Motor Flashcards
How does movement start?
- Decision made in anterior frontal lobe of cerebral cortex
- Activation of motor planning areas
- Control areas (basal ganglia and cerebellum
- Descending tracts (upper motor neurons)
- Spinal interneurons
- Lower motor neurons
- Skeletal muscles (contraction)
What is the motor control hierarchy?
- cerebral cortex
- brainstem
- some UMNs go to segmental (interneurons)
- Lower motor neurons
What are the sites for upper motor neurons?
- Cerebral cortex
2. Brainstem
What are the sites for lower motor neurons?
- Brain stem
2. spinal cord
What are motor control areas?
- Basal ganglia
2. Cerebellum
What are the three types of motor injuries?
- UMN injury
- LMN injury
- Basal ganglia/ cerebellar injury
What is the result of a lower motor neuron injury?
Inability for the muscle to contract
- flacidity
- loss or decrease of reflex
Basal ganglia and cerebellum always connect to ______. A muscle always connects to ______.
UMN; LMN
Resistance to stretch
Tone
Where are LMN located?
- Ventral horn of spinal cord
2. Brain stem
Where do LMN of ventral horn of the spinal cord go to?
Body
Where do LMN of brain stem go to?
head, face, a little bit of the neck
-cranial nerves
What do alpha motor neurons innervate? gamma motor?
- Go to extrafusal muscle fibers to produce contraction
- Go to Intrafusal muscle fibers to maintain sensitivity to muscle spindes
What type of synapse is at the motor neuron? what is the neurotransmitter? What type of receptor?
NMJ; ACh; Nicotinic
One alpha motor neuron and all of the m fibers it supplies
Motor unit
Where do medial ventral horns neuron innervate? lateral ventral horns?
Proximal extremities; Distal extremities
What are the components of a spinal reflex?
- Sensory neuron bringing info in
- Interneuron (possible, but can sometimes be exempt)
- Motor neuron to produce reflex
- may just have 1 and 3 depending on the reflex
Receptor that responds when a muscle is being lengthened and when its being held in a lengthened position
Muscle spindle
What determines if a a motor unit is slow twitch or fast twitch?
the alpha motor neuron
Name the following characteristics that correlates with slow twitch muscles:
- Alpha motor neuron diameter
- M.’s innervated
- Recruitment order
- Speed generation
- Sources of energy
- Fatigue
- Smaller
- Postural
- first
- slow
- Aerobic
- Resistant
Name the following characteristics that correlates with fast twitch muscles:
- Alpha motor neuron diameter
- M.’s innervated
- Recruitment order
- Speed generation
- Sources of energy
- Fatigue
- Larger
- Movement
- Later (we need more force)
- Fast
- Anaerobic
- Sensitive
Receptor that responds to Tendon tension by passive stretching or active contraction
GTO
Sensory receptor that responds to noxious stimuli
Cutaneous receptor
Muscle spindle reflex:
- Dynamic, deep tendon
- Stimulus = stretchING (lengthening a muscle)
- Response = muscle contraction
Phasic stretch reflex
Muscle spindle reflex:
- Stimulus – stretch of a muscle (keeping a muscle in a lengthened position)
- Response = increase the likelihood of a m contraction or force of contraction
Tonic stretch reflex
Are there inter neurons in the phasic stretch reflex?
No
- no interneuron needed because it is coming in and going out of same neuron
Are there interneurons in the tonic stretch reflex?
Yes
- Multisynaptic reflex = two or more synapses going out from the sensory neuron
Are there interneurons in the GTO reflex?
Yes
- Increased contraction results in inhibition of the contraction to reduce risk of muscle injury
- Also thought to play a role in motor recruitment to prevent using the same motor neurons every time a contraction happens, reducing risk of fatigue
Withdrawal reflexes; Respond to nociceptive input
Cutaneous reflexes
Where are UMNs located? where do they project to?
- Cerebral Cortex and Brainstem
- LMN in brainstem and spinal cord
Pathway to spinal cord:
- Synapse in medial ventral horn
- Muscles for proximal m’s (axial and proximal joint m’s)
Medial activating systems
Pathway to spinal cord:
Synapse in lateral ventral horn; Muscles for distal extemities
Lateral activating systems
Pathway to spinal cord:
Synapse throughout ventral horn; Control level of activity
Non-specific activating systems
What are the 5 medial systems tracts?
- Ventral (medial) corticospinal
- Medial vestibulospinal
- Lateral vestibulospina
- Medial reticulospinal
- Tectospinal
Involved in trunk axial, and girdle movements; More involved with medial systems; Some role in planning movements
Premotor cortex
Involved in sequential movements (i.e., throwing a ball); Bimanual movements (movements on both sides of the body), coordinating movements on both sides (i.e., holding something with one hand while manipulating something with the other hand)
Supplementary motor cortex
What neurotransmitter is used in the raphespinal tract? cerulospinal tract?
Serotonin; NE
Control upper motor neuron system; adjust activity in descending motor tracts
DO NOT have direct connections with lower motor neurons
Basal ganglia and cerebellum
Where are the basal ganglia located?
