Quiz 1: PNS, Spinal Cord Flashcards
(164 cards)
1
Q
what’s made in nucleolus?
A
ribosomes
2
Q
what nuclear feature is prominent in neurons?
A
nucleolus
3
Q
dendrites are largely extensions of the…
A
…cell body
4
Q
in some unusual cells, axon comes off of…
A
…dendrites
5
Q
cell body size range in vertebrate neurons
A
10-100 um
6
Q
dendritic tree size scale (um, mm, m?)
A
mm
7
Q
axon length scale (um, mm, m?)
A
m
8
Q
how did the giraffe laryngeal nerve get so long?
A
evolved from fish, which have no neck. simpler to just extend the loop as the neck grew.
9
Q
axon diameter range
A
0.5-20 um
10
Q
myelin only helps for axons above a certain diameter, which is…
A
.5 um
11
Q
which way do apical dendrites go?
A
to the cortical surface
12
Q
why is white matter white?
A
myelination is fatty, and fat is reflective
13
Q
why is gray matter gray?
A
less fat content
14
Q
generic name for bundles of axons
A
tract
15
Q
if we know a function for a tract, we call it a…
A
…pathway
16
Q
funiculus
A
large bundle of fasciculi
17
Q
lemniscus
A
means ribbon/belt. flattened bundle. many of these are sensory pathways
18
Q
general term for crossing fiber
A
decussation (from roman numeral for deca-, X)
19
Q
chiasm
A
large decussation (chi = X)
20
Q
commissure
A
crosses midline to the same area on the other side (like corpus callosum)
21
Q
ganglion, ganglia (pl)
A
locations of all neuronal cell bodies in PNS
22
Q
cortex means…
A
bark/rind/covering.
23
Q
neuropil
A
synaptic region with lots of little processes (axons/dendrites) (pil means hair)
24
Q
avg number of connections per neuron
A
~1,000
25
approx number of neurons in human brain
100 billion
26
is most connectivity local or distant?
local, and yet the bulk of the brain appears to be white matter
27
weigert stains what?
axons, instead of cell bodies
28
in cortex, weigert stain reveals...
...bundles going laterally and across layers
29
what characterizies molecular layer?
there aren't many cells
30
smallest cells
granule cells
31
among the largest cells are the...
...purkinje cells
32
orthodromic spikes
the normal way that spikes go, away from cell body
33
antidromic spikes
an AP going towards the cell body
34
how can we distinguish orthodromic and antidromic spikes, if we are stimulating area A and recording from neuron B? there are 4 ways. (answer has high detail)
1. antidromic spike will have fixed latency, because no synapse is involved. orthodromic spike will have varying latency.
2. because vesicles deplete, orthodromic spike won't follow high freq stimulation. antidromic spike will follow up to about 1 kHz.
3. orthodromic spike would cause EPSP. antidromic would not
4. gold standard is collision failure: orthodromic and antidromic spikes cancel out. this tells you that ortho- and antidromic spikes are traveling along same axon
35
embryo layers, outer to inner
ectoderm, mesoderm, endoderm
36
which layer does nervous system develop from?
ectoderm
37
3 steps of the formation of the neural tube
plate->groove->tube
38
what does the mantle layer separate into?
alar plate (dorsal), basal plate (ventral)
39
what does the alar plate turn into?
sensory structures, dorsal horn
40
what does the basal plate turn into?
motor structures, ventral horn
41
sulcus limitans
structure in center of neural tube
42
3 swellings/vesicles emerge from the front end of the neural tube, what are they? in order from fore- to hind-
prosencephalon (forebrain), mesencephalon (midbrain), rhombencephalon (hindbrain), and then spinal cord
43
3 vesicles develop into 5, what are they? in order from fore-hind
[telencephalon, diencephalon], [mesencephalon], [metencephalon, myelencephalon]
44
diencephalon becomes...
...thalamus and hypothalamus
45
telencephalon becomes...
...cerebrum (cortex and deep nuclei)
46
canal in myelencephalon becomes...
...4th ventricle
47
canal in telencephalon becomes...
...lateral ventricles
48
canal in diencephalon becomes...
...3rd ventricle
49
canal in mesencephalon becomes...
...cerebral aqueduct
50
canal in spinal cord becomes...
trick question. it closes, in normal development
51
myelencephalon becomes...
...medulla
52
metencephalon becomes...
...pons and cerebellum
53
mesencephalon becomes...
...midbrain
54
unlike spinal cord, in brain stem motor functions are near...
...midline
55
unlike spinal cord, in brain stem sensory functions are...
...lateral
56
in nuclei abbreviations, 1st letter, general vs special (G vs S) means...
...function is found throughout the body (general, ie somatosense), or only in one particular organ (special, ie auditory)
57
in nuclei abbreviations, 2nd letter, somatic vs visceral (S vs V) means...
...function is external (somatic) or internal (visceral)
58
in nuclei abbreviations, 3rd letter, afferent vs efferent (A vs E) means...
