Neuro Flashcards
1
Q
What is the somatosensory system?
A
Allows us to sense: touch, temperature, propioception, pain
2
Q
What are teh exteroreceptive sense?
A
mechanoreceptor: touch
thermoreceptors: warming and cooling
nociceptors: sharp and burning pain
3
Q
Receptive field?
A
area in the periphery where application of an adequate stimulus causes response
4
Q
Stumulus transduction?
A
At peripheral terminal stimulus activates receptors and ion channels; generates receptor potential; receptor potential strong enough generates action potentials
5
Q
Intensity of stimulus is encoded by what?
A
Each neuron through frate code of frequency
in many neurons through number of neurons firing the spatial summation code
6
Q
what are the different types of nerve fibers?
A
Aalpha, Abeta (both are large and mylenaited) Adelta (thin and myelinated) C fibers (unmyelinated)
7
Q
Glaborous skin specializes in what?
A
Has severl different types of specilalized sensor receptor
8
Q
Spatial resolution depends on what?
A
receptive field size and innervation density
9
Q
What are mechanoreceptors?
A
mediate tactile/touch sensation, very sensitive to force(low threshold),have myelinated axons, superficial receptors in border between epidermis and dermis
10
Q
What are merkel disks?
A
type of mechanoreceptorss: Responsible for fine touch, 2point discrimination, receptive field, multiple small spots, several disks for one axon, slowly adapting response encodes amount of force
11
Q
What are Meissner’s corpuscles?
A
[mechanoreceptors] Fine touch, 2-point discrimination. Sense abrupt changes in edges. Help adjust grip. Receptive field: single spot. Corpuscle encloses a stack of flattened epithelial cells. Rapidly adapting responses encodes offset of skin indentation.
12
Q
What are Ruffini Endings?
A
Sense stretch of skin, help determined shape of grasp objects. Receptive field: large and diffuse. Ruffini ending is encapsulated. Slowl adapting resposne sto stretching skin
13
Q
What are pacinian corpsucles?
A
[mechanoreceptors] Respond to high frequency vibration; MOst sensitve mechanoreceptor even distribution throughout skin.
Receptive field: large and diffuse
Fluid filled capsule wrapped around bare nerve endings filters out sustained stimuli
Rapidly adapting response
14
Q
What are hair follicle receptors?
A
[mechanoreceptors], respond tot movement of hairs, receptive field is around base of hair. Bare axon wraps around base of hair follicle; rapidly adapting response encodes velocity of hair
15
Q
Spatial summation code is what?
A
OVerall picture in brain is due to sum of information provided by different active and silent fibers
16
Q
Thermoreceptors are what?
A
Encode skin temp (warming, cooling). Discharge continuously (steady rate) @ normal skin temp
17
Q
What are cooling receptors?
A
[thermoreceptor] increase firing when skin is cooled. Free nerve endings with myelinated axons. Small receptive fields; infrequent distribution
18
Q
What are warming receptors?
A
increase firing rate when skin is warmed aboved 32 C. Stop firing when skin is cooled. Free nerve endings with unmyelinated axons
19
Q
What are nociceptors?
A
Respond to stimuli that damage or threaten to damage tissue; 70% of DRG are nociceptors and provide almost all innervation to tooth pulp and cornea
20
Q
What is Mechanonociceptors?
A
[nociceptor] Adelta axon
Respond to intense mechanical force, sometimes intense heat
free nerve ending
small receptive fields
slowly adapting response
mediate fast initial pain, sharp pricking, easy to localize
21
Q
What are polymodal nociceptors?
A
unmyelinated Respond to intesne mechancial force, high heat, noxious chemicals free nerve endings, small receptive fields slowly adapting response mediate slow aching, "burning" pain
22
Q
What does the DC/ML transmit sensations of?
A
light touch
pressure
vibration
propioception
23
Q
What are teh components of the DC/ML system?
A
3 neurons
1st in sensory ganglion
2nd in spinal cord and/or braiinstem
3rd in thalamus
24
Q
In the DC/ML system waht is the 1st neurons responsibility?
A
Peripheral process transmits info from mechanoreceptor
cell body i DRG
Central process transmits info via dorsal root and ascends within ipsilateral dorsal colum
terminates in dorsal column nuclei
25
What is the role of the 2nd Nueron in the DC/ML system?
Cell body in ucleus gracillis or nucleus cuneatus
terminates in ventral posterior lateral nucleus of thalamus
axon decussates to contralat side and ascends in medial lemniscus
26
What is the role of the 3rd neuron in the DC/ML system?
