Brain Anatomy: Five Parts of the Brain

Five Parts of the Brain

• From an embryological origin, the brain consists of five parts.
• Lateral ventricles are the first part of the brain.
• Telencephalon is the endbrain or cerebrum.
• Diencephalon contains the thalamus, hypothalamus, subthalamus and epithalamus.
• Mesencephalon refers to the midbrain.
• The metencephalon is made up of the pons and cerebellum.
• Myelencephalon also known as the medulla.

Central Nervous System (CNS)-Terminology Overview

• The proencephalon (forebrain) includes: the telencephalon, and the diencephalon
• The brainstem is composed of the midbrain, pons, and medulla.
• The rhombencephalon (hindbrain) includes the metencephalon and myelencephalon.

Embryological Origin/Ventricular System and Parts of the Brain

• Lateral Ventricles are located in the telencephalon
• Third Ventricle is in the diencephalon.
• Cerebral Aqueduct (midbrain)
• Fourth Ventricle (pons, medulla, and cerebellum)
• Central Canal (Spinal Cord)
• The two Foramina of Luschka are lateral exits, and the Foramen of Magendie is a median exit.

Ventricular System of the Brain- Medial (Midsagittal) View

• Interventricular Foramen
• Fragments of Septum Pellucidum
• Lateral Ventricle
• Third Ventricle
• Cerebral Aqueduct
• Fourth Ventricle
• Foramen of Magendie
• Central Canal of Spinal cord
• Massa Intermedia

Orientation - Lateral View

• For a 4-legged animal, orientation in the central nervous system is simple
• The rostrocaudal axis goes straight from nose to tail
• The dorsoventral is perpendicular to the rostrocaudal axis from back to belly
• As humans evolved, they developed the ability to stand upright, using lower extremities for locomotion and freeing up upper extremities
• The rostrocaudal axis developed a bend at the diencephalon/mesencephalon level, requiring adjustments to terminology.

Surface of the Telencephalon - Gyri and Sulci

• Gyri and sulci are the two main types of surface folds
• A gyrus is an elevation of the cerebral cortex.
• A sulcus is a groove or indentation that separates the gyri from each other

Lateral View of the Cerebral Hemisphere - Landmarks

• Landmarks include the central sulcus, lateral sulcus, preoccipital notch, and the end of the parietooccipital sulcus
• The end of the Parietooccipital sulcus is only visible on the medial view.

Lobes of the Telencephalon - Frontal Lobe

• The frontal lobe is responsible for voluntary movement, production of language, and higher level executive functions, including planning, initiating and self-monitoring behavior.

Sulci and Gyri of the Frontal Lobe (Lateral View)

• The following sulci and gyri are used to distinguish the frontal lobe:
• precentral sulcus
• superior frontal gyrus
• middle frontal gyrus
• inferior frontal gyrus
• precentral gyrus, which is the primary motor cortex (lateral view represents trunk, upper extremity of face)
• superior frontal sulcus
• inferior frontal sulcus
• Broca’s area is in the left hemisphere and produces language.

Telencephalon - Parietal Lobe

• The parietal lobe functions in processing somatosensory information.
• This involves touch, vibration, proprioception, pain and temperature, and sensory integration.

Sulci and Gyri of the Parietal Lobe (Lateral View)

• The following sulci and gyri are used to distinguish the parietal lobe:
• postcentral gyrus
• primary somatosensory cortex
• postcentral sulcus:
• superior parietal lobule
• intraparietal sulcus
• angular gyrus
• supramarginal gyrus.
• Represents touch, vibration, proprioception, pain and temperature of trunk, upper extremity, and face

Telencephalon - Occipital Lobe

• Responsible for processing visual information, including color, shape, object recognition, spatial position, and movement.

Sulci and Gyri of the Occipital Lobe - Lateral View

• Occipital gyri
• Primary visual cortex, as seen on the lateral aspect of the occipital lobe, close to the occipital pole.

