Podcast
Questions and Answers
At which spinal level(s) does the fasciculus cuneatus begin?
At which spinal level(s) does the fasciculus cuneatus begin?
- C2
- C8
- S5
- T6 (correct)
Which of the following is NOT a characteristic of the fasciculus gracilis?
Which of the following is NOT a characteristic of the fasciculus gracilis?
- It carries DC-ML axons to the nucleus gracilis.
- It is slender in shape.
- It carries axons from T6 to C2 dermatomes. (correct)
- It is found throughout the length of the spinal cord.
What is the significance of the posterior intermediate septum and sulcus?
What is the significance of the posterior intermediate septum and sulcus?
- It regulates motor function of the limbs.
- It separates the dorsal columns into the fasciculus gracilis and fasciculus cuneatus. (correct)
- It is involved in the processing of pain signals.
- It carries sensory information from the limbs.
Which of the following is a correct statement about the spinothalamic tract in the cervical spinal cord section?
Which of the following is a correct statement about the spinothalamic tract in the cervical spinal cord section?
What happens to the dorsal columns as they ascend in the spinal cord?
What happens to the dorsal columns as they ascend in the spinal cord?
Where is the spinothalamic tract located in the spinal cord?
Where is the spinothalamic tract located in the spinal cord?
What is the reason why the spinothalamic tract is more elongated in the cervical spinal cord section compared to the thoracic section?
What is the reason why the spinothalamic tract is more elongated in the cervical spinal cord section compared to the thoracic section?
What is the main reason why the dorsal columns are larger in the thoracic spinal cord compared to the cervical spinal cord?
What is the main reason why the dorsal columns are larger in the thoracic spinal cord compared to the cervical spinal cord?
What is the primary function of the DC-ML pathway?
What is the primary function of the DC-ML pathway?
What is the primary function of the inferior olivary nucleus?
What is the primary function of the inferior olivary nucleus?
What is the significance of the somatotopic organization of the medial lemniscus (ML) in the medulla?
What is the significance of the somatotopic organization of the medial lemniscus (ML) in the medulla?
What is the clinical implication of a lesion affecting half of the medulla at the level described in the text?
What is the clinical implication of a lesion affecting half of the medulla at the level described in the text?
What is the key anatomical change that occurs to the medial lemniscus (ML) as it ascends through the pons?
What is the key anatomical change that occurs to the medial lemniscus (ML) as it ascends through the pons?
Why is the somatotopic organization of the medial lemniscus (ML) in the pons important?
Why is the somatotopic organization of the medial lemniscus (ML) in the pons important?
What is the anatomical landmark that displaces the medial lemniscus (ML) dorsolaterally within the midbrain?
What is the anatomical landmark that displaces the medial lemniscus (ML) dorsolaterally within the midbrain?
What is the primary function of the spinothalamic tract (ALS)?
What is the primary function of the spinothalamic tract (ALS)?
If a patient had a penetrating injury that destroyed ½ of the spinal cord at C1, what would be the clinical presentation?
If a patient had a penetrating injury that destroyed ½ of the spinal cord at C1, what would be the clinical presentation?
What is the significance of the fact that both the medial lemniscus (ML) and the spinothalamic tract (ALS) are positioned laterally in the midbrain?
What is the significance of the fact that both the medial lemniscus (ML) and the spinothalamic tract (ALS) are positioned laterally in the midbrain?
What is the major difference in the somatotopic organization of the medial lemniscus (ML) in the medulla and the pons?
What is the major difference in the somatotopic organization of the medial lemniscus (ML) in the medulla and the pons?
What happens to the somatosensory fibers as they ascend the spinal cord?
What happens to the somatosensory fibers as they ascend the spinal cord?
Where do the Fasciculus Gracilis (FG) fibers synapse?
Where do the Fasciculus Gracilis (FG) fibers synapse?
What is the clinical consequence of a lesion affecting the medial lemniscus (ML) in the midbrain?
What is the clinical consequence of a lesion affecting the medial lemniscus (ML) in the midbrain?
What is the medial lemniscus?
What is the medial lemniscus?
What is the somatotopic organization of the spinothalamic tract?
What is the somatotopic organization of the spinothalamic tract?
What is the role of the dorsal root ganglia (DRGs) in the somatosensory pathways?
