Motor 1 and 2 Flashcards
Motor system is made up of which 2 parts?
Brain and spinal cord.
Purpose of motor system
For coordinated motor movements
What is succinylcholine made up of ? What does it do ?
It is made from 2 acetylcholine. It stimulates muscle contraction.
What is the inhibitor of acetylcholine?
Acetylcholinesterase
List out the types of motor neurons and its functions
- Upper motor neuron (passes sensory information down to interneurons)
- Lower motor neuron
- Alpha MN = innervate extrafusal fibers
- Gamma MN = innervate intrafusal fibers
What is 1 motor unit
1 alpha motor neuron to a few muscle fibers
What is a motor neuron pool
A few alpha motor neurons to a muscle group
What is the origin of lower MN?
Ventral horn of spinal cord
What is mixed spinal nerve?
Contains the info from sensory and lower motor neuron
How many pairs of spinal nerves are there?
31
Which part of spinal cord innervates the distal and proximal limbs?
Cervical - for upper limb
Lumbar and sacrum - for lower limb
Acetylcholine is stimulated by which neuron?
Alpha motor neuron
How does acetylcholine cause muscle to contract?
Generates AP -> EPSP -> PSAP -> muscle twitch
What is the relationship between AP and muscle contraction?
More AP, longer maintained muscle contraction
What is size principle?
Recruitment of motor unit will start from the smallest to the largest
Where is the location of alpha MN and gamma MN in a muscle spindle?
Alpha MN is located outside of muscle spindle, Gamma MN is located inside of muscle spindle
What is the function of muscle spindle?
Detect muscle length change
What is the function of golgi tendon?
To detect muscle tension
Alpha MN receives how many inputs?
Receives input from
1. Spinal interneurons
2. Muscle spindles (Sensory input)
3. Upper motor neuron in brain
What is the function of spinal interneurons ?
Facilitate motor, sensory and autonomic functions in CNS
What are the 2 common causes of injury to Alpha MN
- Poliovirus - kills cells in ventral horn
- Amyotrophic lateral sclerosis (ALS) - neurodegenerative disease that targets motor neurons controlling voluntary muscles.
Damage to alpha MN will cause ?
- Muscle weakness
- Atrophy (wasting)
- Fasciculations (visible twitches)
- Fibrillation potentials (twitches only detected by EMG)
Will change of Alpha MN type affect a muscle phenotype?
Yes! Based on the crossed- innervation, change in Alpha MN type will change muscle phenotype accordingly (e.g. Slow Alpha NM will cause slow twitch in muscles. (vice versa))
Which part of the brain influence voluntary motor activity ?
Neocortex, basal ganglia = Strategy
Motor cortex, cerebellum = Tactics
Brain stem, spinal cord = Execution
Which motor pathway controls conscious control of muscles? Where does this pathway originate from?
The pyramidal pathway. It originates from the cerebral cortex and outputs to the muscles in the body and face.
Which motor pathway controls unconscious, reflexive or responsive control of muscles? Where does it originate from and to where?
The extrapyramidal pathway. It originates from the brain stem to postural or anti gravity muscles.
Pyramidal tracts are named as such because? It can be divided into ?
They are named as such as they pass through the pyramids of the medulla oblongata.
It can be divided into 2 tracts:
1. Corticospinal tract
2. Corticobulbar tract
Which tract carries information from cerebral cortex to spinal cord ?
Corticospinal tract
What is Corticospinal tract main source and other sources of input ?
Main: Primary motor cortex
Others: premotor and supplementary motor
Corticospinal tract mainly innervates muscles of?
Distal muscles of hands and feet
Explain the decussation of Corticospinal tract
85% decussates at the pyramids in medulla and continues down spinal cord via lateral Corticospinal tract
15% does not decussate, and just continue down via medial Corticospinal tract
Where does Corticospinal tract terminates ?
55% at cervical level
25% at sacral level
20% at thoracic level
Damaged upper motor neuron is also known as?
Upper motor neuron lesion
In Corticospinal tract, lesion cranial to decussation would lead to deficits on which side?
Contralateral side
In Corticospinal tract, lesion caudal to decussation would lead to deficits on which side?
Ipsilateral side
What is Corticobulbar tract composed of?
Motor neurons of cranial nerves
Where does Corticobulbar tract start and terminates?
Originate: cerebral motor cortex
Terminates: Motor nuclei of brain stem
What muscles does Corticobulbar tract control?
Face, head, neck
Corticobulbar tract control muscles of ?
Face, head, neck
How many extrapyramidal tract are there? List them out
- Reticulospinal tract
- Vestibulospinal tract
- Rubrospinal tract
- Tectospinal tract
Where do extrapyramidal tract originates and terminates? Do they pass through the pyramids ?
Originate from brain stem.
Terminates at spinal cord.
Does not pass through the pyramids.
What does reflexive or responsive movement of muscles help with ?
They will help to control balance, locomotion, posture and tone.
Which of the extrapyramidal tract decussates and which side do they innervate?
Does NOT decussates = provide ipsilateral innversations:
- Reticulospinal tract
- Vestibulospinal tract
DOES decussates = provides contralateral innervations:
- Rubrospinal tract
- Tectospinal tract
The reticulospinal tract is made up of? and where does it end?
