1
Q
What are all the extra ocular muscles?
A
lateral and medial recti
superior and inferior recti
superior and inferior obliques
2
Q
What extraocular muscles are responsible for horizontal eye movements?
A
lateral and medial recti
3
Q
What extraocularmuscles are responsible for vertical eye movements when eyes look straight ahead?
A
to look up: superior rectus and inferior oblique
to look down: Inferior rectus and superior oblique
4
Q
What extraocular muscles are responsible for vertical eye movements when eyes are abducted?
A
to look up: superior rectus
to look down: Inferior rectus
5
Q
What extraocular muscles are responsible for vertical eye movements when eyes are adducted?
A
to look up: inferior oblique
to look down: superior oblique
6
Q
Which extraocular muscles are controlled by abducens nerve? Is the connection ipsilateral or contralateral?
A
lateral rectus
ipsilateral
7
Q
Which extraocular muscles are controlled by trochlear nerve? Is the connection ipsilateral or contralateral?
A
superior oblique
contralateral
8
Q
Which extraocular muscles are controlled by oculomotor nerve? Is the connection ipsilateral or contralateral?
A
medial and inferior recti and inferior oblique (ipsilateral)
superior rectus (contralateral)
9
Q
Which extraocular muscles are controlled contralaterally?
A
Superior rectus and superior oblique
10
Q
What are the 5 types of eye movements?
A
Saccade
Smooth pursuit
Vergence
VOR
OKR
11
Q
When is gain of VOR higher, at fast or slow movement?
A
fast
12
Q
When is gain of OKR higher, at fast or slow movement?
A
slow
13
Q
What is the delay between the target moving and the saccade to the target?
A
200ms
14
Q
What is a near reflex triad?
A
reflexes that take place when we shift our gaze from far to near object
1. Convergence
2. Increased lens curvature
3. Pupillary constriction
15
Q
What needs to be encoded for accurate saccades? How is this info encoded?
A
amplitude -> duration of neuronal activity
direction -> activation of a particular gaze centre in reticular formation
16
Q
What is optokinetic nystagmus?
A
switch between saccades and smooth pursuit
e.g. when a train moves past)
17
Q
What brain areas are known as gaze centers? What eye movement does each encode?
A
Paramedian pontine reticular formation (PPRF) for horizontal eye movements
Rostral interstitial nucleus for vertical movements
Vergence gaze centre
18
Q
What is the function of superior colliculus? What about the eye movement does superior colliculus encode?
A
Reflexive saccades and head movements
Encodes movement coordinates, regardless of initial position of an eye (place code)
19
Q
What is the function of frontal eye field?
A
Voluntary saccades, scanning of visual field, inhibiting saccades to distractors
20
Q
To which part of a visual field are saccades more precise?
A
in the centre
21
Q
What happens to the activity of a neuron in frontal eye field with regards of how far is the target from the response field of a neuron?
A
target in response field -> strong response
target close to response field -> very weak response
target far from response field -> moderate response
22
Q
Describe the pathway from frontal eye field to extraocular muscles for horizontal movements
A
FEF -> superior colliculus (ipsi) -> + -> PPRF (contra) -> + -> abducens nucleus (ipsi) (and -> - -> abducens nucleus (contra)) -> + -> lateral rectus (ipsi)
ALSO Abducens nucleus -> + -> oculomotor nucleus (contra) -> medial rectus
23
Q
What happens after an injury to FEF?
A
can’t make saccades to contralateral side
Can’t redirect gaze from a salient stimulus
24
Q
What happens after an injury to superior colliculus?
A
increased delay and decreased accuracy, frequency and velocity of saccades
25
What is necessary for an accurate movement? What are the steps?
plan based on:
sensory input from environment, knowledge of the world and the body and feedback
1. locate hand and object
2. plan (endpoint)
3. inverse kinematics (what motion in necessary)
4. inverse dynamics (what forces are necessary)
5. execute
26
What is kinematics?
motion (what)
position, velocity, acceleration, joint angels, muscle length
27
What is kinetics?
forces (how)
muscle forces and joint torques that cause motion
28
What is inverse kinematics?
have an endpoint, calculate what movement is necessary to get there
29
What is inverse dynamics?
have an endpoint, calculate what torques and forces are necessary to get there
30
What are upper motor neurons?
originate from M1 and project to:
brainstem
spinal cord
31
What are lower motor neurons?
originate from brainstem or spinal cord and project to muscles
32
What is an internal model of movement?
desired behavior -> inverse model -> motor command -> actual behavior
after motor command, efference copy -> forward model -> predicted behavior and sensory consequences
Ideally predicted behavior matches actual behaviour
33
What causes movement errors?
variability in sensory or motor inputs, errors in internal representation
34
What is feedforward control of movement? What are its properties?