Cell body in VPL of thalamus
Axons pass through posterior limb of termial capsule
Terminates in SI cortex (postcentral gyrus, primary somatosensory cortex)
27
What does the faciculus gracilis contain?
Located medially, contains axons from below T7
28
What does the faciculus cuneatus contain?
Axons from about T7 in DC/ML system and it's located laterally
29
What is the role of Somatotopy in the 1st neuron of the DC/ML system?
Sacral dermatomes located medially, and each level on the way up located progressively laterally helps perserve info about location and nature of stim
30
What occurs in a unilateral spinal cord leasion in relation to DC/ML system?
Loss of light touch, pressure, vibration and propioception on ipsilateral side below lesion
31
What happens in posterior cord syndrome?
Loss of light touch, pressure, vibration and propioception from dermatomes below level of lesion but other sensory and motor functions remain intact
32
What occurs in large central cord lesion?
Loss of everything but sacral region can be spared.
33
Where are the second neruon cell bodies located in the DC/ML system?
Caudal medulla, axons dessucate as internal arcuate fibers
axons form medial leminiscus through rostral medulla pons ad midbrain
terminate in VPL
34
What occurs with lesion of medial leminiscus?
Loss of light touch, pressure, vibrationa nd propioception from dermatomes below lesion on cotnralateral side of body (medial medullary system)
35
The third neuron for DC/ML system are located where?
Cell body in VPL(ventral posterior lateral nucleus) of thalamus
axons pass through posterior limb of interal capsule
terminates in SI cortex
36
What is teh difference between VPL ad VPM in the THalamus?
VPL(ventral posterior lateral nuclues) sensation from body
| VPM (Ventral posterior medial nucleus) sensation from body
37
Somatotopy occurs how in hte the thalamus?
most medial is face goes to foot as move laterally
38
How do axons from thalamus fan out?
As the corona radiata, fiibers from VPL and VPM pass to SI cortex
39
What occus with lesions of thalamus or SI cortex?
Loss of sensation from contralateral half of body
40
What brodmann area is responsible for limb movement?
area 3a
41
What brodmann area is responsible for basic tactile information
area 3b
42
What brodmanna rea is responsible for motion and direction of movment of objects?
area 1
43
What brodmann area is responsible for limb position, shapes of objects
area 2
44
What is the relationship between SI and SII cortex?
Located along upper border of Sylvian fissure and insular cortex, SI neurons project to SII cortex
45
Parietal association corticiess, what is a unimodal association cortex?
vision, auditory or somatosensory and a lesion causes agnosias (inability recognize object)
46
what is multimodal parietal association cortices?
combine sensation with motivation, attention, relevane
| lesions lead to contralateral neglect
47
Anesthesia means what?
lack of sensation
48
analgesia means?
lack of pain
49
hyperalgesia means what?
increased pain from normally painful stimulus
50
allodynia
pain froma normally non-painful stimulus
51
hypoalgesia means what?
Decreased pain sensation
52
Pruritus means what?
itching
53
nociceptive pain is what type of pain?
Pain resulting from tissue damage
well localized, throbbing quality
typically responds to NSAIDS
54
What type of pain is neuropathic pain?
Pain directly from damage to nerves
often has burning, lancinating, electrical qualty
resistant to NSAIDS and opoids
55
What sensation does the anterolateral system transmit?
Pain and temperature sensation to higher brain levels
56
What is the input to the anterolateral system?
noxious mechanical, thermal, or chemical stimulus to free nerve endings of Adelta or C fibers of nociceptors
57
Adelta fibers mediate what type of pain?
Mediate initial pain which is immediate, short-lasting, pricking quality
58
C fibers mediate what type of pain?
delayed, long lasting, burning quality
59
Where do central processors of nociceptors enter as part of teh anterolateral system?
Enter spinal cord dorsal horn, and synapse onto second order spinal neurons in lamina I/II. Some nociceptors synapse in lateral endge of spinal cord and a few near central canal.
60
What chemical synapse is involved at the second order spinal neruon synapse in anterolateral system?
Chemical synapses involves glutamage and substance P
61
What is the spinothalamic tract?
the majoroity of the second order ascending fibers termiante in thalamus, most prominent pain pathway
62
What is the Ventral posterior lateral nucleus?
Part of thalamus, 3rd order axons to SI cortex. Principally relays nucleus for discriminatory somatosensory info, localize pain
63
What is the central lateral nuclues?
