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Spinal Pathway
Spinal Sensory and Motor Pathways
| Question | Answer |
|---|---|
| Where do somatic sensory pathways relay information to? | From somatic receptors to primary somatosensory area in the cerebral cortex |
| How many neurons are involved in sensory pathways? | 3 |
| What structure carries signals into the cerebellum and the reticular formation of brain? | Axon collaterals of somatic sensory neurons |
| What order neurons conduct impulses to CNS? | 1st order |
| What neurons conduct impulses from brainstem or spinal cord to thalamus? | 2nd order |
| What neuron conducts impulses from thalamus to primary somatosensory cortex? | 3rd order |
| What kind of information does the posterior column carry? | Discriminative touch and conscious proprioception |
| What is also in the posterior column? | Medial lemniscus |
| What kind of activities use discriminative touch and proprioception? | Recognition of exact location object touches skin, two-point discriminations, stereognosis, awareness of position of body parts and direction of movement, ability to sense weight of an object, ability to sense vibration |
| What is stereognosis? | Ability to perceive shape of an object through touch? |
| Where are 1st order neurons found in? | Dorsal ganglia |
| Where are 2nd order neurons found in? | Spinal cord of brainstem |
| Where are 3rd order neurons for pain/touch found in | Ventral posterior nucleus of thalamus |
| What kind of information does the posterior column carry? | Discriminative touch and conscious proprioception |
| What kind of activities does discriminative touch and proprioception aid in? | Recognition of exact location object touched skin, two-point discrimination, stereognosis, awareness of position of body parts and direction of movement, ability to sense weight of object, ability to sense vibration |
| What is stereognosis? | Ability to perceive shape of an object through touch |
| What does it mean that the posterior column-medial lemniscus pathway runs ipsilateral? | Sensory fibers enter spinal cord and ascend in the posterior column of same side without synapsing? |
| In posterior column, from where do first order neurons enter the spinal cord? | Cell body in dorsal root ganglia |
| In the posterior column-medial lemniscus, where do fibers from the lower parts of the body ascend in? | Fasciculus gracilis |
| In the posterior column-medial lemniscus, where do fibers from the upper parts of the body ascend in? | Fasciculus cuneatus |
| In the posterior column-medial lemniscus, where do 1st order neuron and 2nd order neurons synapse in? | Medulla - gracilis (lower) or cuneate (upper) nucleus |
| In the posterior column-medial lemniscus, what are the 2nd order neurons referred to as and why? | Internal arcuate fibers - when axons of neurons cross the midline, forms an arc |
| In the posterior column-medial lemniscus, after the 2nd order neuron crosses the midline, where will it be packed? | Medial lemniscus |
| In the posterior column-medial lemniscus, where does the 2nd order neuron synapse with the 3rd order neuron? | VPL nucleus of thalamus |
| In the posterior column-medial lemniscus, at the level of the thalamus, what kind of awareness is exhibited? | Crude vibrations |
| In the posterior column-medial lemniscus, what structure do 3rd order neurons have to pass through to reach the cortex? | Internal capsule |
| What kind of information is carried in the anterior spinothalamic tract? | Crude touch and pressure |
| What does it mean the the anterior spinothalamic pathway is contralateral? | Sensory fibers enter spinal cord and synapse with 2nd order in dorsal root where it will cross midline |
| In the anterior spinothalamic pathway, what happens before 1st order synapses with 2nd order? | Travel up or down - one or two segments in Lissauer's tract |
| What is the Lissauer's tract? | AKA dorsolateral tract - tract that connects several segments of spinal cord |
| Where is the Lissauer's tract located? | Tip of dorsal horn and surface of spinal cord |
| Why would you need Lissauer's tract? | Need to involve several segments - like in withdrawal reflex or cross extensor reflex |
| In the anterior spinothalamic pathway, what area does the 2nd order neuron have to cross into? | Anterior funiculus (AKA column) |
| In the anterior spinothalamic pathway, how does the 2nd order cross to the anterior column on the opposite side? | Through anterior white commissure |
| What is the anterior white commissure? | Small white matter between anterior horns of spinal cord in front of central canal |
| What is on both sides of the anterior white commissure? | 2nd order neurons on both sides |