Desired state -> forward controller (inverse model) -> motor command -> actuator muscle
- open loop
- no delay
- simple movements only
- no correction during the movement (ballistic), only the next trial
35
What is feedback control of movement? What are its properties?
Desired stare -> comparator -> forward controller (inverse model) -> motor command -> actuator muscle -> sensor (muscle spindle) -> input processing -> sensed state -> comparator
- slow
- delay
- prediction can be implemented
- proportional error-correction
- feedback only becomes available during the movement, not before initiation
36
Where are the LMNs controlling skilled limb movements located in spinal cord? What are the characteristics of local circuit neurons?
lateral ventral horn -> UMN axons descend in lateral white matter
Short-distance local circuit neurons
37
Where are the LMNs controlling posture and balance located in spinal cord? What are the characteristics of local circuit neurons?
medial ventral horn -> UMN axons descend in medial white matter (easier bilateral communication)
Long-distance local circuit neurons + bilateral connections for better coordination
38
How many motor nerve endings can innervate 1 muscle fiber?
Just one
39
What is a motor unit?
One motor neuron that innervates multiple muscle fibers
40
What is an innervation number?
hoe many fibers are innervated by 1 motor neuron
Bigger number -> muscles that require a lot of force
Smaller number -> muscles for fine movement
41
How does EMG work?
detects summed currents of motor units during muscle contraction
42
What are the 3 types of motor units and their properties?
1. Slow -> small neuron, slow contraction, little force, fatigue resistant
2. Fast fatigue resistant -> bigger neuron, fast contraction, moderate force
3. Fast fatigable -> big neuron, fast contraction, large force
All fibers are intermingled in a muscle
Recruited in order 1-3 -> smaller neurons (s) need less stimulation to get excited -> Henneman's size principle
43
What happens to muscle fibers during training?
muscle fiber can bet bigger, change (become more fatigue resistant), firing properties can change
During strength training:
- increased capabilities of myosin
- more contractile proteins
- more ff fibers
During endurance training:
- more mitochondria
- more oxidative capacity
- more fr fibers
44
What are the 3 basic spinal reflexes?
stretch, muscle tension and flexion
45
What are the 2 main types of motor neurons? What are their functions?
alpha-motor neuron -> innervates extrafusal fibers, turn the muscle on (produce force) -> afferent signal disappears after stretch becomes constant
gamma-motor neuron -> innervates intrafusal fibers, sense continuous muscle stretch, reinforce alpha-neuron activity
46
Describe stretch reflex
muscle spindle monitors passive stretching
more load is added on the muscle -> spindle stretches -> signal to contract the muscle more
monosynaptic
negative feedback loop btw motor and sensory neurons
47
Describe muscle tension reflex
Golgi tendon organ senses increase in force
when force is too strong -> relax the muscle to protect from rupture + activate antagonist muscle
polysynaptic
48
Describe flexion reflex
withdrawal from painful stimulus
together with crossed-extension reflex
polysynaptic
49
Where can reflex strength be modified?
alpha-motor neuron
interneurons
sensory axon terminals
50
Is there convergence or divergence in spinal reflexes?
convergence of sensory input on a few motor neurons
necessary for precise spinal control
51
What is spasticity?
exaggerated stretch reflex due to UMN lesion (hyperreflexia)
rigidity
52
Which spinal reflex is modulated by the brain stronger than others?
Stretch reflex -> monosynaptic
53
What happens to spinal reflexes after SC lesion?
Abnormal muscle tone (hyper/hypotonus) -> spasticity
Immediately after: reduced reflexes
Gradually come back (exaggerated)
54
What are the 4 types of neuromuscular disorders?
motor neuron disorder
axonopathy
NMJ disorder
muscle disorder
55
What is myasthenia gravis?
autoimmune NMJ disorder
nicotinic receptors blocked by antibodies
affected muscles depend on antibody type
56
What type of motor neurons is tonically active?
S
57
What type of motor neurons is phasically active?
fr/ff
58
What determines properties of a muscle fiber?
firing properties of the motor neuron that innervates that fiber
59
What can change the type of muscle fiber?
Denervation + reinnervation by a different motor neuron
altered activation pattern of a neuron
altered stimulation on a neuron
60
Which type of motor neuron is more likely to survive the longes in ALS? Which degenerate first?