Part of the thalamus (intralaminar nucleus), 3rd order axons project to many areas of cortex particulary limbic. Involved in emotional suffering
64
What is the spinoreticular tract?
Many 2nd order axons ascend from spinal cord and terminate in medulla and pons, in reticular formation.
MEDIATES change in attention to painful stimulus
65
What is teh spinomesencephalic tract?
Some 2nd order axons terminate in teh midbrain in teh superior colliculus and in a region of gray matter surrounding cerebral aqueduct; and is involved in pain modulation
66
Lesion of the insular cortex results in what?
integrates sensory, affective and congitive components of pain and when lesioned the patient don't display appropiate emotional response to pain
67
What descending pathways inhibit pain?
Neurons that have cells in periaqueductal gray midbrain send axons down to raphe nuclei in medulla and locus ceruleus
68
What trigeminal nuclei is involved in fine touch?
Main sensory nucleus in the pons
69
What trigeminal nuclues is involved in pain and temp?
Spinal trigeminal nucleus, a long column-like nucleus extending from pons to cervical spinal cord.
70
Where do nociceptors of teh face synapse at?
They descend spinal trigeminal tract and terminate in spinal trigeminal nucleus of V
71
What is Temperomandibular Joint Disorder
is a chronic pain localized at teh temperomandibular joint or in muscles of mastication and recurrent headaches
72
What are the layers of the cornea in order from outside to inside?
```
Epithelium
bowman's membrane
stroma
descemets membrane
endothelium
```
73
What s the bowmans membrane?
acelluluar layer of unorganized collagen fibers, barrier to infection
74
What is the Stroma?
Organized type 1 collagen bundles, binds water, maintains corneal clairty, contributes to corneal thickness
75
What is the Descemet's membrane?
THe corneal endothelial cells, increases in thickness with age
76
What is the endothelium of the cornea?
Simple squamous eppithelia that pumps water outof the stroma
77
What is the major refractive structure of the eye?
The cornea, ~50 D, protect the eye from the environment
78
What are the three structures of the Uvea?
Choroid, Cillary body, Iris
79
What are the three layers of the choroid out to in?
veseel layer
choriocapillary layer (capillaries arragned in one plane, fenestrated)
Bruch's membrane 3-4 micronsamorphous hyaline membrane that retinal pigment epithelia rests on
80
Describe the cillary body of the eye?
Contacts three regions, has projections called cillary processes. trabecular meshwork within cillar body near limbus (aqueous humor rains from anteriror chamber via the trabecular meshwork)
81
Describe the parts of the Iris?
Covers lens, anterior aspect made of vascular loose CT and determines eye color
posterior surface lined with double layer of pigmented epithelium to absorb light
two muscles masses rest upon pigmented epithelium
82
What are the two muscle masses that rest upon the pigmented eithelium and regulate iris opening?
Radially arranged myoepithelial cells form the dilator pupillae between teh vascular and pigment layer contract to dialate the eye
The concentric smooth muscle bundles at the pupil margin form the sphincter pupillae muscle, cotnract constricts
83
What is the anterior chamber of the eye?
Contains aqueous humor that is avascular. Involved in maintaining intraocular pressure [drection of aqueous flow: from cillary procsses to posterior chamber to trabecular meshwork to Schlemm's canal to veins of sclera)
84
What is the Lamina Cribosa?
Network of collagen fibers through which the fibers of the optic nerve exit the eye
85
What is the structure of the lens?
transarent, structure(avascular, little ECM, no organelles) capsule surrounds lens, epitherlium is on the anterior surface, lens fibers forms the body of the lens
86
What is the secondary structure of refactive power in the eye?
The lens which is supported by system of fibers attatched to the cillary body
87
What is accomodation of the lens?
Lens thinner when focused on distant objects and thicker when on neaer objects
88
What action of the cillary muscle causes the lens to get thinner?
When the cillary muscle is relaxed
89
What is the vitreous body?
nearly acellular, major macromolecules are type 2 collagen and hyaluronic acid.
It's transparent 99% water and avascular nutritive
90
Where is the ganglion cell layer not present?
At the fovae
91
Where are cones the most present as opposed to rods?
At foavae cones are most present, and then most rods around fovae
92
What are the major funtions of the retinal pigment epithelium?
absorbs light
transports nutrients
spatial buffering of ions in the subretinal space
reisomerization of all-trans retinal
outer segment renewal
secretion of growth factors for maintenance and structural integritiy of retina
93
What are the two suppliers of blood ot the retina?
inner retina from central retinal artery, and the choroid artery from the short posterior cillary atery from the cillary artery systems
94
What are the anatomical fovaeal specializations?
