The human nervous system consists of neurons and tissues that regulate stimuli and responses. The human nervous system is a complex information processing system that consists mainly of the brain, spinal cord and nerves.
In this article we will tell you all about the human nervous system its structure and its function. If you touch a hard stove, instantly the message is conveyed to your brain and the bran orders you to jerk your hand away. This happens within a second. Similarly, when an insect sits on your arm, your brain receives the information and sends back a stimulus for you, to jerk your hand or to flick insect away before is stings you. How do these actions happen? An organ system in the human body which carries messages from one part of the body to another and makes us feel and react to things and situations is called nervous system. Therefore, the study of human nervous system is very important for everyone.
There are two sections of human nervous system is described below.
- The central nervous system (CNS)
- The peripheral nervous system (PNS)
The Central Nervous System (CNS)
The central nervous system acts as a control center of the whole nervous system. It comprises brain and spinal cord.
1. The Brain:
The human brain is surrounded by a bony case called the cranium. An adult human brain consists of billions of neurons and the weighs is about three pounds. Three layers of connective tissues called meninges and the fluid present in these layers protect the brain. The brain is furtherly divided into three main parts, called fore brain, mid brain and hind brain.
A. Fore brain
The forebrain is the largest and most complex part of the brain, located at the front of the brain. Its main function is to regulate and process sensory information, control voluntary movements, and perform complex cognitive processes such as learning, memory, language, and problem-solving. Additionally, the forebrain is involved in regulating vital bodily functions such as body temperature, hunger, thirst, and sleep through the activities of the hypothalamus. Overall, the forebrain plays a crucial role in the integration of sensory information, motor control, and higher-level cognitive functions necessary for survival and adaptation to the environment.
B. Mid brain
It is central part of the brain. Its basic function is to transfer information and impulses between the fore-brain and the hind brain. This area of the brain controls temperature, hearing, vision, and sleep and wakefulness. Additionally, the mid brain controls several reflexes, such as adjusting the pupil size to regulate the quantity of light entering the eye.
C .Hind brain
The hind brain consists of three parts, i.e. cerebellum, pons and medulla oblongata.
The cerebellum is the second biggest brain region. It is mainly concerned with posture, balance and locomotion of the body.
Pons is a small oval structure present above the medulla oblongata. it serves as a bridge for the conduction of impulses between the cerebrum, medulla oblongata and the cerebellum. It is concerned with the rate of breathing, sleeping and also regulate eye movement and facial expressions.
Medulla oblongata is connecting the brain to the spinal cord. It regulates respiration, digestion, heart rate, swallowing, vomiting, coughing, sneezing, and other bodily functions. Medulla oblongata keeps on working even if the rest of the brain does not work.
2. The spinal cord
The spinal cord extends from the medulla oblongata. The spinal cord is located in the vertebral column. It is a tabular structure made up of bundles of neurons. Its length may vary according on the body’s height. The spinal cord connects the brain to nerves that are found throughout the body .All the signals that go to the body or come to the brain pass through the spinal cord. Communication between the brain and the rest of the body is impeded by a damaged spinal cord. This result in paralysis.
The peripheral nervous system (PNS)
The peripheral nervous system consists of sensory and motor neurons, which are distributed throughout the body. Sensory neurons carry the impulses from the receptors to the central nervous system while the motor neurons carry the massages from the central nervous system to the effectors (muscles or glands). The peripheral nervous system consists of 12 pairs of cranial nerves, which emerge from the brain and mainly serve the head and neck. It also contains 31 pairs of spinal nerves, which branch off from the spinal cord and reach the rest of the human body.
Neurons and their types
Brain has more than 100 billion nerve cells, which are called neurons.
The fundamental structural and functional component of the nervous system is the neuron. The brain, spinal cord, and nerves are all parts of the nervous system, which is made up of neurons.
A neuron is fatherly divided into cell body and axon. The nucleus and the majority of the cytoplasm are found in the cell body, a thicker area of the neuron. There are threads like projections on the cell body called dendrites. The axon is a protrusion that extends far from the cell body and carries impulses. Usually a neuron has a single axon. Fatty substances covering the axon form a myelin sheath. Neuron transmits messages in the form of electrochemical waves called nerve impulses. A single nerve is the combination of many neurons.
Types of Neurons
On the basis of their functions, neurons are of three types.
Sensory neurons are nerve cells that detect and transmit sensory information from various parts of the body (ears, eyes, tongue, nose etc.) to the brain and spinal cord.
Motor neurons take impulses away from central nervous system to effectors (Muscles and glands)
Associative / Inter neurons
Associative neurons present in the central nervous system, link the sensory and motor neurons. They analyze the messages for proper responses.
Added by: Muhammad Sadiq