Lecture 7 & 8 - Motor Systems Flashcards
What are simple pattern reflexes?
- stereotyped/predictable, unlearned, automated, spinal reflexes that do NOT require cortical input.
what are complex postural adjustments? (what systems do they involve?)
- reflexes involving the spinal cord, as well as supraspinal centres (brainstem (extrapyramidal system), cerebellum)
- they are NOT stereotyped, flexible and goal-orientated (adaptive)
- they MOSTLY coordinate with voluntary movements
- hence require cortical input
what components do voluntary movements involve?
- spinal cord, brainstem, motor cortex
what are upper motor neurons? (name examples)
UMN - 1st order motor neurons whose cell bodies and axons both stay within the CNS
(e.g., cortical motor neurons - pyramidal tract, brainstem motor nuclei - red nucleus, tectum, reticular formation, vestibular nuclei)
what are lower motor neurons?
LMN - 2nd order motor neurons who’s cell bodies lie in the CNS but axons project to peripheral skeletal muscles.
(e.g., alpha and gamma motor neurons of spinal ventral gray horn, motor neurons of brainstem cranial nerves)
alpha motor neurons receive input from which 3 major sources?
- motor cortex and brainstem (pyramidal, extrapyramidal)
- spinal interneurons (spinal circuit)
- muscle sensory (proprioceptive systems)
What are the two motor neuron pools in the ventral gray horns and their functions??
- ventral, medial (proximal limbs - old system)
- dorsal, lateral (distal limbs - young system)
the MEDIAL descending motor systems (most extrapyramidal tracts) descend via the ____ and terminate in the ____ to coordinate _____.
- ventral funiculus
- medial ventral motor neuron pool
- posture, orientation
the LATERAL descending motor systems descend via the _____and terminate in the _____to coordinate
- lateral funiculus
- dorsal lateral motor neuron pool
- movement of limbs (esp. fine movement of distal limbs)
what are the two pathways which make up the PYRAMIDAL SYSTEM? where do they originate and what type of movement do they initiate?
- corticospinal tract
- corticonuclear/bulbar tract
- cortex
- voluntary movement
what are the extrapyramidal pathways? where do they originate and what type of movement do they initiate?
- tectospinal (tectum)
- vestibulospinal (vestibular nuclei)
- reticulospinal (reticular formation)
- rubrospinal (red nuclei)
- brainstem
- involuntary movement
- the three sulci that develop earliest in the embryo are?
- why are they deep?
- central sulcus
- lateral/Sylvian sulcus
- calcarine sulcus
- to allow more surface area to accommodate more neurons of primary cortices
all sensory input first arrives in the _____cortices of each sensory areas.
- primary
the primary and secondary cortices of all sensory modalities are ______ hence deal with only the given sensory modality.
- unimodal
tertiary or higher association cortices are _____ hence integrate all sensory modalities
- multimodal/heteromodal
sensory input is decoded/interpreted in the _____cortices
- secondary
unlike sensory systems, motor commands are initiated in the ______ cortex, transferred to the _____ and leaves the brain from the _____.
- higher order/tertiary motor cortex (PFC)
- secondary motor cortices (SMA, PMC)
- primary motor cortex (M1)
there is no clear anatomical boundary between the ____ and _____ .
- PFC and secondary motor areas.
the frontal eye field is located
rostral/anterior to the PREMOTOR area
the PFC deals with _____
the secondary motor areas deal with _____
- the primary motor area deals with ___
- strategy (overall plan)
- tactics
- execution
- The LATERAL (dorsal) PFC processes
- the MEDIAL PFC processes
- the ORBITAL (ventral) PFC processes
- planning, problem-solving, rational thinking
- awareness, social self-awareness
- emotional behaviour (anticipates behavioural response when planning action)
which motor area works closely with the BASAL GANGLIA and has input into the pyramidal pathway?
SMA
What is the SMA concerned with? (x5)
- learning sequence of movements
- mental rehearsal of movement
- storing skilled movement
- generating internal cues for movement
- bilateral coordination (esp. upper limbs)
which motor area works closely with the CEREBELLUM and DORSAL PARIETAL CORTEX, and inputs to the pyramidal pathway?
PMC
what is the PMC concerned with? (x3)
- movement by externally generated cues
- anticipating voluntary movement (coordinated ongoing movement)
- SENSORIMOTOR TRANSFORMATION (integrates sensory information to motor commands)
what causes APRAXIA and what are the symptoms?
- lesion of the PMC and SMA
- unable to execute a pre learned voluntary movement
- unable to imitate a movement
Where are the Giant Cells of Betz located specifically?
in LAYER V of the PRIMARY MOTOR CORTEX (M1), where most pyramidal tracts originate
The CORTICOBULBAR tract forms the _____ for the voluntary movement of the ______, terminating on _____ which are the ______.
- UMN’s
- face, head and neck
- brainstem cranial nerve nuclei
- LMN’s
most fibres of the CORTICOBULBAR tract travel via the ____ of the IC
- genu
The pyramidal tract consists of ___% input from secondary motor areas, ___% input from M1 and ___% input from primary somatosensory
- 40
- 40
- 20
in humans, the CORTICOSPINAL tract contains about ___axons.
1 million
damage to the pyramidal tract can cause (x3)
- muscle weakness (M1)
- Apraxia (SMA, PMC)
- disturbance of motor actions (Primary sensory cortex)
the pyramidal tract descends firstly through the ____limb of the IC, the ____of the Crus cerebri, and through the ____.