...in/sensory (afferent) or out/motor (efferent)
59
dorsal groove in neural tube
sulcus limitans [I don't think this is right -Sally]
60
3 meninges, outer to inner
dura, arachnoid, pia
61
tela choroidea=
pia+ependyma
62
ependyma
thin lining of ventricular system
63
tela choroidea+blood vessels=
choroid plexus
64
what goes through the 3rd ventricle?
a connection between both diencephalons
65
why are lateral ventricles C-shaped?
evolutionary history, stretching and formation of human brain. deep nuclei follow this contortion. not really like this in rodents
66
in human, which 2 descriptive axes hold steady?
the "eriors": superior/inferior (up/down) and anterior/posterior (front/back)
67
in human, which 2 descriptive axes rotate 90°?
dorsal/ventral, and rostral/caudal
68
what barrier demarcates peripheral and central nervous systems?
the meninges (dura/arachnoid/pia)
69
describe nervous system branching above parasympathetic/sympathetic nervous systems
PNS>motor>autonomic>PS/S
70
plexus
complex network, comprising nerves and/or ganglia
71
receptors
transduce energy into electrical signals
72
effectors
act in response to a nerve impulse
73
PNS equivalent of CNS's tract
nerve
74
PNS equivalent of CNS's nucleus
ganglion
75
typical cell type in dorsal root ganglion
pseudo-unipolar
76
swelling on dorsal root
dorsal root ganglion
77
dorsal root and ventral root fuse to form...
...spinal nerve
78
where is the transition from CNS to PNS?
around the dorsal/ventral root
79
simple spinal nerves are found at what level?
near abdomen, etc
80
describe a complex plexus such as those in the arm
multiple spinal cord levels criss-crossing, converging and diverging, like highway on- and off-ramps
81
fibroblasts
build up extracellular matrix in nerves, like collagen
82
roles of connective tissue
mechanical stability
83
epineurium
surrounds entire nerve, and also exists between fascicles
84
perineurium
surrounds each fascicle
85
endoneurium
surrounds each axons (only in PNS, outside myelin sheath)
86
-neuriums are only in...
...PNS. there are NO "naked" axons in PNS as there are in CNS
87
optic nerve isn't really a nerve because...
...it's not in PNS
88
fascicle
small nerve bundle of axons, within a nerve
89
mallory trichome stain stains for...
...connective tissue
90
leading edge of paired plasma membranes in schwann cell
mesaxon
91
how long is a schwann cell?
~100 um
92
dense line is inner or outer face of mesaxon?
inner edge
93
compact myelin
the mature state of myelination, when all cytoplasm has been pressed out
94
unmyelinated axons are still protected by....
...Schwann cells, which can ensheath many cells. this is not the same as myelination.
95
when a Schwann cell wants to myelinate a single axon...
...it withdraws itself from all other axons
96
nerve fiber names in descending order of speed/diameter (two nomenclatures)
I, II, III, IV
| Aα, Aβ, Aδ, C
97
which muscle fibers are most excitable, following EXTRACELLULAR stimulation? largest or smallest?
largest
98
which muscle fibers are most excitable, following INTRACELLULAR stimulation? largest or smallest?
smallest
99
how could you measure size of motor axons in a muscle nerve, which has motor and sensory axons?
cut dorsal (sensory) root, wait a week, then examine cross-section, which will only contain motor axons
100
3 ways to classify receptors
```
sensory modality (visual, auditory, etc)
area of functional interest (exteroceptors, proprioceptors, etc)
free nerve ending vs specialized receptor cells
```
101
exteroceptors
transduce external world contact, teloceptors
102
interoceptors
respond to internal state
103
labeled line concept
each set of afferents carries information that's interpreted in a particular way. ie, extreme touch never turns into pain
104
receptive field
area where the receptor responds to touch (ie a touch receptor will respond to a patch of skin)
105
pacinian corpuscle
onion-like cutaneous exteroceptor. large receptive fields, rapidly adapting (you don't feel your socks)
106
alar/basal, sensory/motor, sulcus limitans rule only holds for...
...gray matter. bundles aren't necessarily organized the same way
107
effectors of motor neurons
striated muscle, glands, smooth and cardiac muscle
108
efferent pathway consists of...
...somatic motor neurons, pre/post ganglionics
109
each muscle connects to something that spans a length of spinal cord, called...
...spinal motor neuron pools, a nucleus of distributed motor neurons
110
what's the advantage to low divergence in motor units?
high specificity. this varies when you need more specificity, like in fingers vs. quads
111
adult spinal cord length
~18 in
112
adult vertebral column length
~ 28 in
113
why is vertebral column longer than spinal cord?
in development, the vertebral column lengthens, while the spinal cord doesn't
114
cauda equina
collection of nerve roots that innervate lower body. take up space in vertebral column after spinal cord tapers out. looks like a "horse's tail"
115
name the 4 spinal cord regions, rostral-caudal
cervical, thoracic, lumbar, sacral
116
2 ways to characterize spinal gray matter
nuclei (marginal zone, etc)
| rexed's laminae (I-X)
117
cytoarchitectonic divisions of gray matter take into account...
