Primary sensory afferents never cross the midline Flag this Question Question 21

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Primary sensory afferents never cross the midline

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Question 21 pts

For the DCML (Dorsal Column Medial Lemniscus), the primary sensory afferent enters the spinal cords and ascends the spinal cord in the                            [ Select ]                       ["lateral corticospinal tract", "dorsal columns", "anterolateral tract"]         before synapsing on a 2nd order neuron in the                            [ Select ]                       ["spinal cord", "brainstem", "thalamus"]         .

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Question 31 pts

After the primary sensory afferent synapses on the second order neuron, the second order neuron                           [ Select ]                       ["synapses in the thalamus", "crosses midline", "travels down to the lower extremities"]         and travels to the                            [ Select ]                       ["brainstem", "thalamus", "spinal cord"]         where it synapses on a 3rd order neuron.

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Question 41 pts

After the second order neuron synapses on a                            [ Select ]                       ["1st", "2nd", "3rd"]         order neuron, the axon of that neuron extends up into the                            [ Select ]                       ["Primary motor cortex located in the frontal lobe", "Somatosensory cortex located in the frontal lobe", "Somatosensory cortex located in the parietal lobe", "Primary motor cortex located in the parietal lobe"]         .

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Question 51 pts

***This is an example of a test question***

Osmium is a heavy metal that binds to lipid and turns black. Which of the following would you expect to be labeled most darkly?

Explanation / Answer

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Primary sensory afferents never cross the midline

False because For the dorsal column-medial lemniscus pathway,internal arcuate fibers in lower medulla the pathway crosses the midline

Question 21 pts

For the DCML (Dorsal Column Medial Lemniscus), the primary sensory afferent enters the spinal cords and ascends the spinal cord in the Dorsal column before synapsing on a 2nd order neuron in the spinal cord

Reasons The first order neurones arise from the sensory receptors in the periphery. They enter the spinal cord, ascend 1-2 vertebral levels, and synapse at the tip of the dorsal horn – an area known as the substantia gelatinosa.

Question 31 pts

After the primary sensory afferent synapses on the second order neuron, the second order neuron synapses in the thalamus and travels to the brainstem where it synapses on a 3rd order neuron.

Reasons

The second order neurones carry the sensory information from the substantia gelatinosa to the thalamus. After synapsing with the first order neurones, these fibres decussate within the spinal cord, and then form two distinct tracts:

Although they are functionally distinct, these tracts run alongside each other, and they can be considered as a single pathway. They travel superiorly within the spinal cord, synapsing in the thalamus.

Question 41 pts

After the second order neuron synapses on a 3rd order neuron, the axon of that neuron extends up into the Somatosensory cortex located in the parietal lobe

Reasons The third order neurones carry the sensory signals from the thalamus to the ipsilateral primary sensory cortex of the brain. They ascend from the ventral posterolateral nucleus of the thalamus, travel through the internal capsule and terminate at the sensory cortex.

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