- posterior (Genu for corticonuclear)
- intermediate (inner third) portion
- medullary pyramids
the corticospinal tract is divided into ____
lateral and anterior corticospinal tracts
the lateral corticospinal tract constitutes ___%
90
the lateral corticospinal tract decussates at the ____ and terminates in ___ at ____levels, whilst the anterior corticospinal tract decussates at the ____ and terminates in ____.
- pyramids (pyramidal decussations)
- the ventral horn (lateral motor neuron pool)
- cervical and lumbosacral
- level of the spinal cord
- ventral horn (medial motor neuron pool)
which two extrapyramidal tracts receive input from pyramidal tracts?
- rubrospinal
- reticulospinal
the TEGMENTUM contains (x3)
- ALL ascending pathways
- SOME descending pathways (extrapyramidal)
- ALL brainstem nuclei (except pontine nuclei)
the BASE contains (x2)
- ONLY descending pathways (pyramidal tracts, corticopontine tract)
- pontine nuclei
the crus cerebri + midbrain tegmentum =
cerebral peduncles
the midbrain contains ___(x3) and is thus predominantly a ____.
- red nuclei, superior colliculi, substantia nigra
- motor centre
Parkinson’s disease is caused by
loss of dopaminergic neurons in the Substantia Nigra Pars Compacta (SNc)
the PONS can be divided into _____(x2)
- basilar pons, pontine tegmentum
the pontine tegmentum contains _____
locus coeruleus
the basilar pons contains (x3)
pontine nuclei, pontocerebellar tracts, corticopontine pathways, pyramidal tracts
pontine nuclei synapse with ___ and project to the cerebellum through the ____ as the _____.
- corticopontine fibres (from the cortex)
- middle cerebellar peduncles
- pontocerebellar tracts
pyramidal decussations occur at the ___level of the____.
- caudal
- medullary pyramids
the medulla contains centres for (x3)
- respiratory (rhythmic breathing)
- cardiovascular (blood pressure, heart rate)
- chewing and swallowing
Proprioceptive information to Alpha motor neuron pools come from?
the musculoskeletal system
what are the three major proprioceptors?
- muscle spindles (muscle stretch)
- Golgi tendon organ (muscle contraction)
- joint receptors (joint position)
a spinal stretch reflex is ____ (knee-jerk)
a spinal withdrawal reflex is _____ (withdrawing leg from sharp object)
- monosynaptic
- polysynaptic
what are the two extrapyramidal tracts involved with postural reflexes?
- vestibulospinal
- reticulospinal
where are cell bodies of the RETICULOSPINAL tract located?
- rostral medullary reticular formation
- caudal pontine reticular formation
the fibres of the RETICULOSPINAL TRACTS descend ____ and _____ via the _____to _____of the spinal cord.
- ipsilaterally
- bilaterally
- ventral funiculus
- all levels
the RETICULOSPINAL tracts is MOSTLY an _____biased tract, that is important for (x3)
- extensor
- gross movement (extending limbs)
- locomotion
- postural and gait adjustments (balance) during movement
the reticulospinal tracts is a _____myelinated tract, hence is _____. Therefore, before lifting a heavy object, the muscles of the leg are excited ___ the muscles of the arms.
- highly
- fast-acting
- legs
- arms
The vestibular nuclei consist of (x2) and are located on___.
- medial (head stabilisation during movement)
- lateral (muscle tone for balance)
- rostral medulla
The medial vestibulospinal tract travels via the _____and only terminate in ______ spinal cords
- ventral funiculus
- cervical
The nuclei of the TECTOSPINAL CORD are found in the ____of the ____.
- superior coliculi
- midbrain
The tectospinal tract controls _____ in response to _____.
- reflex movements of the head, neck and upper limbs
- all relevant sensory stimuli
The tectospinal tract descends ____, where the larger portion descends _____, decussating at ____to ______, and the smaller portion descends _____ to ______. Both tracts terminate in ____ spinal cords.
- bilaterally
- contralaterally
- the midbrain
- innervate neck and shoulder muscles
- ipsilaterally
- inhibit muscles on the opposite side.
- cervical
The RUBROSPINAL tract originates in the ____ and descends ____, decussating at _____.
- red nucleus
- contralterally
- the midbrain
The RUBROSPINAL TRACT descends via the ____ with the ____, terminating in _____ levels of the spinal cord.
- lateral funiculus
- lateral corticospinal tract
- cervical
The RUBROSPINAL TRACT innervates all _____ of the upper limbs for _____ and is a ___biased tract.
- flexor muscles
- grabbing behaviour
- flexor
The rubrospinal tract receives input from _____.
- motor cortex (pyramidal pathways)
What happens to the rubrospinal tract, if a pyramidal tract lesion occurs?
- the flexor tone will be disinhibited, which means the upper limbs will be constantly flexed (newborns and stroke patients)
what is decorticate rigidity?
lesion of the UMN above the midbrain level, resulting in removal of cortical input to RUBROSPINAL and RETICULOSPINAL tracts, leading to constant flexion of the upper limbs and extension of lower limbs.
what is decerebrate rigidity?
- lesion of UMN below the midbrain
- removal of rubrospinal tract
- removal of cortical input to reticulospinal tract
- leads to constant extension of upper and lower limbs
what pathways descend via the LATERAL FUNICULUS?
- lateral corticospinal tract
- rubrospinal tract
(mostly unilateral)
what pathways descend via the VENTRAL FUNICULUS
- vestibulospinal
- reticulospinal
- tectospinal
- anterior corticospinal tract
(mostly bilateral)
where do all descending pathways decussate?
- vestibulospinal = ipsilateral
- reticulospinal = ipsilateral
- tectospinal = midbrain
- lateral corticospinal = pyramid
- anterior corticospinal = spinal cord
- rubrospinal = midbrain
