It’s situated in the anterior & middle cranial fossae Cerebrum is divided into 2 parts Diencephalon : Forms the central core T...
It’s situated in the anterior & middle cranial fossae Cerebrum is divided into 2 parts Diencephalon : Forms the central core Telencephalon : Forms cerebral hemispheres The diencephalon It’s a midline structure with symmetrical right & left halves It can be divided into 4 major parts : Thalamus, Subthalamus, Epithalamus & Hypothalamus Thalamus It’s a large ovoid mass of grey matter (No axons) Serve as a cell station to all the main sensory system, except the olfactory pathway It’s situated on each side of the 3rd ventricle Subthalamus Lies inferior to the thalamus (Situated between the thalamus & the Tegmentum of the midbrain) It’s involved in the control of muscle activity Epithalamus It’s consist of Habenular nucleus & Pineal gland (Endocrine gland) Pineal gland secretions can influence (Mainly inhibitory) the endocrine activities of : Pituitary (Directly or indirectly), Pancreas, Parathyroids, Adrenals & Gonads Hypothalamus It’s involved in almost all the body activities Relations of the hypothalamus from anterior to posterior Optic chiasma Tuber cinereum & the infundibulum Mammillary bodies 3rd ventricle Situated between the 2 thalami Communicates anteriorly with the lateral ventricles through the inter ventricular foramina (Foramen of Monro) Communicates posteriorly with the 4th ventricle trough the cerebral aqueduct It’s walls are lined by ependyma Cerebral hemispheres (Telencephalon) Largest part of the brain 2 hemispheres are separated by a deep midline fissure : The longitudinal cerebral fissure Corpus callosum connects the hemispheres across the midline Tentorium cerebelli separates the cerebral hemispheres from the cerebellum To increase the surface area of the cerebral cortex, each hemisphere has formed folds (Gyri) & gyri are separated by sulci (Fissures) Each hemisphere is divided into 4 lobes : Frontal, parietal, temporal & occipital (Named according to the cranial bones under which they lie) The main sulci & Gyri Lateral view of the left cerebral hemisphere Medial view of the right cerebral hemisphere The structures situated interior to the cerebral hemispheres: Lateral ventricles Basal nuclei White matter & nerve fibers Basal ganglia It’s a collection of grey masses in the white matter of the hemispheres There are 3 main parts Corpus striatum : Divided by the internal capsule into Caudate & Lentiform nucleus Amygdaloid nucleus : Situated in the temporal lobe Claustrum White matter of the cerebral hemispheres It’s composed of myelinated nerve fibers The nerve fibers are classified into 3 groups Commissural fibers Association fibers Projection fibers Commissural fibers Connect corresponding regions of the 2 hemispheres They are as follows Corpus callosum Anterior & posterior commissures Fornix Habenular commissure Association fibers Connect various cortical regions within the same hemisphere Projection fibers Afferent & efferent nerve fibers passing to & from the brainstem to the cerebral cortex Examples Internal capsule (Anterior, posterior limbs & genu) Corona radiata Optic radiation Internal capsule & its nerve fiber arrangement Relationships between internal capsule, basal ganglia, and thalamus in horizontal section. Notice that descending motor fibers for the face, arm, and leg (F, A, L) run in front of ascending sensory fibers (f, a, l) in the posterior limb of the internal capsule