Avascular zone, excavation of inner retinal neruons, foveal pit, high cone desnity, absence of rods
95
What is an important difference between rods and cones withthe amount of light?
Rods "saturate from light and cones do not, and at room light rods are usually saturated
96
WHat do photoreceptors in response to light?
They hyperpolarize
97
What is the photopigment used?
Made up of a chromophore (11-cis retinal) and a protein component which normally absorbs light at 375 nm
opsin "red-shifts"
98
Where do rods most strongly absorb light in the spectrum?
in the blue-green area
99
How does phototransduction occur?
isomerization of chromophore (11-cis to trans)
opsin activates transducin
transducin activates PDE
PDE converts cGMP to GMP
Low cGMP closes ion channels
cone hyperpolarizes (inward flux of Ca2+ and Na+)
100
What is the mechanism by which viagra can cause visual disturbances?
It is a PDE inhibitor, leading to vasodilation
results n an increase in cGMP
results in an opening of cyclic-nucleotide-gated ion channel and thus depolarization of the cell
101
All photreceptors act in the same way by hyperpolarizing which causes them to waht?
Release less neurotransmitter
102
When a cone is depolarized at the off center position it releases what neurotransmitter?
Glutamate
103
Activiity of a single cone gives rise to what?
2 parallel pathways, by connecting two different bipolar cell types,an ON CENTER type
and an OFF CENTER type
glutamate hyperpolarizes the ON center bipolar and depolarizes teh off center bipolar
104
Bipolar cells in the retina talk to what cells?
Amacrine cells which provide lateral connections
| Ganglion cells produce action potential
105
What are the two types of ganglion cells?
parasol ganglion cells-large with large receptive field projecting to magno layer
midget ganglion cells project to parvo layers and are smaller celsl with smaller receptive fields but are more sustained
106
What are photoreceptors interconnected by?
Elaborate system of inhibitory interneurons called horizontal cells, whhich havea reciptrocal inhibitory synaptic relationship
107
What is achromatopsia?
Autosommal recessive disesase where cones cannot hyperpolarize in response to light
108
A tumor that presses onto the side of the optic chiasm tends to alter what field of vision?
The lateral field, "blinder"
109
Where is the majority of V1 located?
Inside the calcarine
110
What is teh result of a unilateral optic nerve lesion?
Blindness in affected eye only
111
What is the result of lesion of the optic chiasm?
Causes bitemporal hemianopia b/c it interrupts the fibers from nasal portion of retina
112
What is the result of unilateral optic tract lesion?
Causes contralateral homonymous hemianopia because it interrupts fibers from temporal portions of the retina on the ipsilateral side and the nasal portion on the opposite side
113
What is the result of unilateral lesion of optic radiation in anterior temporal lobe (Meyer's loop)
leads to contralateral upper quadrantanopia
114
What is the result of unilateral lesion of optic radiation in the parietal lobe?
Leads to contralateral lower quadrantanopia
115
What is the role of occipital lobe lesion?
Can lead to homonymous hemianopia. B/c the optic radiation fans out widely before entering visual cortex, lesionso f the occipital lobe tend to spare foveal vision.
116
What is the result of lesion of cortical areas of occipital pole?
Represents the macula and characterized by a homonymous hemianopic central scotoma.
117
What is teh central pathway for teh light reflex?
afferent limb=CN2
| efferent=CN3
118
What is pretectal area?
connects chiasm to edinger-westphal nuclei; and visceral
119
Edinger-westphal nucleus of the midbrain givves rise to waht?
preganglionic parasympathetic fibers, which exit the midbrain with oculomotor nerve and synapse with post-ganglionic neurons at cilary ganglion
120
What happens when lesion of pulvinar of thalamus occurs?
Leads to lateral neglect
121
What is the superior colliculus?
Mesencephalic laminated structure
receives input primarily from parasol cells
involved in controlling eye muscles and orienting reflex
122
What si damage of V5/MT resulting in?
Associated with an impairment in the detection of motion.
123
What happens when V4 is damaged?
cerebral achromatopsia
124
What is the Pinna?
The eterior of the ear that channels and filters sound to external canal, amplifies freq @ 3000 Hz
125
What is the structure of the tympanic membrane?
3 layer translucent membrane, with 1 cm^2 vibratory surface
126
What are the mechanisms used to amplify sound to overcome transfer of waves from air to sound?
