somatosensory Flashcards
(115 cards)
1
Q
Gray matter
A
neuron cell bodies with little myelin
site of information processing, synaptic integration
2
Q
White matter
A
abundantly myelinated axons
carry signals from one part of the CNS to another
3
Q
posterior (dorsal) root of spinal nerve only carries ____ ____
A
sensory fibers
4
Q
anterior (ventral) root of pinal nerve carries only ___ ____
A
motor fibers
5
Q
What are columns or funiculi of white matter?
A
three pairs of these white matter bundles
6
Q
ascending tracts carry..
A
sensory information up the spinal cord
7
Q
descending tracts carry…
A
motor information down the spinal cord
8
Q
What is decussation?
A
as the fibers pass up or down the brainstem and spinal cord they cross over from the left to the right side and vice versa
9
Q
What is contralateral?
A
when the origin and destination of a tract are on opposite sides of the body
10
Q
What is ipilateral?
A
when the origin and destination of a tract are on the same side of the body;does not decussate
11
Q
What are the ascending tracts?
A
gracile fasciculus cuneate fasciculus spinothalamic tract spinoreticular tract posterior and anterior spinocerebellar tracts
12
Q
What are the two neurons involved in descending tracts?
A
upper motor neuron- originates in cerebral cortex or brainstem and terminates on a lower motor neuron
lower motor neuron- in brianstem or spinal cord
13
Q
What is the cause of chickenpox?
A
varicella-zoster virus
14
Q
Where does the chickenpox virus remain for life?
A
posterior root ganglia
15
Q
What is shingles?
A
localized disease caused by the virus traveling down the sensory nerves by fast axonal transport when immune system is comprimised
16
Q
What are symptoms of shingles?
A
painful trail of skin discoloration and fluid-filled vesicles along path of nerve, usually in chest and waist on one side of the body, pain and itching
17
Q
What is meningitis? what is the cause?
A
inflammation of the meninges
- most serious between ages of 3 months and 2 years
- caused by bacterial and/or viral invasion of the CNS
- Pia mater and arachnoid ar emost often affected
18
Q
Signs of meningitis
A
high fever, stiff neck, drowsiness, intense headache
- may progress to coma then death within hours of onset
19
Q
how is meningitis diagnosed?
A
by examining CSF for bacteria
- lumbar puncture draws fluid from subarachnoid space between two lumber vertebrae
20
Q
What is spina bifida?
A
congenital defect in whihc one or more vertebrae fail to form a complete vertebral arch for enclosure of the spinal cord
21
Q
When does spina bifida occur?
A
first 4 weeks of development, so folic acid supplementation must begin 3 months before contraception
22
Q
What is a complete transection?
A
complete severance of cord
-immediate loss of motor control below level of injury
23
Q
Where along the spine would spinal cord trauma pose the threat of respiratory failure?
A
above C4
24
Q
What doe sthe medulla oblongata control?
A
caridac center- adjusts rate and force of heart
vasomotor center- adjusts blood vessel diameter
respiratory centers- control rate and depth of breahting
reflex centers- for coughing, sneezing, gagging, swallowing, vomiting, etc.
25
Pyramids of the medulla oblongata contain descending fibers called corticospinal tracts, what do they carry?
motor signals to skeletal muscles
26
In the medulla oblongata, what does the inferior olivary nucleus do?
relay center for signals to cerebellum
27
What is the reticular formation of the medulla oblongata?
loose network of nuclei extending throughout the medulla, pons, and midbrain
- contains cardiac, vasomotor and respiratory centers
28
Metencephalon
develops into the pons and cerebellum
29
Pons
anterior bulge in brainstem, rostral to medulla
30
cerebral peduncles
connnect cerebellum to pons and midbrian
31
Characterisitics of the pons
ascending sensory tracts, descending motor tracts, pathways in and out of cerebellum, cranial nerves V VI VII VIII, reticular formation whcih contains additional nuclei concerned with sleep, respiration, posture
32
Parts of midbrain & function
- substantia nigra- dark gray to black nucleus, motor center that relays inhibitory signals to thalamus and basal nuclei preventing unwanted body movement
- cerebral crus- bundles of nerve fibers that connect the cererbrum to the pons, carries corticospinal tracts
33
What part of the brain leads to tremors of parkinson's?
the midbrian- degeneration of neurons
34
Where is the reticular formation?
loosely organized web of gray matter that runs vertically through all levels of the brianstem, clusters of gray matter scattered throughout pons, midbrain and medulla, occupies space between white fiber tracts and brianstem nuclei, and many connections with many areas of cerebrum
35
What does the reticular formation control?
