ch. 12 - somatic sensory system Flashcards
(102 cards)
1
Q
somatic sensation
A
enables our body to feel, to ache, to chill, and to know what its parts are doing
2
Q
four main groups of stimuli
A
- touch
- temperature
- pain
- body position
3
Q
touch - skin
A
- can be hairy or glabrous
- largest sensory organ
- protects
- prevents evaporation
4
Q
mechanorecptors of the skin
A
- each has unmyelinated axon branches with mechanosensitive ion channels
- pacinian corpuscle
- ruffini’s endings
- meissner’s corpuscle
- merkel’s discs
- krause end bulbs
5
Q
pacinian corpuscle
A
deep in the dermis, large enough to be seen with your naked eye
6
Q
ruffini’s endings
A
found in both hairy and glabrous skin
7
Q
meissner’s corpuscle
A
located in the ridges of glabrous skin (fingertips)
8
Q
merkel’s discs
A
found in the epidermis, consists of nerve terminal and flattened non-neural epithelial cell
9
Q
krause end bulbs
A
lie in the boarder regions of dry skin and mucous membrane, the nerve terminals look like the knotted balls of string
10
Q
which mechanoreceptors have small receptive fields?
A
meissner’s corpuscles and merkel’s discs
11
Q
which mechanoreceptors have large receptive fields?
A
pacinian corpuscles and ruffini’s endings
12
Q
which mechanoreceptors are fast adapting?
A
meissner’s and pacinian corpuscles
13
Q
which mechanoreceptors are slow adapting?
A
merkel’s discs and ruffini’s endings
14
Q
follicles
A
- innervated by free nerve endings
- where hair grows
- bending of hair causes change in AP firing rate
15
Q
which mechanoreceptor is most sensitive to 200-300 Hz vibrations?
A
pacinian corpuscles
16
Q
which mechanoreceptor is most sensitive to 50 Hz vibrations?
A
meissner’s corpuscles
17
Q
what happens when mechanoreceptor membrane is deformed?
A
mechanosensitive channels open, depolarizing receptor potential
18
Q
prolonged stimulation causes…
A
decreased receptor potential
19
Q
two point discrimination
A
our ability to tell the detailed features of a stimulus
* varies across the body
20
Q
why are fingertips most sensitive to two point discrimination?
A
- more mechanoreceptors
- small receptive fields
- more brain power
- high resolution mechanisms
21
Q
primary afferent axons
A
- bring info to brain or spinal cord
- enter at dorsal roots
- varying diameters and size correlate with the type of receptor
22
Q
which primary afferent axon type is slowest?
A
C fibers (unmyelinated)
23
Q
spinal cord
A
30 pairs of dorsal and ventral roots
24
Q
cervical (c)
A
1-8
25
thoracic (t)
1-12
26
lumbar (l)
1-5
27
sacral (s)
1-5
28
spinal nerves
pass through notches in vertebral column
29
dermatome
area of skin innervated by both dorsal roots of a single spinal segment
30
what is the relationship between spinal segments and dermatomes?
one to one
31
what happens when dermatomes are mapped?
delineate a set of bands on the body surface
32
adjacent dorsal roots innervate....
overlapping areas
33
shingles - herpes zoster (chickenpox)
infection of dorsal root ganglion
34
each half of spinal gray matter is divided into...
- dorsal horn
- intermediate zone
- ventral horn
35
second-order sensory neurons
neurons that receive sensory input from primary afferents
36
A-beta axons
- large
- synapse on second-order sensory neurons
- also send axons to brian
- responsible for perception
37
dorsal column-medial lemniscal pathway
- for touch and vibration
| - A-beta sensory axons travel to brain on IPSILATERAL side through dorsal column
38
dorsal column axons
- connect to dorsal column nuclei at medulla-spinal cord junction
- decussate, sensory info is now CONTRALATERAL
- ascends in medial lemniscus
39
medial lemniscus
travels through medulla, pons, and midbrain to ventral posters (VP) nucleus of the thalamus, which then goes to the primary somatosensory cortex (S1)
40
lateral inhibition
neighboring cells inhibit one another
41
dorsal column nuclei and thalamic nuclei are..
relays that alter info as it passes through
42
trigeminal touch pathway
sensation in face carried through trigeminal nerves (CNV)
43
trigeminal nerve
- enters the pons
- innervates face, mouth, dura mater, tongue
- synapse on IPSILATERAL trigeminal nucleus, decussates, then thalamus, then S1
44
some sensation comes from which other cranial nerves?
