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CDS 3500 unit 3 > PNS > Flashcards

PNS Flashcards

1
Q

what’s a nerve?

A
  • bundle of many axons in the PNS
  • coming down from neurons (cell bodies) in the CNS
  • grouped together and coated in myelin
  • innervate muscles by conducting messages from the CNS to muscle fibers (efferent)
  • conveys sensroy input from muscles back to brain (afferent)
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2
Q

spinal nerves

A
  • convey motor input to body
  • convey sensory input from body
  • emerge from SC
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3
Q

cranial nerves

A
  • convey motor input to head, mouth, articulators, and some internal organs
  • emerge from brainstem
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4
Q

ganglia

A
  • collection of neurons (nerve cell bodies) outside the CNS
  • found in the PNS
  • perform a certain function, outside the CNS
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5
Q

functions of spinal, cranial nerves and ganglia

A
  • serve as a connecting system between CNS and body

- engage/provide voluntary and involuntary control over body

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6
Q

motor (efferent) neurons

A

sending info from the CNS to the body

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7
Q

sensory (afferent) neurons

A

sending info to the CNS from the body

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8
Q

somatic nervous system

A

voluntary control of skeletal muscle

-innervation to/from all skeletal muscles

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9
Q

outgoing somatic NS

A
  • dependent upon tracts leaving the cortex, traveling down the spinal column, and synapsing with new motor neurons before exiting the CNS
  • efferent nerves leaving the CNS, now traveling as part of the PNS and synapsing directly with muscle causing muscle movement
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10
Q

incoming somatic NS

A
  • afferent nerves entering the CNS, coming directly from skin or muscle
  • synapsing with other sensory neurons along the way, now traveling as part of the CNS
  • provides sensory info from the PNS
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11
Q

reflex arcs

A
  • provides conscious, voluntary control
  • directly mapped sensory-motor systems, in the PNS
  • located at the level of the spinals nerves involved in the PNS
  • bypasses the CNS all together
  • provides immediate responses to external stimuli
  • act in a protective manner
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12
Q

upper motor neurons location

A
  • ALL located in the CNS
  • axons do not leave the CNS
  • they remain within the brain, the brainstem, and/or the spinal cord
  • orginate in the pre-motor cortex of the frontal lobe
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13
Q

UMN form the..

A
  • corticospinal tracts

- corticoblbar tracts

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14
Q

corticospinal tracts

A

projection fibers traveling vertically

-sending axons to synapse with lower motor neurons in the SC

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15
Q

cortiobulbar tracts

A
  • projection fibers traveling vertically

- sending axons to synapse with cranial nerve nuclei in the brainstem

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16
Q

UMNs provide…

A
  • DIRECT activation system from the CNS to the PNS

- referred to as the direct pathway, pyramidal tract

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17
Q

Lower motor neurons

A

-those neurons which convey the neuron impulse to its final destination

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18
Q

location of the LMN

A
  • cell body is in the CNS

- axon extends OUT of the SC or brainstem, and INTO the periphery

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19
Q

function of the LMNs

A

-receive incoming UMN message from the motor cortex
-transmit the incoming motor impulse to the muscle itself
-cause the muscle to fire/move/contract
entire system= final common pathway

20
Q

other names for LMNs

A

-2nd order neurons, cranial nerve neurons, anterior horn cells, alpha motor neurons

21
Q

motor homunculus

A
  • anatomical representation of the degree of innervation

- primary motor cortex via outgoing, efferent tracts

22
Q

sensory homunculus

A

anatomical representation of the degree of sensory input
-provided in the primary sensory strip
via afferent, or incoming tracts

23
Q

corticospinal tract - direct pathway

A
  1. from the pre-central gyrus (primary motor cortex)
  2. through the corona radiati (subcortical white matter in the cerebrum)
  3. converges together at the internal capsule (CNS)
  4. to the cerebral peduncle in the midbrain of the brainstem
  5. to the medulla, the lowest part of the brainstem- where the fibers cross midline to the other side=PYRAMIDAL DECUSSATION
  6. to the level of the SC where the desired muscle is
  7. to the anterior horn neuron in the SC
  8. to the dorsal and ventral motor roots which form the spinal nerve
24
Q

where do paired spinal nerves end up?

A
  • they occur at each vertebral interval

- emerging from the SC, one on each side of the body

25
Q

31 pairs of spinal nerves

A
  • 8 cervical
  • 12 thoracic
  • 5 lumbar
  • 5 sacral
  • 1 coccygeal
26
Q

STUDY SPINAL NERVES

A

-axons extending from LMNs SLIDE 30

27
Q

where do the motor fibers or spinal nerves originate?

