. This continues through L5.
91
Describe the spinal curvature from top to bottom
C spine is cervical lordosis (front curve), T-spine is kyphosis (back curve) L-spine is lordosis, sacral is kyphosis
92
What is abnormal side-side bending of the spine called?
Scoliosis
93
What is unusual forward curvature of the spine called?
Pathological kyphosis
94
What is unusual backward curvature of the spine called?
Pathological lordosis
95
What are the connection points for the vertebrae called?
The superior/inferior articular processes
96
What is the joint of the articular processes called?
A facet joint
97
Describe the basic structure of a vertebrae
A large vertebral body, an arch on the posterior side made of the pedicle (short portion) and the lamina (longer portion). The transverse processes extend laterally, the spinous process projects posteriorly, with superior and inferior articular processes extending up/down from the meeting point of the pedicle and lamina.
98
Where would spinal nerves exit the vertebrae?
Via the intervertebral foramen
99
Where would you inject steroids to help back pain?
As close to the facet joint as possible
100
What are the distinguishing characteristics of a cervical vertebrae?
A large vertebral foramen, bifid spinous process, holes in the transverse foramen for veins/arteries, a hollowing out above the pedicle for the nerves to leave, a large vertebral foramen, and a small vertebral body.
101
Where do the vertebral arteries/veins enter?
C6 transverse foramen
102
What arteries provide blood to the brain?
The L/R carotids and the L/R vertebral arteries
103
What is the name of the top 2 cervical vertebrae?
The atlas (C1) and Axis (C2)
104
What is unique to C1?
Anterior/posterior tubercles (instead of a body/spinous process), a facet for the dens and very large superior articular facets
105
What is unique to C2?
The dens, a flat superior articular facet, large spinous process, the first appearance of a bifid spinous process and the first vertebral body.
106
What does the dens do?
Provides structural support, and the ability to move the neck side to side
107
What allows the neck to bend up/down?
The connection between the occipital condyles and the atlas
108
What is the big hole at the base of the skull?
Foramen magnum
109
What connects the atlas and the occipital bone?
The atlantooccipital ligament
110
What gave the name for C1?
Atlas, the god who supported the weight of the world on his shoudlers
111
Describe the occurrence rate for bifid spinous processes in the general population
Vast majority have one for C2 - C5, 50% have one in C6, 0.3% of the population have one in C7
112
Describe the general trend of the vertebral foramen
Starts large at the top, and gets smaller as you go down because the cord gets progressively smaller
113
What are the ligaments that run the length of the spine? Which is the largest?
The anterior/posterior longitudinal ligaments, the anterior is the larger
114
What ligaments connect the transverse processes?
The inter-transverse ligaments
115
What ligaments connect the tips spinous processes?
The supraspinous ligaments
116
What ligaments connect the body's of the spinous processes?
The interspinous ligaments
117
What ligaments connect the vertebral arches together?
The ligamentum flava
118
What is the distinguishing characteristic of the ligamentum flava compared to other ligaments?
Consistency; this ligament is rubbery/flexible, and has a "stretchy" feeling when you hit it with a needle
119
Why is the ligamentum flava not always a reliable indicator of appropriate depth for an epidural?
Because some of the population may be missing the ligament, or have incomplete fusion of the ligamentum flava
120
What is the correct order from outer to inner ligaments of the anterior spine to reach the meninges?
Supraspinous ligaments -> interspinous ligaments -> ligamentum flava
121
What is the enlarged ligament at the top of the c-spine?
The nuchal ligament
122
What is the attachment point for the supraspinous ligament on the skull?
The external occipital protuberance (its the bump you can feel)
123
Describe the connection of the atlantooccipital ligaments
Anterior and posterior, the posterior connects the back of the atlas between the arch and the atlas. Both ligaments connect the atlas and occipital bone.
124
Why does bending forward allow you to access the interlaminar foramen of the lumbar spine, but not the thoracic spine?
The thoracic spinous processes are large and caudad, so when you bend forward not much is exposed, as opposed to the lumbar spinous processes which go straight back. So more is exposed from the lumbar region when you bend forward
125
What is the opening on the posterior spine between the vertebrae?
The interlaminar foramen
126
What is the spinal process of C7/T1?
The vertebral prominens
127
What are the unique features of thoracic vertebrae?
