The brain is easily damaged by compression, so the fluid surrounding the central nervous system must be maintained at a constant volume. Fluid movement within the brain is limited by the blood-brain barrier, brain-cerebrospinal fluid barrier, and the blood-cerebrospinal fluid barrier.
The dense fluid protects the brain and spinal cord from shock a brain that weighs 1,500 g in air weighs only 50 g when suspended in CSF (Livingston, 1965). The brain is suspended in cerebrospinal fluid (CSF) which also fills spaces called ventricles inside it. Blood is then drained from the brain through a network of sinuses that drain into the right and left internal jugular veins. The blood supply to the brain involves several arteries that enter the brain and communicate in a circle called the circle of Willis. Brain stem structures are almost completely enveloped by the cerebellum and telencephalon, with only the medulla oblongata visible as it merges with the spinal cord. A well-developed cerebellum is visible at the back of the brain. The two hemispheres of the brain are separated by a prominent central fissure. Such heavy energy usage generates large quantities of heat, which must be continually removed to prevent brain damage.Ī bulbous cerebral cortex is composed of convoluted grey matter internally supported by deep brain white matter. The mature brain consumes some 20% of the energy used by the body, while the developing brain of an infant consumes around 60%. However, both sexes have similar brain weight to body weight ratios (She Brains - He Brains). An average male brain has approximately 4% more cells and 100 grams more brain tissue than an average female brain. The normal adult human brain typically weighs between 1 and 1.5 kg (3 lb) and has an average volume of 1,600 cm³ (98 in³). Click here for an animated sequence of slices. Sagittal slice from a MRI scan of a human brain. But the human brain is unique, in part, because it relies on some million billion synaptic connections, making it an extremely intricate and densely connected neural network. Human consciousness involves both the extended capacity of the modern neocortex in particular as well as profoundly developed prototypical structures of the brain stem. Basic systems that alert the nervous system to stimuli, sense events in the environment, and monitor and maintain the internal environment of the body ( homeostasis) are similar in some ways to those of the most basic vertebrates. Humans thus enjoy unique neural capacities despite the fact that much of the human neuroarchitecture resembles that of more primitive species. Singular among those of all animals, the human brain possesses the largest and most massive neocortex. Human encephalization is especially pronounced in the neocortex, the most complex portion of the cerebral cortex.7 Comparison of the brain and a computer.