What is the role of the dorsal root ganglia (DRGs) in the somatosensory pathways?
What is the difference between the DC-ML and the spinothalamic pathways?
What is the difference between the DC-ML and the spinothalamic pathways?
Which of the following is NOT a characteristic of the second order somatosensory neurons in the DC-ML pathway?
Which of the following is NOT a characteristic of the second order somatosensory neurons in the DC-ML pathway?
Why is the somatotopic organization of the spinothalamic tract significant?
Why is the somatotopic organization of the spinothalamic tract significant?
What does the term "cross the midline" refer to in the context of the somatosensory pathways?
What does the term "cross the midline" refer to in the context of the somatosensory pathways?
Which of the following sensory modalities is NOT transmitted by the Dorsal Column-Medial Lemniscus (DC-ML) pathway?
Which of the following sensory modalities is NOT transmitted by the Dorsal Column-Medial Lemniscus (DC-ML) pathway?
A patient presents with impaired ability to differentiate between different tactile sensations on their left hand. What is the most likely location of the lesion?
A patient presents with impaired ability to differentiate between different tactile sensations on their left hand. What is the most likely location of the lesion?
What is the term for the ability to recognize objects by touch, which is a component of fine discriminatory touch?
What is the term for the ability to recognize objects by touch, which is a component of fine discriminatory touch?
A patient reports losing the ability to feel vibration on their right hand, but can still feel pain and temperature on the same hand. Where is the lesion most likely located?
A patient reports losing the ability to feel vibration on their right hand, but can still feel pain and temperature on the same hand. Where is the lesion most likely located?
Where do the first-order neurons of the DC-ML pathway synapse?
Where do the first-order neurons of the DC-ML pathway synapse?
A physician is examining a patient who has lost the ability to sense their left leg position with their eyes closed. The patient can still distinguish fine textures on the left leg. Which of the following is the most likely location of the lesion?
A physician is examining a patient who has lost the ability to sense their left leg position with their eyes closed. The patient can still distinguish fine textures on the left leg. Which of the following is the most likely location of the lesion?
Which of the following is NOT a characteristic of unconscious proprioception?
Which of the following is NOT a characteristic of unconscious proprioception?
What is the name of the structure where the second-order neurons of the DC-ML pathway cross the midline?
What is the name of the structure where the second-order neurons of the DC-ML pathway cross the midline?
Which of the following is NOT a characteristic of the somatosensory homunculus?
Which of the following is NOT a characteristic of the somatosensory homunculus?
A patient presents with a complete loss of fine touch sensation on their right side of the body, including their right arm and leg. Which of the following is the most likely explanation?
A patient presents with a complete loss of fine touch sensation on their right side of the body, including their right arm and leg. Which of the following is the most likely explanation?
Which of the following statements about the DC-ML pathway is TRUE?
Which of the following statements about the DC-ML pathway is TRUE?
What is the function of the thalamus in the DC-ML pathway?
What is the function of the thalamus in the DC-ML pathway?
Flashcards
Conscious Proprioception
Conscious Proprioception
Sensations that allow perception of limb position and movement, relayed via thalamus to the cortex.
Unconscious Proprioception
Unconscious Proprioception
Information about muscle stretch and tension, processed by the cerebellum without conscious awareness.
Pain Sensation
Pain Sensation
Perception of damaging stimuli like mechanical stress, temperature extremes, and chemicals.