| What is the implication of having 2nd order neurons on both sides of the anterior white comissure? | If this is damaged, then both sides are compromised |
| In the anterior spinothalamic pathway, where does the 2nd order neuron synapse with the 3rd order? | Travels from anterior column to VPL nucleus of thalamus |
| In the anterior spinothalamic pathway, at the level of the thalamus, what is kind of awareness is exhibited? | Vague awareness and crude localization of touch and pressure |
| In the anterior spinothalamic pathway, how does the 3rd order neuron send info to cortex | Through internal capsule to cerebral cortex |
| In the anterior spinothalamic pathway, what kind of awareness is exhibited at the cortex? | Full awareness and localization for pressure and touch |
| What kind of information is carried through lateral spinothalamic tract? | Pain, temperature, tickle, and itch |
| Compare anterior and lateral spinothalamic tract | Identical to each other except for function and location |
| What is the function of anterior and lateral spinothalamic tract? | Anterior - Crude touch, pressure. Lateral - pain, temperature, tickle, itch |
| In the lateral spinothalamic tract, where does the 1st order neuron synapse with the 2nd order? | Dorsal horn |
| In the lateral spinothalamic tract, what neurotransmitter is thought to be released ? | Substance P |
| What tract is considered a subdivision of the spinothalamic tract? | Spinotectal tract |
| What is the function of the spinotectal tract? | Drives reflexes that turn head to look at stimulus |
| How does the spinotectal tract differ from the spinothalamic? | Instead of continuing to thalamus and cortex, will synapse in superior colliculus of midbrain |
| How does the spinotectal tract drive reflexes? | Transmits typical spiniothalamic impulses (like touch) into tectum of brain. Tectum - reflexes |
| What are additional pathways to the lateral spinothalamic tacts? | Spinoreticular and spinomesencephailc |
| What is the function of the spinoreticular tract? | Bring awareness and alertness to injury |
| Why is the spinoreticular tract ipsilateral? | Enters dorsal horn and synapses but does NOT cross. Travels up ipsilateral side in lateral column |
| Where does the spinoreticular tract terminate in? | Reticular formation |
| What is the function of the spinomesencephalic tract? | Connects to limbic system – fear and aversion reactions associated with pain |
| Where does the spinomesencephalic tract terminate in? | Periaqueductal grey region |
| What do the neurons in PAG contain? | Endorphins/encephalic (opioids) |
| Where do the neurons in the upper motor neurons begin? | Cortex or brainstem |
| Where do the neurons in the upper motor neurons terminate in? | Brainstem or spinal cord |
| Where do the corticobulbar tract terminate in? | Brainstem |
| Where do the corticobulbar tract synapse on? | Cranial nerve nuclei (III, IV in midbrain; V-VIII in pons; IX-XII in medulla) |
| Where do the corticospinal tract terminate in? | Spinal cord |
| Where do the corticospinal tract synapse on? | Motor neurons in ventral horn of spinal cord q |
| For the extra pyramidal pathway, where does it sart and end in? | Brainstem; spinal cord |
| Where do the lower motor neurons begin in? | Brain stem or spinal cord |
| What does the lower motor neuron innervate? | Muscles |
| Where are the cell bodies of lower motor neurons in the spinal cord? | Ventral horn |
| Where are the cell bodies of lower motor neurons in the brainstem? | Motor nuclei of cranial nerves in brainstem |
| What tract is involved in upper motor neuron lesions? | Corticospinal tract |
| What side would indicate an upper motor neuron lesion? | Contralateral |
| What are some symptoms of an upper motor neuron lesion? | Spastic muscles, exaggerated or pathological reflexes, paresis or paralysis when voluntary movement attempted |
| What are symptoms of a lower motor neuron lesion? | Flaccid muscles and atrophy, loss of reflexes, paresis or paralysis when voluntary movement attempted |
| What is usually affected in lower motor neuron lesions? | Motor neurons in ventral horn of spinal cord and after |
| What side is affected for lower motor neuron lesions? | Ipsilateral |
| For the corticospinal tracts, what structures do the descending fibers have to pass through? | Internal capsule, crus cerebri of midbrain, basilar portion of pons, pyramids of medulla |
| For the corticospinal tracts, what happens at the junction of the medulla and spinal cord? | Most fibers cross at decussation of pyramids |
| For the corticospinal tracts, what do the crossed fibers form? | Lateral corticospinal tract |
| For the corticospinal tracts, based on the name, what column does the lateral corticospinal tract descend in? | Lateral column of spinal cord |