Made of Pontine reticular nuclei (in pons) + Medullary reticular nuclei (in medulla)
Inserts: Spinal cord
Reticulospinal tract controls which part of the body?
- Trunk for posture
- Antigravity muscles of limbs
Functions of reticulospinal tract
- Motor activity
- Posture maintenance*
- Control of autonomic functions -> by controlling sym (F or F etc) and parasym (rest, digest etc) outflow
- Locomotion* (ability to move from one place to another)
Lesion in reticulospinal tract can lead to?
Decreased postural control
Function of vestibulospinal tract
- Reflexes*
- Upright posture maintenance
Origin and termination of vestibulospinal tract
Origin: Vestibular nucleus in medulla
Terminates: Both Ventral horns of spinal cord
Vestibulospinal tract divides into ?
Medial (to medial of spinal cord) and lateral (to lateral of spinal cord)
Lesion at vestibulospinal tract leads to?
- Ataxia
- Posture instability
Rubospinal tract originates and terminates? and where does it decussates?
Origin: Red nucleus at midbrain
Decussates: midbrain level
Terminates: spinal cord
Function of rubospinal tract
- Modulate flexor muscle tone
- Modulate reflex activity
- Inhibit anti-gravity muscles to allow better coordination of limbs like better movements between the joints
Tectospinal tract originate and terminates? Where does it decussates?
Origin: Superior colliculus of midbrain
Decussates: Midbrain level
Terminates: Spinal cord
Function of tectospinal tract
Mediates reflexes of eyes and head in response of visual input by superior colliculus
Electromyogram (EMG) detects what?
Proportional Muscle strength (small activation = small activity in EMG etc)
EMG can be used for?
- Biofeedback for voluntary control
- Gamification
Motor cortex is made up of which areas ?
- Area 6 = Supplementary area (SMA) + Pre motor area (PMA)
- Area 4 = Primary motor area (M1)
Stimulation of area 6 allows…?
more complex motor functions as it lies anterior to area 4
Function of area 6 (SMA and PMA)
SMA - innervates distal motor units (more complex movements)
PMA - innervates proximal motor units (coordinate larger body parts)
Damage to area 4 will cause damage to which side of the body?
Contralateral side
What is the function of Posterior parietal cortex, and what will happen if there is a lesion?
Posterior parietal cortex helps to keep track of body position and spatial awareness.
Lesion here will cause individual to move weirdly due to incorrect judgement of of distances/ unable to execute smooth movements
Prefrontal cortex is also known as area? and when is it activated?
AKA area 8.
Activates during planning and decision-making stages, just before execution of movement
Posterior parietal cortex is made up of area? Where does these areas receive their input?
5 and 7.
Area 5 receives input from somatosensory cortex (S1)
Area 7 receives input from higher order visual cortex.
Order of area activation in cerebral cortex during movement planning
- S1 and Posterior Parietal Cortex: These areas provide sensory input and spatial awareness, helping form a movement plan.
- Area 8: Involved in higher-level planning and initiation of eye and head movements.
- Area 6: Important for motor planning and coordination of movements.
- Area 4: Executes the planned movement by sending signals to muscles.
Purpose of mirror neurons, and when are they active?
To learn new things through observation. Important for understanding, identifying and imitating other people.
They are active when watching and preparing to perform the movement
Mirror neurons are mainly found in?
Area 6
Mirror neurons activates more strongly and less strongly when…why?
MN activates more strongly when performed by the same/ similar species.
MN actives less strongly if same task is done differently
This is because MN cells has very specific preferences
Does direction of movement affects firing rate of M1 neurons?
Yes
The Babinski sign, a reflex response, occurs when there is damage to ?
the corticospinal tract
In the 6 pathways from pyramidal and extrapyramidal, which ones are lateral and medial?
Lateral: Corticospinal, corticobulbar, rubospinal
Medial: Reticulospinal, Vestibulospinal, Tectospinal
Major structures of cerebellum
- Folia and Lobules (x10) - to increase S.A.
- Deep cerebellar nuclei - Relay its output to brain stem
- Vermis - Separates the 2 hemi. Contributes to medial pathways
- Cerebellar hemispheres - Contribute to lateral pathways
Function of cerebellum, and does it trigger movement when stimulated?
Function: Initiate sequence of muscle contraction
It does not initiate any movement if stimulated. AKA silent area of brain
Cerebellum has how many lobes and what are their names
- Posterior, anterior and flocculonodular
Lateral zone of cerebellum controls?
Planning and coordinating voluntary movements of the distal limbs.
Intermediate zone of cerebellum controls?
Controls proximal limb muscles for large movements
What is the motor loop through the lateral cerebellum ?