Connection points for the ribs, caudad spinous processes, heart shaped vertebral body, loss of bifid spinous processes
128
What are the connection points for ribs called?
Costal facets
129
What is the term for multiple costal facets on a single vertebrae?
Demi-facets
130
What is the name of the connecting points of a rib and the transverse process?
the costal tubercle, creating the costotransverse joint
131
Where do you lose demi facets?
In the L-spine
132
What is a unique feature of T5 - T8?
The left side of the body is rounded, the right side is flatter, this is due to the contact of the descending aorta
133
What is the total number of ribs? Describe the basic groups.
12. 1 - 7 are true ribs, connect directly to the sternum. 8 - 10 are false ribs and connect the the cartilage that attaches rib 7 to the sternum. 11 and 12 are floating ribs, not connecting to the sternum at all.
134
What parts make up the sternum?
Manubrium (top part), body, xiphoid process
135
What connects the manubrium and the body?
The sternal angle
136
What are the unique features of the L-spine?
Large kidney bean shaped body, large but straight spinous processes, smaller and triangle shaped vertebral foramen
137
Where are you able to start being able to access the dural sac?
In the L-spine
138
Where does the cord end?
L1
139
What vertebrae locks into the sacrum?
L5
140
What does the spine sit on?
The promontory
141
What does the promontory seperate?
The abdominal and pelvic cavities
142
What are the unique features of the sacrum?
Transverse lines from fusion, large openings on the front/back (anterior/posterior foramina), the coccyx (apex)
143
Describe the differences between the anterior/posterior sacral foramina
A higher density of nerves exit the anterior sacral foramina, a much smaller amount exit the posterior, and only innervate the gluteal region
144
Why is it preferable to access sacral nerves from a posterior approach?
The nerves in the back only innervate the gluteal region and there is a lesser amount of nerves from a posterior approach
145
What houses the dural sac and cauda equina?
The sacral canal
146
What produces the sacral canal?
the fusion of S1 - S5 vertebral foramen
147
What is the collection of nerves after the termination of the cord called?
Cauda Equina
148
What is the opening at the base of the sacrum?
The sacral hiatus
149
What is proximal to the iliac crests? Why is this a valuable landmark?
The body of L4, from here you can palpate the spinous process of L4, giving you 2 landmarks for access to the CSF
150
Describe the location of the iliac spines
There are superior/inferior on each side. Follow the crest of the hip down towards midline. The first bump is the superior iliac spine, the lower bump is the inferior iliac spine
151
How would you use anatomic landmarks to locate the sacral hiatus?
Locate the L/R superior iliac spines, make an equilateral triangle shape. The base of the triangle is about where the sacral hiatus is.
152
What are the raised bumps at the opening of the sacral hiatus?
The Sacral Cornu
153
What ridge is midline on the sacrum? What created them?
The median sacral crest (fusion of the spinous processes of S1 - S5)
154
What ridges are left/right of the median sacral crest? What created them?
The medial sacral crests (created from the fusion of the superior/inferior articular processes of S1 - S5)
155
What is the outermost ridges of the sacrum? What created them?
The lateral sacral crests (created by the fusion of the transverse processes of S1 - S5)
156
Give the simple version of each ridge of the sacrum.
Median sacral crest = spinous process
Medial sacral crests = superior/inferior articular processes
Lateral sacral crests = transverse process fusion
157
Describe how to access the posterior sacral foramina? Which one is the ideal target, why?
Locate the posterior iliac spine, from there, 1cm proximal and 1 cm inferior. This give you access to S2 foramen. This is ideal, because the hole is oriented towards us (S1 faces off at a diagonal angle), and there are landmarks to easily guide us to S2
158
What is the insertion point for the inguinal ligament(s)?
The anterior superior iliac spine(s) (one on each side)
159
Describe the connection point for the inferior pelvis
The pubic symphysis, a cartilaginous connection
160
What ligament connects the pelvis and spine? What is the connection point on the spine?
The iliolumbar ligaments, and the transverse processes of L4/5
161
What ligament secures the tailbone to the sacrum? What are their names?
The sacral-coccygeal ligaments, and the anterior and posterior S-C ligaments
162
What ligament gets in the way of accessing the sacral hiatus?
