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VET 404: Neurology > Sensory Systems > Flashcards

Sensory Systems Flashcards

1
Q

types of sensation

A
  1. special
  2. somatosensory
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2
Q

pathway of sensory info

A
  1. sensory afferent
  2. dorsal root ganglia
  3. spinal cord
  4. reflex arc OR ascending pathway
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3
Q

what do receptors do

A

change energy into electrical activity (action potential) that changes the membrane potential to signal to the next neuron in the pathway

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4
Q

receptor modalities

A

mechanoreceptors
thermoreceptors
electromagnetic
chemoreceptors
nociceptors

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5
Q

receptor categories

A

exteroceptors
interoceptors
proprioceptors
nociceptors

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6
Q

stimulus

A

results in a change in receptor potential

if exceeds threshold, will cause an AP to be generated

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7
Q

ways to classify stimuli

A
  1. modality
  2. intensity
  3. duration
  4. location
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8
Q

temporal summation

A

increased frequency

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9
Q

spatial summation

A

increased number of nerves

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10
Q

adaptation

A

slower rate of AP firing with continued stimulus

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11
Q

phasic receptors

A

rapid; detect changes in stimuli and inform about its rate of change

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12
Q

tonic receptors

A

slow; detect continuous stimuli and informs about its presence and strength

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13
Q

three sensory system

A
  1. medial lemniscal system
  2. ascending reticular formation
  3. spinocerebellar tracts
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14
Q

conscious proprioception

A

proprioceptive information sent to the contralateral cerebrum

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15
Q

subconscious proprioception

A

proprioceptive information sent to the ipsilateral cerebrum

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16
Q

function of the cerebellum

A

mediates coordinated movement; requires:
- proprioceptors
- vestibular system
- motor system

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17
Q

proprioceptive mechanoreceptors

A

provide information about the effects of gravity on muscles and the differences between actual and intended movements

located in the head (vestibular system) and limbs (joints, muscles, skin)

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18
Q

muscle spindle

A

fibers in skeletal muscle that detects changes in length (stretch)

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19
Q

intrafusal fibers

A

SMALL fibers located within a spindle shaped collagen capsule that runs in parallel with extrafusal fibers

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20
Q

what are intrafusal fibers innervated by

A

1a afferent neurons
y efferent neurons

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21
Q

function of intrafusal fibers

A

sense proprioception
chain fibers: detect static muscle length
bag fibers: detect dynamic muscle length

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22
Q

extrafusal fibers

A

LARGE standard muscle fibers

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23
Q

what are extrafusal fibers innervated by

A

alpha motor neurons

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24
Q

muscle spindle reflex

A

“stretch” reflex

monosynaptic reflex in response to muscle stretch; signals to motor neurons (that innervate the same muscle) to fire, causing contraction

