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The Skull and Brain
Published in Melanie Franklyn, Peter Vee Sin Lee, Military Injury Biomechanics, 2017
Tom Gibson, Nicholas Shewchenko, Tom Whyte
The main parts of the brain are the cerebrum, cerebellum and brainstem. The cerebrum is the most superior part of the brain and is composed of two hemispheres accounting for 83% of the total brain mass. The surfaces of the cerebral hemispheres have ridges and furrows called gyri and sulci, respectively. A number of deeper chasms in the brain tissue are referred to as fissures, which divide the brain into lobes and separate the hemispheres. The only attachment between the hemispheres is a fibrous bundle called the corpus callosum. The cerebellum is the second largest part of the brain, accounting for around 11% of the total brain mass. It is located underneath the occipital lobes in the posterior cranial fossa of the skull. The brainstem is located at the base of the skull where the spinal cord enters the cranial cavity (Figure 8.4).
Tissue Structure and Function
Published in Joseph W. Freeman, Debabrata Banerjee, Building Tissues, 2018
Joseph W. Freeman, Debabrata Banerjee
The cerebrum is split into a right and left hemisphere. The hemispheres are joined by a dense bundle of nerve fibers called the corpus callosum. The corpus callosum allows signals to be sent from one hemisphere to the other. The cerebral cortex lies at the top layer of the cerebrum. This area coordinates cognition, learning, memory, sensory perception, volunteer movement, and motor planning.3,20 It has a wrinkled gray appearance (called gray matter). Beneath the cerebral cortex are connecting fibers between neurons called the white matter.20 The wrinkles of the cerebral cortex consist of sulci (small grooves), fissures (larger grooves), and gyri (bulges between grooves).20
Brain–Computer Interface
Published in Shampa Sen, Leonid Datta, Sayak Mitra, Machine Learning and IoT, 2018
Abhishek Mukherjee, Madhurima Gupta, Shampa Sen
As mentioned before, the largest part of the brain is the cerebrum. It is divided into two symmetrical hemispheres—right and left hemispheres—connected together by the calossum, as observed in Figure 16.1. The cortex is composed of grey and white matter, and these are nothing but bundles of neurons having special and distinctive orientations. The white matter is just the axons with myelin sheaths, while the grey matter is composed of everything else pertaining to the neurons. The cerebral cortex is the region of cortex associated with the cerebrum. It is composed of a greater number of layers compared to the cortex associated to the cerebellum. The cerebral cortex is a highly convoluted structure, composed of ridges known as gyri and fissures called sulci. Functional demarcation results in dividing each hemisphere into parietal, temporal, occipital, and frontal lobes. They all have distinct functions and yet are integrated which each other. The schematic structure and position of the lobes can be observed in Figure 16.2. As we can see, the frontal lobe is the largest of the four; it is our emotional control center and home to our personality. Thus, as expected, it is involved in a multitude of activities such as cognition (memory, problem solving, information processing, etc.), behavioral responses, and motor functioning and control. The occipital lobe is involved in visual processing while the temporal lobe takes care of sound and language. This lobe also harbors the amygdala and hippocampus, regions involved in emotions and memory, respectively. Parietal lobes function as an integration center for sensory inputs from different senses, and are also involved in spatial orientation, awareness, and sensation of self, as well as navigation. Between the cerebrum and brainstem lie the thalamus and hypothalamus. The hypothalamus acts as a relay center between the nervous system and the endocrine system. The thalamus communicates motor and sensory data to the cortex; also, it comprehends wakefulness and sleeping patterns.
A mesoscale finite element modeling approach for understanding brain morphology and material heterogeneity effects in chronic traumatic encephalopathy
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
A. Bakhtiarydavijani, G. Khalid, M. A. Murphy, K. L. Johnson, L. E. Peterson, M. Jones, M. F. Horstemeyer, A. C. Dobbins, R. K. Prabhu
The human brain is both heterogeneous (white/gray matter, fractal vasculature) and anisotropic (e.g. radial cortical organization, oriented fiber tracts). Gray matter is located on the outer surface of the brain and contains numerous cell bodies and neuronal somas. The gray matter surrounds the white matter that mostly consists of myelinated axon tracts. In addition, to accommodate the large cortical sheet in a limited volume, the neocortical gray matter is more folded in large-brained animals (Allman 2000). The gyri and sulci are the convex and concave folds of the cerebral cortex, respectively. The gyri often about the inside surface of the cranium, except in major fissures or involutions such as the insula. The major cortical features (e.g. the Sylvian fissure and central sulcus) are readily identifiable with some detailed variation in the folding from person to person. Recent efforts into the development of these convolutions (initiating after the 23rd week of gestation) generate stress fields in the brain (Raghavan et al. 1997; Bayly et al. 2013; Budday et al. 2014; Goriely et al. 2015). These stress fields may be released with time considering the viscoelastic behavior of brain tissue. The extent of brain convolutions also vary due to malformations such as lissencephaly and polymicrogyria that enhance or reduce folding on the brain surface (Allman 2000). Furthermore, the brain is encased in a multilayered, fibrous structure that includes the pia, arachnoid, and dura mater, of which the pia mater is on the surface of the brain and follows its folds. An understanding of these features is then required to decide what features to include in a head model that can be achieved using computational approaches.