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Spinal Sensory Motor
Spinal Sensory Motor Pathways
| Question | Answer |
|---|---|
| White matter is what? | Bundle of nerve fibers running together |
| What are the bundle of nerve fibers in white matter called? | Tracts or fasciculus |
| What are the 3 columns in the spinal cord? Where are they located | Posterior - b/w midline and dorsal horn of spinal cord Lateral - b/w dorsal and ventral horns Anterior - b/w midline and ventral horn of spinal cord |
| What kind of nerves are in each column? | Posterior - pure sensory Lateral - both sensory and motor Anterior - both sensory and motor |
| What are the tracts in the posterior column? | Gracile fasciculus - ascend from lower part of body Cuneat fasciculus - ascend from upper part of body |
| What are the tracts in the lateral column? | Corticospinal Rubcrospinal Reticulospinal Vestibulospinal |
| What are the tracts in the anterior column? | Tectospinal |
| What are the ascending tracts? | Sensory nerve fibers Take info from spinal cord to higher regions |
| What are the descending tracts? | Motor nerve fibers Takes info from higher regions to spinal cord |
| In reflex arc, how many neurons need to be engaged? | Depends. Has to be at least 2. (1 motor, 1 sensory) |
| Where would the inhibitory pathway for pain travel down to? | Spinal cord, in grey matter, in substantia gelatinosa |
| What is the function of the somatic sensory pathway? | Relay info from somatic receptors to primary somatosensory area in the cerebral cortex |
| How many neurons are involved in the somatic sensory pathway? | 3 |
| What carries signal to both the cerebellum and reticular formation of the brainstem in the somatic sensory pathway? | Axon collaterals |
| Describe the path for the first order neuron in the somatic sensory pathway. | Have cell bodies in their dorsal root ganglia and central processes that enter the spinal cord via the dorsal root |
| Are first order neurons in the somatic sensory pathway spinal or cranial nerves? | Either |
| Describe the path for the second order neuron in the somatic sensory pathway. | Cell bodies in the CNS grey matter. Give rise to axons that cross midline before ascending to the thalamus |
| Describe the path for the third order neuron in the somatic sensory pathway. | Project from ventral posterior nucleus of thalamus to primary somatosensory cortex in parietal lobe (post-central gyrus) |
| Where will the second order neuron in the somatic sensory pathway cross to the opposite side? | Either spinal cord (midline) or in brainstem |
| If transmitting info for touch or pain, where is the cell body for third order neurons in the somatic sensory pathway? | Ventral posterior nucleus of thalamus |
| For the pathway for pain and temperature, where will the second neuron cross over? | At the midline |
| What side of the patient loses pain and temperature if the spinal cord is cut? | Depends on midline If cut at spinal cord, then opposite side If cut at medulla, then same side If cut at pons, then both (at opposite side) |
| What pathway does the information for pain and temperature relayed on? | Spinothamic pathway |
| For the spinothalamic pathway, describe the path for the first order neuron | Connects to second neuron in dorsal horn of the spinal cord, on same side the nerve impulse comes from |
| For the spinothalamic pathway, describe the path for the second order neuron | Single axon crosses the midline to other side of spinal cord and goes up brain along with other axons forming the lateral spinothalamic tract and connects to 3rd order neuron |
| For the spinothalamic pathway, describe the path for the third order neuron | Cell body in ventral posterolateral nucleus of thalamus |
| What pathway does the information for touch and proprioception relayed on? | Lemniscal pathway |
| The info for discriminative touch and proprioception aids in what activities? | Recognition of exact location of object touching skin Two point discriminations Stereognosis Awareness of position of body parts and direction of movement Ability to sense the weight of object Ability to sense vibration |
| What kind of info is relayed in the posterior column-medial lemniscus pathway? | Proprioception Discriminative touch (fine touch) Vibration |
| For the posterior column-medial lemniscus, describe the path for the first order neuron | Cell body in DRG enters spinal cord and ascend in posterior column of same side without synapsing |
| Fibers from the lower part of the body ascend in what tract in the dorsal column? | Fascilus gracilis |
| Fibers from the upper part of the body ascend in what tract in the dorsal column? | Fasciculus cuneatus |
| Where do the first order neurons synapse with the second order for the posterior column-medial lemniscus pathway? | Gracile nucleus and cunate nucleus of medulla, respectively |
| What are the second order neurons referred to in the posterior column-medial lemniscus pathway? | Internal arcuate fibers |
| What do the second order neurons travel as when it crosses the midline in the PCML pathway? | Medial lemniscus |
| For the posterior column-medial lemniscus, describe the path for the second order neuron | Internal arcuate fibers cross the midline, making an arc Will be packed in small area called medial lemniscus Will travel to the VPL nucleus of thalamus |
