Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Block 5; Week 3 > Kenyon1-Motor Neurons > Flashcards

Kenyon1-Motor Neurons Flashcards

1
Q

What is a lower motor neuron? Where are their cell bodies found?

A

these are neurons that innervate muscle directly. axons end in neuromuscular jcns w/ skeletal muscle fibers.
cell bodies are found in brainstem or spinal cord
**they just tell the muscle what to do & it has no choice.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What NTs & receptors are involved in the neuromuscular jcns of lower motor neurons?

A

Ach is the NT

Nicotinic Receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where are the cell bodies of upper motor neurons found?

A

brainstem or cerebral cortex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What do upper motor neurons synapse with?

A

upper motor neurons OR
lower motor neurons OR
local circuit neurons
OR a combination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Is it excitatory or inhibitory?
Lower motor neurons:
Upper motor neurons:

A

Lower motor neurons: excitatory

Upper motor neurons: excitatory or inhibitory or both

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

If you see a neuron in the brainstem synapsing with a lower motor neuron–>it could be 1 of 2 things. What are your options?

A

Upper Motor Neuron

OR Local Circuit Neuron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Upper motor neurons descend from the motor cortex or the brainstem. What is the motor cortex involved in? Brainstem?

A

Motor cortex: planning, initiating, & directing voluntary movements.
Brainstem: basic movement & postural control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The UMN descend & communicate with which 2 things? which is a more major pathway? Is this excitatory or inhibitory?

A

Local Circuit Neurons (major pathway)
Lower Motor Neurons (minor pathway)
Can be excitatory or inhibitory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What do the local circuit neurons do? Is this excitatory or inhibitory?

A

they synapse with the LMN

can be excitatory or inhibitory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What do the LMN do? Is this excitatory or inhibitory?

A

they synapse @ the neuromuscular jcn w/ the skeletal muscle
this is excitatory always.
If the LMN are inhibited, no excitation of the skeletal muscle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Sensory inputs go to which things in the general pathway?

A

to the local circuit neurons & LMN
so essentially to both types of motor neurons…
also go to the cerebellum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

T/F The local circuit neurons & LMN are located far apart.

A

False. they are close together.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What do the basal ganglia contribute to the descending systems?

A

they gate proper initiation of movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does the cerebellum contribute to the descending systems?

A

sensory motor coordination of ongoing movements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

So…we know that the LMN control the movements of the skeletal muscles. But where are they located really?

A

When they are found in the spinal cord: they are in the ventral horn!
When they are found in the brainstem: found in somatic or branchial motor nuclei

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

The LMN that control the skeletal muscles of the body are found where?

A

in the ventral horn of the spinal cord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The LMN that control the skeletal muscles of the head are found where?

A

in the somatic & branchial motor nuclei of the brainstem

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Which lower motor neurons are found in the somatic motor nucleus in the brainstem?

A

Oculomotor
Trochlear
Abducens
Hypoglossal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Which lower motor neurons are found in the branchial motor nucleus in the brainstem?

A

Trigeminal
Facial
Ambiguus
Spinal Accessory Nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Once again, aside from the brainstem…where do you find the upper motor neurons?

A

In the cortex
Primary Motor Cortex & Premotor Cortex
Cingulate Gyrus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the function of the primary motor cortex & premotor cortex in terms of UMN?

A

planning, initiating, and directing series of movements in limbs & eyes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Where would you find the UMN for a lower limb in the premotor cortex or primary motor cortex?

A

you find this in the medial portion of the cortex.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Where would you find the UMN for an upper limb in the premotor cortex or primary motor cortex?

A

you would find this in the lateral portion of the cortex.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

The fcn of the cingulate gyrus with respect to UMN is what?

A

expression of emotions especially with facial muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Where exactly are upper motor neurons found in the brainstem? What is their corporate function?

A 
Vestibular Nuclei
Reticular Formation
Superior Colliculus
**regulate muscle tone
**orient eyes, head, body with respect to incoming info.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

From the brainstem, what direction do the UMN go?

A

they project medially & inferiorly to the cervical spinal cord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Which is located more laterally in the brainstem…the vestibular nuclei or the reticular formation?

A

the vestibular nuclei

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Cerebellar neurons influence the activity of which types of neurons? What is the function of the cerebellum?

A

they influence the activity of UMN
**they compare actual movement via proprioceptive input to intended movement & command corrections.
They basically modulate ongoing movements

29
Q

The basal ganglia are responsible for what situation in Parkinson’s? In Huntington’s?

