The Brainstem Flashcards
What makes up the brainstem?
The midbrain, pons and medulla
Where is it located?
Inferior to the diencephalon and is continuous with the spinal cord
What are the 12 cranial nerves?
Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear, glossopharangeal, vagus, accessory, hypoglossal
What important structures are located here?
-Red nucleus - midbrain
-Reticular formation - pons and medulla
-Vestibular nuclei
-The respiratory centre - pons and medulla (innervates intercostal muscles and diaphragm for breathing)
-The cardiac centre - medulla
Swallowing and vomiting centres
What are the inputs and outputs to the red nucleus?
Input - spinocerebellum, cerebral cortex
Output - skeletal muscle (via anterior horn cell then gamma/alpha MN) via rubrospinal tracts
Describe the rubrospinal tract
This is a contralateral tract due to the crossing at the midbrain. It is involved in assisting the CST with motor functions. It terminates in the cervical spine so it’s main role is in upper limb function to innervate gross movements of proximal limbs and fine movements of distal limbs e.g. fingers.
What are the inputs and outputs to the reticular formation?
Input - spinocerebellum, basal ganglia, cerebral cortex
Output - skeletal muscle (via anterior horn cell then gamma/alpha MN) via medial and lateral reticular spinal tracts.
What is the overall function of the reticular formation
Assists with ongoing movement, posture and tone - therefore affects the alpha and gamma motor neurones. It also affects the cardiac centres, habituation and sleep.
Describe the components of the medial reticulospinal tract
The MRST originates from the pons. It is involved in facilitating extensor reflexes and inhibiting flexor reflexes by increasing the tone of postural muscles in the trunk and proximal parts of muscles, it therefore helping with balance and support, e.g. the crossed extensor reflex. It has a role in reciprocal innervation.
Describe the components of the lateral reticulospinal tract
The LRST originates from the medulla. It is involved in facilitating flexor reflexes and inhibiting extensor. This is done by decreasing the level of tone of the postural muscles, therefore aiding with protective mechanisms such as the flexor withdrawal reflex. This also has a role in reciprocal innervation.