The posterior sacral coccygeal ligament
163
Describe the basic structure of a disc
It is sandwiched between the hyaline cartilage end plates, is made of a fibrous outer anulus fibrosus and jelly like interior called the nucleus pulposus
164
What precisely is the shock absorber in between the vertebrae?
The nucleus pulposus
165
Which vertebrae do not have discs?
Above C1, and above C2
166
Why do discs preferentially herniate posteriorly rather than anteriorly?
Because the anterior has a crisscross pattern of ligaments that are extremely strong/sturdy. Whereas the posterior lacks this same structural support from the ligaments, making it easier to herniate out the back
167
Describe the basics of how a slipped disc causes pain
The disc escapes and presses on a nerve against the bone of the lamina
168
How does a laminectomy relieve back pain from a slipped disc?
This doesn't fix the disc, it just removes what the disc is pressing the nerve against (bone). By removing the bone, there is nothing for the disc to press the nerve into.
169
Describe the 3 layers of the meninges, inner to outer
Pia mater, arachnoid layer, dura mater
170
In terms of the meninges, where are the blood vessel located?
Superior to the pia mater, inferior to the arachnoid layer
171
In terms of the meninges, where is CSF located?
Sub-arachnoid layer
172
Where would an epidural sit? Where would go for intra-thecal?
Right outside the dural layer (hence, epidural), for intra-thecal, you would want to go through the arachnoid layer, but not the pia mater.
173
Why do you need to give a loading dose with an epidural?
Because there is fat in the epidural space, and the fat can absorb some of the drug. You need to saturate the fat to ensure the medication can get by the fat.
174
Why does an epidural's effects not instantly stop with cessation of the epidural?
The fat has absorbed some of the drug, and will slowly release it after an epidural has been dc'd
175
What is the end of the spinal cord called?
The conus medullaris
176
What is the continuous ligament that anchors the spinal cord to the sacrum?
The Filum Terminale
177
What makes L4/5 a preferable site for CSF access?
Easy landmarks to identify the spot, the cord is now gone, so upon puncturing the space the nerves can "move out of the way" of the needle, whereas the cord cannot
178
What encompasses the cauda equina and CSF at the base?
The dural sac
179
What is the enlargement at L4/5?
The lumbar cistern
180
What are the parts of the filum terminale?
The internum and externum
181
What is the difference between the internum and externum?
The internum connects the end of the cord (conus medullaris) to the end of the dural sac. The externum connects the end of the dural sac to the sacral bone.
182
Why does the termination point of the cord change as we age?
The cord and spinal bones grow as we age (from a very young age). The cord grows rapidly, whereas the bones grow slower, leading to a gradual heightening of the end point, L3 when young, L1 when mature.
183
Describe the 2 enlargements of the cord
C3 - C6, denser collection of nerves because your extremities need a lot of innervation. T11 - L1, same as above, lower extremities need a lot of innervation
184
What is the cistern superior to the c-spine?
The cisterna magna, it sits right below the cerebellum
185
Where does the ligamentum flava end?
Ends around C2 (can vary based on the person). The ligament is missing between C1 and the base of the skull
186
Why is a hit to the back of the head more dangerous than the front?
The front has more "support", whereas a hit on the back puts a lot of strain on the small ligament supporting the dens.
187
What are the terms for the motor pathway?
The pyramidal tracts or the cortico-spinal tracts
188
What are the names of the extrapyramidal tracts?
Rubro-spinal tract, Reticulo-spinal tract, Olivo-spinal tract, Vestibulo-spinal tract
189
What is the definition of a tract? What about nerve?
Tract = collection of axons in the CNS
Nerve = collection of axons in the PNS
190
Where do the posterior ascending tracts terminate?
They end in the somatosensory cortex/post-central gyrus
191
What is the collective term for sensory information going into the dorsal horns and up the column?
The DCML pathway (Dorsal Column Medial Lemniscus System)
192
What part of the DCML does information from the lower extremities travel?
The Gracile Fasciculus
193
What part of the DCML does information from the upper extremities travel?
Primarily the Cuneate Fasciculus, but it does briefly enter the Gracile Fasciculus
194
What is the primary classification of neuron in the dorsal columns?
A-beta fibers
195
What is the name of the pain pathways?
The antero-lateral pathways or the antero-lateral spinothalamic tracts
196
What tract provides muscle feedback to the CNS? What specific part of the CNS interprets this information?
