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TSM4: STRUCTURE / FUNCTION RELATIONSHIPS IN THE NERVOUS SYSTEM 26/09/08 LEARNING OUTCOMES Give an overview of the basic functions of the nervous system LATERAL ASPECT OF THE BRAIN – CEREBRUM (FOREBRAIN) Looking at the lateral (outermost) surface of the brain, a deep cleft can be seen that crosses superioposteriorly across the centre of the cerebrum called the lateral sulcus The lateral sulcus is bisected by the central sulcus which descends from the great longitudinal fissure at the top of the brain and terminates centrally at the lateral sulcus Part of the parieto-occipital sulcus can be seen near the posterior border Anterior to the central sulcus and inferior part of the lateral sulcus is the frontal lobe Immediately posterior to the frontal lobe and superior to the lateral sulcus is the parietal lobe, whose posterior border is roughly at the line of the parieto-occipital sulcus Immediately posterior to the frontal lobe and inferior to the lateral sulcus is the temporal lobe with a posterior border along the same line as the parietal lobe Posterior to the parietal and temporal lobes is the occipital lobe, occupying the posterior-most section of the cerebrum MEDIAN SAGITTAL ASPECT OF THE BRAIN Inferior to the frontal and parietal lobes the corpus callosum can be seen which joins the two cerebral hemispheres together Running anteriorly across the occipital lobe from the posterior margin to the parieto-occipital sulcus is the calcarine sulcus Inferior to the corpus callosum is the thalamus, hypothalamus and pituitary respectively The pituitary stalk descends from the hypothalamus at the superior border of the temporal lobe At the level of the pituitary stalk is an anterior projection called the optic chiasm Inferior to the hypothalamus along the midline are the mammillary bodies The midbrain occupies a small area inferior and posterior to the thalamus with two posterior projections, the superior and inferior colliculi BLOOD SUPPLY The arterial supply to the brain is from two pairs of arteries: the vertebrals and internal carotids o These arteries divide and form a dense arterial network on the ventral brain surface o Three main paired branches that supply the cerebrum are the anterior, posterior and middle cerebral arteries o The middle cerebral artery is the most important and is often involved in strokes The primary motor cortex has lateral and medial elements anterior to the central sulcus supplied by the middle and anterior cerebral arteries respectively The primary somatosensory cortex has lateral and medial elements posterior to the central sulcus which are similarly supplied by the middle and anterior cerebral arteries respectively o The lateral regions of the above are responsible for areas above the waist o The medial region of the above are responsible for areas below the waist Froca’s area (motor language) is superior to the lateral sulcus on the anterior side and is supplied by the middle cerebral artery Wernicke’s area (‘sensory language’) is inferior to the lateral sulcus on the posterior side and is also supplied by the middle cerebral artery The primary visual cortex at the posterior border of the medial surface is supplied by the posterior cerebral artery