VII, IX, X
45
somatosensory cortex
- in partiel lobe
| - most complex levels of processing
46
S1 - primary somatic sensory cortex
- brodmann's area 3b
- input from VP of thalamus
- highly responsive to only somatosensory input
- lesions impair somatic sensation
- electrical stimulation causes sensation
47
brodmann's area 3a
receives dense input from thalamus like 3b but focus on body position rather than touch
48
brodmann's area 1
- receives info from area 3b
| - mainly texture info
49
brodmann's area 2
- receives info from area 3b
| - emphasizes size and shape
50
layer IV
- where thalamic input terminates
| - project to other layers
51
mountcastle's idea
cells with similar characteristics in vertical columns in S1
52
somatotopy
mapped by S1 stimulation or by recording from S1 neurons after somatic stimulation
53
another name for somatotopy mapping
homunculus
54
features of somatotopy mapping
size of cortical sensory region determined by density and importance of input
55
somatotopic map plasticity
map changes based on loss or increased use
| - use fMRI in humans
56
phantom limb
feeling for missing limb by stimulating regions whose S1 representations border those of the limb
57
posterior partiel cortex
- brodmann's area 5 and 7
- large receptive fields
- elborate stimulus preferences
- integrates with visual, attention, and movement
58
agnosia
inability to recognize objects
59
neglect
part of body or world ignored
| - usual left side ignored due to right hemisphere damage
60
posterior partiel cortex is essenital for...
- perception and interpretation of spatial relationships
- body image
- coordinated body movements
61
nociceptors
free, branching, unmyelinated nerve endings that signal that body tissue is being damaged or is at risk of being damaged
62
pain
the feeling, or perception, of irritating, sore, aching, throbbing, miserable, or unbearable sensations arising from part of the body
63
nociception
the sensory process that provides signals that trigger pain
64
types of damaging stimuli
- oxygen deprivation
- chemicals
- temperature extremes
- mechanical stress
65
what causes mechanically gated channels to depolarize and release AP?
being stretched or deformed
66
some channels open in response to...
- proteases: enzymes that digest proteins
- ATP
- K+
- bradykinin
- H+
67
temperature range for warmth
37-43 C
68
heat above what temperature causes tissues to burn?
43C
69
production of what leads to H+ build up in extracellular fluid?
lactic acid
70
what depolarizes nociceptors?
histamine
71
polymodal nociceptors
respond to thermal, chemical and mechanical stimuli
72
hyperalgesia
unusual sensitivity to skon, joints, or muscles that have already been damaged or inflamed
73
features of hyperalgesia
- increased intensity
- reduced threshold
- spontaneous
74
sensitizing chemicals
- bradykinin
- prostaglandins
- substance P
75
bradykinin
stimulates long-lasting intracellular changes that make heat-activated ion channels more sensitive
76
prostaglandins
chemicals generated by enzymatic breakdown of lipid membrane
77
substance P
a peptide synthesized by nociceptors; causes vasodilation and release of histamine
78
first pain
fast and sharp due to A-gamma fibers
79
second pain
dull and longer de to C fibers
80
primary afferent cell bodies
- in dorsal root ganglia
- branch out of lissauer
- synapse on substantis gelatinosa neurons
81
what is the NT for the pain afferents?
glutamate
82
what stimulates substance P release?
capsaicin
83
capsaicin
can be analgesic by depleting substance P from nerve endings
84
referred pain
cross-talk between visceral nociceptor activation and cutaneous sensation
85
spinothalamic pathway
- pain and temperature
- decussate immediately and run in ventrally in tract
- don't synapse until thalamus
- don't communicate until medial lemniscus
86
trigeminal pain pathway
- small diameter fibers in nerve synapse on neurons in spinal nucleus in brainstem
- second-order neurons decussate and connect to thalamus vis trigeminal lemniscus
87
afferent regulation of pain
- hyeralgesia
- reduced by A-beta fiber activity
- gate theory of pain
88
gate theory of pain
certain neurons of the dorsal horns, which project an axon up the spinothalamic that, are excited by BOTH large-diameter sensory axons and unmyelinated axons
89
descending regulation of pain
periventricular and periaqueductal great matter (PAG) neurons synapse on raphe nucleus, suppressing pain
90
raphe nucleus
- serotonergic
| - project to dorsal horn and depress nociceptive neuron activity
91
opioids
poppy, morphine, codeine, heroin
92
opioids produce powerful analgesia as well as...
- mood changes
- nausea
- drowsiness
- mental stupor
- constipation
93
endorphins
endogenous opioids, expressed in pain pathways
94
what is the antagonist of endorphins?
naloxone
95
effects of endorphins
- block glutamate release
| - hyperpolarize cell
96
what regions of the body have temperature sensitive neurons to help maintain body temperature?
hypothalamus and spinal cord
97
temperature sensitive spots are sensitive to...
either hot OR cold... NOT BOTH
98
trpv1
- above 43C
| - capsaicin
99
trpv8
- below 25C
| - methanol
100
when are differences in temperature rates most pronounced?
during and right after changes
101
cold receptors
A-gamma and C fibers
102
warm receptors
only C fibers
