2.6 Motor Systems Flashcards Preview

AA > 2.6 Motor Systems > Flashcards

Flashcards in 2.6 Motor Systems Deck (42):
1

Frontal lobe

Anterior half of cortex, motor functions

2

Parietal lobe

Posterior half of cortex, sensory functions

3

Motor pathways

Descending tracts or pathways in the brain and spinal cord that control effectors (muscles)

4

How many neurons do motor pathways use?

TWO

5

Upper motor neurons

Motor neurons originating in primary motor cortex: inhibitory / excitatory axon fibers synapse directly onto lower motor neurons

6

Upper motor neuron output is strongly influenced by what?

Premotor and prefrontal area
Basal nuclei
Cerebellar neurons

7

Lower mor=tor neurons

In ventral brainstem or anterior horn of spinal cord; always excitatory because they synapse directly onto skeletal muscle fibers

8

Cranial nerves

Innervate face and head

9

Spinal nerves

Innervate limbs & trunk

10

Somatic motor system effectors are...

Striated skeletal muscles

11

Motor unit

Just 1 motor neuron and all of the muscle fibers downstream of its axon that it contacts with presynaptic acetylcholine -producing terminals
(can be many thousands as it is one terminal per muscle fiber)

12

Motor pools

Multiple motor units dedicated to one major muscle (ex. bicep) or group of synergistic muscles (ex: abdominals)

13

Motor map

Somatic muscle groups mapped onto primary motor cortex

14

Fine motor areas are... (motor map)

LARGER

15

Why are fine motor areas larger on map?

1) Density: more neurons controlling more motor units
2) Specialization: fewer striated muscle fibers per neuron =>finer motor control

16

Cortical

Pertaining to cerebrum or cerebral cortex

17

Direct muscle control comes from..

Primary motor cortex

18

Complex movement sequences come from..

Premotor area

19

Planning and visualizing come from...

Prefrontal area

20

Basal nuclei region of brain

(Corpus striatum)
Has dopamine producing that ensure movements match the intended purpose

21

Functions of basal nuclei

-Initiates and terminates movements via brainstem motor centers (which leas to indirect pathways.. muscles that maintain posture)
-Provide feedback to motor cortex (which leads to direct pathways.. muscles used for movement)

22

Additional function of basal nuclei

-Mediates habit learning where conscious motor acts are transformed or hard-wired into unconscious motor habits
(procedural memory … “practice makes perfect)

23

Neurodegeneration of dopaminergic neurons

Parkinson's disease, Huntington's disease and some OCDs

24

Cerebellum

Most neuron dense region of the brain

25

Cerebellum functions (4)

-Regulates balance during movements... via motor cortex
-Learned motor coordination and timing.. "when to release the ball"
-Provides input to primary motor cortex.. coordinates fine movements, especially of eyes hands and feet
-Provides input to brainstem.. regulates muscle tone in postural muscles (via proprioreceptive vestibulospinal and excitatory reticulospinal inputs)

26

Direct pathways

Direct from cortex to motor neurons, control skilled movements in face and limbs

27

Indirect pathways

Control posture, locomotion and habitual movements

28

Upper motor neurons in direct pathway

Originate in cerebral cortex; axon fibers may synapse directly to motor or interneurons in brainstem or spinal cord

29

Two tracts of direct pathways

-Corticospinal tract
-Corticobulbar tract

30

Corticospinal tract

Control of movements of the trunk and limbs (brain to limbs and trunk)

31

Corticobulbar tract

Control of movements in face, tongue, pharynx (head)

32

Most corticospinal tracts decussate in _______; descend in ______

Medulla
Lateral Corticospinal tracts
-Control upper and lower distal limbs

33

Upper motor neuron of corticospinal tracts

Axon fibers run from motor cortex --> through pyramids of medulla

34

Anterior corticospinal tracts

Tracts don't cross until they reach the specific region where they exit spine
-Trunk and proximal limbs

35

Corticospinal tracts originate in..

Trunk and limb regions of primary motor cortex (percentile gyrus)

36

Corticobulbar tracts lower motor neurons

Cranial motor neurons

37

Where de signals of indirect pathways originate?

Brainstem, ultimately regulate target muscles in trunk and proximal limbs

38

Two types of indirect pathways

-Vestibulospinal
-Reticulospinal

39

Vestibulospinal origin

Vestibular nuclei in brainstem; integrate balance based on input from vestibular organs

40

Vestibulospinal function

Innervates extensor muscles in trunk & proximal lower limbs
-maintain upright posture

41

Reticulospinal origin

Originates in RAS (controls motor arousal)

42

Reticulospinal function

Innervates ALL motor neurons, maintains muscle tone during ongoing muscle movements