Biology XI: 21 Neural control & coordination(3 Central Nervous Syst

Central Nervous System Human Brain Protected by the skull Protective covering: Cranial meninges Cranial meninges (Three-layered): Dura mater (outer), Arachnoid (middle), pia mater (inner) Brain is divided into 3 parts: Forebrain: Has the cerebrum, thalamus and hypothalamus Cerebrum (major part of the brain) is divided by a deep cleft into the left and right cerebral hemispheres. Corpus callosum: A tract of nerve fibres that connect the two hemispheres Cerebral Cortex: Layer of cells covering the cerebral hemispheres. It is also called ‘grey matter” due to its greyish appearance, imparted by the high concentration of neuron cell bodies. Cerebral cortex consists of 3 areas:Motor areas, Sensory areas, Association areas (not clearly distinguishable into motor or sensory) Association areas: Responsible for complex functions like inter-sensory association, memory and communication Fibres of tracts present in the inner parts of the hemispheres are called “white matter” due to the opaque white appearance, imparted by the myelin sheath covering. Thalamus: Coordinates sensory and motor signalling Hypothalamus: Controls body temperature, hunger and thirst; contains neurosecretory cells which secrete hormones Limbic System = Inner parts of the cerebral hemispheres + Amygdale + Hippocampus Limbic System + Hypothalamus = Involved in the regulation of emotions, sexual behaviour and motivation Midbrain Location: Between the thalamus/hypothalamus of the forebrain and the pons of the hindbrain Cerebral aqueduct: Canal passing through the midbrain Corpora quadrigemina: 4 round swellings (lobes) on the dorsal portion of the midbrain. Hindbrain: Pons + Cerebellum + Medulla Hindbrain and midbrain form the brain stem. Pons: Fibre tracts that connect various portions of the brain Cerebellum has a convoluted surface to provide space for more neurons. Medullaconnects to the spinal cord, and controls respiration, cardiovascular reflexes and gastric secretions.