字幕表 動画を再生する 英語字幕をプリント Nervous System - Get to Know Our Nervous System a Bit Closer Today we will talk about an organ that rules all of our body and that is our brain. As it is the most sensitive organ, our brain is kept inside the bony covering called skull. From doing physical activity to solving logical problems, from dealing with emotions and feelings to creativity, brain is responsible for all. Therefore, it never sleeps. Our brain can be divided into three main parts; the cerebrum, the cerebellum and brain stem. Cerebrum is the largest part of brain, which can be further divided into right and left halves called hemisphere. Each cerebral hemisphere has four lobes namely frontal lobe, parietal lobe, occipital lobe and temporal lobe. Each lobe performs different functions. Cerebellum is responsible for movement and coordination. It gives you sense of balance and thus prevents you from falling down. Brain stem includes mid brain, pons and medulla oblongata. It controls your body's involuntary actions like breathing, heart rate and blood pressure. Brain comes under a system called nervous system. Structurally, nervous system is classified into two types: Central Nervous System (CNS) and Peripheral Nervous System (PNS). The Central Nervous System comprises of the brain and spinal cord. The spinal cord is the bridge that connects the brain to peripheral nervous system. It starts from medulla oblongata and stretches to lumbar region of the spine or vertebral column. The Peripheral Nervous System is a network of nerves spread across our body. Think of Peripheral Nervous System as a network of highway that connects the body with Central Nervous System. This highway has two way traffic. Let's see how. When you hold a hot cup of coffee, sensory neurons in your hand transmit signal to brain through sensory neurons, also called afferent neurons, that the cup is hot. Your brain process that information and send response through motor neurons, known as efferent neurons, that you must put that cup back. PNS consists of total 43 pairs of nerve, among which 12 originate in brain, named as cranial nerves and 31 originate from spinal cord, hence called as spinal nerves. Here you hear the word “neuron”. Neuron is the basic unit of nervous system. It is the nerve cell which transmit electrical signals to brain. A neuron has three parts: Dendrites, soma or cell body, and axon. Dendrites serve as input device for neuron because it receives input from other nerve cells. Soma or cell body of neuron contains nucleus. Axon serve as output device from where it transmit electrical response to other neurons. I hope this helps you in understanding nervous system.