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Neuroscience > Unit 2 - Sensory Systems > Flashcards

Unit 2 - Sensory Systems Flashcards

1
Q

sensory receptors that generate APs directly

A

somatic and olfactory receptors
(the receptor cell itself generates AP to communicate w/ sensory neuron)
vs. graded potential (photoRs, hair cells, gustatory Rs):
make graded potential to elicit 1st AP in (post-synaptic) sensory n

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2
Q

Adaptation

A

decreased response to a sustained stimulus bc temporarily lose sensitivity (R stops working/inactivates);

  • NOT the same as habituation (learned)
    • amt/speed of adaptation depends on the R type
  • quantified w/ Steven’s number*
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3
Q

2 phases to sensory receptor response

A

w/ stimulus presentation: (generally…)

  1. Dynamic (phasic): rate of fire == speed of stimulus presentation
  2. Static (tonic): amplitude/rate of fire == intensity of stimulus
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4
Q

Steven’s Law

A

way of quantifying the level of adaptation of a R to a stimulus;
I == S^n n = Steven’s number
I = percieved intensity of stimulus; S = actual stimulus intensity
n1 increased sensitivity (for intense stimuli, ie: weight, pain)

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5
Q

information conveyed by sensory systems

A
  • intensity
  • timecourse
  • location
  • modality (type of sense - sound, touch, taste, etc.)
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6
Q

synesthesia

A

psychological experience where segregation of modalities breaks down
ie: experience colors when hear sound
(matching brain areas DO show increased activity in brain scans)
- genetic basis?

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7
Q

types of sensory transduction (sensory receptor mechs)

A
  1. Mechanoreceptors: pressure/stress transferred to cytoskeleton –> opens channel, permeable to Na+ and K+
  2. Photoreceptors: rhodopsin + light –> activate transducin –> hyperpolarization (closes Na+ channels)
  3. others
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8
Q

population and frequency codes

A

2 mech.s of encoding information about stimulus intensity, allow for dynamic range of “sensation” (very low - very high intensity)

  1. Frequency code: w/ high frequency stimuli –> high firing rate
  2. Population code: w/ larger area stim. –> more cells activated
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9
Q

Response Region

A

the field within which the receptor recognizes sensation

  • receptor cells: small field, = defined by sense organ.
  • higher order neurons: larger, for all convergent inputs to that neuron
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10
Q

Sense most represented by cortical maps

A

Vision! –> “retinotopic maps”
- mapped onto multiple different parts of cortex (ie: V1, V2, …)
and superior colliculus

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11
Q

Sensory maps in superior colliculus

A
  1. Multiple visual maps in several layers
    • -> represent diff. visual characteristics
  2. maps of OTHER sensory modalities as well (to inform vision)
    * integrates distinct sensory modalities to direct eyes accordingly*
    * * strokes affecting the sup. colliculus will cause poor orientation to visual and auditory stimuli**
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12
Q

stimulus properties

A

features of sensations such as pitch, shape, etc.
–> inhibitory neurons increase contrast in sensory signal
=> allow feature extraction

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13
Q

somatic sensory system

A

codes and transmits information about the body.
receptor types include:
- cutaneous (external stimuli)
- proprioreceptive (sense limbs in space - muscle length/position, joint angles)
- visceral (internal: distention/pain)

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14
Q

nocioception

A

pain sensation

– pain Rs = nocioceptors

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15
Q

hypalgesia

A

decreased sensation of pain

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16
Q

Analgesia

A

no/extremely reduced pain sensation

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17
Q

hyperalgesia

A

increased sensation of pain

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18
Q

allodynia

A

when innocuous stimuli cause pain

ie: lukewarm water = painful for sunburned skin

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19
Q

Paresthesia

A

Tingling sensation

considered a pain response

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20
Q

Pruritis

A

chronic itching,

sensation by pain receptors

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21
Q

Merkel Disc (S.A. I)

A

cutaneous mechanoreceptor; axons = A-beta;
* high localization in fingers and lips*
Rec. F: very small (~exact); slow adaptation
stim: skin indentation, *thresh: >15microm
dynamic: speed of indent
static: depth of indent

22
Q

Ruffini ending (S. A. II)

A

cutaneous mechanoreceptor; axon = A-beta
RF: large
stim: lateral skin stretching
slow adaptation

23
Q

Hair follicle

A 
cutaneous mechanoreceptor, axon = A-beta/delta, C; 
RF: 1 hair follicle, *fast adaptation*
stim: move hair - stretch channel
dynamic: velocity of hair mvmt
static: -----
24
Q

Pacinian Corpuscle

A

mechanoreceptor, axon = A-beta;
RF: large **in tendons and joints, NOT cutaneous*
stim: indentation and vibration; thresh: <1 microm
dynamic: 1 for presence * fast adaptation
static: —-

25
Q

Meissner’s Corpuscle

A 
Cutaneous mechanoreceptor, axon = A-beta; 
* high localization in fingers and lips*
RF: tiny   * fast adaptation*
stim: light touch
dynamic: 1 for presence
static: ----
26
Q

TRPM8

A 
thermoreceptor for cooling, A-delta axons
- free nerve endings - 
thresh: 20-40 C
Na+ channel
* menthol = agonist
27
Q

TRPV3

A

thermoreceptor for warmth, axon = C

  • releases ATP to activate P2X –> depolarization
    thresh: < 45 C
28
Q

TRPV1

A

thermoreceptor for noxious heat, axon = A-delta;

  • free nerve endings -
    thresh: <45 C
    agonist: capsaicin (in chili peppers)
  • firing continues after end of stimulus!*
29
Q

TRPV2

A

thermoreceptor for painful heat, axon = C;

    • senses changes in pH in tissue (injury –> low pH)
      thresh:&raquo_space; 45 (~53) C
  • firing continues after end of stimulus!*
30
Q

Sensitization of nocioceptors causes…

A

(increase sensitivity of receptors after injury, ie: sunburn, etc.)