Premotor cortex + sensory cortex -> Pontine nuclei in pons -> lateral cerebellum -> ventrolateral caudalis in thalamus -> Primary motor cortex
Afferent (input pathways) of cerebellum from other pars of brain
- Cerebropontile tract
- Origin: motor, premotor and sensory areas in cerebral cortex
- Terminates: Pons* - Pontocerebellar tract
- Origin: Pontine nuclei in pons
- Terminates: Lat. hemi. cerebellum - Vestibulocerebellar tract
- Origin: Vestibular nuclei in brain stem
- Terminates: flocculonodular lobe - Olivocerebellar tract
- Origin: Olivary nucleus in medulla
- Terminates: cerebellar cortex (outer layer of cerebellum) - Reticulocerebellar tract
- Origin: Reticular info from brain stem
- Terminates: Cerebellar cortex and vermis
What are the pathways for Denate nuclei and what does it do?
Cerebellar cortex -> denate nuclei -> thalamus -> cerebral cortex
It does fine motor planning and coordination
What is the pathway for fastigial nuclei? What does it do?
Vermis -> fastigial -> brain stem
It maintain posture, balance and influence proximal limbs
What is the pathway for interposed nuclei?
Intermediate zone -> interposed nuclei -> thalamus <-> cerebral cortex
OR
Cerebral cortex -> thalamus -> red nucleus in brainstem
To cerebral cortex - For controlling proximal limbs
To red nucleus - For adjustment of motor execution
1 function unit of cerebellum has ?
A large purkinje cell and deep nuclear cell
What excites and inhibits the deep nuclear cell?
Excites: Afferent input from brain and peripheral
Inhibited by GABA neurotransmitters by purkinje cells
Vestibulocerebellum helps with?
Balance movements
Spinocerebellum helps with?
Movement of distal limbs
Cerebrocerebellum helps with?
Planning voluntary movements (aka motor imagery)
Clinical abnormalities if there is damage to cerebellum
- Dysmetria - inability to control the distance, speed, or force of a movement –> 2. past pointing
- Ataxia - uncoordinated movement
- Cerebellar nystagmus - eyeball tremor
- Hypotonia - decreased muscle tone
Striatum is made up of ?
Caudate nucleus + Putamen
Internal capsule is what kind of structure and what does it do?
It is a white matter structure and helps transmit information to and fro cerebral cortex, brain stem and spinal cord
Explain the basal ganglia circuitry
Initiate movement (direct):
Excited motor cortex -> excite striatum -> inhibit globus pallidus -> less suppressed thalamus* -> excite cortex -> more movement
Inhibit movement (indirect):
Excited motor cortex -> excite striatum -> inhibit globus pallidus -> excite subthalamic nucleus* -> stimulate globus pallidus -> inhibit thalamas -> inhibit cortex -> less movement
Both happen together.
If one is more than the other, it is abnormal (e.g. in parkinson, subthalamic nucleus is overactive -> less movement, rigidity )
Purpoose of basal ganglia circuitry
Modulate voluntary movements
Putamen works with what structures to refine complex patterns of motor activity?
- Subthalamic
- Ancillary circuits
- Substantia nigra
Lesion in subthalamic will cause what?
Hemiballismus - violent large movements on one side of the body
Lesion in putamen will cause what?
Chorea - random uncontrolled jerks/ twitches
Lesion in striatum will cause what?
Athetosis - Uncontrolled slow continuous movements
Lesion in substantia nigra will cause?
Parkinson’s diesease - rigidity, tremor
What is caudate circuit for? What does it act on?
Cognitive control of motor movements (Subconscious, happens within seconds)
It acts on all lobes of cerebrum
Lesion in caudate circuit will lead to?
Unable to store knowledge, always have to relearn
State the caudate circuit pathway
Area 6, M1, S1 -> caudate -> internal globus pallidus -> ventroanterior (VA) and ventrolateral (VL) nuclei of thalamus -> area 8 and 6
How many neurotransmitters are in the basal ganglia?
- Dopamine
- GABA
- Acetylcholine
Dopamine comes from and goes to?
Comes from substantia nigra, goes to caudate and putamen
GABA comes from and goes to?
comes from caudate and putamen, goes to substantia nigra and globus pallidus
Acetylcholine comes from, and goes to?
Comes from cerebral cortex and goes to caudate and putamen
Damage to basal ganglia can cause symptoms called?
Parkinsonism (problems with speech, movement , posture)
What is hyperkinesia ?
Motor overactivity (e.g. Huntington’s disease)
What is hypokinesias?
motor underactivity (e.g. Parkinson’s)
Symptoms of Parkinson’s disease
- tremor, bradykinesia (posture instability), rigidity
In PD, how many % dopamine producing neurons are destroyed?
> 70% = Super low dopamine levels
In normal, about 4% loss only
How is dopamine made?
Tyrosine -> (tyrosine hydroxylase) -> DOPA (dopa decarboxylase) -> dopamine
How PD affects neurotransmission?
Loss of dopamine release in striatum -> acetylcholine higher -> overstimulates target neurons -> abnormal signaling -> abnormal mobility
Treatment of PD
- I-Dopa (only useful in early stage of PD as in the end, there wont be enough dopamine still. Body will convert I-Dopa into dopamine.)
- Monoamine oxidase inhibitors (inhibits break down of dopamine)
- Transplanted fetal dopamine cells (replace dead dopamine producing neurons into new fetus ones)
- Deep brain stimulation (DBS) (If not responding to drugs)