somatic motor control (motor coordinaiton), cardiovascular control, pain modulation, sleep and consciousness, habituation (brain ignores repetitive, incosequential stimuli)
36
What is the largets part of the hindrbain? (second largest part of the brain as a whole)
cerebellum
37
What deos the cerebellum consist of?
right and elft cerebellar hemispheres connected by vermis
38
Characteristics of cerebellum
cortex of gray matter with folds and four deep nuclei in each hemisphere
39
What is the arbor vitae?
white matter branching pattern of the cerebellum
40
cerebellar peduncles
three pairs of stalks that connect the cerebellum to the brianstem
41
inferior peduncles
connected to medulla oblongata
42
middle peduncles
connected to the pons
43
superior peduncles
connencted to the midbrian
44
functions of cerebellum
monitors muscle contractions and aid sin motor coordination, evaluation of sensory input, timekeeping center, hearing, planning and scheduling
45
What might lesions of the cerebellum result in?
emotional overreactions and troubel with impulse control
46
What are the two parts of the forebrain?
- diencephalon- enclose thrid ventricle, most rostral part of the brianstem
- telencephalon- develops cheifly into the cerebrum
47
What are the three embryonic derivatives of the diencephalon?
thalamus, hypothalamus, epithalamus
48
What is the thalamus?
ovoid mass on each side oft he brian perched at the superior end of the brainstem beneath the cerebral hemispheres
49
What are the functions of the hypothalamus?
hromone secretion, autonomic effects (heart rate, bp, etc.), thermoregulation, food and water intake, rhythm of sleep and waking, memory, emotional behavior
50
What part of the forebrain is the cerebrum a part of?
telencephalon
51
What is the cerebrum and functions?
largest and most conspicuous part of human brian
| -seat of sensory perception, memory, thought, judgement, and voluntary motor actions
52
What si the white fibrous tract that connects the two cerebral hemispheres?
corpus callosum
53
What is the gyri and sulci of the cerebrum?
gyri- increases SA for information-processing capability
| sulci- some divide each hemispheres into five lobes named cranial bones overlying them
54
What are the 5 lobes of the cerebrum?
frontal lobes, parietal lobe, occipital lobe, temporal lobe, insula (hidden by other regions)
55
frontal lobe
voluntary motor functions, motivation, foresight, planning, memory, mood, emotion, social judgement, and aggression
56
parietal lobe
receives and intergrates general sensory info, taste, and soem visual processing
57
occipital lobe
primary visual center of brain
58
temporal lobe
areas for hearing, smell, learning, memory, and some aspects of vision and emotion
59
insula
understanding spoken language, taste and sensory information form visceral receptors
60
what is the sensory homunculus?
diagram of the primary somesthetic cortex which resebles an upside-down sensory map of the contralateral side of the body
61
somatotopy
point-topoinnt correspondence between an area of the boyd and an area of the CNS
62
What are somatic senses?
mechanoreceptive- tactile (touch, pressure, vibration, ticle), position (static and rate of movement of body parts)
thermoreceptive- hot and cold
pain- damage to tissue
63
what is touch?
stimulation of tactile receptors in the skin
64
What is pressure?
deformation of deep tissue
65
what is vibration?
rapid repetitive sensory signals
66
What are the types of mechanoreceptors in the hand?
meissner, merkel, pacinian corpuscle, ruffini endings
67
What is the iggo dome receptor?
gorup of merkel discs, which create a very sensitive recptor, concentrated in the finger tips
68
nerve signal transmission of the iggo dome receptor
alpha beta myelinated fibers (msot specialized endings)- fast transmission
alpha delta myleinated fibers (free nerve endings) - slower
69
Sensory nerve characterisitcs
C- slow pain
alpha delta
alpha beta- fast pain
70
Where is the cell body located?
dorsal root ganglia
71
The doral root ganglion cell has an axon wiht 2 branches, what are they?
peripheral- terminates in specialized receptors
| central- terminates in dorsal honr of the spinal cord
72
Spinal pathways for somatic signal; dorsal column-meidal lemniscal
large, myelinated fibers
somatotropic organization
fine touch, proprioception, pressure, vibraiton
73
spinal pathways for somatic signals; anterolateral pathways
small, myelinated fibers
| pain, temp, crude touch, itch
74
the medial branch of the dorsal column pathway
ascends through dorsal columns to brain stem
75
lateral branch of the dorsal column pathway
many divisions and synapses within SC
- local neuron activation which will eventually enter DC
- spinal reflec mediation
- spinocerebellar tract
- spinocervical tract
76
spinocerebellar in the dorsal column pathway
convey proprioceptive information to the cerebellum (ipsilateral tract)
- dorsalp muscle spindle information
- ventral- golgi tendojn organ information
77
spino-olivary in dorsal column pathway
proprioceptive information to the olivary nucleus then to cerebellum
78
spinocervical in dorsal column pathway
vestigial in humans
79
Dorsal column-medial lemniscal pathway is responsible for what?
deep touch, vibration, and proprioception are carried in the dorsal cavities
80
What are the 1st, 2nd, and 3rd order neurons responsible for in the dorsal column-medial lemniscal pathway?
