Neuromotor System Flashcards
Nuclear bag fibers
Cell nuclei arrangement:
Deformation signals info about:
Jumbled together in middle
Rate of change (velocity) of muscle length
Nuclear chain fibers
Cell nuclei arrangement:
Deformation signals info about:
Aligned in single row
Static length of muscle
Spindle afferents that only innervate nuclear chain fibers
Type II
Signal muscle immediate length
Spindle afferents that wrap around both nuclear chain and nuclear bag fibers
Type 1a
Signal both muscle length an velocity
Muscle tone is fine-tuned by tonic discharge of ____ activated by ______ pathways (2)
Gamma motor neurons
Reticulospinal, vestibulospinal
Coordinates muscle tone in every muscle of body by modulating alpha motor neurons and gamma motor neuron firing frequency
Cerebellum
Contractile force of motor unit =
Force-generating capabilities of muscle’s fiber type x # fibers innervated by motor neuron
Dorsal groups of motor neurons innervate ___
flexors
Ventral groups of motor neurons innervate ___
Extensors
Medial groups of motor neurons innervate ____
axial (proximal) muscles
Lateral groups motor neurons innervate ____
Distal muscles
Lateral dorsal groups motor neurons innervate ___
most distal muscles (hands)
5 main descending motor systems
Corticospinal Corticobulbar Reticulspinal Vestibulospinal Tectospinal (Rubrospinal) unimportant
Project their axons across different levels of cord.
Yoke together proprioceptive systems and alpha/gamma motor neurons in networks called ____
Propriospinal interneurons in intermediate zone
Central pattern generators
Input of central pattern generators
Sensory fibers Supraspinal neurons (corticospinal system)
Output of central pattern generators
(mostly inhibitory) alpha and gamma motor neurons
Intrinsic hand muscle motorneurons are located in _____
Dorsal part of ventral horn at C7-T1
Lesion of facial nucleus will result in ____
contralateral lower facial hemiparisis
Major functions of corticobulbospinal tract
Individual muscle control
Facilitation of flexors
Command system for activating central pattern generators
Rubrospinal system
Originates in:
Function:
Red nucleus
Facilitate neck and upper limb flexors
Tract involved in integrating CPG function
Reticulospinal tract By facilitating (MRST) or inhibiting (LRST) stereotypic movements and compound limb movements
Reticulospinal system involved in:
Maintenance of posture
Modulation of muscle tone
CPG coordination
Damage at or below red nucleus when lateral corticospinal tract is disrupted causes ____
decerebrate rigidity
Lateral vestibulospinal tract’s bias for extension is unopposed
Tracts that have biased flexion
Rubrospinal
Medullary reticulospinal
Tracts that have biased extension
Lateral vestibulospinal tract
Pontine reticulospinal tract
Functions of vestibulospinal tract and tectospinal tract
Postural control through facilitation of extensors
Coordination of head, neck and axial spine movements
Central control on motor system: planning and preparation
Frontal lobe
Central control of motor system: motor or procedural learning
basal ganglia
Central control of motor system: hitting the target
Accuracy and sequencing of complex voluntary movements
Cerebellum
Premotor area (PMA) involved in \_\_\_\_\_\_ Represents:
Planning and preparing movements in response to external cues, particularly visual
Ownership of limbs and perception of their movements (sense of agency)
Supplementary motor areas (SMA) involved in ____
Internally generated movements
Lesion of lateral corticospinal tract in spinal cord produce ____
ipsilateral loss f voluntary movement below level of lesion, mostly in distal extremities
Lesion of corticospinal tract occurring above pyramidal decussation will cause _____
CONTRALATERAL paralysis/paresis
Lesion of hypoglossal nucleus will cause (3) (ipsilateral/contralateral) signs:
Location of nucleus:
1.Tongue deviate TOWARD side of lesion
2.Dysphagia (swallowing)
3.Dysarthria (articulation)
CONTRALATERAL
Medulla
Oculomotor nuclear complex located in:
midbrain
Oculomotor nuclear complex innervates (ipsilateral/contralateral) superior rectus