  1. allodynia (decrease threshold)
  2. increase response to = stimulus intensity
  3. increase spontaneous activity (may fire beloe threshold)
31
Q

1st order neuron in somatic sensation

A

carries sensory info for ipsilateral side,
from sensory R to spinal cord (dorsal horn).

lose 2 pt discrimination, vibratory and/or propriocep. if damaged

32
Q

2nd order neuron in somatic sensation

A

carries contralateral sensory info,
from dorsal column (dorsal horn) to thalamus (esp. VPL).
* maintains spatial segregation from 1st order neuron*

33
Q

3rd order neuron in somatic sensation

A

carries contralateral sensory info,

from thalamus to cortex (esp. post-central gyrus).

34
Q

organization of sensory info in dorsal column

A

sacral/lumbar nn: most medial, extend whole length from inferior to superior **GF
thoracic nn: in middle of gracile and cunate fasciculi (thinnest set)
cervical nn: most lateral, only appear in cervical segment of spinal cord (~superior), **CF

35
Q

relative receptive field sizes of 1,2,3 order neurons

A

3rd order neurons have largest receptive field (bc most # sensory receptors feed into it);
* 2nd order neurons have RF 40-100x larger than 1st order nn.

36
Q

Shingles

A

varicella-related virus,
rests dormant in dorsal root ganglion;
when flares up –> affects that single dermatome.

37
Q

what % of neurons extend from spinal cord into brain?

A

only 25% 1st order neurons go to the dorsal column nuclei in medulla (GN and CN);
– other 75% stay in spinal cord and make “propriospinal connections” (for reflexes, central pattern generation, etc.)

38
Q

Spinothalamic tract

A

Pathway of 1-3rd order neurons, carries pain and temperature info.
Dorsal horn –[cross midline]–> VLF (spinal cord) –>
a) reticular formation, b) central gray, c) thalamus (VPL; Central Lateral Nuc.) –> Cortex (1 somatosensory area; limbic areas)

39
Q

Path of 1st order neuron in STT

A
  1. nocioceptor –> Dorsal root
  2. Lissauer’s tract –> Substancia Gelatinosa ==> interneuron.
    ** NTs = glutamate and SP; if enough –> Long Term change:
    alter 2nd mess, so modulate synaptic f(x)**
  3. int.n –> marginal zone & lamina V (dorsal horn) ==> 2nd o.n.
40
Q

Path of 2nd order neuron in STT

A
  1. Dorsal horn --> Ventral 1/2 of Lateral Funiculus (“VLF”)
    * cross midline via anterior white commissure     w/in 2 segments
  2. ascend to… a) Reticular formation
    b) Central Gray
    c) Thalamus
41
Q

Path of 3rd order neurons in STT

A

(3 targets)

  1. reticular formation (medulla): evoke arousal [cortex]
  2. central gray (midbrain): modulate STT
  3. Thalamus
    a) Central Lateral nucleus: emotion/suffering [limbic cortex]
    b) VPL nucleus: map/localize pain [1 somatosensory cortex]
42
Q

role of Ventral Posterolateral nucleus (VPL) in pain sensation

A

sends 3rd order neuron of STT to primary somatosensory cortex,
for localization of pain information.
* ipsilateral from thalamus to cortex (not to body)*

43
Q

Role of Central Lateral nucleus in pain sensation

A

sends 3rd order neuron of STT to limbic cortical structures (cingulate gyrus and insula) for “emotional/suffering”responses to pain.
* large receptive fields bc do not localize pain* (not somatotopic)
= fast, general “feeling” response to pain

44
Q

Cordotomy

A

surgical procedure for pain management in terminally ill patients,
= unilateral cutting of VLF in spinal cord.
–> unilateral (contralateral) analgesia and athermia AT and below the level of the cut.
BUT: pain returns bc other pathways take up pain info!!

45
Q

Syringomyelia

A

a central cord degeneration syndrome where a hole develops in the center of the spinal cord; usually expands up and down spinal column.
–> cuts off only STT axons crossing the midline at the affected point (remember rule of w/in 2 segments for crossing)

46
Q

Bladder pain referred to

A

Lower back and supra-public regions

47
Q

Heart pain referred to

A

Males: Chest and left arm
Females: back and left shoulder

48
Q

Kidney pain referred to

A

Back

49
Q

Esophagus pain referred to

A

Chest

Sometimes confused for heart attack

50
Q

Duodenum pain referred to

A

Mid epigastric region

51
Q

Lung pain referred to

A

Upper back

52
Q

Migraine pain referred to

A

Cranium and orbits

Neuroscience (9 decks)

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