Dorsal Column-Medial Lemniscus Pathway
Dorsal Column-Medial Lemniscus Pathway
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1st Order Neuron
1st Order Neuron
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Nucleus Gracilis
Nucleus Gracilis
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2nd Order Neuron
2nd Order Neuron
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Spinothalamic Tract
Spinothalamic Tract
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Dorsal Columns
Dorsal Columns
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Fasciculus Gracilis
Fasciculus Gracilis
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Fasciculus Cuneatus
Fasciculus Cuneatus
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Posterior Intermediate Sulcus
Posterior Intermediate Sulcus
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Nucleus Cuneatus
Nucleus Cuneatus
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Cervical Enlargement
Cervical Enlargement
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Sacral to Cervical Mapping
Sacral to Cervical Mapping
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Sensory Homunculus
Sensory Homunculus
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Brodmann Areas 5,7
Brodmann Areas 5,7
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Ipsilateral Symptoms
Ipsilateral Symptoms
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Contralateral Deficits
Contralateral Deficits
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Stereognosis
Stereognosis
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Dorsal Root Ganglion (DRG)
Dorsal Root Ganglion (DRG)
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Contralateral Spinal Horn
Contralateral Spinal Horn
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Internal Arcuate Fibers
Internal Arcuate Fibers
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Medial Lemniscus (ML)
Medial Lemniscus (ML)
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Somatosensory Pathways
Somatosensory Pathways
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Fasciculus Gracilis (FG)
Fasciculus Gracilis (FG)
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Fine Discriminatory Touch
Fine Discriminatory Touch
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Sacral Lateral Organization
Sacral Lateral Organization
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Somatotopic Organization
Somatotopic Organization
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Inferior Olivary Nucleus
Inferior Olivary Nucleus
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Contralateral Sensation
Contralateral Sensation
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Spinothalamic Tract (ALS)
Spinothalamic Tract (ALS)
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Caudal Medulla
Caudal Medulla
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Mid-Pons
Mid-Pons
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Red Nucleus
Red Nucleus
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Dorsolateral Positioning
Dorsolateral Positioning
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Midbrain
Midbrain
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Study Notes
Somatosensory Pathways Touch & Pain
- Students should be able to accurately summarize the functional anatomy of the somatosensory pathways for touch and pain by the end of the session.
- Students should also be able to describe clinical deficits and tests for somatosensory pathway lesions by the end of the session
- Somatosensation is the detection of stimuli from the body surface, like touch, pain, temperature, and the sensing of limb position and movement (proprioception).
- Somatosensation is crucial for diagnosing neurological issues and localizing the affected part of the nervous system.
- Fine discriminatory touch allows for the discrimination of surface characteristics (rough, smooth, sharp, dull etc).
- Fine touch also includes sensing pressure, vibration, and the differentiated location of touch.
- Stereognosis is the ability to recognize an object through touch, often with manipulation
- Limb position and movement is detected by the brain at two levels: conscious and unconscious
- Conscious proprioception involves sensing limb position and movement, relayed to the cerebral cortex via the thalamus.
- Unconscious proprioception provides information on muscle stretch and tension to the cerebellum, which is not consciously perceived.
- Pain, temperature, itch, and crude touch sensations are perceived through various types of stimuli.
- The Dorsal Column-Medial Lemniscus (DC-ML) pathway transmits information about fine discriminatory touch, vibration, pressure, and proprioception, with the 1st-order neurons in the dorsal root ganglia.
- DC-ML pathways have first-order axons that ascend in the dorsal column and synapse in the medulla on the nucleus cuneatus and nucleus gracilis, from which the second-order axons decussate to form the medial lemniscus.
- Third-order neurons originate in the thalamus and project directly to the ipsilateral somatosensory cortex.
- The spinothalamic pathway (ALS) transmits innocuous stimuli (temperature, itch, crude touch), as well as damaging stimuli (mechanical, thermal, and chemical- pain, nociception).
- Somatosensation relies on first, second, and third-order neurons with varying myelination, fiber diameters etc.
- Different pain sensations (sharp versus dull, or fast versus slow) are transmitted via separate pathways using Aδ and C fibers.
- Aδ fibers transmit sharp, fast pain, C fibers transmit dull, slow pain) and itch.
- The 1st order neuron cell bodies are located in the dorsal root ganglion (DRG).
- Central processes of DRGs enter the spinal cord via the dorsal root.
- ALS pathway neurons cross the midline via the anterior white commissure. Its target nuclei include the ventral posterolateral (VPL) thalamic nucleus.
- The spinothalamic pathway axons project to the VPL thalamus which then projects to the primary somatosensory cortex.
- Both pathways project to the thalamus and ultimately to the primary somatosensory cortex for conscious sensation.
- The primary somatosensory cortex (SI) receives input from particular skin areas.
- The sensory homunculus represents the specific body areas overrepresented in the SI cortex, with higher densities of receptors corresponding to larger areas.
- The primary somatosensory cortex processes input further.
- Clinical tests help evaluate whether somatosensory pathways are injured. These tests include fine touch, texture discrimination, conscious proprioception, two-point discrimination, vibration sense, and stereognosis.
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