The spinocerebellar tracts, and the cerebellum
197
What is the basic information being sent through the anterior/posterior cords?
Motor goes through the anterior cord (efferent, anterior roots) and sensory travels in the posterior cord (afferent, posterior roots)
198
What is the name of Laminae I? What classification does its nerve fibers fit? What type of sensory information is processed here?
The laminae marginals, A-delta fibers and sharp pain
199
What is the name of Laminae II/III? What classification does its nerve fibers fit? What type of sensory information is processed here?
Substantia Gelatinosa, C-fibers and slow pain
200
What are the pain laminae? What kind of pain do they transmit?
Laminae I, II, III and V.
I = sharp pain
II/III = slow pain
V = generalized pain
201
Give a basic description of how pain travels when it comes into the dorsal horn.
The pain enters the dorsal horn, makes the necessary connections in the grey matter, crosses over via the anterior white commissure, then travels up the column (antero-lateral tracts or antero-lateral spinothalamic tracts) on the opposite side where the signal entered
202
What are the generalized connections in laminae I - VI? Do they crossover?
The mechanoreceptors detecting pressure/stretch, and they do not crossover.
203
What is the term for laminae VII?
Intermediolateral nucleus
204
What is primarily found in laminae VII and VIII?
Motor neurons
205
What are the 5 spinal tracts and their basic function?
Spino-cerebellar - feedback about muscles
DCML - Sensory information transduction
Spino-thalamic tracts - pain pathways
Cortico-spinal tracts - primary motor pathway
Extrapyramidal tracts - secondary motor pathway
206
Where does crossover from the DCML pathway occur?
In the lower medulla
207
Where does pain crossover?
At the same level in entered, enters one side then goes to the other side before transmitting up
208
Describe the path that sensation from the foot travels to its endpoint. How does information an upper extremity differ?
Information comes into the dorsal horn, and begins to travel up the column via the gracile fasciculus and ascends to the lower medulla where crossover occurs, here a synapse occurs, and the signal continues to travel up the brainstem, passing through the medial lemniscus in the pons, to the midbrain and then to the diencephalon (thalamus). In the thalamus it must pass through the ventro-basal complex, then pass through the internal capsule and end in the somato-sensory area or post-central gyrus.
The upper extremity follows this same path, except it enters via the cuneatus fasciculus
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What is point to point discrimination?
The ability to distinguish to separate points of contact, requires a high density of pressure sensors
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Describe the pathway of the primary motor tract, including other names for it.
Pyramidal tracts, corticospinal tracts. Originates in the pre-central gyrus (motor cortex), goes to the internal capsule, the pyramids of the medulla where cross over occurs, then down the lateral corticospinal tracts (columns)
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Where does signal cross over in the medulla occur?
At the pyramidal decussation
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What is the precursor to the anterior median fissure?
The rivet/groove of the medulla, which is also called the anterior median fissure of the medulla
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What percentage of our motor output follows the lateral corticospinal tract? The anterior corticospinal tract? The uncrossed lateral corticospinal tract?
90%, 8% (per the diagram, in lecture Dr. Schmidt says it can be 8 - 10%) and 2%.
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Where does the lateral corticospinal tract cross over?
In the medulla
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Where does the anterior corticospinal tract cross over?
At the level of the spinal cord where the signal wants to exit
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What is the name of the secondary motor pathway?
Anterior corticospinal tract
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Per lecture, what is a function of the anterior corticospinal pathway?
Innervation of the intercostal muscles
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Which motor pathway does not cross over?
The tertiary corticospinal tract or the uncrossed lateral corticospinal tract
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Where do most of the motor neurons converge in the spinal cord?
Laminae 7 - 9
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What is the name of the pain pathway ?
Antero-lateral spinothalamic tracts
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Where does fast pain ascend? What kind of fiber is it?
Via the lateral spinothalamic tract, a-delta
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What is the primary neurotransmitter for fast pain?
Glutamate
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Where does most fast pain signaling terminate? What unique properties does this give to fast pain signaling?
Higher up in the brain, generally to the somatosensory area (post central gyrus), it must go through the ventro-basal complex . It follows the same pathway as the DCML, except that fast pain does not have to go through the internal capsule. This allows to "understand" the pain more, meaning we know exactly where it is, the quality of the pain and the severity.
