Internal features of the brain D.Nimer D.Rania Gabr D.Safaa D.Elsherbiny

Objectives Describe the types of fibers in the internal capsule. Identify the basal ganglia nuclei. Identify main parts of the diencephalons and name the main functions of each part Briefly describe the brain ventricles and meanings. Describe the organization of the cerebral cortex. (Layers and columnar organization). Locate the motor, sensory and other cortical areas. Describe the cortical areas related to the written and spoken language. Identify the structures in coronal, sagittal and horizontal sections of brain.

White Matter Underlies the cortex and contains:  Nerve fibers, Neuroglia cells & Blood vessels.  The nerve fibers run in different directions and originate, terminate or sometimes both, within the cortex.

White Matter Types : the white matter contains 3 types of nerve fibers: Commissural fibers: connect the same cortical areas of the two cerebral hemispheres. Association fibers: connect cortical areas in the same cerebral hemisphere. Projection fibers: connect the cerebral cortex with the subcortical areas.

Association Fibers Definition: connect one cortical area with another cortical area in the same hemisphere. Types 1- Short Association Fibers: they connect adjacent cortical areas. 2-Long Association Fibers: they connect distant cortical areas. They include: 1.Superior longitudinal fasciculus (arcuate fasciculus): 2.Inferior longitudinal fasciculus: 3.Uncinate fasciculus: 4.Cingulum: Function: processing of information (such as language) in the same hemisphere. Short association fibers Long association fibers

1.Uncinate fasciculus: connects frontal to temporal lobe Long Association Fibers

2. Superior longitudinal fasciculus (arcuate): connects the frontal, parietal, temporal and occipital lobes

3- Inferior longitudinal fasciculus: connects occipital to temporal pole 4- Cingulum: connects the cingulate gyrus with the parahippocampal gyrus and ends in the uncus

Definition: They connect the same cortical areas of the two cerebral hemispheres. Types: 5 1.Corpus callosum. 2.Anterior commissure. 3.Posterior commissure. 4.Hippocampal commissure. 5.Habenular commissures. Commissural Fibers

Corpus Callosum O F P C Forceps minor Forceps major  Connects the corresponding regions of the two hemispheres except the temporal lobes, that are connected by anterior commissure  The callosal fibers linking the frontal poles curve forward forming anterior forceps (forceps minor)  The callosal fibers linking the occipital poles curve backward forming posterior forceps (forceps major)

Parts: Parts: it is divided into 4 parts: Rostrum: it is continuous with the lamina terminalis. Genu: is the anterior end of the corpus callosum. Its fibers form the forceps minor, which connects the two frontal lobes. Splenium: is the posterior end of the corpus callosum. Its fibers form the forceps major, which connects the two occipital lobes. Body (trunk): is the central part of the corpus callosum. Its fibers form the radiation of corpus callosum. The posterior fibers form the tapetum, which connects the 2 temporal lobes. Parts of Corpus Callosum

Arterial supply: by the anterior cerebral artery. The posterior cerebral artery may supply the splenium. Function: transfer of information (memory and language) between the 2 hemispheres. Lesion: Callosal apraxia. The memory and language processes will not be accessible to the nondominant hemisphere causing left side disorders.

 Anterior commissure: It connects the two temporal lobes  Hippocampal Commissure: connects the 2 hippocampi  Posterior Commissure: 1. The two superior colliculi. 2. The pretectal nucleus and the Edinger-Westphal nuclei for the bilateral light reflex. 3. The two-occulomotor nuclei for the upward gaze.  Habenular Commissure: connects the habenular nuclei located above the thalamus (Olfaction)

pyramidal decussation pyramid Corticospinal tract Definition: they connect the cerebral cortex with the subcortical areas and form a compact bundle called the Internal Capsule.  Consist of:  Afferent fibers conveying impulses to the cerebral cortex.  Efferent fibers conveying impulses away from the cortex. Types: they are divided into ascending and descending fibers: 1.Ascending projection fibers: are mainly thalamocortical fibers. 2.Descending projection fibers: such as corticospinal and corticobulbar fibers. Commissural Fibers Projection Fibers

Deeper to the cortex, these fibers are arranged radially as the corona radiata. Then the fibers converge downward, form internal capsule, between thalamus and basal ganglia. Continue in the crus cerebri of the midbrain, basilar part of pons, & pyramid of medulla oblongata.

Internal Capsule Bundle of projection fibers, passes through the interval between the Thalamus (T) and the basal ganglia: Caudate (C) & Lentiform nucleus (L) Has 5 parts: 1- Anterior limb: 2-Genu: 3-Posterior limb: 4-Retrolenticular part: 5-Sublenticular part (not shown): C T L

Basal ganglia are masses of gray matter situated deep within each cerebral hemisphere. They are: Corpus striatum. Amygdaloid nucleus. Claustrum. Substantia Nigra. Subthalamic Nuclei. Basal Ganglia

The diencephalon consists of the third ventricle and the structures that form its boundaries. It is divided into: Thalamus. Subthalamus. Hypothalmus. Epithalamus. Diencephalon

The ventricles are four cerebrospinal fluid-filled cavities located within the brain. Two lateral ventricles. Third ventricle. Fourth ventricle. Lateral ventricles communicate through interventricular foramina (of Monro) with third ventricle. The third is connected to the fourth by cerebral aqueduct (of Sylvius). Ventricular System