| For the corticospinal tracts, what do the uncrossed fibers form? | Anterior corticospinal tract |
| For the corticospinal tracts, based on the name, what column does the anterior corticospinal tract descend in? | Anterior column of spinal cord |
| For the corticospinal tracts, when does the anterior corticospinal tract cross over? | At level of spinal cord in anterior horn |
| What is the function of the corticospinal tract? | Coordinated, precise, and voluntary skeletal muscle movements |
| What structures does the corticospinal tract receive input from? | Sensory cortex, cerebellum, etc |
| What is the function of the tectospinal tract? | Controls movements of the head in response to visual stimuli |
| Where does the tectospinal tract begin? | Superior colliculus of midbrain |
| What is the significance of where the tectospinal tract begins? | IT is where spintotectal tract terminates |
| Do the fibers of the tectospinal tract cross over? | Yes, fibers cross soon after origin and descend through brainstem |
| What column does the tectospinal tract travel in? | Anterior |
| Where does the tectospinal tract terminate in? | Upper cervical segments of spinal cord |
| What does the tectospinal tract also connect with? | Nuclei of cranial nerves III, IV, VI |
| What is the significance of CN III, IV, VI? | Coordination of eye movements |
| The spinal accessory nerve is originated from what CN? | CN 1-6 |
| Where does the lateral vestibulospinal tract begin? | Lateral vestibular nucleus |
| What do the vestibular nuclei belong to? | Group of nuclei belonging to vestibular part of CN VIII |
| Why is the lateral vestibulospinal tract ipsilateral? | Fibers don’t cross midline but descend ipsilaterally |
| What column does the lateral vestibulospinal tract descend in? | Anterior column of spinal cord |
| What is the function of the lateral vestibulospinal tract? | Regulate muscle tone in response to movements of the head – plays role in balance and equilibrium |
| What structures does the lateral vestibulospinal tract receive input from? | Inner ear via vestibulocochlear nerve and cerebellum |
| Where does the reticulospinal tract begin? | Pontine – reticular formation of pons; Medullary – reticular formation of medulla |
| How do the pontine and medullary reticulospinal tract differ? | Pontine – remains uncrossed, descends in anterior column ; Medullary – crossed and uncrossed, descends in lateral column |
| What is the function of the reticulospinal tract? | Influence reflexes, voluntary movements, and carry autonomic information from hypothalamus to lateral horn |
| What voluntary movements are influenced by the reticulospinal tract? | Allows for inhibition of antagonist muscle when agonist is contracted |
| What structures does the reticulospinal tract receive input from? | Cerebral cortex, cerebellum, hypothalamus |
| How is pain modulated? | Spinomesencephalic tract – stimulation of PAG neurons sends impulses down to dorsal horn of spinal cord and block release of substance P |
| What muscles are inhibited in the lateral vestibulospinal tract? | Flexor |
| What muscles are excited in the lateral vestibulospinal tract? | Extensor |
| What is the implication for inhibition of flexor and excitation of extensor muscles in the vestibulo tract? | Function is balance which needs extensor side |
| What tract is older than corticospinal? | Rubrospinal tract |
| What is the implication of rubrospinal being older than corticospinal? | Crawling before walking. Damage to CPT can be overcome with time by RS |
| What tract causes automatic swinging of arms when walking? | Rubrospinal |
| Why is the rubrospinal tract called a crossed pathway? | Fibers cross over at level of nucleus |
| Where does the rubrospinal tract begin? | Red nucleus of midbrain |
| Describe the path for the rubrospinal tract | Begins at red nucleus, crosses midline while still in midbrain, goes all the way down to spinal cord (lateral column) and synapses with ventral horn then goes to muscle |
| What muscles are inhibited for rubrospinal tract? | Extensor |
| What muscles are excited for the rubrospinal tract? | Flexor |
| What is the direction of nervous system development and myelination? | Starts at spinal cord then goes all the way up? |
| What is the implication of the direction of nervous system development? | Babies already have everything at reflexes except at cortical level. So will have rubrospinal in action then will have cortical once cortical has full myelination |
| The fibers in rubrospinal tract are concerned with what? | Muscle tone and posture, skeletal muscle control |
| Rubrospinal tract receives input from what structures? | Cerebellum, cerebral cortex, branches of corticospinal tracts |
Created by:
nnguyen44
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