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Motor Flashcards

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1
Q

What motor hemisphere do we use to write with the left hand?

A

The right motor hemisphere

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2
Q

How is the motor system organized?

A

Hierarchically
Cortex is at top of everything, the spinal cord on the bottom, with parallel pathways(lateral and ventromedial) descending from the cortex to the spinal cord sometimes passing through brainstem structures

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3
Q

Why is the motor system important?

A

It’s the basis of all the other systems in the brain?

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4
Q

Do muscles pull or push?

A

Muscles can only pull. They pull tendons which then pull bones

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5
Q

What is the center of rotation of the elbow called?

A

The fulcrum

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6
Q

When the bicep and Brachialis contract and the tricep relax, therefore pulling the forearm up, what is this called?

A

Flexion

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7
Q

When the tricep contracts and the bicep and Brachialis relax, therefore lowering the forearm, what is this called?

A

Extension

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8
Q

What are muscles(bicep and brachialis) that cooperate to increase force and movement called?

A

Synergist or agonist muscles

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9
Q

What are opposing muscles(bicep and tricep) called?
What happens when these muscles co-contract?

A

Antagonist muscles
When antagonist muscles co-contract, they stiffen a joint.
* Keep in mind that although these muscles are antagonists and can co-contract, when that happens they are both still PULLING, just in opposite directions causing the stiffening

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10
Q

What is the ability to know where one’s body is in space not necessarily with sensory input?

A

Proprioception

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11
Q

What causes an action potential in the muscle?

A

Action in the motor neuron

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12
Q

How fast are action potentials fired(in the motor system)?

A

20 times every second in both the axon and muscle fibers

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13
Q

What is the primary neurotransmitter of motor neurons?

A

Acetylcholine

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14
Q

How many neuromuscular synapses does each muscle fiber get input from?

A

Each muscle fiber gets input from ONE neuromuscular synapse, one alpha motor neuron

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15
Q

What are the two types of skeletal muscle fibers we primarily discuss in motor function?

A

Fast and Slow Twitch muscles

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16
Q

If you kept giving actinal potentials to fast with muscles, how long will the force diminish? What about slow twitch muscles?

A

Fast twitch(bigger, white) muscles fatigue rapidly and the force will diminish in about 1-2 minutes.
Slow twitch(smaller, red) muscles fatigue very slowly and the force will last for hours.

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17
Q

What type of muscle fiber has a fast build-up and loss of force(~ 25 ms), with lots of stored energy?

A

Fast twitch muscle fibers

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18
Q

What type of muscle fiber has a slow build-up and loss of force(~ 250 ms), with very little stored energy?

A

Slow twitch muscle fibers

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19
Q

Why do slow-twitch(endurance) muscle fibers have little stored energy and through which process do they generate energy?

A

Slow-twitch muscle fibers have a lot of mitochondria, however, they use oxidative metabolism to produce ATP which is a low process. Their large amount of mitochondria means they have fewer contractile proteins -> less power. Though the process is slow, they will never run out of ATP so they fatigue slowly.

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20
Q

Why do fast-twitch(sprinting) muscle fibers have little stored energy and through which process do they generate energy?

A

Fast-twitch muscle fibers have very few mitochondria and use glycolysis/anaerobic metabolism to produce ATP quickly-> more power. There is also more room for contractile proteins-> more power.

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21
Q

How is the number of fast/slow twitch cells that you have determined at birth?

A

Motor neurons in the spinal cords stimulate the muscle and that leads to more fast/slow composition

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22
Q

What is the primary purpose of the soleus muscle? The gastrocnemius muscle?

A

Both are located in the calf:
Soleud: Posture, endurance
Gastrocnemius: flex knee and foot, has many uses

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23
Q

Where are alpha motor neurons located?

