Neurophysiology

Question 1

Where does the pyramidal motor pathway begin?

Answer 1

Motor cortex (precentral gyrus)

Question 2

What role does the pyramidal motor pathway play?

Answer 2

Complicated voluntary movements

Question 3

What do pyramidal motor cell axons come together to form?

Answer 3

Internal capsule in the Fore-brain

Question 4

Fibers from the internal capsule in the forebrain travel through where?

Answer 4

Cerebral peduncles, pons, and medulla to form MEDULLA PYRAMIDS

Question 5

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?

Answer 5

Certain regions of the middle pons & middle medulla

NOTE: this break away tract is called the “CORTICOBULBAR TRACT”

Question 6

Where is the pyramidal decussation of the pyramidal motor pathway?

Answer 6

in the CAUDAL MEDULLA where 85-90% of the fibers cross & become the LATERAL CORTICOSPINAL TRACT

Question 7

What is the function of the lateral corticospinal tract?

Answer 7

Controls proxmial musculature

Question 8

Where do the remaining fibers of the pyramidal tract form (the fibers that don’t cross to form the lateral corticospinal tract)?

Answer 8

Anterior Corticospinal Tract which eventually decussate at the level of the spinal cord

Question 9

What is the function of the Anterior corticospinal tract?

Answer 9

Controls distal musculature

Question 10

What do lesions ABOVE the MEDULLA cause?

Answer 10

Lead to problems w MOTOR control on the CONTRALATERAL SIDE

Question 11

What is the function of the reticulospinal pathway?

Answer 11

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

Question 12

Where do the fibers for the reticulospinal pathway originate from?

Answer 12

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

Question 13

Which pathway plays a role in reflexive head movements in response to visual stimuli?

Answer 13

Tectospinal pathway

Question 14

Where do the fibers from the tectospinal pathway originate from and where do they eventually synapse?

Answer 14

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)

Question 15

The cochlear and vestibular nerves combine to form the vestibulocochlear nerve which then carries info to which 3 places?

Answer 15

1. Primary auditory cortex
2. Cerebellum
3. Spinal cord

ALL for hearing and balance

Question 16

Where does the cochlear nerve fibers originate from? Where do they travel to?

Answer 16

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

Question 17

Where does the 2nd order neuron of the cochlear nerve travel to?

Answer 17

Ascend on both sides of the trapezoid body to the SUPERIOR OLIVARY COMPLEX w/in the brainstem (1st location of bilateral auditory input)

Question 18

Where is the 1st location of bilateral auditory input?

Answer 18

Superior olivary complex w/in the brainstem

Question 19

What does the fibers from the superior olivary complex (3rd order neurons) form? And where does it eventually synapse?

Answer 19

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

Question 20

Where does the vestibular nerve originate and what is its function?

Answer 20

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

Question 21

Most of the vestibular nerve synapse with what?

Answer 21

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

Question 22

The lateral vestibular nuclei form which pathway? Where do they travel? What are their function?

Answer 22

Form: Lateral Vestibulospinal pathway

Travel: along IPSI spinal cord

Function: helps control MOVEMENTS that allow us to WALK UPRIGHT

Question 23

The Medial vestibular nuclei form which pathway? Where do they travel? What are their function?

Answer 23

Form: Medial Vestibulospinal pathway

Travel: Along EITHER side to THORACIC segments of spinal cord

Function: Integrate head movements w EYE movements

Question 24

Which pathway carries PAIN and TEMPERATURE information from the BODY?

Answer 24

Spinothalamic Pathway

Question 25

Where do the peripheral nerve endings of the Spinothalamic pathway synapse?

Answer 25

Substantia gelatinosa w/in the dorsal horn of the spinal cord

Question 26

Where do the fibers from the spinothalamic tract travel after the substantia gelatinosa?

Answer 26

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)

Question 27

Which pathway carries pain and temperature info from the face?

Answer 27

Trigeminothalamic pathway

Question 28

Where does the trigeminothalamic pathway originate and where do they descend to?

Answer 28

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

Question 29

What happen to the axons from the neurons w/in the trigeminal complex?

Answer 29

They cross the spinal column in the medulla and ascend CONTRALATERALLY until they terminate in the thalamus

Question 30

What does a lesion to the trigeminothalamic pathway above the crossover point result in?

Answer 30

Loss of pain or temperature info from the contralateral side of the face

Question 31

Which pathway carries info about touch, pressure, and vibration?

Answer 31

Medial Lemniscus Pathway

Question 32

Where do peripheral info from mechanoreceptors to the upper body travel along in the medial lemniscus pathway?

Answer 32

Cuneate tract (located more laterally)

Question 33

Where do lower body info from the medial lemniscus pathway travel along?

Answer 33

Gracilis tract (located more medially)

Question 34

Where does the cuneate tract (medial lemniscus pathway) enter the spinal cord? Where does it ascend to?

Answer 34

Enter the CERVICAL regions of the spinal cord Ascends to the cuneatus nuclei in the CAUDAL medulla

Question 35

Where does the Gracilis tract enter the spinal cord? Where does it ascend to?

Answer 35

Enter the LUMBAR regions of the spinal cord Ascends to the gracilis nuclei in the caudal medulla

Question 36

Axons from the 2nd neurons in the caudal medulla cross the midline and become what fibers (from the cuneat and gracilis tract)?

Answer 36

Internal arcuate fibers These fibers travel contralaterally until terminating in the VPL