Neuroscience Anat (Motor Pathways) Flashcards
State the location of UMN for pyramidal and extrapyramidal systems.
State the location on LMN for cranial and spinal nerves.
UMN
1. cell body located in cerebral cortex (pyramidal)
2. cell body located in brainstem (extrapyramidal)
LMN
1. cell body located in ventral horn of spinal cord (spinal nerves)
2. cell body located in brainstem (cranial nerves) - 10 out of 12 cranial nerves exit from brainstem
PYRAMIDAL SYSTEM (DESCENDING MOTOR PATHWAYS)
- Arises from ____ ____
- 2 tracts: (1) and (2) [Expand on the pathways for both tracts]
PYRAMIDAL SYSTEM
- Arises from PRECENTRAL GYRUS
- 2 tracts:
(1) corticospinal tract
- spinal nerves (LMN, pyramidal) –> UMN in cerebral cortex –> LMN in ventral horn of spinal cord
(2) corticobulbar tract
- cranial nerves (LMN, pyramidal) –> UMN in cerebral cortex –> LMN in brainstem
EXTRAPYRAMIDAL SYSTEM (DESCENDING MOTOR PATHWAYS)
State the tracts involved.
(1) RUBROSPINAL TRACT
- arises from red nucleus
- influences flexor muscles
(2) VESTIBULOSPINAL TRACT
- arises from vestibular nucleus
- influences muscles (erector spinae) that maintain balance (posture) and hearing (CN VIII)
(3) TECTOSPINAL TRACT
- arises from superior colliculus (tectum) (nuclei in midbrain)
- influences muscles involved in visual reflexes
(4) RETICULOSPINAL TRACT
- arise from reticular formations (extensive nuclei within brainstem)
- influences skeletal muscles responsible for visceral functions
CORTICOSPINAL TRACT
- Origin: ____ ____ (specifically the ____ cortex)
- Pathway:
CORTICOSPINAL TRACT
- Origin: CEREBRAL CORTEX (specifically the MOTOR cortex)
- Pathway:
(1) Cerebral cortex
(2) Corona radiata
(3) Internal capsule
(4) Midbrain - crus cerebri
(5) Medulla - pyramids
(6) (MORE COMMON) If decussation occurs at MO–> lateral corticospinal tract = synapse onto LMN at VH of spinal cord
(7) (LESS COMMON) If decussation does not occur at MO –> ventral corticospinal tract = synapses onto LMN at VH of spinal cord
CORTICOBULBAR/ CORTICONUCLEAR TRACT
- UMN - from ____ cortex in ____ –> converge to form ____ tract
- LMN - ____ motor nuclei (most influenced ____ by UMNs from both ____ and ____ sides of the brain) except CN ____ and ____
State the clinical significance of influence on LMN.
CORTICOBULBAR/ CORTICONUCLEAR TRACT
- UMN - from MOTOR cortex in CEREBRUM –> converge to form CORTICOBULBAR tract
- LMN - BRAINSTEM motor nuclei (most influenced BILATERALLY by UMNs from both IPSILATERAL and BILATERAL sides of the brain) except CN VII (LOWER HALF OF FACE) and CN XII
CLINICAL SIGNIFICANCE:
In stroke patients, where one side of tract is affected, the other side of tract can compensate to allow for continuous normal function.