1st order neuron travels up the ipsilateral SC terminating in th emedulla oblongata
decussation of 2nd order neuron in medulla
3rd order neuron in thalamus carries signal to cerebral cortex
81
In DCML pathway; where do third order neurons project to?
1 and 2 somatosensory cortex
82
In DCML; what is 1 somatosensory cortex?
brodmann's area 1,2,3
83
In DCML; what is 2 somatosensory cortex?
brodmann's area 5 and 7A
84
What is the somatosensory area and where?
- arranged as a sensory homunculus
- very discrete localization in 1 somatosensory cortex
- 2 somatosensory cortex organization is not as defined
85
Where does input first arrivein the somatosensory cortex?
at layer IV
86
What layers receive diffuse, nonspecific input?
I and II
| control overall level of excitability
87
What do layer II and III in the somatosensory cortex do?
send information to related sutes on opposite sites on opposite sides of the brain
axons travel thru corpus callosum
88
What do layers V and VI of the somatosensory cortex do?
regulation of signal transmission
| output to basal ganglia, spinal cord, brain stem and thalamus
89
what are the functions of the primary somatosensory cortex?
```
Localize different sensations in different body parts
Judge degrees of pressure
Judge object weights
Determine object shapes
Determine material textures
```
90
Fucntions of the somatosensory association cortex
deciphers meaning from sensory input
91
Where does the somatosensory assocaition cortex receive signals from?
1 somatosensory cortex
thalamus
visual cortex
auditory cortex
92
What happens when the somatosensory association cortex is inhibted?
Amorphosynthesis
| -inability to recognize complex objects and forms on the opposite side of the body
93
What is a dermatome?
specific area of the skin taht receives sensory input from a pair of spinal nerves
94
A diagram of the cutaneous regions innervated by each spinal nerve
dermatome map
95
Up to how much do dermatomes overlap their edges?
as much as 50%
96
Why must you anesthetize three successive spinal nerves?
to produce a total loss of sensation in one dermatome
97
Why does 2 point discrimination occur?
because of laterl inhibition
98
Where does lateral inhibiton occur?
at each level of DCML pathway
- gracile and cuneate nuclei
- VPL of thalamus
- somatosensory cortex
99
What are the 3 stimuli types for pain?
mechanical, themral and chemical (bradykinin, acid, ACh, prostaglandin, substance P)
100
Painreceptors are non-adapting. Increase in sensitivity is called what?
hyperalgesia
101
What sensations are carried in the spinothalamic pathway?
pain, pressure, temp, light touch, tickle, and itch
102
When do most people feel temperature as pain?
45 degree C, tissue damage
103
What does pain from heat correlate with?
rate of tissue damage and NOT the total damage
104
Intensity of pain correlates with what?
rate of tissue damage and NOT total damage
105
First order pain fibers alpha delta account for what?
fast pain
- excite 2nd order neurons that travel in the neospinothalamic tract
- highly somatotropic organization
- 2nd order neurons terminate in VPL of thalamus
106
First order pain fibers C account for what?
slow pain
- excites 2nd order neurons that travel in the paleospinothalamic tract
- poor localizaiton
- 2nd order neurons terminate in VPL of thalamus
107
Where is the termination of most paleospinothalamic tract neurons?
brainstem
- reticular nuclei
- tectal area of mesencephalon
- periaqueductal grey
108
What are the NTs of endogenous pain modulation?
enkephalin and serotonin
109
What are the brainstem areas effect in endogenous pain modulation?
- Periaqueductal grey
- Periventricular nuclei
- Raphe magnus nucleus
- Nucleus reticularis paragigantocellularis
110
What NT is involved in both pre and post synaptic inhibition of C and alpha delta fibers?
enkephalin
111
What are the causes of referred pain?
ischemia, chemical stimuli, cramps, over distention
112
Hyperalgesia
excessive pain receptor sensitivity
| sunburned skin
113
Tic Douloureux
'suicide disease'
| severe, lancinating/stabbing pain in the sensory distribution of the trigeminal nerve
114
Brown-Sequard syndrome
transection of spinal cord on only one side
-motor- ipsilateral--> motor function lost below the site of injury
-sensory- ipsilateral--> DCML sensations lost
contralateral--> spinothalamic sensations lost
115
Headache
- menengitis- inflammation of the meninges
- low CSF pressure- distortion of dural surfaces due to the brain not floating freely in the CSF
- Migraines- vascualr headache, nausea, loss of vision, visual/auditory hallucinations