- Cerebrum - caudate, putamen, globus pallidus (internus, externus)
- Diencephalon - sub thalamic nucleus
- Midbrain - substantial nigra (pars compact, pars reticulata)
What basal ganglia are input areas?
- Caudate (psychological factors)
2. Putamen
What basal ganglia are processing areas?
- Globus pallidus externus
2. Subthalamic nucleus
What basal ganglia are output areas?
- Globus pallidus internus
2. Pars reticulata
What basal ganglia is responsible for making dopamine and is a regulatory region?
Pars compacta
What basal ganglia is referred to as “striatum”
Caudate and putamen
What basal ganglia is referred to as the lenticular nucleus?
GPi, GPe, and putamen
What BG pathway facilitates the lateral pathways and inhibits medial pathways?
Direct pathway
What BG pathway facilitates medial pathways and inhibits lateral pathways?
Indirect pathways
The direct pathway receives input information in the _____. It processes information in the _____. It then goes to output nuclei located in the ____, then to the _____. The information either goes to the ______ to [excite/inhibit] the lateral systems OR goes to the ____ to [excite/inhibit] the medial systems.
Putamen; GPe; GPi; substantia niagra reticulata; motor thalamus; excite; pedunculopontine nucleus; inhibit
The indirect pathway receives input information in the _____. It processes information in the _____ and the ______. It’s output nuclei are located in the ____ or the _____. The information either goes to the motor thalamus to [excite/inhibit] the lateral systems OR goes to the pedunculopontine nucleus to [excite/inhibit] the medial systems.
Putamen; GPe, subthalamic nucleus; GPi, substantia niagra reticulata; inhibit; excite
Dopamine increase moves things in the brain towards the [direct/ indirect] pathway or facilitates the [medial/ lateral] systems
direct; lateral
What are the functions of the basal ganglia?
- Sequencing movements
- Regulating muscle tone and force
- Selecting synergies (direct pathway) and inhibiting synergies (indirect pathway)
- Motor learning
What is a hypokinetic BG disorder? what are the hyperkinetic BG disorders?
Parkinson’s disease;
- Huntington’s disease
- Dystonias
- Choreoathetotic CP
- Hemiballismus
Most common BG disorder; Unknown cause; for onset of disease; Neurodegenerative disease with unknown cause of dopamine production decrease
Parkinson’s disease
What is the result of PD’s dopamine production decrease? (etiology and symptoms)
- dopanuergic neurons dying due to low dopamine; getting down to 15 - 20% of these neurons result in symptoms of parkinson disease; results in Increase in activity of indirect pathways - Facilitates medial systems
Sx:
1. Akinesia – difficulty initiating movements
2. Bradykinesia - slow movements
3. Tend to have a tremor at rest (“pill rolling” tremor)
Someone loses dopanuergic neurons and devolops symptoms of parkinson’s disease but you DO know what the cause (event or drug); i.e., Muhammad Ali had disease due to getting hit in the head, Synthetic opiate drug, and Drugs used to treat Schizophrenia
Parkinsonism and parkinsonian syndrome
Basal ganglia and cerebral cortex damage involved; Increase in involuntary movements; Pts also develop dementia
Huntington’s Disease
Genetic movement disorder; Dysfunction in basal ganglia; Usually non-progressive; Involuntary sustained muscle contractions; Twisting or repetitive motions or abnormal posture
Dystonia
What are the most common types of dystonias?
Focal dystonias
- affects just one part of the body, often limited to a particular activity
What is the focal dystonia where deteriation in handwriting due to involuntary muscle contractions in upper limb? What is the focal dystonia where the 4th and 5th fingers flex involuntarily?
Writer’s cramp; musician’s cramp
Damage to BG structures that results in rapid involuntary movements and slow writing movements
Choreoathetotic CP
- Chorea = “dance”; rapid movements
- Athetotic = slow writhing
Damage to sub thalamic nuclear that results in ballistic movements (Proximal part of the extremity moves and the rest of the extremity goes along with it) on the contralateral side
Hemiballismus
Where is the cerebellum located and what are its functions?
- posterior to the braistem (pons and medulla) Functions: 1. Balance 2. Coordination 3. Eye movement
Where are the deep cerebellar nuclei located? what is its function?
embedded in the white matter (FYI gray matter is outer and white matter arbor vita is deep to it)
- output region
What are the gyri/sulci of the cerebellum referred to as?
folia (means leaf)
Where are the interneurons of the Cb located? where are Purkinje cell bodies located?
outer and inner layers of the Cb; middle layer
Where do Purkinje cells project to?
- deep cerebellar nuclei
2. vestibular nuclei (in brainstem)
What lobe of the Cb is its own part?
Flocculonodular (lateral parts are flocculus and middle is nocullus)
- anterior and posterior lobes are together as one, contains the vermal, paravermal, and lateral regions
Where does afferent (input) information from the SC and brainstem enter the Cb?
Inferior cerebellar peduncles
- connect btwn Cb and medulla
Where does afferent (input) information from the pons enter the Cb?
