Central Nervous System Wednesday November 28 2012 12 42 PM Protective Structures of the Brain 1 Cranium 2 Meninges 3 Cerebrospinal fluid CSF 4 Blood Brain barrier 1 Cranium Cranial bones forming the cranial vault which is a bony encasement of the brain the lobes of the cerebral hemispheres are named for the overlying cranial bones 2 Meninges Outermost meninx Dura mater double layered Periosteal Layer attached lines to the internal surface of the cranial bones o o Meningeal Layer is separated from middle meninx by the subdural space dura mater surrounding spinal cord is single layered Middle meninx arachnoid mater separated form the meningeal layer of the dura mater by the subdural space the arachnoid is separated from the innermost meninx the pia mater by the subarachnoid space Subarachnoid space contains CSF CSF around the brain Innermost meninx pia mater attached to the surface of the cerebrum the cerebral blood vessels enter exits the brain pons through the pia mater 3 Cerebrospinal Fluid CSF Hypotonic filtrate of blood blood in the choroid plexus is filtered into spaces subarachnoid space ventricles in brain and central canal in spinal cord CSF provides protection against trauma CSF absorbs dissipates pressure CSF provides buoyancy to the brain lighter appears to weigh less due to CSF around inside the brain CSF provides nutrients glucose and oxygen to neurons neurons use exclusively glucose O2 for energy production required for function of the brain CSF removes metabolic wastes from neurons to the venous circulation to be eliminated by the kidneys 4 Blood Brain Barrier Major Regions of the Brain 1 Cerebrum 2 Diencephalon 3 Brainstem 4 Cerebellum 1 Cerebrum 83 total mass of the brain Surface of the cerebrum involuted with hills elevated ridges GYRI valleys grooves SULCI and deeper grooves FISSURES A median fissure called the Longitudinal Fissure partially separates the cerebrum into two cerebral hemispheres Left Right Each cerebral hemisphere is divided into 5 lobes by the Sulci Frontal Lobe central sulcus Parietal Lobe central sulcus parieto occipital sulcus o o o Occipital Lobe parieto occipital sulcus o o Temporal Lobe lateral sulcus separates frontal and parietal lobe for the temporal lobe Insula deep to the lateral sulcus cannot be seen externally 2 Cerebral hemispheres held together by the corpus callosum Coronal section of the cerebrum 3 regions o o o Cerebral Cortex outer region composed of gray matter gray matter composed of unmyelinated structures dendrites cell bodies and unmyelinated axons Cerebral White Matter inner region composed mainly of myelinated axons Basal Nuclei classes of cell bodies inside the cerebral white matter 3 Functional Areas in the Cerebral Cortex outer gray matter o Motor Areas control voluntary movements all 4 areas are located in frontal lobe of each cerebral hemisphere except Broca s area only in Left cerebral hemisphere Primary motor cortex located in the precentral gyrus in each cerebral hemisphere Precentral gyrus contains large neurons PYRAMIDAL CELLS the axons bundle to form the pyramidal tracts tracts descend into lower brain regions and the spinal cord before the pyramidal tracts descend into the spinal cord the pyramidal tracts DECUSSATE The pyramidal tracts from the precentral gyrus In the LEFT cerebral hemisphere crossover to the right side to innervate skeletal muscles on the right side of the body In the RIGHT cerebral hemisphere cross over to the left side to innervate skeletal muscles on the left side of the body Deccussation of the pyramidal tracts Decussations of the pyramids explains the control of the cerebral cortex in the cerebral hemispheres of voluntary skeletal muscle movement Premotor cortex Broca s area only in the LEFT cerebral hemisphere connected to the Wernicke s which is also in the left cerebral hemisphere called the Arcuate Fasciculate example of association tract Frontal eye field o Sensory Areas located in all the lobes in each cerebral hemisphere Somatosensory cortex located in the postcentral gyrus receives sensory input from the skin and the joints for spatial discrimination The sensory tracts decussate hence input from the left side is received by the right postcentral gyrus input from the right side is received by the left postcentral gyrus Damage to the pre central post central gyrus in the left cerebral hemisphere loss of sensation paralysis on the right side of the body Gustatory cortex taste located in the insula Visual cortex located in the occipital lobe Auditory cortex located in the temporal lobes Olfactory cortex located in both the temporal frontal lobes o Association Areas associated with the sensory areas to provide quality to the sensory input Cerebral White Matter 2nd Region in Cerebral Hemisphere Composed of tracts made up of mainly myelinated axons myelin white fatty protein 3 types of Cerebral White Matter Tracts 1 Commissural Tracts 2 Projection Tracts precentral gyri a Descending Tracts Motor output from the cerebral cortex pyramidal tracts from b Ascending Tracts Sensory input to the cerebral cortex spinal thalamic tract from spinal cord to thalamus and then projected to the cerebral cortex 3 Association Tracts arcuate fasciculate connects the Broca s area to the Wernicke s area in the LEFT cerebral hemisphere Basal Nuclei 3rd region in the cerebrum Consists of clusters of neuronal cell bodies deep in the cerebral white matter 3 Prominent Basal Nuclei 1 Caudate Nucleus 2 Globus Pallidus 3 Putamen o o Putamen globus pallidus LENTIFORM NUCLEUS Lentiform nucleus caudate CORPUS STRIATUM basal nuclei The descending pyramidal tracts course through the basal nuclei to give them a striated appearance hence the basal nuclei are also referred to as the corpus striatum 2 Lateral Ventricles are located in the cerebral hemispheres one in each Diencephalon 2nd region of the adult brain Contains the 3rd ventricle connected to the 2 lateral ventricles by the interventricular foramen Thalamus Hypothalamus Epithalamus Brainstem 3rd region Midbrain o Corpora Quadrigemina 2 Superior Nuclei Superior Colliculi Visual Reflex centers tracking reflex 2 Inferior Nuclei Inferior Colliculi Auditory Reflex centers startle reflex 2 Pigmented Nuclei Red Nuclei Substantia Nigra black due to high levels of melanin used in synthesis f dopamine Neurons in the substantia nigra release dopamine at their axon terminal in the basal nuclei Degeneration of these dopaminergic neurons in the substantia nigra to the basal
View Full Document
Unlocking...