Telencephalon - Temporal Lobe

• Works in processing auditory information (hearing)
• Is responsible for hearing and understanding of language
• Memory is connected to the left hemisphere

Sulci and Gyri of the Temporal Lobe (Lateral View)

• Responsible for language, and located in the posterior superior temporal gyrus of the left hemisphere
• Superior temporal sulcus
• Inferior temporal sulcus
• Superior temporal gyrus
• Middle temporal gyrus
• Inferior temporal gyrus

Telencephalon - Insular Lobe

• Functions in processing gustatory information (taste)
• Works in the interoception (processing of visceral sensations)

Sulci and Gyri of the Insular Lobe

• Short insular gyri
• Central sulcus of the insula
• Long insular gyrus and gyri

Lobes of the Telencephalon - Medial View Summary

• Frontal lobe (Frontal)
• Parietal lobe (Superior)
• Temporal lobe (Inferior)
• Occipital lobe (Occipital)

Sulci and Gyri of the Cerebral Cortex (Medial View)

• Ends
• Anterion Paracentral gyrus (Lobule)
• Primary Motor Cortex
• Cingulate gyrus
• Superiour frontral gyrus
• Cingulate Sulcus
• Uncus
• Marginal of Cingulate
• Cueves
• Lingual
• Calcarine Sulcus
• Visual Cortex
• Parahippocampal

Historical Variation of the Medial View

• In some textbooks, you may see an additional lobe called Lymbic
• This lobe was named by Paul Broca, a 19th Century French physician
• Found with functions, such as emotions

Lobes of the Telencephalon - Superior View Summary

• Median longitudinal fissure
• Frontal lobe
• Central sulcus
• Parietal lobe
• Occipital lobe

Sulci and Gyri of the Cerebral Hemispheres (Superior View)

• Median longitudinal fissure
• Superior frontal gyrus
• Middle frontal gyrus
• Superior frontal sulcus
• Precentral sulcus
• Central sulcus
• Postcentral sulcus
• Precentral gyrus
• Postcentral gyrus
• Occipital gyri.

Sulci and Gyri of the Cerebral Hemispheres (Inferior View)

• Olfactory sulcus
• Orbital gyri
• Gyrus rectus
• Uncus
• Parahippocampal gyrus
• Occipitotemporal gyri
• Occipital gyri.

Classification of the Cerebral Cortex based on Histology: Brodmann Areas (Lateral & Medial Views)

• Korbinian Brodmann (1868-1918), classified the cerebral cortex into more than 50 areas, based on histological similarities
• At the time, he did not know the functional significance of these areas
• The classification is still in use, since many of the areas he described have been linked to specific functions
• Area 4 is the primary motor cortex
• Areas 1, 2, 3: primary somatosensory cortex
• Area 17: primary visual cortex

Diencephalon

• Thalamus Location: above the hypothalamic sulcus in each hemisphere, lateral to the third ventricle.
• The thalamus Functions: relaying sensory information (except smell) to the sensory cortex areas, and modulating movement.
• The hypothalamus Location: is below the hypothalamic sulcus and above the midbrain, lateral to the third ventricle
• Is responsible for homeostasis, the neuroendocrine control of hormones, and regulation of eating and drinking
• Subthalamus Locations: Near the junction between the midbrain and thalamus.
• Regulation of movement through the subthalamic nucleus
• Epithalamus Locations: Near the roof of the third ventricle, including a pineal gland
• Production of melatonin, which regulates the circadian rhythm and the sleep-wake cycle

Brainstem and Cerebellum

• Brainstem (Midbrain, Pons, and Medulla)-Cerebellum
• Midbrain Location: Between diencephalon and pons- Functions: Eye movements, Near accommodation vision, and Pupillary
• Pons Locations: Between the Midbrain and Medulla, and Anterior to the fourth Ventricle-Function: Lateral eye movement,Facial expression, chewing face
• Is a place where facial touch vibration runs
• Medulla- Location:between pons and spinal cord. Anterior to the functions are related to functions like breathing regulation heartbeat
• A Midbrain consist of the tegmentum and cerebri

Landmarks- Reference to the Cerebellum

• Reference point is tentonum cerebelli

Cerebellum-

• Located in - Posterior cranial fossa
• Functions regulates precision and movement

Spinal Cord

• It runs inside the vertabral canal and ends the Medullea
• Important functions for Receives sensory, motor commands from the body and carries information to the brain spinal reflox