A

Ventral horns of the spinal cord

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24
Q

Another name for alpha motor neurons

A

lower motor neuron

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25
From the ventral horn, where does the motor neuron leave or send out its input to the muscle fiber?
It leaves through the ventral root(motor axons)
26
What is a motor unit?
A motor unit is the smallest unit of muscle that can be controlled by the central nervous system. It comprises one alpha motor neuron and all the muscle fibers that it innervates. One motor unit either activates fast or slow twitch muscles but never both
27
What is the relation between a motor unit and its size?
A smaller motor unit is usually used for a very small and precise movement that does not require a lot of force. A large motor unit is usually used for gross movements that do not require precision. The average size is about 10 fibers per unit.
28
What is a motor neuron pool?
All alpha motor neurons that innervate one muscle
29
What happens when motor neurons are dying?
Fasciculations; You will experience injury discharge where the body fires uncoordinated action potentials and you then involuntarily move/twitch.
30
How do motor neurons determine muscle force?
1)The firing rate of active motor neurons 2)The number of active motor neurons: "recruitment" -> both are directly proportional to the power needed
31
What controls the alpha motor neurons?
Controlled by inputs from the muscle, spinal cord, and brain 1) Group 1a and 2 sensory axons: Direct Sensory Input from spindles and it is the fastest 2) Input from spinal interneurons then goes to alpha motor neurons 3) Supraspinal: Input from Upper Motor Neurons(in the brain), this directly controls the alpha motor neurons * if Input from Upper Motor Neurons did not work, you can still receive input to initiate movement with the first two ways
32
What are two mechanosensory endings that muscles use to sense movement?
1)Force measurement with the Golgi tendon organs 2)Length measurement with muscle spindles/stretch receptors
33
How do the Golgi Tendon Organs sense movement?
They sense movement through the force that is generated by the muscle. Provide inhibitory feedback control of muscles The tension in the collagen fibers within the tendon increases when the muscle contracts and this pinches on the axons and causes more action potentials. This is associated with group 1B axons
34
How do the Muscle Spindles/Stretch Receptors sense movement?
They sense movement through very small changes in the length of the muscle sensed by the spindles. this is associated with 1A axons.
35
What are stretch receptors known for?
They are known for reflexes like the knee-jerk(the muscle retracts and causes the jerk)
36
Why do we have reflexes?
To correct an unexpected error, and to inhibit the antagonistic muscle movement
37
What are Extrafusal muscles fibers for?
these fibers are responsible for generating force and shortening the muscle length, are innervated by alpha motor neurons
38
What are Intrafusal muscle fibers for?
these are responsible for sensing small changes in length and stretch down to the mm; regulating the sensitivity of spindles. Contractile elements on the ends are able to contract/relax as the muscle shortens/lengthens. Note: muscle contraction with no change in the muscle tone in the intrafusal fibers would go slack and the organ would be left dangling
39
What do gamma motor neurons do?
They help keep the proper amount of tension and innervate the contractile elements of the intrafusal fibers. When the muscle shortens, Gamma fires more action potentials so it tenses
40
What is the stretch reflex?
a monosynaptic reflex; it uses a single synaptic relay in the central nervous system(all other reflexes are polysynaptic)
41
What happens when nociceptors in the right foot are activated when stepping on something sharp?
Signals are sent to the spinal cord which activates the alpha motor neurons innervating flexor muscles in the right foot to pull the foot away and flex it. Simultaneously, signals are sent to the spinal cord to activate the extensor muscles in the left foot so that you do fall over and action potentials are sent up the spinal cord to shift the center of gravity to the other side
42
Where are upper motor neurons? And what type of movement do they associate with?
Upper motor neurons are above the level of the spinal cord (brain stem and cortex). They are associated with voluntary movement, whereas our reflexes are thanks to our alpha motor neurons
43
Which part of the brain handles strategy?
The higher-order "association" areas of the cortex, basal ganglia Area 6: SMA, PMA
44
What are the components of Area 6 of the motor cortical areas?
Supplementary Motor Area Premotor Area -> important for planning of movements, generating intent to move and converting plan to action
45
Which part of the brain handles tactics?
The motor cortex and cerebellum Area 4: primary motor cortex M1
46
Which part of the brain handles execution?
brainstem, cerebellum, and spinal cord
47
What type of loop are the Basal Ganglia and Cerebellar loops?
Feedback loops
48
What is the process/purpose of the lateral pathway?
Contains the corticospinal tract and descends down lateral sections of the spinal cord, controls lateral muscles; alpha motor neurons that innervate muscles in the hands and feet(distal muscles). Associates with voluntary movement
49