Middle Cb peduncles
- largest of the peduncles
- The pathway is motor cortex to the base of the pons. These axons synapse on neurons in the base of the pons. These neurons send their axons which cross the midline of the pons and enter the Cb through the middle cerebellar peduncle
- AKA corticalpontine fiber, travel with corticospinal pathways
Where does efferent information (output) exit the Cb and where does it go to?
Superior Cb peduncles
- connects with red nucleus in the midbrain
What part of the Cb controls fine movement? what is the name of the tract?
Lateral hemispheres
- cerebrocerebellum (controls distal parts of the extremities, like hands, therefore fine movement)
What are the functions of the cerebrocerebellar tract?
- Control of distal limb movements
- Planning of movements, particularly learned, skilled movements
- Coordination of movements
- Ability to judge time intervals and produce accurate rhythms
What region of the body does the vermal region of the Cb control? Paravermal?
- Trunk
- Limbs
Where does the vermal region of the Cb get input from?
- Spinal cord from trunk
- Vestibular nuclei
- Auditory and vestibular information through brainstem nuclei
Where does info from the vermal region go to?
- Vestibular and Reticular N (Balanance, coordination, extension)
- Motor Cortex
What are the vermal region of the Cb functions?
- Postural adjustment of trunk
2. Stereotyped movements – modulation of basic walking patterns generated in the SC
Where does input to the paravermal come from? where does its output go? what is its function?
input = SC (limbs) Output = motor cortex and red nucleus Fxn = corrects movements if there are errors
What is the tract that goes through the flocculonodular lobe of the Cb?
Vestibulocerebellum
Where does input to the flocculonodular lobe come from? where does its output go to? What is its function?
input = vestibular apparatus and vestibular nuclei output = vestibular nuclei fxn = Maintenance of equilibrium (balance) [vestibulospinal tract]; Control of eye movements
When injury occurs to the cerebellum, are the symptoms ipsi- or contralateral to the injury? what is the typical response?
- ipsilateral to injury (Injuries directly to Cb can cause problems but Also due to input or output fibers [pathways, peduncles])
- hypotonia; usually transient and tone returns to normal levels over time
If a person has truncal ataxia, where is the injury? limb and gait ataxia? Hand ataxia?
Truncal = vermal or vestibulocerebellar lesions (difficulty sitting or standing) or can be due to paravermal lesion
Limb and gait = paravermal lesion
hand = lateral hemisphere lesion
Injury that results in dysequilibrian, truncal ataxia, and abnormal eye movements
Vestibulocerebellum injury
Injury that results in dysarthria (speech impairment due to motor problems) and truncal ataxia
spinocerebellar lesion in vermal region
injury that results in gait ataxia (wide base gait; pt not able to walk in straight line; different step lengths)
- can be the result of nutritional deficiencies that damage the anterior lobe of the Cb due to poor diets seen in alcoholism
spinocerebellar lesion in paravermal region
What are the symptoms of limb ataxia?
- Dysdiadochokinesia - inability to perform rapidly alternating movements
- Dysmetria - inability to move the correct distance or location; Will not hit a target
- Action tremor (intention tremor) - tremor during a movement
- Difficulties with time intervals - difficulties maintaining a regular rhythm
What is seen in injuries to the cerebrocerebellum?
dysarthria and hand ataxia (lateral activating system)
Where are the UMN for the lateral corticospinal tract?
- Primary motor cortex
- secondary motor cortex (motor planning areas: premotor, supplementary)
- primary somatosensory cortex
Where are the UMN for the corticobulbar tract?
- Primary motor cortex
- secondary motor cortex (motor planning areas: premotor, supplementary)
- primary somatosensory cortex
Same for lat corticospinal for face, lats, and SCM
Where are the UMN for rubrospinal tract?
Red nucleus in mid brain
Where are the UMN for lat reticulospinal tract?
reticular formation in brainstem
Where are the UMN for tectospinal tract?
Superior colliculus in midbrain
Where are the UMN for medial reticulospinal tract?
reticular formation in the brainstem
Where are the UMN for medial vestibulospinal tract?
vestibular nuclei in brainstem
Where are the UMN for lateral vestibulospinal tract?
Vestibular nuclei in brainstem
Where are the UMN for medial corticospinal tract?
Cerebral cortex
What does lateral corticospinal tract control?
Fine movement, voluntary movement, and fractionation of movement in the distal extremities
What does corticobulbar tract control?
voluntary movement in the face, lats, and SCM
What does rubrospinal tract control?
facilitates flexion in upper extremities only
What does lateral reticulospinal tract control?
Flexion in all extremities
What does tectospinal tract control?
Goes to cervical and thoracic cord and orients head and eyes toward stimulus (visual map of the world)
Where does the medial reticulospinal tract control?
Extensor muscles to keep you upright
What does the medial vestibulospinal tract control?
Keeps the eyes stable (moving your head up and down while reading a paper)
What does the lateral vestibulospinal tract control?
input detects how the head is moving and tract controls body extensors to keep us upright for correct balance and posture
i.e., if you are falling, input saying head is rapidly going to the ground, Tract responds by extending body, arms, etc. to keep head from smashing into the ground
What does the medial corticospinal tract control?
extension of axial and girdle muscles
