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Neurobiology > Hirsch - Spinal Motor > Flashcards

Hirsch - Spinal Motor Flashcards

1
Q

Eadweard Myubridge

A

Motion recording

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2
Q

Motor Pathways

A

Upper motor neurons in brainstem and cortex

Lower motor neurons in spinal cord

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3
Q

Spinal cord - know the locations in the picture

A 
Dorsal Horn
Dorsal roots
Lateral white matter
Ventral Horn
Ventral roots 
Medial white matter
  • grey matter (inside)
  • white matter (outside)
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4
Q

Dorsal Horn

A

inputs from sensory cells, cell bodies of local circuit neurons

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5
Q

Dorsal Roots

A

somas of sensory neurons

axons travel into the cord and out to sensory receptors = afferent

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6
Q

Lateral white matter

A

carries fibers from motor cortex

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7
Q

Ventral Horn

A

cell bodies of motor neuron

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8
Q

Ventral roots

A

axons of lower motor neurons that travel out towards muscles = efferent

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9
Q

medial white matter

A

carries fiber from brainstem

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10
Q

SAME-DAVE

A

sensory-afferent, motor-efferent

dorsal-afferent, ventral-efferent

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11
Q

Levels of spinal cord

A 
(from top )
cervical - arm movement
thoracic - information transfer
lumbar - leg movement
sacral
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12
Q

different types of fibers

A 
Dorsal roots (sensory afferents)
Ventral roots (motor efferents)

SAME-DAVE

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13
Q 
Dorsal Roots (sensory afferents)
SAME-DAVE
A 
muscle spindles
golgi tendon organs
tactile
sharp pain/temp
dull pain
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14
Q 
Ventral Roots (motor efferents)
SAME-DAVE
A

alpha-motorneuron -> larger

gamma-motorneuron -> small

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15
Q

Motor unit

A

group of muscle fiber that receive input from a single motor neuron
single action potential to many muscle fibers

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16
Q

Somatotopic arrangement of Lower Motor Neurons (Ventral horn)

A

motor neurons that innervate proximal muscles are central

motor neurons that innervate distal muscles are lateral

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17
Q

Different alpha- motor neurons

A

Smaller
Larger
Intermediate sized

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18
Q

Small alpha motor neuron

A

slow
muscle fibers that generate small but lasting contraction
180 muscle fibers per neuron (or smaller for eye movement)

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19
Q

larger alpha motor neuron

A

fast fatigue
generate larger forces - jumping
1-2K fibers; less precision, more power

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20
Q

Intermediate sized alpha motor neuron

A

fatigue resistant

intermediate properties

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21
Q

Motor pool

A

group of motor neurons that innervate a single muscle
can comprise more than one type of motor unit (slow, fast, intermediate..)
ex) calf muscle used for standing, jumping, walking …

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22
Q

Muscle spindle

A

each spindle contains intrafusal fibers arranged in parallel with the extrafusal muscle fibers

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23
Q

Nuclear bag

A

response to rate of change (velocity)

24
Q

nuclear chain

A

track muscle length

25
Q

sensory afferents

A

Group Ia

Group II

26
Q

Group Ia

A

sensory afferent
wrap around the bag and chain fibers
most active when stretching

27
Q

Group II

A

sensory afferent
wrap around the chain fiber only
most active when stretched

28
Q

intrafusal fibers

A

innervated by gamma-motor neurons

29
Q

gamma-motor neuron

A

regulate the sensitivity of the muscle spindle

pulling at both ends of bag and chain fibers; stretching the regions where afferent endings are wrapped

30
Q

Golgi tendon organs

A
  1. capsules encasing Group Ib afferents
    * organs are embedded in the tendons that connect muscle to bone
  2. signal information about force
31
Q

Group Ib

A

wrap around collagen fibrils

32
Q

afferent activity is greatest when…

A

the muscle contracts

33
Q

muscle spindles and golgi tendon organs

A

(passive stretch) from short to long
II sensitive to length
Ia sensitive to velocity and length
Ib not sensitive