| At the level of thalamus, describe the awareness of touch. (PCML) | Crude touch or vibration No awareness of discriminating senses |
| For the posterior column-medial lemniscus, describe the path for the third order neuron | Pass through part of internal capsule to reach the cerebral cortex Cerebral cortex allows activity that info relayed aids in |
| What kind of information is relayed in the anterolateral pathway? | Crude touch and pressure |
| What tract does the information for crude touch and pressure relayed on? | Anterior spinothalamic tract |
| For the anterolateral pathway, describe the path for the first order neuron | Cell bodies in DRG enter spinal cord via dorsal root and synapse with second order neuron in dorsal horn on same side |
| What happens prior to synapsing with second order neurons in the anterolateral pathway? | Travel up or down one or two segments in Lissauer's tract |
| What is the lissauer's tract? | AKA dorsolateral tract Between tip of dorsal horn and surface of spinal cord |
| What is the function of Lissauer's tract? | Connects several segments of spinal cord because fibers coming into spinal cord need to go to other segments Basically, travels between segments |
| What would be an example of needing Lissauer's tract? | Withdrawal reflex and cross extensor reflex - need to involve several segments |
| For the anterolateral pathway, describe the path for the second order order neuron | From dorsal horn, axon will cross midline to opposite anterior funiculus and travel to VPL of thalamus to synapse with 3rd order neuron |
| Through what structure does the second order neuron pass through to cross midline of anterolateral pathway? | Anterior white commissure |
| What is the anterior white commissure? | Small white matter between anterior horns of spinal cord in front of central canal |
| What makes up the anterior white commissure? | Made by 2nd order neurons on both sides |
| What side would be compromised if the anterior white commissure is damaged? | Both sides |
| At the level of thalamus, describe the awareness of senses. (anterolateral pathway) | Vague awareness and crude localization of touch and pressure |
| For the anterolateral pathway, describe the path for the third order neuron | Travel to cerebral cortex via internal capsule |
| At level of cerebral cortex, describe awareness of senses. (anterolateral) | Full awareness and localization of touch and pressure |
| What tracts make up the spinal lemniscus? | Anterior and lateral spinothalamic tract |
| What kind of information is relayed in lateral spinothalamic tract? | Pain, temperature, tickle, and itch |
| Compare lateral and anterior spinothalamic tract. | Identical except for function and location |
| For the lateral spinothalamic pathway, describe the path for the first order neuron | Cell bodies in DRG enter spinal cord via dorsal root and synapse with second order neuron in dorsal horn on same side Also travels up or down in Lissauer's tract |
| For the lateral spinothalamic pathway, describe the path for the second order neuron | From dorsal horn, axon will cross midline to opposite lateral funiculus and travel to VPL of thalamus to synapse with 3rd order neuron |
| What is the NT used at synapse of 1st and 2nd order neurons in the lateral spinothalamic tract? | Substance P |
| For the lateral spinothalamic pathway, describe the path for the third order neuron | Travel to cerebral cortex via internal capsule |
| What is the relative size of cortical areas to sensory receptors? | Proportional |
| What is the relative size of cortical areas to sensitivity of each part of the body? | Proportional |
| For the spinotectal tract, where does the 2nd order neuron synapse? | Superior colliculus of midbrain |
| Why is the spinotectal tract considered a subdivision of the spinothalamic tract? | Functionally, transmits typical spinothalamic impulses into tectum of midbrain |
| What is the significance of collateral structures? | Utilizes different parts of the brain for different functions for information traveling in the brainstem Synapses with other neurons which activate reflex or inhibit pain |
| What is the implication for the second order neuron synapsing in the superior colliculus instead of thalamus? | Drives reflexes |
| In taste, what is the afferent and efferent? | Afferent - taste Efferent - salivating |
| Hearing reflex, what is the afferent and efferent? | Afferent - sound Efferent - reflex |
| What are the additional pathways to the lateral spinothalamic tract that help mediate pain? | Spinoreticular Spinomesencephalic |
| Describe the spinoreticular tract | Enters dorsal horn and synapses but does NOT cross Travels up same side of SC in lateral column Terminates in reticular formation |
| What is the function of the spinoreticular tract? | Bring a sense of awareness and alertness to the injury |
| Is the spinoreticular tract a collateral of the spinothalamic? | No, has its own identity |
| Describe the spinomesencephalic tract | Enters dorsal horn and synapses but does NOT cross Travels up same side of SC in lateral column Terminates in periaqueductal gray region of midbrain |
| What is the periaqueductal grey region? | Area surrounding cerebral aqueduct |
| What do the neurons in PAG contai? | Encephalic/endorphins (opioids) |
| What region has connections to the limbic system? | PAG |