A
  • in the grey matter or the H-shape
  • at a group of cells called the anterior (ventral) horn cells
  • which occur at the point of connection (synapse) between the incoming motor fibers from the CNS and the new alpha motor neuron in the SC, sending a new motor fiber out to the PNS, where it is then a nerve
28
Q

extrapyramidal tracts (indirect pathways) function

A
  • coordinate and adjust posture, balance
  • coordinates and regulates rate, force, timing of movements
  • inhibit/control muscle tone, amount of movements
  • regulate and inhibit reflexive movements
29
Q

methods of indirect pathways

A
  • relies upon and works best with BG and cerebellum
  • works with pyramidal pathways
  • modifies messages generated by primary motor cortex
  • it is a more complicated round-about
  • POLYsynapatic
  • does not provide direct input to the LMNs (just edits and fixes)
  • has functions outside the system of tracts moving through the pyramidal structure of the brainstem
30
Q

extrapyramidal tract structures

A
  • BG (globus pallidus, caudate nucleus, putamen)
  • substantia nigra and subthalamic nucleus
  • midbrain (of the brainstem) –> red nucleus and reticular formation
  • cerebellum
31
Q

reticular formation

A
  • collection of cells scattered amongst some cranial nerve nuclei and some fiber tracts within the brainstem
  • long extension of these cells, throughout midbrain, pons and medulla
  • mediates basic level of consciousness
  • major player in mediating messages sent to the LMNs
32
Q

red nucleus

A
  • cluster of cells on the midbrain
  • receives input from motor cortex and BG and feedback from the cerebellum
  • further modifies motor messages on their way down
33
Q

BG structures involved in indirect motor pathways

A

-substantia nigra and subthalamic nuclei

34
Q

substantia nigra

A
  • techincally located within the brainstem (midbrain) but functionally considered part of the BG
  • information to and from the BG
  • critical producer of dopamine
35
Q

subthalamic nucleus

A
  • technically part of the thalamic nuclei but functionally considered part of the BG
  • receives input from globes pallidus, motor cortex
  • head right back into the globes pallidus
36
Q

indirect motor pathway concepts

A
  • some decussate
  • some remain ipsilateral
  • some do both
  • ALL provide indirect influence upon LMNs
  • ALL engage in multi-synaptic circultry
  • final synapse with inter-neurons to indirectly influence the movement executed by the LMNs
37
Q

interneuron

A

is a neighboring neuron that is in the gray matter of the SC

  • it is sitting there and its main job is to receive input from the indirect system (all the fixed info)
  • they send the edited info directly to the LMNs
38
Q

various extrapyramidal tracts

A
  • corticorubral
  • corticoreticular
  • vestibulospinal
39
Q

corticorubral tract

A
  • INDIRECT
  • ipsilateral - then proceeds
  • from motor, premotor and sensory strip –> brain stem red nucleus
  • rubrospinal (contralateral) –> from the cerebellum and BG to red nucleus - inhibitory control (not too much movement)
40
Q

corticoreticular

A
  • ipsilateral- then proceeds
  • from motor, premotor, and sensory strip –> reticular formation in the BS (pons and medulla) –> cerebellum
  • supports posture and walking
  • reticulospinal (ipsilateral and contralateral) - from reticular formation to LMNs –> maintains tone from trunk and posture
41
Q

vestibulospinal

A

ipsilateral and contralateral

  • from vestibular nuclei, below 4th ventricle, within pons and medulla –> cerebellum and SC
  • incorporate info about balance, position, movement of head
42
Q

corticobulbar tracts

A

-direct motor innervation from CNS to cranial nerves within the brainstem, for control of face, neck, and head

43
Q

corticobulbar tract pathway

A
  • pre-central gyrus
  • corona radiati
  • internal capsule
  • cerebral peduncle in the midbrain (to cerebellum to the brainstem)
  • where the cranial nerves exit at various places within the brainstem, to innervate face, head, neck
44
Q

12 cranial nerves

A

NOT the same spinal nerves

  • attached to brain stem, uppermost spinal cord
  • exit the brainstem through the foramina of the skull
  • serve muscles/organs of head and neck
  • not all are LMN (only the ones with motor capacity)
45
Q

reflex arcs- another function of spinal nerves

A
  • automatic, “stimulus response” mechanism
  • survival mechanism
  • subconcious muscle control
  • without having to send sensory info through afferent tract all the way up to the CNS to secure some kind of response
46
Q

what happens in a reflex arc

A
  • sensory receptor
  • sensory neuron, in the dorsal root ganglion
  • to the sensory/dorsal root of the SN
  • enters the dorsal aspect of the SC to posterior horn
  • synapses with an interneuron
  • interneuron synapses with the LMN
  • immediately sends impulse straight back out and right back to the muscle telling it to move

CDS 3500 unit 3 (5 decks)

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