S
due to reinnervation most muscle fibers become s fibers (homogenous)
ff degenerate first
61
What happens in neuropathy?
less motor units
larger motor units
spontaneous activation (twitches)
more force at slight contraction, less force at prolonged stimulation
62
What happens in myopathy?
less fibers
less force
63
What is the typical pattern of degeneration in muscular dystrophy?
proximal muscles degenerate first
distal muscles preserved -> compensatory growth
64
what is the role of dystrophin protein? what happens when its not functioning properly?
keeps muscle fibers attached to each other
mutation in dystrophin gene in Duchenne muscular dystrophy
patients suffer from contraction-induced injury
65
How is contraction-induced injury normally healed? What happens in DMD?
satellite cells and muscle stem cells help muscle regrow
in DMD these are lost
66
What are UMN symptoms in ALS?
hyperreflexia
spasticity (inc. muscle tone)
widespread impairment of fine motor movement
weakness, no atrophy
67
What are LMN symptoms in ALS?
weakness, atrophy, no muscle tone
spontaneous twitches of denervated fibers
loss of reflexes
geographic impairmant
68
What is walking composed of?
Stance phase (60%)
Swing phase (40%)
Alteration btw flexion and extension
flexion -> beginning of swing phase
extension 1 -> end on swing
extension 2 -> beginning of stance
extension 3 end of stance
69
What happens to cat walking if lesion is above brainstem?
cat can still walk spontaneously
intact connection between mesencephalic locomotion region and the spinal cord
70
What happens to cat walking if lesion is below brainstem?
can't walk spontaneously, but can perform rhythmic stepping
e.g is lesion btw the front and hind paws, hind paws can walk following the lead of front paws
71
What are the central pattern generators in spinal cord? How do they work?
Mutually inhibiting half-centers -> alteration btw flexion and extension within one leg
When extension interneuron is activated it activates the corresponding extension motor neuron and simultaneously inhibits flexion interneuron, so flexion motor neuron is also silent
72
What activates the central pattern generators in spinal cord?
descending pathways or muscles (proprioceptive fibers)
stretch of a muscle spindle in the hip inhibits knee extension and activated knee flexion
73
What brain regions control spinal locomotion region? What is their function?
Visual cortex -> visual feedback -> signals sent to motor cortex
Mesencephalic locomotion region -> initiates the movement and controls speed/pattern (walk vs. gallop) -> projects to medial reticular formation
Cerebellum -> adjusts motor pattern based of feedback -> fine tuning
74
Where are visuomotor transformations of walking performed? What happens there when an obstacle is seen?
in Area 5 in posterior parietal cortex
e.g. activity increases when need to lift leg higher due to obstacle
Area 5 has memory for hind limb -> is lesioned, animal will forget about an obstacle and hit it with leg
75
What is transmitted thru medial white matter in spinal cord?
Axons from UMNs from brainstem for axial and proximal limb muscles controlling posture, balance and locomotion (ipsi and contralateral)
76
What is transmitted thru lateral white matter in spinal cord?
Axons of UMNs from motor cortex for distal limb muscles controlling skilled movements
77
What cortical regions control movement?
M1, premotor cortex, supplementary motor area, cingulate motor area
78
How are kinematics and kinetics encoded?
Separately in M1
Kinetics -> more firing when more force is needed
Kinematics -> firing at preferred direction -> tuning curve (broad -> many neurons needed to encode direction correctly)
This is known as population code -> directional analysis -> sum of all vectors = encoded direction of an arm
79
What is a motor map?
dynamic recruitment of neurons in M1 -> based on learning (becomes more efficient) -> adaptation code (changes in firing)
80
What is the role of parietal cortex in voluntary movement?
where pathway -> spacial awareness
sensory guidance of action (independent form pure perception -> illusion with circles)
Affordances of an object and visuomotor transformations (inferior parietal) -> contains different neurons for manipulation in the dark/light, manipulation of different shapes and just looking at the object that can be manipulated
Also different neurons for goal of action (put in container vs put in mouth) even if the movement (eg. grasping) is the same. Some neurons tho respond to both (executing)
81
What is the role of premotor cortex in voluntary movement?
intention to act, encode abstract representations of action (eg. not mentioning what hand is to be used)
externally guided planning
rule-dependent activity -> which action is appropriate given the current rule and sensory input
contains mirror neurons -> same activity when others are doing the action and u doing the same action yourself
82
What is the role of supplementary motor cortex in voluntary movement?
plans, sequences, and initiates voluntary movements that are internally generated (not dependent on external stimuli)
urge to move, readiness potential/intention
selection and execution of movements
active before and during the movement
if lesioned, problems initiating or suppressing movements
83
Motor neurons with cell bodies in the cerebral cortex or the brainstem are part of which motor system?
