External and internal features of the medulla Flashcards
(27 cards)
What are the three main components of the brainstem?
Midbrain, pons, and medulla oblongata.
What are the key functions of the medulla?
Controls autonomic functions (heart rate, respiration, blood pressure), reflexes (vomiting, coughing, sneezing), and serves as a pathway for motor/sensory tracts.
Name the prominent external features of the ventral medulla.
Pyramids (corticospinal tracts), olives (inferior olivary nucleus), and cranial nerve exit points (IX, X, XI, XII).
Which cranial nerves emerge from the medulla?
Glossopharyngeal (IX), Vagus (X), Accessory (XI), and Hypoglossal (XII).
How does the closed medulla differ from the open medulla?
Closed: Contains the central canal; features gracile/cuneate tubercles (sensory nuclei).
Open: Forms the floor of the 4th ventricle; includes hypoglossal/vagal triangles and vestibular area.
What occurs at the sensory decussation in the medulla?
Axons from the gracile and cuneate nuclei cross to form the medial lemniscus, transmitting proprioceptive/tactile info to the thalamus.
What happens at the pyramidal decussation?
~85% of corticospinal tract fibers cross to form the lateral corticospinal tract, controlling contralateral voluntary movement.
Compare Medial and Lateral Medullary Syndromes.
Medial (Anterior Spinal Artery): Contralateral hemiparesis, proprioception loss; ipsilateral tongue weakness (XII).
Lateral (PICA, Wallenberg): Ipsilateral Horner’s, dysphagia; contralateral pain/temperature loss (body); ipsilateral facial sensory loss.
A patient presents with left Horner’s, right body pain/temperature loss, and dysphagia. Where is the lesion?
Left lateral medulla (Wallenberg Syndrome, PICA infarct).
Which arteries supply the medulla?
Anterior Spinal Artery (medial medulla).
PICA (posterior/lateral medulla).
Vertebral Artery (branches to central regions).
What is the role of the reticular formation in the medulla?
Regulates consciousness, cardiovascular/respiratory control, and reflexes (e.g., vomiting, swallowing).
Where does the spinothalamic tract run in the medulla, and what does it carry?
It travels laterally; carries contralateral pain/temperature sensations from the body.
What do the gracile and cuneate tubercles represent, and what type of sensory information do they relay?
Gracile tubercle: Marks the gracile nucleus (medial), relaying proprioception/tactile info from the lower body.
Cuneate tubercle: Marks the cuneate nucleus (lateral), relaying similar info from the upper body.
Note: These are part of the dorsal columns (fasciculus gracilis/cuneatus).
Where are the hypoglossal and vagal triangles located, and what nuclei lie beneath them?
Hypoglossal triangle (medial): Overlies the hypoglossal nucleus (CN XII, motor to tongue).
Vagal triangle (lateral): Overlies the dorsal vagal nucleus (CN X, parasympathetic output).
Location: Open medulla (floor of 4th ventricle).
What is the function of the MLF in the medulla?
Coordinates head/eye movements by linking vestibular nuclei to CN III, IV, and VI nuclei. Lesions cause nystagmus or gaze palsies.
What is the role of the inferior olivary nucleus, and where is it located?
Function: Relays proprioceptive info to the cerebellum (motor coordination).
Location: Dorsolateral to the pyramids, forms the olive prominence on the ventral surface.
Trace the pathway of the dorsal columns through the medulla.
First-order neurons (dorsal root ganglia) → ascend ipsilaterally in fasciculus gracilis/cuneatus.
Synapse in gracile/cuneate nuclei (closed medulla).
Second-order neurons decussate → form medial lemniscus → project to thalamus.
Name the three vital centers in the medulla and their roles.
Cardiac center: Adjusts heart rate/force.
Respiratory center: Controls breathing rhythm.
Vasomotor center: Regulates blood pressure.
Where do the spinocerebellar tracts run in the medulla, and what is their purpose?
Location: Lateral/ventrolateral medulla (near inferior olive).
Function: Carry unconscious proprioceptive info to the cerebellum (ipsilateral for dorsal, contralateral for ventral).
What triad of symptoms defines Horner’s syndrome, and what medullary structure is involved?
Symptoms: Ptosis (drooping eyelid), miosis (constricted pupil), anhidrosis (no sweating).
Structure: Disruption of sympathetic fibers in lateral medulla (e.g., PICA infarct).
What nucleus lies beneath the vestibular area in the open medulla, and what is its function?
Nucleus: Vestibular nuclei (CN VIII).
Function: Balance/spatial orientation; integrates with MLF for eye movements.
How does the corticospinal tract arrange in the medullary pyramids before decussation?
Ventral medulla: Pyramids contain ~85% fibers that decussate to form lateral corticospinal tract (contralateral motor control).
Remaining 15% form anterior corticospinal tract (ipsilateral).
List five reflex centers housed in the medulla.
Vomiting, coughing, sneezing, swallowing, and hiccupping.