| What is the implication of connecting to the limbic system for the spinomesencephalic tract? | Limbic system deals with memory and emotional expression Therefore Responsible for fear and aversion reactions associated with pain |
| What is syringomyelia? | Formation of a cavity in central grey region of the spinal cord May be due to gliosis following trauma |
| In the motor pathway, how many neurons are needed? | 2 From departure to destination |
| In motor pathways, where could the neuron end up in the spinal cord? | Ventral horn - motor Lateral - visceral motor |
| In motor pathways, where could the neuron end up in the brain stem? | Cranial nerve nuclei |
| Describe the pathway for upper motor neurons | Begin in cortex and/or brainstem and terminate in brainstem or spinal cord |
| What kind of nerves is the corticobulbar tract associated with? | Cranial nerves |
| Where does the corticobulbar tract terminate? | Brainstem CN III, IV in midbrain CN V-VIII in pons CN IX-XII in medulla |
| Describe the path for the extra pyramidal pathway | Start in brainstem and end in spinal cord |
| Where does the corticospinal tract terminate? | Spinal cord Ventral horn |
| Describe the pathway for lower motor neurons | Begins in brainstem or spinal cord and innervates muscles |
| Where in the brainstem does the lower motor neuron arise from? | Cranial nerve Cell body in motor nuclei of CN |
| Where in the spinal cord does the lower motor neuron arise from? | Ventral horn |
| For upper motor neuron lesions in the corticospinal tract, what side of the body would the signs be presented? | Contralateral |
| What are the implications of an upper motor neuron lesion? | Spastic muscles (increased muscle tone, no inhibitory influences) Exaggerated or pathological reflexes (i.e. Babinski sign) Paresis (weakness) or paralysis when voluntary movement attempted |
| What are the implication of a lower motor neuron lesion? | Flaccid muscles and atrophy Loss of reflexes Paresis or paralysis when voluntary movement attempted |
| For lower motor neuron lesions, what side of the body would the signs be presented? | Same side |
| For the corticospinal tract, what structures do the descending tracts pass through? | Internal capsule Crus cerebri of midbrain Basilar portion of pons Pyramid of medulla |
| What happens at the junction of the medulla and spinal cord for the corticospinal tract? | Most will cross at decussation of pyramids Those that do form the lateral corticospinal tract That that don't form the anterior corticospinal tract |
| Describe the path for the lateral corticospinal tract | Descend in the lateral column of spinal cord |
| Describe the path for the anterior corticospinal tract | Descend into the anterior column of spinal cord and cross in spinal cord before synapsing in anterior horn |
| Which fibers are responsible for coordinated, precise, and voluntary skeletal muscle movements? | Anterior and lateral fibers |
| The corticospinal tract receives input from what structures? | Sensory cortex, cerebellum, etc |
| Anterior corticospinal also synapse with motor neurons of ventral horn on same side for core (trunk) muscles. What is the implication of this? | Because core receives input from both sides of the brain, damage to one side won't cause completely paralysis |
| What is the implication of the anterior corticospinal tract movement and where it synapses for limbs? | Eventually, all will end up on opposite side So damage to one side will affect the other completely |
| What tract is older than corticospinal? | Rubrospinal tract |
| What is the implication of rubrospinal tract being older than corticospinal? | Crawling before walking Damage to CPT can be overcome with time by RS |
| Automatic swinging of arms when walking is due to what tract? | Rubrospinal |
| What 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) Synapses with ventral horn then goes to muscle |
| What muscles are inhibited for the 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 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 |
| Where does the tectospinal tract begin? | Superior colliculus of midbrain |
| What should be noted about the superior colliculus of midbrain, in regards to tracts? | Spinotectal tract terminates there Tectospinal tract begins there |
| Describe the path for tectospinal tract pathway | From superior colliculus, fibers soon cross and descend through brainstem to anterior column of spinal cord Terminate in upper cervical segments of spinal cord |
| What other structures connects with the tectospinal tract? | CN III, IV, VI - coordinate head and eye movement |
| What is the function of tectospinal tract? | Control movement of head in response to visual and auditory stimuli |
| Which cranial nerve descend into segments of the spinal cord | CN 1-6 |
| Where is the spinal accessory nerve is derived from what nerves? | C1-C6 |
| Describe the path for the lateral vestibulospinal tract? | Begins at lateral vestibular nucleus (from CN VIII) Descends ipsilaterally to anterior column of spinal cord No crossing at midline |
| What is the function of the lateral vestibulospinal tract? | Regulate muscle tone in response to movements of the head Therefore Role in balance and equilibrium |
| What muscles are inhibited in the lateral vestibulospinal tract? | Flexor |
| What muscles are excited in the lateral vestibulospinal tract? | Extensor |
| What is the implication |
Created by:
nnguyen44
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