Module 3 - Somatosensory systems: major ascending pathways Flashcards
What is the caudal medulla?
The transition area between the spinal cord and the brainstem
What is the obex?
The obex (from the Latin for barrier) is the point in the human brain at which the fourth ventricle narrows to become the central canal of the spinal cord. The obex occurs in the caudal medulla. The decussation of sensory fibers happens at this point.
At every brainstem level rostral to obex, 3 general areas can be identified, what are they?
- Area posterior to ventricular space (tectum, inferior and superior medullary vela)
- Area anterior to ventricular space (tegmentum)
- Large structures “appended” to anterior surface of brainstem (crus cerebri, basal pons, pyramids)
What is in the tectum of the brainstem?
- superior colliculus
- inferior colliculus
What 4 structures are in the tegmentum of the brainstem?
- reticular formation nuclei
- cranial nerve nuclei and tracts
- ascending tracts from spinal cord
- descending tracts
What X structures are in the base of the brainstem?
- Crus cerebri
- Basal pons
- Pyramids
- Substantia nigra
- Cerebral peduncle
On this anterior image of the brainstem, identify the:
- thalamus
- midbrain
- pons
- medulla
On this anterior image of the brainstem, and specifically within the medulla, identify the:
- pyramids
- decussation of the pyramids
- anterior median fissure
On this anterior image of the brainstem, identify the anterolateral structures of:
- the Olives (bump produced by the large
inferior olivary nucleus) - Preolivary sulcus (rootlets of CNXII
emerge from this sulcus) - Postolivary sulcus
In this posterior image of the medulla, locate the:
- closed portion
- open portion
- obex
- Gracile tubercle
- Cuneate tubercle
- Posterointermediate sulcus
- Posterior median sulcus
Where is the fasciculus grascilis and what is it implicated in?
Ascending - fine touch and proprioception from ipsilateral lower limb
Where is the fasciculus cuneatus and what is it implicated in?
Ascending - fine touch and proprioception from ipsilateral upper limb
Where is the spinocerebellar tract and what is it implicated in?
Propriotception from limbs to cerebellum
Where is the lateral corticospinal tract and what is it implicated in?
Motor to ipsilateral ventral horn, mostly limb musculature
Where is the spinothalamic tract and what is it implicated in?
Pain and temperature from the contralateral side of the body
Where is the anterior corticospinal tract and what is it implicated in?
Motor to ipsi- and contra-lateral ventral horn mostly axial musclature
On this anterior image of the brainstem, where is the:
- basal pons
- cerebral peduncles (crus cerebri)
- interpeduncular fossa
The tectum, of roof of the midbrain, contains the inferior and superior colliculi. Can you locate them on this posterior image of the brainstem?
On this micrograph of the caudal medulla, can you locate the anterior spinocerebellar tract (it carries motor to ipsi- and contra-lateral ventral horns; mostly axial musclature)
On this micrograph of the medulla, can you locate the pyramids? What are they associated with?
The medullary pyramids are paired white matter structures of the brainstem’s medulla oblongata that contain motor fibers of the corticospinal and corticobulbar tracts – known together as the pyramidal tracts. The lower limit of the pyramids is marked when the fibers cross (decussate).
On this micrograph of the medulla, where are the nucleus gracilis located? What are they implicated in?
Fine touch and proprioception
On this micrograph of the medulla, where are the nucleus cuneatus located? What are they implicated in?
On this micrograph of the medulla, where is the fasciculus gracilis? What is it implicated in?
fiber bundle that carries tactile and proprioceptive information from the lower half of the body, the fasciculus gracilis is part of the posterior columns and terminates in the nucleus gracilis.
On this micrograph of the medulla (#4), where is the fasciculus cuneatus? What is it implicated in?
fiber bundle that carries tactile and proprioceptive information from the upper limbs and torso, the fasciculus cuneatus is part of the posterior columns and terminates in the nucleus cuneatus.