UMNs
84
Upper motor neurons synapse on local circuit neurons and/or lower motor neurons
T/F
true
85
what is a motor pool?
all of the motor neurons that project to a given muscle
86
Local circuit neurons that run the entire length of the spinal cord and connect the medial parts of the spinal cord gray matter are primarily involved in which type of movement?
Postural control
87
_______ innervate striated muscle fibers, and _______ innervate specialized fibers called _______.
α motor neurons; γ motor neurons; muscle spindles
88
Compared to the general population, weightlifters would be expected to have a higher ratio of which motor unit(s) in their legs?
ff
89
Asynchronous firing of motor neurons provides a means by which a population of motor neurons can maintain constant force over a finite time interval
T/F
true
90
Which neurons coil around the middle of intrafusal fibers?
Group I
91
Which part of the lower motor neuron circuit prevents muscles from generating excessive tension and maintains steady muscle tone during muscle fatigue?
Golgi tendon organs
92
During the flexion-crossed extension reflex, stimulation would lead to _______ of ipsilateral flexor muscles and _______ contralateral flexor muscles
excitation; inhibition of
93
What is pallidum?
globus pallidus and the substantia nigra pars reticulata
94
The major outputs of the basal ganglia are from the putamen.
T/F
true
95
Increased activity from the _______ to the subthalamic nucleus increases the _______ input to the VA/VL complex of the thalamus.
cerebral cortex; inhibitory
96
D1 and D2 receptors are _______, with D1 receptors _______ cAMP and D2 receptors _______ cAMP.
metabotropic; increasing; decreasing
97
Dopamine is released into the striatum from the substantia nigra pars compacta. Which neural response would you expect to see?
Activation of the frontal cortex by activating the direct pathway and inhibiting the indirect pathway
98
Upper motor neurons in the cerebral cortex are located in which lobe(s) of the brain?
Frontal
99
What is Spike-triggered averaging?
correlating upper motor neuron activity with muscle activation
100
Which motor area of the brain receives extensive multisensory input from the parietal and frontal lobe?
Premotor cortex
101
Where are mirror neurons located in the brain?
in the ventrolateral portion of premotor cortex
102
What is a muscle field?
group of muscles whose activity is directly facilitated by a given upper motor neuron
103
What type of movement can activation of the superior rectus muscle result in>
elevation and intorsional movement
104
Which of the 2 (saccades vs. smooth pursuit) are initiated faster; and which one is faster while its happening?
smooth pursuit movements are initiated faster
saccades are faster
105
Oculomotor neurons encode eye position and eye velocity signals. Why an eye position signal?
preventing the eye to return to start position
106
Activation of the right PPRF leads to which eye movements?
both eyes to the right
107
How are the upper motor neurons in the superior colliculus organized?
As a topographical map of eye movement vectors
108
Each movement-related neuron in the superior colliculus has a movement field. What is a movement field of a neuron?
neuron controls the saccades to that visual field
109
Which brain region is this statement about:
Visual neurons respond to a specific region of visual space and synapse on motor neurons that move the eye to that same region?
superior colliculus
110
Activity in the superficial, visual layer of the SC is not sufficient for a saccade to occur
T/F?
true
111
Retinal activity always causes activation of cells in the upper layers of the SC
T/F?
true
112
Damage to the dorsal visual stream in the parietal lobe would affect which type of eye movement?
Smooth pursuit
it depends on visual motion processing, which is a core job of the dorsal (“where") visual stream in the parietal lobe
113
What constitutes Parkinson's disease?
idiopathic Parkinsonism (motor symptoms) + DA neuron loss -> response to l-dopa + Lewy bodies (not always tho)
114
What is likely to model of causes for PD?
primary genetic factors + alpha-synclein misfolding -> genetic and environmental modifiers
115
What are the 2 gene-finding strategies for PD?
genome-wide linkage: Which chunk of chromosome is inherited with the disease in families?
genome-wide association: Which single nucleotide polymorphisms in the population are more common in people with the trait?
116
What genes have been associated with PD?
PARK1 - alpha-synuclein:
point mutation -> multiple copies -> more alpha-synclein production -> misfolding -> stick together -> cascade aggregation
PAR8 -> LRRK2 mutation -> regulates autophagic activity
GBA -> encodes lysosomal enzyme
sensorimotor systems
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