...cell architecture. density, shapes of gray matter
118
what are the two increased densities of gray matter in spinal cord called?
cervical and lumbo-sacral enlargements
119
why are there gray matter spinal cord enlargements?
more motor neurons to control limbs
120
why does spinal cord get larger as you go rostral?
because you collect sensory and motor fibers from the periphery as you go to the brain
121
how does ratio of white:gray matter change as you go caudal?
it gets much smaller as you go caudal
122
nucleus thoracicus or nucleus dorsalis location
at the base of the dorsal horn
123
where does parasympathetic nervous system emerge?
craniosacral
124
where does sympathetic nervous system emerge?
thoracolumbar
125
parasympathetic preganglionic locations
cranial nerve nuclei for III, VIII, IX, and X, and S2-4
126
sympathetic preganglionic locations
lateral horn of T1-L2
127
parasympathetic ganglia locations
on or near end organs
128
lateral horn
little triangle that sticks out between the dorsal and ventral horns on the same level as the central canal; only occurs in the thoracic region and thus can be used as an identifying feature
129
ramus
branch
130
ANS
homeostasis, regulation of internal environment
131
3 principles of pathway organization
```
modality
laterality (symmetry)
topography/somatotopy (mapping)
```
132
name for pathways that remain in the spine, don't go to brain
propriospinal (locomotion is one example)
133
what information does spinothalamic tract carry, and what's another name for it?
pain/temperature; also known as ALS anterior lateral system
134
5 types of somatosensory information
fine tactile-discriminatory (small two-point touch, textures, figure out what an object is)
```
crude touch (knowing something is there
pain/temp (these two are often the same pathway?)
```
proprioceptive (states of muscles/joints)
autonomic (from viscera, smooth muscle, glands)
135
fine tactile sensation pathway
dorsal column/medial lemniscal
136
how are touch receptors innervated?
several or multiple axons come in and weave through the corpuscle
137
what's weird about spike propagation in somatosensation?
antidromic/orthodromic spike definition breaks down, since spike can propagate towards cell body in pseudo-unipolar cell
138
2 slow adapting touch receptors
merkel's disk, ruffini's corpuscle
139
2 fast adapting touch receptors
meissner's corpuscle, pacinian corpuscle
140
specific classes of nerve axons are paired with specific...
...receptor types
141
what's on the midline in the diencephalon?
3rd ventricle
142
anterolateral system carries what information?
pain/temp/crude touch
143
what type axons carry pain/temp/crude touch?
C/IV, Aδ
144
which type axons carry fine touch?
Aβ
145
first synapse in anterolateral system?
in dorsal horn, at/near level of entry
146
first synapse in fine touch pathway?
all the way up the spinal cord
147
general topography outer to inner in SC white matter?
lower stuff is further out, because as we go up we keep adding stuff to the center
148
belly button spinal cord section
T10. but actually innervates T8, a little bit higher.
149
is cerebellum ipsilateral or contralateral?
ipsilateral
150
spinocerebellar pathways carry what info?
unconscious proprioception
151
topography throughout LCST tract?
high to low is medial to lateral
152
where does lateral corticospinal tract (LCST) originate?
60% frontal cortex, 40% parietal cortex. this is why it's better to call it a descending tract than a motor tract.
153
where is cingulate sulcus?
curving above the cingulate gyrus, which curves above the corpus callosum
154
upper vs lower motor neuron
lower motor neuron refers to actual motor neurons. upper motor neurons refer to the descending spinal tract
155
3 results of lower motor neuron lesion
flaccid paralysis (limp)
areflexia (no reflexes)
severe muscle wasting (atrophy. look like a skeleton)
156
4 results of upper motor neuron (anywhere along pathway, above the actual lower motor neurons) lesion
spastic paralysis (tense, stiff)
hyper-reflexia
mild muscle wasting
babinski reflex appears (contraction of the toe. normal in infant, abnormal in adult)
157
level of decussation of dorsal column (aka medial lemniscal system)
in the medulla, by the 2nd order neurons that project from the nucleus gracilis or nucleus cuneatus
158
level of decussation of anterolateral system (pain/temp/coarse touch pathway)
in the spinal cord, a few levels up from where ever the dorsal root ganglion cell enters the spinal cord
159
topography of homunculi in primary somatosensory and motor cortex
from medial to lateral: legs, trunk, arms, neck, head (approximately, b/c there may be some blending between areas)
160
in the spinothalamic pathway/ALS, which lamina of the dorsal horn do the dorsal root ganglia project to/2nd order neurons originate in?
lamina I, IV, V
161
which parts of the body do axons in the fasciculus gracilis carry information about? what kind of information?
lower limbs; fine tactile discrimination (but there's not a lot of it in the lower limbs so fasciculus gracilis is smaller)
162
which parts of the body do axons in the fasciculus cuneatus carry information about? what kind of information?
upper limbs; fine tactile discrimination (and there's a lot of it in our hands so fasciculus cuneatus is bigger)
163
where does the lateral corticospinal tract decussate?
in the pyramidal decussation in the medulla
164
which is bigger, fasciculus or funiculus?
funiculus
