Our visual system is critical to accessing information and communicating with others. The visual pathway begins with a photon of light traveling through the pupil of the eye to the retinal photoreceptors to induce a signaling cascade responsible for transmitting electrical information to the brain.

There are in the order of 86 billion neurons within a human brain. Communication between these neurons is achieved at highly specialized junctions called synapses. Synapses can be chemical or electrical.

We discuss the fundamental units of the nervous system: neurons and supporting cells, which are formed from radial glial cells, progenitor cells that divide to generate new neurons, which then migrate to their destination. An understanding of the anatomy of neurons and their function enables us to decipher how information travels within the nervous system and how neurons communicate with each other through synapses to form networks capable of performing sophisticated and complex tasks. We then discuss how ions traverse the cell membrane and the critical role ion channels play in establishing resting membrane potential, and how action potentials are generated and propagated along the axon.

The brain and the encased skull constitute an incompressible system that encloses a volume of approximately 1450 ml. Normally, the intracranial volume is made up of 80% brain tissue, 10% cerebrospinal fluid(CSF), and 10% intravascular blood. The basic principle of physics in relation to intracranial content is described by the Monroe–Kellie doctrine. This hypothesis states that the total volume of the brain, CSF, and intracranial blood should be constant. Any increases in the volume of one of the components must be at the expense of the other two to maintain adequate brain function.

A thorough knowledge of gross human neuroanatomy is important in understanding basic and clinical neuroscience. In this chapter we describe the key anatomical features of the human brain followed by a discussion on the main developmental processes and signaling mechanisms of neurogenesis and embryology. Finally, we introduce the reader to different model organisms commonly used in neuroscience research.

Brain tumors in adults and children range from devastating malignant tumors with a dire prognosis to benign tumors that can be totally resected with a favorable outcome. The incidence rate for primary brain tumors in adults in the United States is approximately 23.8 per 100,000 persons. Of those, approximately two thirds are benign or borderline in nature. The most common benign tumor in adults is meningioma. The incidence in the pediatric population is approximately 6.1 per 100,000 children. However, the incidence of malignant brain tumors is higher in children than adults. We discuss the most common benign brain tumors in adults followed by a discussion on pediatric brain tumors.

Artificial intelligence(AI), a term first coined by John McCarthy in the 1950s, is best thought of as the design of intelligent agents that can recognize and process stimuli to make decisions, similar to humans. The use of AI and artificial neural networks(ANNs) in medicine has been widely adopted to improve the efficiency of diagnostic medicine, and these include ANN-based analysis of electrocardiograms, electroencephalograms, radiographs, and automated computerized systems based on ANNs for detection of cancer data.

The somatosensory system is responsible for sensation such as touch. It is a subset of the sensory nervous system that represents the visual, olfactory, auditory, and gustatory pathways discussed in Chapter 6. There are five types of somatosensory receptors: mechanoreceptors, proprioceptors, pain receptors, thermoreceptors, and chemoreceptors.