A

Parkinson’s hypokinetic–not enough wanted movements.

Huntington’s hyperkinetic–too many unwanted movements.

30
Q

What is the function of the basal ganglia?

A

initiation of movements

suppression of unwanted movements

31
Q

Which structures make up the basal ganglia? Where is it found?

A 
found in the forebrain
made of forebrain nuclei including: 
caudate
putamen
globus pallidus
substantia nigra
subthalamic nucleus
32
Q

What do local circuit neurons basically do?

A

they basically receive input from UMN & sensory neurons & excite or inhibit lower motor neurons.

33
Q

Describe the relative position in the spinal cord of LMN that are controlling distal muscles v. proximal muscles.

A

Distal Muscles–Located Laterally in Spinal Cord

Proximal Muscles–Located Medially in Spinal Cord

34
Q

Compare & contrast local circuit neurons that control posture v. those that control limbs.

A

Posture: They are located medially in the spinal cord. They have long projections & commissural axons. They control a larger set of muscles.
Limbs: They are located laterally in the spinal cord. They have short projections. They control a limited set of muscles.

35
Q

Where are the axons of UMN that control limbs found in the spinal cord? Do they cross over pyramids on their journey?

A

they are found laterally near the local circuit neurons they project to…
they are found in the lateral white matter–>here there is the lateral corticospinal tract
**they do cross over pyramids on their journey

36
Q

Where are the axons of UMN that control postured located in the spinal cord? Do they cross over pyramids on their journey?

A

they are found in medial white matter (closer to the local circuits that they communicate with)
Here in the medial white matter you can find: Reticulospinal, Vestibulospinal, & a little Ventral Corticospinal Tracts
**don’t cross over the pyramids on their journey.

37
Q

What is a motor unit?

A

the motor neuron & its muscle fibers

LMN innervates 3-3000 muscle fibers

38
Q

Where are the LMN for a given muscle found?

A

clustered in the ventral horns in one or more spinal segments

39
Q

T/F LMN are found in organized arrangements in the muscles they control.

A

False. They are found scattered throughout the muscles they control.

40
Q

Which of the following is a ratio of LMN to muscle fibers for an eye muscle & which is for the gastrocnemius?

1: 2000
1: 3

A

1: 3 eye muscle–fine control
1: 2000–gastrocnemius

41
Q

T/F The motor neuron type is matched perfectly with the type of muscle fibers it innervates.

A

True. Different motor neurons used for fast fibers v. slow fibers.

42
Q

What are the 3 flavors of motor units?

A

Slow motor units
Fast Fatigable Motor units
Fast Fatigue-Resistant Motor units

43
Q

When you see red muscle–think which type of motor unit? When you see pale muscle?

A

Red Muscle–think slow motor units

Pale Muscle–think fast fatigable motor units

44
Q

So…if you were making a human body & deciding which motor units to put in the posture muscles…which would be your first choice? 2nd? 3rd?

A

1st Choice: Slow fibers (can be continuously active w/o tiring)
2nd Choice: Fast Fatigue Resistant Fibers
3rd Choice: Fast Fatigable Fibers (best for large forces of short bursts)

45
Q

Describe how the various motor units perform in terms of force generated & time at 100% of maximum force.

A

Slow Fibers: Not much force, best at staying at 100% for a long time!
Fast Fatigue-Resistant Fibers: Medium force, medium capacity to stay at 100% for a small period
Fast Fatigable Fibers: Greatest force, lowest capacity to stay at 100%

46
Q

As the synaptic activity driving muscle contraction increases…say going from standing to walking to running to jumping…what happens to fiber recruitment?

A

Start at slow, move next to fast fatigue-resistant & finally fast fatigable.

47
Q

What are the 3 feedback systems in the spinal cord that help control muscle length & tension?

A

Muscle Spindles
Golgi Tendon Organs
Flexion Reflex–helps you to move away from danger in periphery

48
Q

What do muscle spindles help you to control? Which reflex are they involved in?

A

help you to control muscle length
deep tendon reflex aka stretch reflex aka myotatic reflex
**muscle tendon receives a blow & the muscle stretches.

49
Q

What do golgi tendon organs help you to control?

A

help you to control muscle tension

50
Q

You start off with sensory info from the muscle spindle…how do you eventually get a muscle twitch?

