Neurophysiology Flashcards
Where does the pyramidal motor pathway begin?
Motor cortex (precentral gyrus)
What role does the pyramidal motor pathway play?
Complicated voluntary movements
What do pyramidal motor cell axons come together to form?
Internal capsule in the Fore-brain
Fibers from the internal capsule in the forebrain travel through where?
Cerebral peduncles, pons, and medulla to form MEDULLA PYRAMIDS
Where do the fibers that innervate CRANIAL NERVES break away from the fibers that travel to eventually form the medulla pyramids? What is this break away tract called?
Certain regions of the middle pons & middle medulla
NOTE: this break away tract is called the “CORTICOBULBAR TRACT”
Where is the pyramidal decussation of the pyramidal motor pathway?
in the CAUDAL MEDULLA where 85-90% of the fibers cross & become the LATERAL CORTICOSPINAL TRACT
What is the function of the lateral corticospinal tract?
Controls proxmial musculature
Where do the remaining fibers of the pyramidal tract form (the fibers that don’t cross to form the lateral corticospinal tract)?
Anterior Corticospinal Tract which eventually decussate at the level of the spinal cord
What is the function of the Anterior corticospinal tract?
Controls distal musculature
What do lesions ABOVE the MEDULLA cause?
Lead to problems w MOTOR control on the CONTRALATERAL SIDE
What is the function of the reticulospinal pathway?
Complex voluntary movements AND integration of sensory information to direct motor control
NOTE: this pathway offers an alternative to the pyramidal motor pathway for motor control
Where do the fibers for the reticulospinal pathway originate from?
RETICULAR formation (diffuse collection neurons) w/in the PONS and MEDULLA
NOTE: these fibers descend ipsilaterally & eventually synapse w neurons at ALL levels of the spinal cord
Which pathway plays a role in reflexive head movements in response to visual stimuli?
Tectospinal pathway
Where do the fibers from the tectospinal pathway originate from and where do they eventually synapse?
Originates in the SUPERIOR COLLICULUS and immediately cross the midline and then descend through the pons and medulla –> travelling anterior to the MLF
The fibers eventually synapse at the CERVICAL LEVEL of the SPINAL CORD (neck)
The cochlear and vestibular nerves combine to form the vestibulocochlear nerve which then carries info to which 3 places?
- Primary auditory cortex
- Cerebellum
- Spinal cord
ALL for hearing and balance
Where does the cochlear nerve fibers originate from? Where do they travel to?
Spiral Ganglion of the cochlea
Traveling through the Organ of Corti and exiting via internal meatus and ending their cell bodies located in the cochlear nuclei of the MEDULLA
Where does the 2nd order neuron of the cochlear nerve travel to?
Ascend on both sides of the trapezoid body to the SUPERIOR OLIVARY COMPLEX w/in the brainstem (1st location of bilateral auditory input)
Where is the 1st location of bilateral auditory input?
Superior olivary complex w/in the brainstem
What does the fibers from the superior olivary complex (3rd order neurons) form? And where does it eventually synapse?
Forms the LEMNISCUS pathway and eventually synapses on the INFERIOR COLLICULUS of the midbrain and medial geniculate body in the thalamus (4th order neuron) before traveling to the primary cortex
Where does the vestibular nerve originate and what is its function?
Originates from the VESTIBULAR GANGLION (at the distal end of the internal auditory meatus)
These fibers join the cochlear nerve of CN8 and carry sensory info from the semicircular canals and otolith organs of the ear
Most of the vestibular nerve synapse with what?
The 4 vestibular nuclei in the medulla and pons
The remaining fibers directly project to the CEREBELLUM via the inferior cerebellar peduncle to control movements necessary for balance
The lateral vestibular nuclei form which pathway? Where do they travel? What are their function?
Form: Lateral Vestibulospinal pathway
Travel: along IPSI spinal cord
Function: helps control MOVEMENTS that allow us to WALK UPRIGHT
The Medial vestibular nuclei form which pathway? Where do they travel? What are their function?
Form: Medial Vestibulospinal pathway
Travel: Along EITHER side to THORACIC segments of spinal cord
Function: Integrate head movements w EYE movements
Which pathway carries PAIN and TEMPERATURE information from the BODY?
Spinothalamic Pathway
Where do the peripheral nerve endings of the Spinothalamic pathway synapse?
Substantia gelatinosa w/in the dorsal horn of the spinal cord
Where do the fibers from the spinothalamic tract travel after the substantia gelatinosa?
Fibers leave the SG cross the midline and become the LATERAL spinothalamic pathway
They remain contralateral until they terminate in the ventral posterior thalamus (VPL)
Which pathway carries pain and temperature info from the face?
Trigeminothalamic pathway
Where does the trigeminothalamic pathway originate and where do they descend to?
Originates: Trigeminal ganglion cells, as well as facial pain and temp receptors that extend into the brainstem at the level of the pons
The axons descend into the medulla (forming the SPINAL TRACT of the CN5), where they synapse onto 2nd order neurons in one of two sub-regions of the trigeminal complex of the spinal cord
What happen to the axons from the neurons w/in the trigeminal complex?
They cross the spinal column in the medulla and ascend CONTRALATERALLY until they terminate in the thalamus
What does a lesion to the trigeminothalamic pathway above the crossover point result in?
Loss of pain or temperature info from the contralateral side of the face
Which pathway carries info about touch, pressure, and vibration?
Medial Lemniscus Pathway
Where do peripheral info from mechanoreceptors to the upper body travel along in the medial lemniscus pathway?
Cuneate tract (located more laterally)
Where do lower body info from the medial lemniscus pathway travel along?
Gracilis tract (located more medially)
Where does the cuneate tract (medial lemniscus pathway) enter the spinal cord? Where does it ascend to?
Enter the CERVICAL regions of the spinal cord
Ascends to the cuneatus nuclei in the CAUDAL medulla
Where does the Gracilis tract enter the spinal cord? Where does it ascend to?
Enter the LUMBAR regions of the spinal cord
Ascends to the gracilis nuclei in the caudal medulla
Axons from the 2nd neurons in the caudal medulla cross the midline and become what fibers (from the cuneat and gracilis tract)?
Internal arcuate fibers
These fibers travel contralaterally until terminating in the VPL