State the motor functions of the cranial nerves (somatomotor and visceromotor)
CN III - OCULOMOTOR N
- somatomotor = EOM (SR, IR, MR, LO, LPS)
- visceromotor = IOM (ciliary muscle, sphincter pupillae)
CN IV - TROCHLEAR N
- somatomotor = EOM (SO)
CN V - TRIGEMINAL N
- somatomotor = V3 - muscles of mastication (masseter, temporalis, pterygoid) and 1st phargyngeal arch (mylohyoid, anteriro belly of digastric, tensor tympani, tensor veli palatini)
CN VI - ABDUCENS N
- somatomotor = EOM (LR)
CN VII - FACIAL N
- somatomotor = skeletal muscles of facial expression and muscles that originate from 2nd pharyngeal arch (stylohyoid, stapedius, posterior belly of digastric)
- visceromotor = all glands in face except parotid gland (lacrimal, submandibular, sublingual)
CN IX - GLOSSOPHARYNGEAL N
- somatomotor = stylopharyngeus
- visceromotor = parotid gland
CN X - VAGUS N
- somatomotor = all muscles in pharynx except stylopharyngeus, all muscles in palate except tensor veli palatini, all muscles of the larynx
- visceromotor = other glands such as heart, lungs, digestive system
CN XI - SPINAL ACCESORY N
- somatomotor = SCM and trapezius
CN XII - HYPOGLOSSAL N
- somatomotor = all muscles in tongue except palatoglossus
TRIGEMINAL NERVE (somatomotor)
- Name the LMN and state location
- State whether this is bilateral/unilateral UMN
- State the muscles they supply
- State the pathway
TRIGEMINAL NERVE (somatomotor)
- LMN = trigeminal motor nucleus (located in pons)
- UMN = (bilateral) precentral gyrus
- Muscles = muscles of masticaiton (temporalis, masseter, pterygoid) and 1st pharyngeal arch (mylohyoid, stapedius, anterior belly of digastric, tensor tympani, tensor veli palatini)
- Pathway: precentral gyrus (primary motor cortex) –> trigeminal motor nucleus –> muscles
GLOSSOPHARYNGEAL NERVE (somatomotor)
- Name the LMN and state location
- State whether this is bilateral/unilateral UMN
- State the muscles they supply
- State the pathway
GLOSSOPHARYNGEAL NERVE (SOMATOMOTOR):
- LMN = nucleus ambiguus (located in MO)
- UMN = (bilateral) precentral gyrus
- Muscles = stylopharyngeal muscle
- Pathwa: precentral gyrus (primary motor cortex) –> nucleus ambiguus –> stylopharyngeus
VAGUS NERVE (somatomotor)
- Name the LMN and state location
- State whether this is bilateral/unilateral UMN
- State the muscles they supply
- State the pathway
VAGUS NERVE (SOMATOMOTOR):
- LMN = nucleus ambiguus (MO)
- UMN = (bilateral) precentral gyrus
- Muscles = all intrinsic muscles of pharynx except stylopharyngeus, all intrinsic muscles of palate except tensor veli palatini, all muscles of larynx
- Pathway: precentral gyrus –> nucleus ambiguus –> tensor veli palatini
SPINAL ACCESSORY NERVE (somatomotor)
- Name the LMN and state location
- State whether this is bilateral/unilateral UMN
- State the muscles they supply
- State the pathway
SPINAL ACCESSORY NERVE (SOMATOMOTOR):
- LMN = spinal accessory nucleus (cervical spinal cord)
- UMN = (bilateral) precentral gyrus
- Muscles = trapezius, SCM
- Pathway: precentral gyrus –> spinal accessory nucleus –> trapezius + SCM
HYPOGLOSSAL NERVE (somatomotor)
- Name the LMN and state location
- State whether this is bilateral/unilateral UMN
- State the muscles they supply
- State the pathway
HYPOGLOSSAL NERVE (SOMATOMOTOR):
- LMN = hypoglossal nucleus (MO)
- UMN = (bilateral) precentral gyrus
- Muscles = all muscles of tongue except palatoglossus
- Pathway: precentral gyrus –> hypoglossal nucleus –> all muscles of tongue except palatoglossus
FACIAL NERVE (somatomotor)
- Name the LMN and state location
- State whether this is bilateral/unilateral UMN
- State the muscles they supply
- State the pathway
FACIAL NERVE (SOMATOMOTOR):
- LMN = facial motor nucleus (lower part of pons)
- UMN = (bilateral except contralateral for muscles of lower part of face) precentral gyrus
- Muscles = muscles of facial expression + stapedius + posterior belly of digastric + stylohyoid
State the result of an UMN and LMN lesion.
UMN LESION:
- only contralateral lower part of face is paralysed, upper face will be normal
- this is because contralateral upper quadrant of face has bilateral UMN supply
LMN LESION:
- both upper and lower part of face on the same side (ipsilateral) will be paralysed
Name the 4 cranial nerves with autonomic (viscero-motor) parasympathetic functions
- 10
CN III = oculomotor N - IOM (ciliary muscle, sphincter pupillae)
CN VII = facial N - all facial glands except parotid (sublingual, submandibular, lacrimal)
CN IX = glossopharyngeal N - parotid gland
CN X = vagus N - hearts, lungs, digestive system
CN X - VAGUS NERVE
IN VISCERAL AFFERENT REFLEX,
(1) 1st order neuron =
(2) 2nd order neuron =
IN VISCERAL EFFERENT REFLEX,
(1) Preganglionic neuron =
(2) Postganglionic neuron =
CN X - VAGUS NERVE
IN VISCERAL AFFERENT REFLEX,
(1) 1st order neuron = inferior glossopharyngeal ganglion + vagal ganglion
(2) 2nd order neuron = nucleus of tractus solitarius
IN VISCERAL EFFERENT REFLEX,
(1) Preganglionic neuron = dorsal vagal nucleus
(2) Postganglionic neuron = cardiac ganglia
