Which of the following best describes the function of the anatomical structure indicated by the black arrow in the image below?
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Options:
explanation: The image shows a stained axial section through the midbrain level of the brainstem. The midbrain can be differentiated from the pons or medulla levels of the brainstem by the presence of the large crus cerebri anteriorly (bottom of the image) and the colliculi posteriorly (top of the image). The structure at the level of the midbrain which influences the modulation of pain responses is the periaqueductal grey matter surrounding the cerebral aqueduct of Sylvius in the centre of the image. However, the black arrow indicates the substantia nigra, which is a collection of pigmented neurons located in between the crus cerebri (anterior) and the tegmentum (posterior) of the cerebral peduncles. The neurons in this region produce dopamine, a neurotransmitter which is relayed to the basal ganglia to promote accurate control of voluntary movements.
name: Influencing the modulation of pain responses
label: e
answer: no
explanation: The image shows a stained axial section through the midbrain level of the brainstem. The midbrain can be differentiated from the pons or medulla levels of the brainstem by the presence of the large crus cerebri anteriorly (bottom of the image) and the colliculi posteriorly (top of the image). Conjugate eye movements are mediated through the medial longitudinal fasciculus which connects the oculomotor, trochlear and abducens nerves bilaterally. It is found at the level of the midbrain anterior to the cerebral aqueduct and the periaqueductal grey matter, and anterolateral to the trochlear nucleus. However, the black arrow indicates the substantia nigra, which is a collection of pigmented neurons located in between the crus cerebri (anterior) and the tegmentum (posterior) of the cerebral peduncles. The neurons in this region produce dopamine, a neurotransmitter which is relayed to the basal ganglia to promote accurate control of voluntary movements.
name: Contributing to controlling conjugate eye movements
label: d
answer: no
explanation: The image shows a stained axial section through the midbrain level of the brainstem. The midbrain can be differentiated from the pons or medulla levels of the brainstem by the presence of the large crus cerebri anteriorly (bottom of the image) and the colliculi posteriorly (top of the image). The structure at the level of the midbrain which is involved in the control of movements of the superior oblique muscle of the eyeball is the trochlear nucleus which controls the trochlear nerve (CN IV). This nucleus is located anterior to the cerebral aqueduct and the periaqueductal grey, bilaterally. However, the black arrow indicates the substantia nigra, which is a collection of pigmented neurons located in between the crus cerebri (anterior) and the tegmentum (posterior) of the cerebral peduncles. The neurons in this region produce dopamine, a neurotransmitter which is relayed to the basal ganglia to promote accurate control of voluntary movements.
name: Controlling the movements of the superior oblique muscle of the eyeball
label: c
answer: no
explanation: The image shows a stained axial section through the midbrain level of the brainstem. The midbrain can be differentiated from the pons or medulla levels of the brainstem by the presence of the large crus cerebri anteriorly (bottom of the image) and the colliculi posteriorly (top of the image). The black arrow indicates the substantia nigra, which is a collection of pigmented neurons located in between the crus cerebri (anterior) and the tegmentum (posterior) of the cerebral peduncles. The neurons in this region produce dopamine, a neurotransmitter which is relayed to the basal ganglia to promote accurate control of voluntary movements.
name: Producing dopamine for the control of motor functions within the basal ganglia
label: a
answer: yes
explanation: The image shows a stained axial section through the midbrain level of the brainstem. The midbrain can be differentiated from the pons or medulla levels of the brainstem by the presence of the large crus cerebri anteriorly (bottom of the image) and the colliculi posteriorly (top of the image). The midbrain structures, which serve as a relay on the auditory pathway are the inferior colliculi. However, the black arrow indicates the substantia nigra, which is a collection of pigmented neurons located in between the crus cerebri (anterior) and the tegmentum (posterior) of the cerebral peduncles. The neurons in this region produce dopamine, a neurotransmitter which is relayed to the basal ganglia to promote accurate control of voluntary movements.
name: Serving as a relay station on the auditory pathway
label: b
answer: no

Correct answer: a