Contralateral
Oculomotor nuclear complex innervates (ipsilateral/contralateral) inferior rectus
Ipsilateral
Oculomotor nuclear complex innervates (ipsilateral/contralateral) inferior oblique
Ipsilateral
Oculomotor nuclear complex innervates (ipsilateral/contralateral) medial rectus
ipsilateral
Oculomotor nuclear complex innervates levator palpebrae superioris via ____
central caudal nucleus
Trochlear nucleus located in:
midbrain
Trochlear nucleus innervates (ipsilateral/contralateral) _____
Contralateral superior oblique
Abducens nucleus located in:
pons, close to midline beneath floor of 4th ventricle
Abducens nucleus innervates (ipsilateral/contralateral) ____
Ipsilateral lateral rectus
Lesion to abducens nerve results in:
palsy of ipsilateral lateral rectus m. –> affected side fails to abduct on horizontal conjugate gaze to that side
Lesion of abducens nucleus causes damage to ____ and ____
Leading to ____
Lateral rectus motor neurons AND internuclear neurons to contralateral MLF innervating medial rectus
Horizontal conjugate gaze palsy
Trochlear nucleus located in:
Path of axons:
midbrain at level of inferior colliculus
Dorsalateral and caudal –> superior medullary velum –> CROSS –> dorsal surface, just caudal to inferior colliculi
When eye is adducted, superior oblique acts to ____
depress the eye
When eye is abducted, superior oblique acts to ____
intort the eye
Trochlear nerve lesion results in ____
Signs:
paralysis of ipsilateral superior oblique m
Double vision when looking down and medially –> Compensate for extorsion by tilting head towards non-lesioned side
Vertical diplopia when unaffected eye depressed –> tuck chin and tilt forward –> Pathetic look
Lesion of trochlear nucleus produce (ipsilateral/contralateral) signs
Contralateral
Lesion of trochlear nerve produce (ipsilateral/contralateral) signs
Ipsilateral
Oculomotor nuclear complex located in:
midbrain at level of superior colliculus
Lesion of CN3 nucleus OR nerve results in ____
down and out syndrome
Down and Out Syndrome
Symptoms: (4)
- Ipsilateral lateral strabismus and depression: eyes do not line up in same direction
- Ipsilateral ptosis: loss of levator palpebrae superioris
- Ipsilateral mydriasis (dilated pupil) : loss of constrictor pupillae
- Loss of direct and consensual pupillary light reflexes in ipsilateral eye
Internuclear ophthalmoplegia results from:
Lesion to MLF
Ipsilateral adducting eye cannot turn medially, but contralateral eye can but shows NYSTAGMUS
Vertical conjugate gaze controlled by:
Vertical conjugate gaze center in rostral midbrain
Lesions to dorsal midbrain lead to ____
paralysis of vertical gaze
Parinaud’s Syndrome
Eyelid contraction and pupillary deficits
Paralysis of upward gaze (prominent)
Nucleus ambiguus location:
Innervation:
Medulla
Mm. of pharynx, larynx, soft palate, upper esophagus via CN 10 and 9
Lesions of nucleus ambiguus result in:
Dysphagia: atrophy and flaccid paralysis of mm. of soft palate, pharynx and larynx
Dysarthria: Flaccid vocal chord
Facial nucleus innervates:
Mm. of facial expression
Stylohyoid
Posterior digastric
Stapedius
Lesions of abducens nucleus often damage ___ also
CN7 Facial nerve fibers
LMN lesions to facial nerve result in:
Facial hemiplegia
LMN lesions to facial nucleus result in:
Facial hemiplegia
Hyperacusis (sensitivity to loud sounds): loss of inntervation of stapedius mm.
UMN lesion to facial nucleus results in:
lower quadrant palsy b/c neurons innervating upper facial muscles have bilateral innervation
Corneal blink reflex
Involves: (2)
Results in:
Facial nucleus (motor to orbicularis oculi), rostral spinal trigeminal nucleus
Consensual both eyes blink from unilateral stimulation of cornea
Motor nucleus of CN5
Axons carried by:
Innervates:
CNV3
Mm. of mastication, tensor tympani, tensor veli palatini, mylohyoid, anterior digastric
Outer layers of superior colliculus receive input from:
Retina
Cerebral cortex: visual cortex and frontal eye fields
Deep layers of superior colliculus receive input from:
Inferior colliculus
Spinal nucleus of V
Spinal cord