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What do fast pain signals travel parallel to?
The DCML pathway
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Where does slow pain ascend? What kind of fiber is it?
The anterior spinothalamic tract, c-fibers
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What neurotransmitters are used with slow pain?
Glutamate, Substance P, and CGRP (calcitonin gene-related peptide)
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What do slow pain signals travel parallel to?
Thermoreceptors
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Generally, where does fast pain synapse? Slow pain? (give names as well)
Fast pain in laminae I (laminae marginals) , Slow pain in Laminae II/III (substantia gelatinosa) and laminae V
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What is another term for the lateral spinothalamic tract?
Neospinothalamic tract
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What is another term for the anterior spinothalamic tract?
Paleospinothalamic tract
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What areas does slow pain terminate?
Areas in the brainstem (such as the reticular formation in the pons) or other parts of the lower brain. Rarely makes to the cerebral cortex. General trend is to ascend towards the thalamus, does not mean they make it to the thalamus.
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Where do pain signals cross over?
At the same level they come in, crossing over via the anterior white commissure
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Describe the basics about why reflexes are as fast as they are
Because the grey matter has direct connections to the motor laminae, which allows them to make rapid decisions from incoming pain signals
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What is the basic function of each of the extrapyramidal tracts?
Vestibulospinal - eye fixation, muscle orientation during acceleration, assess rotational acceleration
Olivospinal - Fine tune complex movements
Reticulospinal - Regulate muscles tone, even at rest muscle has tone
Rubrospinal - modulation of voluntary movement (if you reach for something, and your arm is shaky, something could potentially be wrong with this system)
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What do many of our anesthesia pain blocking drugs work on?
The DIC (descending inhibitory complex)
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What are the neurotransmitters of the DIC?
Enkephalin and serotonin
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What are some examples of morphine analogs?
Oxycodone, hydromorphone
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What are the 3 main areas of the Descending Pain Suppression System (or DIC)?
The Periventricular/Periaqueductal grey area, the Raphe Magne Nucleus, and the Dorsal Spinal Cord Complex (laminae I - III and the tract of Lissauer)
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Describe the process of the DIC shutting down pain
The signal starts in the Periventricular/Periaqueductal grey area (exact process that stimulates this area is not fully understood) which stimulates neuron 1 (or first order neuron) to secrete enkephalin. Which binds to, and stimulates neuron 2 (second order neuron) in the Raphe Magnus Nucleus to secrete serotonin, which binds to neuron 3 (third order neuron) which secretes enkephalin. The enkephalin can then block the bind to and block the incoming pain neuron (the sensor) and the neuron that would conduct the signal up wards (the sending neuron in the column)
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Where is the RMN (Raphe Magne nucleus) found?
Pons
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What are the constituent parts of the diencephalon?
Thalamus, hypothalamus, epithalamus, subthalamus
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What is a basic difference between the pia and arachnoid layers of the brain relative to the spinal cord?
You can separate these layers in the brain, but it is extremely difficult to separate them in the spinal cord.
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What divides the cerebellum from the cerebral cortex?
The tentorium cerebelli
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What are the basic differences between cranial bone, and musculo-skeletal bone?
Cranial bone is more porous and more densely vascularized
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What supports the cranial sub-arachnoid space?
Trabeculae
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How much CSF is distributed to the arachnoid system, and the cranial ventricular system? What is the total amount combined?
120 in the arachnoid system, 30 in the ventricles, 150 cc total.
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What is the fluid collection beneath the cerebellum? Both names
The magna cisterna, or cerebello-medullary cistern
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Per lecture, what is the most common source of an epidural hematoma/hemorrhage?
An arterial bleed, usually due to trauma such as a broken bone or an incision
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Per lecture, what is the most common source of a subdural hematoma/hemorrhage?
A venous bleed
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Per lecture, what is the most common source of a sub-arachnoid hematoma/hemorrhage?
Most likely arterial, though a venous bleed is fairly likely as well
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Describe a cranial sinus
A venous blood containing structure in the cranium, relative to a vein, it is far more rigid due to the support of extensive connective tissue
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What is the junction where CSF and the sinuses meet? What is its purpose?
Arachnoid granulations, to allow re-absorption of CSF (allow CSF to exit)
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Per lecture, what is the standard ICP range?
10 - 12
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What is the large sinus running front to back?