Area ratio of tympanic membrane to oval window
lever action of the ossicular chain: malleus longer than incus
Buckling of the TM
127
What is teh mechansim of the basilar membrane mechanics?
The base is narrow and stiffer, vibrates more at high sounds
| apex is wider and loose allowing for lower sound
128
How does the cochlea determine pitch?
Position of maximum wave on basilar membrane in cochlea
129
How do hair cilia work?
Endolymph has high K+ and hair have very low K+, tiplinks openwhen hair cells moved by acoustic energy, resulting in hyperpolarization, tip links linked by actin
130
What are the two types of hearing losss?
Conductive adn sensorineural
131
How does sensorinerual occur?
congenital
noise exposure/trauma
medication
age
132
What is the main region for auditory processing?
Heschel's Gyrus, A1 in the temporal region
133
What are teh central auditory pathway?
VCN involved in localizing sounds
DCN involved in recognizing sounds
Nerve to medulla to pons to mibrain to thalamus to cortex
134
What are the three parts of the vestibular apparatus?
Bony labyrinth
membranous labyrinth
sensory receptors
135
What detect linear acceleration in the inner ear?
Maculae in the utricle and saccule
136
How are hair cells depolarized in response to linear acceleration?
The stereocilia bundles are polarized towards a ridge and when deflection toward the kinocilium occurs it leads to cell depolarization
137
What is the ridge of sensory epithelium in the ampulla called?
Crista ampullaris, this senosry epithelium is covered by gelatinous material that makes up the cupola
138
Rotation of the head causes endolymph in the ampula to move this allows what?
THe semicircular canals, and endolymph pushes on teh sensosry epithelium in response to change in speed of head rotation
139
What are the four vestibular nuclei?
```
Caudal Pons:
superior vestibular nucleus
Lateral vestibular nucleus
Rostral medulla:
Medial vestibular nucleus
Inferior vestibular nucleus
```
140
What is the role of the lateral vestibulospinal tract?
Maintains balance and posture on the ipsilateral side of the bodyu
141
What is the role of the medial vestibulospinal tract?
```
adjusts head position in response to postural changes
coordinates eye movements, with head movements and each other
vestibuloocular reflex (VOR)
```
142
What does the vestibuloocular reflex do?
maintains eye postion during head movemnt
143
What si teh central pathway for VOR?
semicircular canals detect head movment and this sends to vesitbular nuclei
vestibular nuclei project to brainstem nuclei that control extraocular muscles
extraocular muscles contract moving eyes to maintain fovveattion
144
What is nystagmus?
rhytmic oscillations of eyeballs
temperature generated convection current causes them
observigna moving object causes tehm
rotation of the head causes them
145
What type of diziness is usually otologic?
verticgo
| nystagmus specifically is uasually ear generated and casuses sensation of spinning
146
What si Ewalds first law?
Stimulation of a semicircular canal generates eye movement in the plane of the that canal
147
What are the three clinical mechanisms to uncover teh otological weakness ?
head thrust test
gaze evoked nystagmus
head shake teest
148
What is Alexander's law?
gaze in the direction of the fast phase of nystagmus increases amplitude and frequency
149
What is Ewalds second law?
excitatory responses for the VORare greater than inhib responses
150
What is superior canal dehiscence?
loss of bone covering over the superior canal, ecitation by various stimuli
tones
excercise
pressure
151
What is BPPV?
Benign paroxysmal postional vertigo
posterior canal canalithiasis
posterior canal actviated by movement-otoconia move in canal simulating movement
nystagmus is toward affected ear and rotary in nature
152
What is labyrinthitis
```
medical emergency
viral or bacterial in origin
hearing loss
elicit signs of unilateral weakness
loss of vestibular function in al canals
```
153
What is vestibular neuronitis?
horizontal and superior canals, posterior canal spared
acute phase nystagmus beating away from affected ear
loss of unilateral VOR
Acute Phase:
1st week sudden and intesnse vertigoand imbalance
need to stay still
nausea and vomitting
1-6 month episodic vertigo, motion sensitivity, gradual improvememnt
greater than 6 mos after initial attack
weakness in balance Fx
30% develop anxiety
may develop BPPV
154
What is Menieres disease
```
inner ear fluid imbalance
episodic vertigo
fluctuating hearing loss
recurrent and episodic vertigo short period
minimal imbalance btw attacks
low frequency tinnitis
```
155
Vestibular migraine?
30-50% of migrainers, and can occur not during headache
spontaneous vertigo both internal and external
positional vertigo, but not specific like BPPV
visuall induced
