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BISC 421 - Module II > Lecture 15 - Spinal Cord + Motor Cortex > Flashcards

Lecture 15 - Spinal Cord + Motor Cortex Flashcards

1
Q

Motor cortex

A

planning, initiating, directing voluntary movements

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2
Q

Brainstem Centers

A

basic movements, postural control

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3
Q

What is the basal ganglia?

A

gating proper initiation of movement

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4
Q

What is the cerebellum?

A

sensory motor coordination of ongoing movment

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5
Q

What are the spinal cord and brainstem circuits

A
  • local circuit neurons

- motor neuronpools

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6
Q

What does SAME-DAVE stand for?

A

sensory-afferent
motor-efferent
dorsal-afferent
ventral-efferent

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7
Q

What is a motor unit?

A

group of muscle fibers that receive input from a single motor neuron

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8
Q

What are lower motor neurons?

A

-motor neurons that innervate proximal mucles

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9
Q

Smaller (S) alpha motor neurons

A
  • conduct slowly

- innervate muscle fibers that generate small, lasting contractions (EX: postural muscles like soleus)

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10
Q

Larger (FF) alpha motor neurons?

A
  • fast

- innervate larger groups of muscle that generate larger forces (EX muscles for jumping)

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11
Q

Intermediate (FR) alpha motor neurons

A

-innervate muscles with intermediate properties

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12
Q

What is the motor pool? What can it comprise?

A
  • group of motor neurons that innervate a single muscle

- can comprise more thane one type of motor unit

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13
Q

What are golgi tendon organs?

A

capsules encasing group 1b afferents

-embedded in tendons that connect muscle to bone

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14
Q

What do golgi tendon organs signal?

A
  • information about force

- afferent atvity is greatest when muscle contracts

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15
Q

What is the monosynaptic stretch reflex?

A

maintains muscle length(classical reflex induced with hammer to the knee)

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16
Q

What does the golgi tendon organ reflex do?

A

maintains tension via negative feedback

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17
Q

Where are upper motor neurons?

A

brainstem and cortex

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18
Q

Where are lower motor neurons?

A

in spinal cord or brain stem

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19
Q

Dorsal horn

A

inputs from sensory cells, somas of local circuit neurons

20
Q

Dorsal roots

A

contain somas of sensory neurons who axons travel out to peripheral sensor receptors and to the cord (afferent)

21
Q

ventral horn

A

somas of lower motor neurons

22
Q

ventral roots

A

contains axons of lower motor neurons that travel out toward muscles (efferent)

23
Q

medial white matter

A

carries fibers from brainstem

24
Q

what are the 4 regions of the spinal cord?

A
  1. cervical
  2. thoracic
  3. lumbar
  4. sacral
25
Q

What does each spindle contain? What are they called?

A

two types of special muscle fibers (intrafusal fibers)

26
Q

How are intrafusal fibers arranged?

A

in parallel with extrafusal fibers

27
Q

What are nuclear bag fibers?

A

sensitive to rate of change in muscle length (velocity)

28
Q

What are nuclear chain fibers?

A

sensitive to muscle length

29
Q

What are Group 1a sensory afferents? When are they most active?

A
  • wrap around the bag and chain fibers

- most active when muscle length changes (EX stretching)

30
Q

What are group II sensory afferents? When are they most active?

A
  • wrap around chain fibers only

- most active when muscle is stretched

31
Q

What are intrafusal fibers innervated by?

A

gama motor neurons

32
Q

What do gama motor neurons do?

A
  • regulate sensitivity of the muscle spindle
  • pull at both ends of bag and chain fibers
  • stretching regions where afferent endings are wrapped
33
Q

What Betz cells?

A
  • very large
  • stout axons form most fibers in descending and corticobulbar tracts
  • example of upper motor neuron
34
Q

What are the 2 descending motor tracts that originate in the motor and premotor cortices?

A
  1. corticobublar (ends in brainstem)

2. corticospinal (ends in spinal cord)

35
Q

The corticobulbar tract is ______ while the corticospinal tract _____ at the _____

A
  • uncrossed

- crosses, midline

36
Q

What is the lateral cortico-spinal tract?

A
  • comprises most of corticospinal tract

- originates from premotor cortex + primary motor cortex

37
Q

Where do most fibers cross?

A
  • at the pyramidal decussation

- terminate on lateral motor neurons (those that move distal muscles like fingers and toes)

38
Q

What is the anterior (ventral) corticospinal tract?

A
  • crosses at the cord

- makes bilateral + polysynaptic connections with medial motor neurons that are used to maintain posture

39
Q

supplementary and premotor cortex

A

movement planning

40
Q

motor cortex

A

movement execution

41
Q

How are cells organized in cortices?

A

arranged in columns that perform common functions

42
Q

What are the 3 steps to the monosynaptic stretch reflex?

A
  1. agonist muscle is stretched, leads to increase in discharge by 1a afferents
  2. monosynaptic excitation of a-motoneuron in lateral horn
  3. disynaptic relaxation of antagonist, 1a afferent synapses with inhibitory interneuron in dorsal horn
43
Q

What kind of diameters do the 1a fibers and a-fibers have? What does this mean?

A
  • large diameters
  • conduct quickly
  • reflex is fast
44
Q

What are the 3 steps of the Golgi tendon organ reflex?

A
  1. agonist contracts, muscle tension increases, 1b afferents fire hard
  2. 1b afferents synapses with inhibitory interneuron
  3. muscle relaxes, tension decreases
45
Q

How are motor neurons (in ventral horn) arranged?

A

somatically

46
Q

What does it mean that motor neurons (in ventral horn) are somatically arranged?

A
  • motor neurons that innervate proximal muscles are medial

- those that innervate distal muscles are lateral

BISC 421 - Module II (14 decks)

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