Brain or Encephalon The content of the two lectures • The parts of the brain or encephalon • The brain stem and cerebellum • The forebrain or prosencephalon: the diencephalon and the telencephalon PHYLOGENY AND ONTOGENY OF THE BRAIN 1. Evolution factors which contributed to development of prosencephalon, mesencephalon and rhombencephalon. 2. Differentiation of rhombencephalon into myelencephalon and metencephalon (pons and cerebellum). 3. Differentiation of prosencephalon into the diencephalon and telencephalon 4. Evolutionary conservatism of mesencephalon and its functional reduction. Smell Vision Hearing The parts of the brain or encephalon: 1. Hindbrain or Rhombencephalon: medulla oblongata and metencephalon (pons and cerebellum). 2. Midbrain or Mesencephalon. 3. Forebrain or Prosencephalon: diencephalon (interbrain) and telencephalon. 4. Brain stem: medulla oblongata (bulbus, myelencephalon), pons and midbrain. The parts of the brain or encephalon: 1. Hindbrain or Rhombencephalon: medulla oblongata and metencephalon (pons and cerebellum). 2. Midbrain or Mesencephalon. 3. Forebrain or Prosencephalon: diencephalon and telencephalon. 4. Brain stem: medulla oblongata (bulbus), pons and midbrain. Short characteristic of the brain stem, truncus encephali Brain stem includes (1) medulla oblongata, (2) pons and (3) midbrain Short characteristic of the brain stem, truncus encephali Brain stem involves many of the ascending and descending neural pathways, some of which extends along the whole brain stem, while others begin or end in the brain stem. Short characteristic of the brain stem, truncus encephali The brain stem contains the abundant grey matter (nuclei), in which neural pathways begin, end or switch over. The brain stem contains nuclei of ten cranial nerve (III-XII) Short characteristic of the brain stem, truncus encephali The brain stem encloses the complex of heterogeneous neurons - reticular formation (Formatia reticularis), in which the specific nuclei are discriminated. Neurons of these nuclei do influence on the human sensation, pain sensation, regulate the cardiovascular and respiratory systems. Neurons of the reticular formation are associated with nuclei of the cranial nerves, cerebellum, motor mechanisms of the brain stem and spinal cord and, therefore, these neurons have influence to the human movements, the human body posture and skeletal muscle tone. Short characteristic of the brain stem, truncus encephali The 4th ventricle and the cerebral aqueduct is situated in the brain stem Median and lateral apertures of Cerebral aqueduct 4th ventricle Choroid plexus Role of choroid plexuses and apertures of 4th ventricle in the circulation of the liquor External anatomy of brain stem Anterior view Myelencephalon: anterior median fissure, sulci (anterolateral and posterolateral); pyramid, roots of the cranial nerves (VI, VII, VIII, IX, X, XI, XII). Pons: basilar sulcus, middle cerebellar peduncles, roots of trigeminal nerve (V). Mesencephalon: Cerebral peduncles, posterior perforated substance, roots of cranial nerves (III, IV). External anatomy of brain stem Lateral view Myelencephalon: sulci (anterolateral and posterolateral); pyramid, olive. Inferior cerebellar peduncles. Cuneate and gracile tubercles; roots of the cranial nerves (VI, VII, VIII, IX, X, XI, XII). Pons: Middle cerebellar peduncles, roots of trigeminal nerve (V). Mesencephalon: Cerebral peduncles, corpora quadrigemina: superior and inferior colliculi and their brachii, roots of cranial nerves (III, IV). External anatomy of brain stem Posterior view Superior and inferior colliculi and their Corpora quadrigemina Myelencephalon: sulci brachii (posterior median and posterolateral). Inferior Cerebral peduncles cerebellar peduncles. Cuneate Sup.medulallary velum Root of trochlear nerve (IV) and gracile tubercles; roots of the Median sulcus cranial nerves Medial eminence Facial colliculus Pons: cerebellar peduncles. Vestibular area Rhomboid fossa. Superior and inferior medullary velum. Median Hypoglossal trigone sulcus, medial eminence, hypoglossal Vagal trigone and vagal trigones, facial colliculus, vestibular area. Mesencephalon: Cerebral peduncles, corpora quadrigemina seu lamina tecti: superior and inferior colliculi and their brachii, roots of cranial nerves (IV). “The most survival" external structure on the brain stem “The most survival" external structure on the brain stem Cerebellar peduncles Roots or rootlets of the cranial nerves (V, VI, VII, VIII, IX, X, XI, XII) Roots of the cranial nerves (V, VI, VII, VIII, IX, X, XI, XII) Levels or floors of the brain stem : Anterior (ventral) - Basis Middle- Tegmentum Posterior (dorsal) -Tectum Midbrain Pons Basis Tegmentum Tectum Myelencephalon Caudal Middle Rostral Brain stem basis Pyramidal tract