what is the process/purpose of the ventromedial pathway?
Control muscles dealing with posture, gait, balance and head position, axial/girdle muscles like torso, hip shoulders, more midlines, vestibular systems
50
where does the ventromedial pathway originate? Where does it collect information from?
the brainstem superior colliculus, cerebellum, vestibular nucleus
51
What is a decussation?
the crossing of nerve fibers
52
Damage to the left side if the brain stem above or anywhere rostral to the medulla will leave you with motor difficulties on what side?
The right side
53
Another name for the pyramidal tract?
The corticospinal tract
54
What pathway decussates at the caudal medulla, starts in the primary motor cortex and has contralateral control?
The lateral pathway
55
What did the Per Roland PET study show?
Different parts of the motor area lights up, showing an increase in activity depending on the different stages of movement ie. thinking of moving, planning/intending the moving, then executing the move. When executing voluntary movement, there is activity in M1 and S1 When moving in a more complex way, sequence of movement, the M1,S1 and SMA lights up When just thinking about moving, the SMA lights up
56
What is paresis?
weakness, low speed, power and agility
57
What is plegia?
paralysis(inability to move)
58
What is Hemiplegia?
Typically damage to the lateral pathway(distal muscles) so the ventromedial pathway is fine(girdle muscle) Hemi: half/one side The inability to move or weakness on one side
59
What is spasticity?
Hypertonia: muscles are too tense Hyperreflexia: exaggerated reflex response(involuntary) clonus: reflexes are out of control and you're fighting yourself to move
60
What does sign of Babinski tell us about someone's spinal motor tract?
Postive:(the toes splay ou) means the patient is either a infant younger than 2 with a developing Corticospinal tract or the adult patient has damage to their CST. Negative: (toes curl in) means the adult patient has a healthy CST
61
What is the input and out of the cerebellum
Input: Motor Control Output: to premtor and motor system in the cerebral cortex and brainstem that are areas of direct spinal cord control
62
How does the cerebellum modulate motor learning?
Since the cerebellum is key to the execution of movement, it modulates learning by modifying synaptic circuits/connections to allow for adapting ex. dancing' it can remove the extraneous motor commands that causes stiffness in dancing and allow for smoother movements
63
What are the three layers of neurons of the cerebellum? that are made of layers of
Molecular, Purkinje, and Granule cell layers
64
Is the motor control in the cerebellum contralateral or ipsilateral?
Ipsilateral; the left cerebellum coordinates movement to the left side of the body
65
Consuming alcohol can affect the cerebellum, how does this affect someone's motor function?
If cerebellum function is interrupted then coordination, balance and more will then be affected
66
What are the steps of the cerebellar loop?
1) Sensorimotor Cortx(A4/6, S1, PPC): the pyramidal cells project to the pons(pontine nuclei) 2)Pontine nuclei projects to the contralateral cerebellum from the cortex 3)The lateral cerebellum projects back to the VLc (thalamus) then to the ipsilateral cortex L cortex-> R cerebellum->L cortex -> R Motor control
67
What is ataxia?
poor condition of voluntary movements, disruption of timing and spatial accuracy slow to begin and end movement sign of cerebellar damage Intention tremor: not at rest, but a tremor when doing voluntary movement disrupted balance
68
What is megalographia?
large handwriting
69
What is hypotonia?
pendular knee jerks
70
What makes up the basal ganglia?
the substantia nigra, subthalamix nucleus, claudate nucleus, putamen-> tg is the Striatum, globus pallidus
71
Steps of the Basal Ganglia loop?
1) Large areas of cortex input/project down to the caudate and putamen 2) Putamen/Caudate projects to the Globus Pallidus 3) GP projects to VLo Thalamus 4) Thalamus projects back to motor/premotor cortex especially SMA
72
What does Hypokinetic mean?
low movement(ex. Parkinsons deisease, despite rresting tremor)
73
What does Hyperkinetic mean?
excessive movement
74
The Basal Ganglia Circuit involves a double negative, inhibiting an inhibitor, with that said, what are the steps of this circuit?
1) Cortex excites the striatum 2) Neurons in putamen release GP neuron inhibitors 3) GP releases Thalamus inhibitors 4) Thalamus excites motor cortex the Putamen inhibits, the inhibitory neurons released from the GP so that the thalamus can excite the cortex and allow movement
75
How is the BGC modulated?
Substantia Nigra: excites the neurons in the Putamen that inhibits the inhibitory neurons of the GP so there's more movement so loss of SN will results in hypokinesia Subthalamic Neurons: excites the inhibitory neuron in GP so there's less movement, loss of SN will result in hyperkinesia
76
Why is dopamine inportant?
Dopamine from substantia nigra is partly responsible for regulating the loop; its loss causes Parkinsons Disease
77
What are some treatments for Parkinson's Disease?
l-dopa; gets converted to dopamine and more dopamine means more balance, deep brain stimulation etc,
78
what are some symptoms of Parkinson's Disease?
asymmetric resting tremor, bradykinesia, rigidity, masked face, stooped posture, shuffling gait, dementia

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