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Clinical Neuroscience weeks 1-3 > Motor Pathways > Flashcards

Flashcards in Motor Pathways Deck (49):
1

walking, chewing, and other pre-programmed movements may be initiated independent of higher brain input. This is mainly an interaction between local circuit neurons and motor neurons

ok

2

Motor cortex mostly responsible for what?

planning, initiating, and directing voluntary movements

3

Brainstem centers responsible for?

regulating tone, and orienting posture with respect to sensory info

4

Cerebellum does what?

acts as a servomechanism, detects the difference between an intended movement and the movement actually performed

5

The cerebellum uses this movement to mediate both real-time and long-term adjustments

ok

6

Basal ganglia does what?

Suppresses unwanted movements an dprepares upper motor neuron circuits for the initiation of movements

7

What the hell is an upper motor neuron

One contained entirely within the central nervous system. No part of this neuron leaves

8

What is a lower motor neuron?

A neuron that has a cell body in the CNS but is projecting its axon into the peripheral nervous system to innervate something anc cause an action

9

What layers of Rexed's laminae are the local circuit, autonomic, and commisural neurons found in?

layers 7 and 8

10

Lower motor neurons are located in what level?

layer 9

11

Lateral corticospinal tract serves what?

Anterior corticospinal tract serves what

ipsilateral motor neurons serving the distal extremities

Anterior corticospinal tract serves axial musculature

12

What corticospinal tract serves axial muscles?

Ventral

13

Does one motor neuron innervate several muscle fibers?

Yes...the larger the cell body of a motor neuron, the greater th enumber of fibers it synapses with

14

Know that fine motor control is achieved by having only a single motor neuron innervate only a few muscle fibers, thus achieving precise control

ok

15

Three general muscle fiber types are

1) Slow Fatigue Resistant
2) Fast Fatigue Resistant
3) Fast Fatiguable

16

The motor neurons of slow resistant fibers tend to be small in size, thus the ratio of muscle fibers per neuron are also small. They also tend to be rich in mitochondria, myoglobin, and capillary beds

ok....dark meat, because of their myoglobin content

17

SLow fatigue resistant muscles function mostly via which type of metabolism

aerobic

18

Fast fatiguable muscle is inervated by much larger motor neurons and thus the muscle fiber to neuron ratio is very high

ok

19

What is a motor unit

a group of muscles innervated by a single lower motor neuron

20

What is the name of neurons that innervate skeletal muscle fibers to form motor units?

alpha motor neurons

21

Alpha motor neurons can receive feedback from sensory organs within the bed of the muscle (spindle organs). The afferent neurons from these sensory organs have cell bodies in the DRG.

ok

22

What is a common excitatory neurotransmitter for alpha motor neurons

acidic amino acids

23

Common inhibitory neurotransmitters

GABA and Glycine

24

muscle spindles give rise to what tpes of afferent nerves

Types Ia and type II

25

What are the two types of sensory organs within the muscle bed

Spindle organs and Golgi Tendon organs

26

Golgi Tendon organs give rise to what type of afferent nerves

Type Ib

27

What does a gamma motor neuron do?

fires in concert with alpha motor neurons to insure that the intrafusal muscle fibers don't become relaxed and non-responsive.

28

Type II afferent nerves from muscle spindles...encodes muscle length information in the frequency of action potentials. Greater length = increased frequency of action potential, decreased lenght means decreased frquency

ok

29

What does type Ia afferent encode

length and velocity of muscle change....quick change in muscle length generates a drastic increase in frquency

30

Know golgi tendon organ stuff

ok

31

Atrophy, decreased reflexes, decreased muscle tone, and fasiculations are all features of what kind of nerve lesion

lower motor neuron.

32

Origins of upper motor neuron cell body located in the motor cortex which is located where?

precentral gyrus

33

What are large motor neurons called?

Betz cells

34

Precentral gyrus also called what?

Brodmann area

35

Premotor area associated with which Brodmann area?

Brodmann area 6

36

Primary somatosensory cortex associated with which Brodmann area

3,1,2

37

Parietal asssociation cortex associated with which Brodmann area?

5,7

38

Corticolubular tract is responsible for what?

fibers from the motor cortex to the cranial nerve motor nuclei

39

Vestibulospinal tract does what

Fibers originate from vestibular nuclei, terminate at the cervical and thoracic spinal cord levles to innervate neck and trunk muscles

40

Reticulospinal tract does what?

Fibers originate from neurons in the reticular system located diffusely in the brainstem. This tract along with the vestibulospinal tract terminates largely at the cervical and thoracic spinal cord level to innervate neck and trunk muscles

41

Rubrospinal tract

fibers originate in the red nucleus. Travels closely with the lateral corticospinal tract and participates in control of arm muscles.

42

Colliculospinal / tecto-spinal tract

Fibers originate from the superior colliculous. Terminates largely at the cervical spine to to innervate neck muscles. Coordinates head movements with eye movements

43

Normal plantar response to stroking the lateral side of the foot with a blunt object=

flexion of the big toe and sometimes other toes

44

Abnormal response to stroking the lateral side of the foot with a blunt object

Babinski sign...extension of the big toe and fanning of the other toes. means you have an upper motor neuron lesion, dawg

45

Lower motor neurons serving the extremities are located where in the ventral horn?

Laterally

46

Lower motor neurons serving the axial musculature located where

medial

47

motor unit=

a group of muscle fibers inervated by a single lower motor neuron (or alpha neuron). Motor units vary in size and their size is determined by the number of fibers that are innervated which is in direct correlation with size of the motor neuron.

48

When excitatory connections are made to motor neurons from afferents projecting above or below the spinal cord segment in which the motor neuron resides, the connection is through....

an excitatory interneuron!!!

49

Corticobulbar pathway

fibers from the motor cortex to the cranial nerve motor nuclei