(passive stretch) from long to short
II less sensitive to length
Ia less sensitive to length; AP recorded from afferent
Ib very sensitive

34
Q

velocity and length of muscle

A

phasic - brief; velocity

tonic - longer; length

35
Q

Monosynaptic stretch reflex

A

maintains muscle length

ex. classical reflex hammer to the knee

36
Q

Know the picture of knee reflex in 13/22 slilde

A

agonist, antagonist, alpha motorneuron, inhibitory, Ia fiber

37
Q

Knee reflex occuring steps

A
  1. agonist muscle is stretched –> increase in discharge by Ia afferents
  2. a. Discharge —-» mono-synaptic excitation of alpha-motor neuron (white cell) in lateral horn which innervates same muscle to contract to restore muscle length
  3. b. Discharge —» di-synaptic relaxation of the antagonist; Ia afferent synapses with an inhibitory inter neuron in the dorsal horn –> suppresses activity in the alpha-motor neuron that innervates the antagonist
38
Q

1a fibers and alpha fibers have

A

large diameters so conduct quickly; fast reflex

39
Q

Golgi tendon organ reflex in knee reflex

A

it maintains tension via negative feedback

  1. agonist contract
  2. muscle tension increases
  3. Ib afferents fire hard
    * Ib afferent synapses with an inhibitory interneuron
  4. reduces firing of the alpha motor neuron
  5. muscle relaxes, tension decreases
40
Q

Top down control of spinal cord from cortex and brainstem
1. lateral white matter
medial white matter

A

lateral white matter (know location) = axons from motor cortex
medial white matter (know location) = axons from brainstem

41
Q

Upper motor neurons reside where? 15/22

A

brainstem and cortex

42
Q

Brainstem to spinal cord

A
  • many things happen, but simply remember…
    brainstem nuclei provide upper motor neurons that project to the cord
    • there are many tracts such as… (study their pictures 16/22)
      1. lateral and medial vestibulospinal tracts
      2. reticulospinal tract
      3. colliculospinal tract
43
Q

premotor cortex in frontal lobe

A

supplemenatary and premotor cortex = movement planning

*more to the frontal lobe

44
Q

motor cortex in frontal lobe

A

movement execution

* further from frontal lobe

45
Q

motor movement planning and execution

A
  1. frontal lobe = idea
  2. premotor cortex = program
  3. supplementary motor area = program
  4. primary motor cortex = execution
46
Q

motor homunculus

A

at primary motor cortex
corticobullbar tract = face
corticospinal tract = upper extremity, trunk, lower extremity

47
Q

histology of motor cortex

A

in primary motor cortex; Betz cells (large, fast conduction) and non-Betz pyramidal neurons exist

48
Q

Betz cells

A

big; fast conduction
axons form most fibers in descending tracts
* descending tract = corticospinal tract, corticobulbar tract

49
Q

descending tract in primary motor cortex

A

corticospinal tract

corticobulbar tract

50
Q

corticospinal tract

A

to the spinal cord

upper motor neuron

51
Q

corticobulbar tract

A

to the brainstem

upper motor neuron

52
Q

Corticospinal tract

A

cortex -> midbrain -> middle pons -> middle medulla -> caudal medulla (pyramidal decussation; nerve crosses to opposite side) -> spinal cord
* subdivision: lateral corticospinal (cross), anterior corticospinal (do not cross)

53
Q

corticobulbar tract

A

cortex-> midbrain-> middle ons-> middle edulla (brain stem)

uncrossed

54
Q

subdivision of corticospinal tract

A

later corticospinal

anterior corticospinal

55
Q

later corticospinal tract

A

80% of cortico-spinal tract; distal muscles (fingers and toes)
most fibers cross at pyramidal decussation in caudal medulla
controls detailed/fine movement

56
Q

anterior corticospinal tract

A

anterior or ventral
crosses at the cord(?)
bilateral & polysynaptic with medial motorneurons (maintain posture)

57
Q

cells in motorcortex arranged in colums that perform common functions

A

motor cortex are believed to be organized according to movements (functions carried by muscles) rather than target muscle *

Neurobiology (11 decks)

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