Superior sagittal sinus, running parallel to the longitudinal fissure
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Describe how the basic components of CSF are transported into the ventricles
There is a sodium pump that is constantly pumping sodium into the ventricles (generally they are in close contact with an artery). As they pump sodium, Cl and water follow. This processes consumes ATP.
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How many ventricles are there? Describe their basic locations.
4 ventricles
The lateral ventricles are the largest and most superior, one on each side of the longitudinal fissure
The 3rd ventricle is inferior to the top of the lateral ventricles, adjacent to the thalamus
The 4th ventricle is the most inferior, and is roughly parallel to the cerebellum and the pons, kind of sandwiched between them.
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Per lecture, what is the composition of CSF? Include pH level.
Glucose: 30% less relative to the blood
K: 40% less relative to the blood
Cl: much higher in the CSF relative to the blood, about equivalent to the sodium concentration
Na: roughly equal in both CSF and the blood
Mg: high in the CSF relative to the blood
Bicarb: no distinct number or ratio given, just stated it is present in the CSF
Protein: minimal to none
pH: 7.31
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Per lecture, what is the primary "meal of choice" for neurons? What is a secondary option?
Glucose, then ketones.
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What is the connection point between the 3rd and 4th ventricles, give all associated names.
The cerebral aqueduct, or the aqueduct of sylvius
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What is at the base of the 4th ventricle?
The central canal
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What is the connection point between the lateral ventricles and the 3rd ventricle, give all associated names.
The interventricular foramen, or the foramen of monroe
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Describe the horns of the lateral ventricles from a lateral viewpoint
This makes a large C looking structure, the anterior horn would make the upper half of the C, the inferior horn would make the bottom part of the C, and the posterior horn would be extending out from the back of the C, kind of like this, -C
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What are the horns of the 4th ventricle called?
The lateral horns of the 4th ventricle
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What are the names of the openings of the lateral horns of the 4th ventricle?
The lateral aperture(s), or foramen of luschka
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What is the name of the other opening of the 4th ventricle (not the horns)?
The median aperture or foramen of mogendie
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What are the 4 exit points of the 4th ventricle?
The lateral apertures (remember there are 2 total), the median aperture and the central canal
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How much CSF does the body make per hour? Total in a day?
roughly 20/hour, 500/day
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What is the theory that says there are areas other than the arachnoid granulations that allow CSF reabsorption?
The glymphatic system theory
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What are potential causes of blockage of the arachnoid granulations?
Blood clots or hemorrhage
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What is non-communicating hydrocephalus?
An obstruction in one of the outlets of the ventricles, such as the cerebral aqueduct. This causes CSF to build up in the ventricles and push on the tissue in an outwards direction. Can collapse the sub-arachnoid space.
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What is a common cause of non-communicating hydrocephalus?
Blockage of the cerebral aqueduct (the aqueduct of sylvius)
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What is communicating hydrocephalus?
Increased pressure in the entire system without obstruction of any of the exit points, such as the arachnoid granulations being blocked. This does not cause the ventricles to expand, but CSF can accumulate and force the tissue downwards.
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Where do the superior sagittal sinus and transverse sinus meet?
The sinus confluence
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What is the layer of connective tissue separating the hemispheres?
The falx cerebri
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What is sinus is above the falx cerebri? Below?
The superior sagittal sinus, and the inferior sagittal sinus
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What connects the inferior sagittal sinus to the sinus confluence?
The straight sinus
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Where is the cavernous sinus located?
Near the face and nose, drains posteriorly into the jugular vein
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Per lecture, what would happen if we lost our CSF?
The brain would lose the ability to "float" and sink, pulling on the connective tissue causing a massive headache.
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Does the brain have pain receptors? Why does loss of CSF cause a massive headache?
No, but the connective tissue (meningeal layers) does have pain receptors. The loss of CSF causes a massive headache because as the brain sinks, it pulls on the connective tissues which stimulates the pain receptors in the connective tissue.
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What is covered on the left part of the parietal homunculus?
Face, lips, eyes, nose
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What is covered on the top left of the parietal homunculus?
Hands, fingers, wrists
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What is covered at the beginning of the top of the parietal homunculus?
Forearm, elbow, arm, shoulder
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What is covered at the top of the parietal homunculus?
Head, neck, trunk
