Tag: life processes: control and coordination

The brain serves as the center of the nervous system in all vertebrates and most invertebrate animals. Only a few invertebrates, such as sponges,  jellyfish, adult sea squirts and starfish do not have a brain.In such organisms, a diffuse neural tissue is present. It is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste and smell. The brain is the most complex organ in a vertebrate's body. 

Ependymal cells are the cube-shaped epithelial cells that forms the epithelial lining of the cavities in brain and central canal of spinal cord. These cells are formed from a layer of embryonic tissue known as neuroectoderm and secrete cerebrospinal fluid for mechanical protection.

Meninges are the membranes that envelop the brain and spinal cord of the central nervous system. 

The spinal cord is a part of the central nervous system. The most important structure between our body and our brain is the spinal cord. It extends from the foramen magnum, where it is continuous with the medulla to the level of the first or second lumbar vertebrae. It is a vital link not only from the brain to the body but also from the body to the brain. The spinal cord is 40 to 50 cm long and 1 cm to 1.5 cm in diameter. 

• The central nervous system (CNS) is the processing center for the nervous system. The two main organs of the CNS are the brain and spinal cord. The brain processes and interprets the sensory information sent from the spinal cord. Both the brain and spinal cord are protected by three layers of connective tissue, called meninges.
• Within the central nervous system is a system of hollow cavities, called 'ventricles'. The network of linked cavities in the brain (cerebral ventricles) is continuous with the central canal of the spinal cord. The ventricles are filled with cerebrospinal fluid, which is produced by specialized epithelium located within the ventricles, called the choroid plexus. 
• Cerebrospinal fluid surrounds, cushions and protects the brain and spinal cord from trauma. It also assists in the circulation of nutrients to the brain.

The bony structure in the head of most vertebrates (in particular, craniates) that supports the structures of the face is called as the skull. It forms a protective cavity for the brain. The cranium and the mandible are the two parts of the skull. The skull forms the anterior most portion of the skeleton and is a product of encephalization, housing the brain, many sensory structures (eyes, ears, nasal cavity) and the feeding system.

The brain is the control center of the body. It consists of three main components- forebrain, brainstem, hindbrain. The brain is important in the human body, because it allows a person to think, feel and store memories, and it controls and coordinates the body's actions and reactions. The brain is an incredibly complex organ composed of many parts, including the cranium, the cerebrum, the brain stem and the cerebellum.

Main function of central nervous system (brain and spinal cord) is to integrate the sensory inputs from internal and external environment as received by sensory neurons and process and finally transmit the nerve impulses to effectors (muscles and glands). Thus, being the centre of processing information, the brain has the maximum number of cell bodies of neurons (the grey matter). Spinal cord provides means of communication between peripheral nerves and brain. Thus, it has H-shaped grey matter (cell bodies of neurons) and white matter else everywhere (the myelinated axons that carry impulses to and from the brain). Since nerves in retina and tongue serve to conduct information along the sensory pathways; they have single axon with highly branched dendrites but no cell bodies. Thus, the correct answer is option A.

• The brain and spinal cord are the two major parts of the CNS. The brain forms the largest portion of the CNS. 
• The brain resembles a cream-colored rope made up of nerves that that relay messages.
• The spinal cord stretches from the medulla oblongata at the base of the brain to the lower back and is housed in a tunnel made by the vertebrae bones of the spinal column. 
• The spinal cord works a bit like a telephone switchboard operator, helping the brain communicate with different parts of the body and vice versa.