Lecture 4 brainstem and corpus callosum

Corpus callosum

• white matter structure

• C-shaped nerve fiber bundle connecting the left and right halves of the brain

• Transfers information b/w hemispheres

Corpus Callosum Parts

• 1. rostrum

• 2. Genu

• 3. Body

• 4. Splenium

• Cingulate gyrus sits above

• Septum pellucidum sits below

Limbic lobe (system)

• functional grouping of structures along the medial and inferior aspects of the cortex

• Involved in long term memory and learning, drive related behavior, olfaction, and emotional function

• Contains: cingulate gyrus, parahippocampal gyrus (uncus), subcallosal gyrus, hippocampus

Insular lobe

• forms the “floor” of the lateral sulcus, sitting deep to the frontal and temporal lobes

• Involved in a variety of functions, including pain and autonomic regulation, as well as taste, auditory, and vestibular processing

Brainstem

• mesencephalon- midbrain

• Rhombencephalon:

  • metencephalon: pons and cerebellum

  • Myelencephalon: medulla

Mesencephalon- midbrain

• The base of the midbrain consists of the cerebral peduncles, which contain nerve fibers descending from the cerebral cortex.

• Cranial nerve nuclei- 3rd (oculomotor), 4th (trochlear) and part of the 5th (reigning) are located in the midbrain tegmentum.

• The red nucleus in the substantial nigra, two prominent nuclei, are also found in the midbrain tegmentum.

• The superior and inferior colliculi, found in the tectum, are involved in visual and auditory functions respectively.

Rhombencephalon- metencephalon (pons and cerebellum)

• pons is composed of two parts, the Pontine tegmentum (dorsal) and the basilar pons (ventral).

• At the level of the pons, the cerebral aqueduct has expanded to form the fourth ventricle.

• The cerebellum is situated posterior to the pons and forms part of the roof (tectum) of the fourth ventricle.

• The basilar pons contain ascending and descending tracts.

• The pontine tegmentum contains the nuclei of the cranial nerves: 5th (trigeminal), 6th (abducens), 7th (facial), and the 8th (vestibulocochlear) nerves

Rhombencephalon- myelencephalon (medulla)

• The medulla lies between the pons and the spinal cord

• It is continuous with the spinal cord just above to foramen magnum in the first spinal nerve

• The posterior surface of the medulla forms the bottom, half of the fourth ventricle floor

• The medulla also has ascending and descending tracts

• The medulla contains, the cranial nerve nuclei from the 9th (glossopharyngeal), 10th (vagus), 11th (accessory), and 12th (hypoglossal) nerves, which regulate respiration, swallowing, sweating, gastric, secretion, cardiac, and vasomotor activity.

• Medulla had pyramids and olives, and the inferior cerebellar peduncles.