A

muscle spindle sensory–>spinal cord–>muscle twitch

51
Q

Which type of motor neuron innervates the muscle spindles?

A

gamma motor neurons (as opposed to alpha motor neurons)

they innervate 8-10 specialized intrafusal muscle fibers in proprioception

52
Q

Which type of motor neuron innervates the body of the muscle itself?

A

the alpha motor neurons

53
Q

what is the muscle spindle wrapped in?

A

fast Ia primary afferent neurons

54
Q

So…the Ia afferent sensory neurons from the muscle spindle give proprioceptive info…they come back towards the spinal cord & can go 2 ways according to the TVP pathway. Explain this.

A

Get back to the spinal cord & will go up to the cuneate & gracilis nuclei so that we have knowledge of where our muscle is…
Also involved in reflex @ the spinal cord level.
Activates an alpha neuron that acts on that muscle.
Activates a motor neuron to a synergist muscle.
Activates local circuit neuron to inhibit antagonist muscles.

55
Q

What will stretching a muscle do to 1a afferent activity?

A

It will increase it.

56
Q

What would happen if you activate the alpha motor neuron to a muscle w/o activating the gamma motor neuron to its muscle spindle?

A

this would be bad.
1a afferent input would shut down as the muscle contracted & shortened
bad b/c cerebellum needs to receive proprioception!

57
Q

What happens when the alpha motor neuron & the gamma motor neurons are activated together?

A

this causes the muscle to contract/shorten & the spindle to shorten. Never lose 1a afferent info.
good b/c control center needs to know what’s going on!

58
Q

What determines the activity of gamma motor neurons? Hint: same thing that determines activity of lower motor neurons.

A

Upper Motor Neurons

59
Q

When would you have low & when would you have high muscle spindle sensitivity & gamma activity?

A

Low Muscle Spindle Sensitivity/Low Gamma Activity:
low activity levels, sitting etc.
High Muscle Spindle Sensitivity/High Gamma Activity:
standing on a moving bus or skiing (need to make sure that the muscles stay the appropriate length)

60
Q

T/F YOu should keep a pretty constant output of info from the 1a afferents. And if you don’t–you know there is a problem.

A

True.
then you would know there is too much stretch of the muscle & i must adjust something–let’s synapse with some alpha neurons.

61
Q

What is a Golgi Tendon Organ?

A

this is found in b/w a tendon & a muscle
it is encapsulated afferent nerve endings of 1b fibers.
they are activated by tension from muscle contraction

62
Q

T/F GTO are equally activated by muscle tension created by muscle contraction & by passive stretch.

A

False. Weak response to passive stretch. STrong to muscle contraction.

63
Q

What will muscle contraction due to afferent activity of muscle spindles & GTO?

A

Muscle Spindles: afferent activity will be decreased

GTO: afferent activity will be increased

64
Q

Describe the afferent pathway from the GTO.

A

afferent 1b fibers from GTO travel to the dorsal horn of the spinal cord & DON’T synapse.
Parts of it ascend via the TVP pathway to the cortex.
Other parts participate in a protective reflex.
It synapses with a local circuit interneuron to inhibit the homonymous muscle & activate the antagonist muscle. This will cause a person to drop whatever they are holding if they weight becomes so heavy that it affects the GTO.
**there are also descending pathways from UMN that affect this reflex-not closed loop.

65
Q

What is the flexion reflex pathway? What is another name for this?

A

aka somatosomatic reflex pathway
**step on a nail and you hop off right away as a reflex!
Pain–>DRG–>Dorsal horn–>synapses–>crosses to go to the cortex as the anterolateral tract.
Interneurons in the spinal cord also activate the flexor on the nail side & the extensor on the other side. Interneurons inhibit the extensor on the nail side & the flexor on the other side.

66
Q

Is the flexion reflex pathway the same as the tomato-somatic reflex?

A

NO

67
Q

What’s the deal with the cat on the treadmill?

A

the cat’s spinal cord was sectioned, and yet it is still able to walk on the treadmill as a reflex & its extensors & flexors alternate properly.
don’t know how it works–lesion to dorsal horn & it still works.
shows how complex reflexes can be.

68
Q

What’s the deal with lower motor neuron syndromes?

A

you can lose LMNs at the spinal cord & periphery (probably in the brainstem too)
get paralysis of the muscle it innervated
paresis (weakness)
areflexia
loss of tone
atrophy
single muscle fiber twitches (fibrillations, fasciculations)

Block 5; Week 3 (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions