Brainstem Anatomy and Physiology Quiz

Overview of the Brainstem: Functions, Nuclei, and Tracts

• The brainstem is a general stalk that connects the brain to the spinal cord and contains many pathways between the brain and spinal cord, as well as pathways to the cerebellum and many important nuclei.
• The brainstem performs fundamental tasks of life, such as breathing, circulation, digestion, and swallowing, and it also sorts information from sensory nerves coming up to the brain and motor nerves going out.
• The medulla oblongata is the hindbrain part of the brainstem that connects to the spinal cord without any separation, and it contains vital systems such as cardiovascular and respiratory, as well as reflexive actions like vomiting, swallowing, coughing, and sneezing.
• Cranial nerve nuclei are clusters of neurons located within the brainstem that serve as the origin or termination points of the twelve cranial nerves, and they exit the brainstem at the medulla.
• The medulla receives information about blood pressure changes from baroreceptors in blood vessels, and it sends this information to the nucleus of the solitary tract in the medulla to initiate reflexive actions to return blood pressure to the desired range.
• Chemoreceptors inside blood vessels detect changes in O2 and CO2 levels in the blood, and when O2 levels fall, the neurons in and around the nucleus of the solitary tract and nucleus ambiguus respond and increase respiration.
• The medulla contains several important nuclei, including the inferior olivary nuclei, nucleus gracilis, nucleus cuneatus, nucleus of the solitary tract, and nucleus ambiguus.
• The brainstem contains several tracts, including the corticospinal tract, corticobulbar tracts, and the medullary pyramids.
• The corticospinal tract carries movement-related information from the motor cortex to the spinal cord, and neurons that travel in the tract are called upper motor neurons.
• At the base of the medullary pyramids, 90% of the fibers intersect and cross to the other side of the brainstem, forming the pyramidal decussation, while the other 10% of the fibers continue into the spinal cord on the same side of the body as part of the ventral or anterior corticospinal tract.
• The corticospinal tract controls the movement of more distal muscles (like hands), while the ventral or anterior corticospinal tract controls the movement of more proximal muscles (like the trunk/vertebral column and surrounding).
• The pons is another hindbrain part of the brainstem that contains many tracts and nuclei, including cranial nerve nuclei, head and face sensations, motor movement of eyes, face, mouth, hearing, equilibrium, autonomic functions, the locus coeruleus, and raphe nuclei (serotonin).