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25
pathway of muscle spindle reflex
1. intrafusal fiber stretches 2. 1a afferent carries signal to DRG 3. 1a afferent synapses onto the alpha motor neuron 4. alpha motor neuron transmits signal to the extrafusal muscle fibers 5. extrafusal fibers contract
26
function of muscle spindle reflex
"smooth" and stabilize movement and posture/muscle tone - antagonizes the stretch of one muscle as a feedback mechanism to prevent over stretching - constantly activated while moving
27
central excitatory state
the status of output of the nervous system - determined by gamma motor neurons
28
gamma motor neurons
located on the ends of muscles; tonically fires to increase the muscle's sensitivity to stretch, which activates alpha motor neurons to fire and contract extrafusal fibers
29
high gamma bias
excitatory state; gamma neurons fire more frequently --> increases sensitivity to stretch in order to keep muscles ready to contract quickly
30
low gamma bias
relaxed state; gamma neurons fire less frequently --> decreased muscle sensitivity to stretch
31
what are the two ways that muscle spindles can cause extrafusal fiber contraction
1. mechanical stretching of extra/intrafusal fibers 2. firing on gamma motor neurons during voluntary movement
32
Golgi tendon organ
located in the tendon; connected in series with muscle fibers detects changes in tension by deforming with contraction/stretch
33
GTO reflex
disynaptic reflex in response to too much tension on a muscle tension initiates an inhibitory pathway that prevents the muscle from contracting OR stimulates antagonizing muscles to contract
34
function of GTO reflex
"smooths" movement; protects muscle from excess tension
35
GTO reflex pathway
tension --> 1b afferent --> inhibitory interneuron --> inhibits activity of efferent --> inhibits contraction
36
large diameter fibers
fast, myelinated fibers in the spinal cord transmit information about touch, pressure, and proprioception
37
small diameter fibers
slow, unmyelinated fibers in the spinal cord transmit information about nociception and temperature
38
thalamus
receives all sensory input (except olfaction) and relays to specific cortical areas
39
specific relay from thalamus
somatotopic projections from thalamus to cortex
40
diffuse projection from thalamus
widespread projections from the thalamus that go to various areas of the cortex
41
thalamo-cortical pathways
white matter tracts between thalamus and cortex corona radiate and internal capsule
42
dorsal column-medial lemniscal pathway (DC-ML)
large, fast, myelinated axons that transmit MECHANORECEPTION and CONSCIOUS PROPRIOCEPTION to the cerebrum
43
medial lemniscus
bundle of thick, myelinated, ascending axons that decussate in the brainstem
44
long tracts
extend from DRG all the way up the spine without an interneuron
45
what are the two types of long tracts
1. gracile tract 2. cuneate tract
46
gracile tract
located in the medial dorsal funiculus receives information from the caudal half of the body
47
cuneate tract
located in the lateral dorsal funiculus receives information from the cranial half of the body
48
dorsal column nuclei
nuclei located at the obex 1. gracile nucleus 2. cuneate nucleus
49
gracile nucleus
contains secondary neurons that synapse with primary neurons from gracile tract
50
cuneate nucleus
contains secondary neurons that synapse with primary neurons from cuneate tract
51
ventro-caudo-lateral nucleus
located in the thalamus site of secondary neuron synapse onto tertiary neurons
52
DC-ML pathway
3 neuron pathway 1. primary neurons reach spinal cord and enter at ipsilateral dorsal funiculus 2. primary neurons extend up gracile/cuneate tracts to the dorsal column nuclei 3. primary neurons synapse with secondary neurons in dorsal column nuclei 4. secondary neurons decussate the to contralateral side of the brain into the medial lemniscus 5. secondary neurons extend through brainstem to ventro-caudo-lateral nuclei in the thalamus where they synapse onto tertiary neurons 6. tertiary neurons extend to the appropriate primary somatosensory cortex in the cerebrum
53
where do secondary motor neurons of DC-ML pathway synapse within ventro-caudo-lateral nuclei
if from cranial 1/2 of body: medial if from caudal 1/2 of body: lateral because of decussation of fibers between spinal cord and thalamus
54
function of the spinomedullothalamic pathway
provides position sense for the pelvic limbs - conscious proprioception
55
function of the spinocervicothalamic pathway
responds to mechanical, thermal, and noxious stimuli - no proprioception - only present in carnivores/domestic animals
56
spinomedullothalamic & spinocervicothalamic pathways
1. primary neuron reaches spinal cord and enters at ipsilateral lateral funiculus 2. primary neuron synapses onto an interneuron located in the dorsal horn 3. interneuron extends up to nuclei in the medulla 4. continues the same as DC-ML pathway
57
reticular formation
primitive midline system; diffuse network that receives input from cerebrum, cerebellum, and spinal cord involved in "true" pain perception - NOT pinprick pain
58
reticular activating system (RAS)
functions in activating the cerebral cortex input: collaterals from all sensory tracts on the way to thalamus output: diffuse (NOT somatotopic) to thalamus and cortex; some descending pathways
59
function of ascending reticular system
sets the level of consciousness of the cerebrum (mentation)
60
signs of RAS dysfunction
pacing/circling, changes in mentation, compulsive walking may have normal reflexes
61
organization of brainstem pathways
dorsal: somatic and visceral efferents ventral: somatic, visceral, and special visceral efferents somatic: lateral visceral: medial
62
sensory nucleus of trigeminal
somatic afferent nucleus; a continuous, elongated region of gray matter in the brainstem that carries sensory info from CN V
63
motor neuron V
carries motor information from CN V out of the brainstem
64
CN V sensory pathway
1. primary afferent enters trigeminal ganglion in the skull 2. primary afferent enters trigeminal nerve to enter the brainstem at the level of the pons 3. primary afferent descends down the medulla along the spinal tract of CN V to the sensory nucleus of trigeminal nerve, where it synapses with the secondary afferent neuron 4. secondary afferent decussates to the contralateral side of the brainstem and ascends to the ventro-caudo-lateral nucleus of the thalamus (along the trigemino-thalamic pathway) 5. secondary afferent synapses with tertiary afferent in the thalamus and extends to the head/face areas of the somatosensory cortex
65
nucleus of solitary tract
visceral afferent nucleus; a continuous, elongated region of gray matter within the brainstem that carries sensory info for taste sensation
66
sensory pathway for taste
1. primary afferent neurons enter respective ganglia (CN VII, CN IX, X), then enter the brainstem 2. primary afferent neurons synapse with secondary afferents at the nucleus of solitary tract 3. secondary neurons ascend both ipsilaterally (most) and contralaterally along the nucleus to a ventral group of nuclei in the thalamus 4. secondary afferents synapse with tertiary afferents in the thalamus, which project to the cortex
67
what CNs does the salivary reflex test
afferent: CN IX efferent: CN IX
68
what CNs does the gag reflex test
afferent: CN IX, CN X, CN V efferent: CN XI, CN XII

VET 404: Neurology (23 decks)

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