Brain Anatomy: Cerebrum, Gyri, and Sulci

Brain Overview

• The outer gray matter of the brain is the cerebrum, also called the telencephalon.
• The cerebrum is the top part of the brain.
• It originates from the telencephalon during embryonic development.
• Gray matter consists of unmyelinated cell bodies.
• The cerebral cortex is the outer gray matter of the cerebrum.
• Gyri are the bumps on the brain surface, increasing surface area.
• Gyrus is the singular form of gyri.
• Sulci are the divots between the gyri.
• Sulcus is the singular form of sulci.

Cerebral Hemispheres and Lobes

• The longitudinal fissure separates the left and right cerebral hemispheres.
• The Faux Cerebrae, a dural septa, dips into the longitudinal fissure, protecting cerebral vessels and dural sinuses.
• The central sulcus separates the frontal lobe from the parietal lobe.
• The frontal lobe is located in front of the central sulcus.
• The parietal lobe is located behind the central sulcus.
• The postcentral gyrus, located behind the central sulcus, contains the primary somatosensory cortex, responsible for sensory information like touch, temperature, and proprioception.
• The precentral gyrus, located in front of the central sulcus, contains the primary motor cortex, responsible for voluntary control of skeletal muscles.
• The premotor cortex is located in front of the precentral gyrus.
• The prefrontal cortex is located further in front of the premotor cortex.
• The parieto-occipital sulcus separates the parietal lobe from the occipital lobe.
• The occipital lobe extends from the parieto-occipital sulcus to the transverse fissure.
• The temporal lobe is separated from the parietal lobe by the lateral sulcus.
• The insula, or island of reel, is a fifth lobe located deep underneath the temporal lobe.

Deeper Structures of the Cerebrum

• The outer gray matter of the cerebral cortex consists of unmyelinated cell bodies.
• White matter consists of myelinated axons.
• The lateral ventricle is a fluid-filled cavity containing cerebrospinal fluid.
• The choroid plexus, found in the walls or roof of ventricles, produces cerebrospinal fluid, specifically in the lateral, third and fourth ventricles.
• The hippocampus, located underneath the choroid plexus, is responsible for memory.

Frontal, Parietal, and Occipital Lobes

• Projection fibers transmit sensory information to and from the cerebral cortex.
• The corona radiata is a specific type of projection fiber.
• The internal capsule transitions into the corona radiata.

Diencephalon

• The insula is located deep to the temporal lobe and is considered the fifth mini lobe.
• The lateral ventricle is a fluid-filled cavity.
• The choroid plexus of the lateral ventricle is located within the lateral ventricle.
• The caudate nucleus, a basal nuclei, dampens unwanted motor movements and is washed by the lateral ventricle.
• The fornix is a fiber track connecting limbic nuclei associated with emotions.
• The third ventricle is located near the fornix.
• The choroid plexus of the third ventricle is found in the third ventricle.
• The pineal gland secretes melatonin, regulating sleep and wake cycles via the suprachiasmatic nucleus in the hypothalamus.
• The thalamus is an egg-shaped structure.
• The intermediate mass is located in the center of the thalamus.
• The hypothalamus is located below the thalamus, connecting to the pituitary gland via the infundibulum.

Brain Stem

• The midbrain contains the superior and inferior colliculi.
• The superior colliculi control reflexive head movements in response to visual stimuli.
• The inferior colliculi control reflexive head movements in response to auditory stimuli.
• The cerebral aqueduct drains the third ventricle.
• The fourth ventricle is a tent-shaped ventricle.
• The pons is located below the midbrain.
• The medulla oblongata is located below the pons.
• The superior cerebellar peduncles connect the midbrain to the cerebellum.
• The middle cerebellar peduncles connect the pons to the cerebellum.
• The inferior cerebellar peduncles connect the medulla to the cerebellum.
• The mammillary bodies are limbic nuclei located inferior and posterior to the hypothalamus.
• The cerebral peduncles are projection fibers transmitting sensory information to the thalamus.
• The pyramids are formed by the decussation of descending corticospinal tracts in the medulla.
• The olives, located on the sides of the pyramids in the medulla, play a role in proprioception.
• The corpus callosum is a commissural fiber that connects the left and right cerebral hemispheres, allowing for left-to-right transmission.
• The septum pellucidum is a membrane located near the lateral ventricle.

Cranial Nerves

• The olfactory nerve (cranial nerve I) picks up odorant chemicals in the nasal cavity.
• It is a sensory nerve for smell.
• The optic nerve (cranial nerve II) transmits sensory information from the retina for vision, with fibers crossing at the optic chiasma.
• The oculomotor nerve (cranial nerve III) is a motor nerve that controls eye movements via extraocular eye muscles.
• The trochlear nerve (cranial nerve IV) is a motor nerve that also plays a role in extraocular eye movements, specifically supplying the superior oblique muscle.
• The trigeminal nerve (cranial nerve V) controls both sensory and motor functions, supplying muscles of mastication and picking up sensory information from the face.
• The abducens nerve (cranial nerve VI) is a motor nerve that innervates the lateral rectus muscle, rotating the eye laterally.
• The facial nerve (cranial nerve VII) controls both motor and sensory function.
• The vestibulocochlear nerve (cranial nerve VIII) has cochlear and vestibular branches, controlling dynamic and static equilibrium and hearing, and plays a role in motor movements.
• The glossopharyngeal nerve (cranial nerve IX) controls both sensory and motor function, supplying the tongue, pharynx, and baroreceptors.
• The vagus nerve (cranial nerve X) controls both sensory and motor function, acting as the main parasympathetic nerve, innervating many organs.
• The accessory nerve (cranial nerve XI) is mainly a motor nerve with brainstem and cervical branches, supplying the trapezius and sternocleidomastoid muscles.
• The hypoglossal nerve (cranial nerve XII) is mainly a motor nerve that supplies muscles of the tongue, controlling tongue movement.

Cerebellum Overview

• The cerebellum unconsciously controls skeletal muscles through proprioception.
• It controls muscle tone and equilibrium.
• The vermis is the worm-like structure between the two parts of the cerebellum, protected by the Fox cerebelli.
• The cerebellar cortex is the outer gray matter of the cerebellum.
• Folia are the folds of the cerebellum.
• The transverse fissure is located between the cerebellum and the occipital lobe, protected by the tentorium cerebelli.
• The arbor vitae, or tree of life, is the white matter of the cerebellum.
• Purkinje cells are located around the edges of the arbor vitae.
• The middle cerebellar peduncles connect the pons to the cerebellum.

Cerebral Cortex Areas

• The Broca's area, located on the left frontal lobe, controls muscles of speech.
• The temporal lobe contains the primary auditory cortex for sound and hearing.
• The Wernicke's area, located in the temporal and parietal lobes, is important for understanding and putting together words.
• The occipital lobe contains the primary visual cortex, where visual stimuli from the retina are perceived.

Explore the cerebrum, the outer gray matter of the brain, originating from the telencephalon. Learn about gyri (bumps) and sulci (divots) and their role in increasing brain surface area. Understand the cerebral hemispheres and lobes separated by the longitudinal fissure and central sulcus.