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Computational Neuroscience and Compartmental Modeling
Published in Bahman Zohuri, Patrick J. McDaniel, Electrical Brain Stimulation for the Treatment of Neurological Disorders, 2019
Bahman Zohuri, Patrick J. McDaniel
Figure 3.5 illustrates the parts of a nerve cell or neuron. Each neuron consists of a cell body, or soma, that contains a cell nucleus. Branching out from the cell body are a number of fibers called dendrites and a single long fiber called the axon. The axon stretches out for a long distance, much longer than the scale in this diagram indicates. Typically, an axon is 1 cm long (100 times the diameter of the cell body) but can reach up to 1 meter. A neuron makes connections with 10 to 100,000 other neurons at junctions called synapses. Signals are propagated from neuron to neuron by a complicated electrochemical reaction. The signals control brain activity in the short term and also enable long-term changes in the connectivity of neurons. These mechanisms are thought to form the basis for learning in the brain. Most information processing goes on in the cerebral cortex, the outer layer of the brain. The basic organizational unit appears to be a column of tissue about 0.5 mm in diameter, containing about 20,000 neurons and extending the full depth of the cortex about 4 mm in humans).38
Cellular and Molecular Basis of Human Biology
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
This includes the brain and spinal cord. It has in many components, including the brain itself (cerebral cortex, cerebellum, diencephalon), brain stem, and spinal cord. The brain cerebral cortex is further divided into several lobes: frontal, parietal, occipital, and temporal, each of which has special controls of body functions (Reece et al. 2014). Frontal lobe: Controlling speech, decision making, and skeletal muscle motion.Parietal lobe: Controlling sensory functions.Occipital lobe: Controlling vision (image and object recognition).Temporal lobe: Controlling auditory functions (hearing).
Introduction: Background Material
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Beyond the diencephalon is the cerebrum (Figure 1.7), comprising the cerebral cortex and the basal ganglia. The cerebral cortex, basal ganglia, and the amygdala – a structure in the medial temporal lobe, just anterior to the hippocampus – constitute the telencephalon. The diencephalon and telencephalon are referred to as the forebrain. The basal ganglia and thalamus are more clearly illustrated in the frontal section of Figure 12.6. The cerebral cortex, where the word cortex refers to a rind or outer covering, is divided into the neocortex, which in humans is almost the whole of the cerebral cortex, and the phylogenetically older allocortex. The cerebral cortex constitutes in humans about 77% of the brain by volume and up to 40% by mass. It is the highly convoluted, outer layer covering the two cerebral hemispheres. Its thickness varies between different regions from less than 2 mm to about 4.5 mm. It contains about 16 billion neurons in a well-defined structure of up to six layers in the neocortex, labeled I–VI, layer I being the most superficial. The large folds, or convolutions, of the cerebral cortex are called gyri (singular, gyrus) and are separated by fissures known as sulci (singular, sulcus). Some of the deep fissures are used as landmarks that divide the neocortex into four lobes that can be identified on the outer surface of each hemisphere: the frontal, temporal, parietal, and occipital lobes (Figure 1.9). The central sulcus separates the frontal lobe from the parietal lobe, and the lateral sulcus separates the temporal lobe from the parietal and frontal lobes. Two other lobes are tucked inside the cerebral hemispheres: (i) the limbic lobe, which is an arc-shaped region on the medial surface of each cerebral hemisphere, and is contiguous with parts of the frontal, parietal, and temporal lobes, and (ii) the insular lobe, located deep within the lateral sulcus. The cerebral cortex is involved in higher functions, including sensory perception, voluntary movement, conscious thought, and language.
The Neurostructure of Morality and the Hubris of Memory Manipulation
Published in The New Bioethics, 2018
The most striking feature of the human brain is the cerebral cortex (Blank 2013, pp. 3–8). Only two millimeters thick, its surface area is approximately 1.5 m and contains some ten to fifteen billion neurons, four times as many glial cells, and an estimated one million billion synaptic connections. Roughly divided into the occipital, temporal, parietal, and frontal lobes on each side, the cerebral cortex contains numerous areas involved in sensory reception, motor control, language, and associated activities having multiple functions. The frontal lobes serve as the center of higher-order processing, which permits the capacity to engage in abstract thinking, planning, and problem solving. The hippocampus, located at the base of the temporal lobe, is vital to both learning and the consolidation of short-term memory. Closely situated at the base of the frontal lobes are the basal ganglia nuclei, which serve a variety of functions including voluntary motor control, procedural learning of routine behaviors, and action selection: the determination of which (of several possible) behaviors to execute at a given time. The frontal lobes constitute nearly forty percent of the total cortical area and, as the last areas to mature, are connected to almost every other part of the brain, including the behaviorally critical limbic system (Blank 2013, pp. 3–6).