Basic Sensory and Motor Mechanisms and Pathway Flashcards Preview

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Flashcards in Basic Sensory and Motor Mechanisms and Pathway Deck (56)
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1

basic components to a reflex arc

1. receptor--free N endings for pain sensation
2. afferent neuron--dorsal root ganglion neuron
3. interneuron
-may terminate directly or indirectly upon motor neurons
-processes may ascend/descend/cross in SC
-KEY component in formation of reflex patterns
4. efferent neuron--alpha or gamma motor neurons in motor nuclei or columns
5. effector--motor end plate at a NMJ

2

interneuron

-terminates directly or indirectly (via another interneuron) upon a ventral horn cell
-course and termination of an interneuron determines the pattern of reflex response
-KEY component in formation of reflex patterns
-3 types: intrasegmental reflex, intersegmental reflex, contralateral crossed reflexes

3

intrasegmental reflex

-type of interneuron
-occur within the same level as the afferent stimulus

4

intersegmental reflex

-type of interneuron
-extend the influence of incoming info among more than one spinal segment
-major fiber bundle associated with intersegmental reflexes is the fascicles proprius

5

fascicles proprius

-distributed around the periphery of the gray matter of SC
-continuous superiorly with the reticular formation
-complex diffuse fascicles is comprised of ascending and descending processes of interneurons

6

contralateral (crossed) reflex

-type of interneuron
-reflex may be conveyed to the other side by way of a commissural neuron
-may be intra or inter segmental depending upon the type, quality, quantity of stimulus

7

pathways from SC go to the brainstem and then sensory info goes to...

the tectum which is made up of the superior and inferior colliculus
-auditory and visual info goes here

8

monosynaptic reflex

-comprise a 2 neuron reflex arc with only one synapse
-no interneuron
-ex: myotatic reflex--tested with jaw jerk or knee jerk reflex
-stimulus: rapid stretching of muscle
-response: contraction of the corresponding M

9

polysynaptic reflex

-involve interneurons to elicit stereotypical response patterns to a particular type of stimulus

10

pain reflex

-type of polysynaptic reflex
-stimulus: noxious stimulus (pain)
-response: withdrawal from stimulus

11

autogenic inhibition reflex

-type of polysynaptic reflex
-stimulus: excessive tension on the tendon
-response: relaxation of the corresponding M

12

reciprocal inhibition reflex

-type of polysynaptic reflex
-stimulus: contraction of agonist M
-response: relaxation of the antagonist M

13

primary neuron

-pseudounipolar neuron whose cell body is located in the spinal ganglion
-peripheral process (dendrite) courses in a peripheral N & the ending is assoc with some type of R
-central process enters CNS and bifurcates to ascend and descend a variable # of segments
-along its course it sends off collaterals to interneurons for reflexes
-primary sensory fiber eventually terminates upon a secondary neuron

14

secondary neuron

-located in the SC (pain/temp path) or medulla (proprioceptive path)
1. collaterals from 2ndary axon also terminate directly or indirectly via interneurons upon motor neurons for various reflexes
2. in a conscious sensory pathway the secondary axon:
-always decussates and ascends as a lemniscus
-terminates upon a tertiary neuron in dorsal thalamus
-sends collateral fibers to reticular formation and tectum

15

tertiary neuron

-soma of the neuron is located in a specific nucleus of dorsal thalamus
-projects to the primary somesthetic cortex via the thalamic radiations of the posterior limb of internal capsule and corona radiata

16

primary somesthetic cortex

-post central gyrus
-plays role in the perception and discrimination of sensory stimuli

17

association cortex

-involved in the integration, modification, and interpretation of sensory info

18

lemniscal systems

-secondary axons in a conscious sensory pathway that have already crossed midline so relay info from the contralateral side

19

general conscious sensory pathway

1. receptor
2. primary neuron with cell body in the ganglion cell and central process terminating in the CNS at the secondary neuron
3. secondary neuron decussates and ascends as a lemniscus and terminates on a tertiary neuron in the dorsal thalamus
-also sends fibers to the reticular formation and tectum
4. tertiary neuron in the dorsal thalamus projects to primary somesthetic cortex in the internal capsule

20

lesion of primary neuron

results in ipsilateral deficits

21

lesion of the tertiary neuron/lemniscus

results in contralateral deficits

22

fast pain/temperature pathway

1. primary neuron: spinal ganglion
2. conveyed by: dorsolateral fasciculus
3. secondary neuron: substantia gelatinosa
4. conveyed by: spinal lemniscus and lateral spinothalamic tract
5. tertiary neuron: ventral posterior lateral nucleus (VPL)
6. cerebral cortex: primary somesthetic cortex in posterior limb of internal capsule

23

crude tactile pathway

1. primary neuron: spinal ganglion
2. conveyed by: short ascending fibers in posterior columns
3. secondary neuron: nucleus proprius intermediate gray
4. conveyed by: ventral spinothalamic tract
5. tertiary neuron: ventral posterior lateral nucleus (VPL)
6. cerebral cortex: primary somesthetic cortex in posterior limb of internal capsule

24

proprioception/2 point tactile pathway

1. primary neuron: spinal ganglion
2. conveyed by: long ascending fibers in posterior columns, fasciculus gracilis, fasciculus cuneatus
3. secondary neuron: nucleus gracilis (lower limb), and nucleus cuneatus (upper limb)
4. conveyed by: medial leminiscus
5. tertiary neuron: ventral posterior lateral nucleus (VPL)
6. cerebral cortex: primary somesthetic cortex in posterior limb of internal capsule

25

VPL vs VPM

-VPL: ventral posterior lateral nucleus--sensory info from body
-VPM: ventral posterior medial nucleus--sensory info from face

26

lower motor neurons

-final common pathway b/c they synapse directly with striated skeletal muscle so allows the motor response
-final effectors of the motor system
-cell bodies located in one of the craniospinal motor nuclei
-processes form the motor Ns that innervate skeletal Ms
-2 types: alpha and gamma

27

alpha motor neurons

-type of LMN
-innervate extrafusal or skeletal M fibers

28

gamma motor neurons

-type of LMN
-innervate the modified muscle cells (intrafusal fibers) that form part of the proprioceptive neuromuscular spindles
-activating them inc muscle tension and muscle tone

29

somatotropic organization of the anterior horn

-lateral portion--distal upper extremities
-proximal upper extremities are more medially
-trunk is in the midline
-neurons in the anterior funicular affect the axial M bilaterally

30

SVE Nuclei:
1. trigeminal motor nucleus
2. facial motor nucleus
3. nucleus ambiguus
4. accessory nucleus

1. mastication Ms
2. mimetic Ms
3. laryngeal and pharyngeal Ms
4. trapezius and SCM