Brain stem basis Pyramidal tract and nuclei of the pons Brain stem tegmentum Gracile and cuneate fasciculi and their nuclei. Medial lemniscus and its decussation. Anterior and posterior spinocerebellar tracts. Anterolateral fasciculus (ALF) or spinothalamic tract Brain stem tegmentum Anterior and posterior spinocerebellar tracts. Inferior olivary nucleus and olivocerebellar tract Brain stem tegmentum Nuclei of the cranial nerves (III-XII) Sensory Motor Motor: Sensory somatic,visceral, special Brain stem tegmentum Nuclei of the cranial nerves (III-XII) Motor: Sensory somatic,visceral, special Brain stem tegmentum Trapezoidal body and lateral lemniscus. Cochlear nuclei and superior olivary nuclei Tegmentum Trigeminal lemniscus. Ventral posteromedial nucleus of the thalamus Trigeminal lemniscus Medial lemniscus Spinothalamic fasciculus Principal sensory trigeminal nucleus Tegmentum Medial longitudinal fasciculus Oculomotor and trochlear nuclei Vestibular nerve and nucleus Reticular formation (formatia reticularis) is the complex of heterogeneous neurons, which are arranges into specific nuclei and which do influence on Tegmentum the human somatic sensation, pain sensation, regulate the cardiovascular Reticular formation and respiratory systems. Slices of brain stem Slices of brain stem Myelencephalon- basis and tegmentum Caudal (inferior) part Slices of brain stem Myelencephalon- basis and tegmentum Middle part Slices of brain stem Myelencephalon- basis and tegmentum Rostral (superior) part Slices of brain stem Pons- basis and tegmentum Trapezoid body Superior and inferior Cerebellar peduncles Slices of brain stem Pons- basis and tegmentum Trapezoid body Pons- basis and tegmentum Upper pons Slices of brain stem Midbrain- basis and tegmentum Cerebral aqueduct, substantia nigra, crura of cerebral peduncles Slices of brain stem Midbrain- basis and tegmentum Substantia nigra – midbrain structure, which neurons control the conscious movements - determine a movement feedback and a correction of movements. Midbrain Substatia nigra – a part of dopaminergic system of the brain The red nucleus or nucleus ruber is a structure in the rostral midbrain involved in motor coordination. It is pale pink in color; the color is believed to be due to iron, which is present in the red nucleus in at least two different forms: hemoglobin and ferritin. It comprises a caudal magnocellular and a rostral parvocellular part. It is located in the tegmentum of the midbrain next to the substantia nigra. The red nucleus as well as the substantia nigra are subcortical Central tegmental tract centers of the extrapyramidal motor system.. Red nucleus Midbrain Tracts of the midbrain basis (corticospinal and corticonuclear) Cerebellum The cerebellum (Latin for "little brain") is a major part of the hindbrain (metencephalon). The cerebellum plays an important role in motor control, and it may also be involved in some cognitive functions such as attention and language as well as in regulating fear and pleasure responses, but its movement-related functions are the most solidly established. The human cerebellum does not initiate movement, but contributes to coordination, precision, and accurate timing. The cerebellum is located in the posterior cranial fossa. The fourth ventricle, pons and medulla oblongata are in front of the cerebellum. It is separated from the overlying cerebrum by a layer of leathery dura mater, the tentorium cerebelli; all of its connections with other parts of the brain travel through the cerebellar peduncles (pedunculus cerebellaris inferior, medius et superior). The cerebellum is divided into two hemispheres and it also contains a narrow midline zone (the vermis). The cerebellum is divided into two hemispheres and it also contains a narrow midline zone (the vermis). Deep nuclei of the cerebellum: fastigial, interposed: emboliform and globose, and dentate. Deep nuclei of the cerebellum: fastigial, interposed: emboliform and globose, and dentate. Cortex of cerebellum Deep nuclei of the cerebellum: fastigial, interposed: emboliform and globose, and dentate. Anterior lobe Posterior lobe Flocculonodular lobe Fastigial-Nucleus fastigii Emboliform-Nucleus embuliformis Dentate-Nucleus dentatus Globose-Nucleus globulosus Cerebellum 1) Paleocerebellum (cortex vermi + nucleus emboliformis et globulosus) or spinocerebellum – controls (monitors) and coordinates the conscious movements and the tone of skeletal muscles; 2) Archicerebellum (lobus flocculonodularis + nucleus fastigii) or vestibulocerebellum – controls the maintenance of body balance (equilibrium) and the movements of eyes and/or heads; 3) Neocerebellum (cortex + nucleus dentatus) or cerebrocerebellum – controls and modulates conscious movements, influences the activity of premotor