On this micrograph of the medulla (#4), where is the spinothalamic tract? What is it implicated in?
The spinothalamic tract is an ascending pathway of the spinal cord. Together with the medial lemnicus, it is one of the most important sensory pathways of the nervous system. It is responsible for the transmission of pain, temperature, and crude touch to the somatosensory region of the thalamus.
decussation
when fibers cross from one side of a structure to the other.
What is this micrograph showing?
Superior/rostral/open medulla
On this micrograph of the superior medulla (#5) where are the pyramids? What are they implicated in?
The medullary pyramids are paired white matter structures of the brainstem’s medulla oblongata that contain motor fibers of the corticospinal and corticobulbar tracts – known together as the pyramidal tracts.
On this micrograph of the superior medulla (#5) where are the inferior olivary nuclei? What are they implicated in?
coordinates signals from the spinal cord to the cerebellum to regulate motor coordination and learning.
On this micrograph of the superior medulla, where is the medial lemniscus? What is it implicated in?
Medial lemniscus: major ascending pathway for carrying tactile and proprioceptive information to the thalamus
On this micrograph of the superior medulla, where is the medial lemniscus? What is it implicated in?
On this micrograph of the caudal pons and cerebellum, where is the medial lemniscus? What is it implicated in?
major ascending pathway for carrying tactile and proprioceptive information to the thalamus.
On this micrograph of the caudal pons and cerebellum, where is the spinothalamic tract? What is it implicated in?
The spinothalamic tract is an ascending pathway of the spinal cord. Together with the medial lemnicus, it is one of the most important sensory pathways of the nervous system. It is responsible for the transmission of pain, temperature, and crude touch to the somatosensory region of the thalamus.
On this micrograph of the caudal pons and cerebellum, where are the corticospinal fibers?
What are the pontine nuclei? What are they implicated in?
Pontine nuclei receive visual, auditory, and somatosensory information from cortical and subcortical regions which is transmitted via mossy fiber axons to cortical granule cells, the most numerous cells in the cerebellum.
Ascending
On this micrograph of the rostral pons/caudal midbrain, where is the inferior colliculus? What is it implicated in?
The inferior colliculus is best known for its role in hearing. It is the largest nucleus of the auditory system in humans, and it is the point in the brainstem where all auditory pathways traveling through the brainstem converge
On this micrograph of the rostral pons/caudal midbrain, where is the medial lemniscus? What is it implicated in?
major pathway for carrying tactile and proprioceptive information to the thalamus. The medial lemniscus is formed in the medulla as fibers from the posterior column nuclei cross the midline.
ascending
On this micrograph of the rostral pons/caudal midbrain, where is the spinothalamic tract? What is it implicated in?
The spinothalamic tract is an ascending pathway of the spinal cord. Together with the medial lemnicus, it is one of the most important sensory pathways of the nervous system. It is responsible for the transmission of pain, temperature, and crude touch to the somatosensory region of the thalamus.
Ascending
On this micrograph of the rostral pons/caudal midbrain, where are the corticospinal fibers?
On this micrograph of the rostral pons/caudal midbrain, where is the cerebral aqueduct? What is it implicated in?
The cerebral aqueduct is a narrow 15 mm conduit that allows for cerebrospinal fluid (CSF) to flow between the third ventricle and the fourth ventricle.
On this micrograph of the superior/rostral midbrain, where is the superior colliculus? What is it implicated in?
Although the complete scope of functions that can be attributed to the superior colliculi has not been fully delineated, the superior colliculi are understood to be important to directing behavioral responses toward stimuli in the environment. In other words, the superior colliculus seems to be able to receive information from the environment and then use that information to initiate a behavioral response appropriate to the current environmental context.
Vision particularly
On this micrograph of the superior/rostral midbrain, where is the red nucleus? What is it implicated in?
This neural network is the part of the motor system involved in generating involuntary movements.