The nervous system, a complex network of neurons or nerve cells, is not just a system of response but a master coordinator of various physical and physiological functions. It enables the body to respond to external and internal stimuli, and its role in managing bodily functions is genuinely remarkable. The fundamental building blocks of this system are its cells, known as neurons.
The human nervous system is mainly divided into two parts, namely:
Central Nervous System: It consists of the brain and spinal cord.
Peripheral Nervous System
Central Nervous System
The central nervous system has two parts:The brain, the most significant part of the central nervous system, is a marvel of nature. It’s the control center for human intelligence, thought, memory, and more. The human brain, weighing approximately 1.36 kg, is a complex organ comprising around 1 billion nerve cells and over 100 billion neuroglia. It’s located at the top of the spinal cord and is protected by the skull.
Brain: The forebrain consists of three parts, namely:
Cerebral Cortex: The cerebrum is the most significant part of the brain and occupies most of the skull. Its surface features numerous grooves (called sulci) and folds (gyri). The cerebrum is divided into two halves, the right and left cerebral hemispheres, separated by a deep groove. A comprehensive bundle of nerve fibers connects these hemispheres called the corpus callosum. Additionally, the cerebrum is divided into five lobes: the frontal lobe, parietal lobe, temporal lobe, occipital lobe, and limbic lobe. The outer part of the cerebrum consists of gray matter, while the inner part is white matter.
Thalamus: The thalamus is the part of the brain located beneath the brainstem. It is composed of gray matter.
Hypothalamus: The part located below the thalamus, made up of white and gray matter, is called the hypothalamus.
Work: It regulates pressure, heat, pain, touch, fear, pleasure, consciousness, memory, thought, intelligence, and advanced mental perception. It also governs various human instincts by coordinating the physiological functions of different body parts.
Work:Function: It controls human mental functions such as anger, shame, pain, etc.
Work: The spinal cord is crucial in coordinating and controlling simple actions between various body parts, aided by afferent nerves. Its principal function is to transmit neural signals between the brain and the peripheral nervous system.
Spinal Cord:The spinal cord is a long, narrow bundle of nerves that extends the central nervous system, including the brain. It is located within and protected by the spinal column. The spinal cord extends from the medulla oblongata at the base of the brain down to the first lumbar vertebra. In humans, it is approximately 18 inches long and features a groove at the junction of the vertebrae. It is composed of 31 segments, with each segment giving rise to a pair of spinal nerves.
The cross-section of the spinal cord is oval and slightly swollen in the cervical (neck) and lumbar (lower back) regions. Sensory and motor neurons are within the white matter surrounding the cord. The inner, butterfly-shaped gray matter primarily contains neuron cell bodies. A central canal filled with cerebrospinal fluid is at the center of the spinal cord.
The spinal cord is covered by three protective membranes, known as meninges: the outer layer is the dura mater, the middle layer is the arachnoid mater, and the innermost layer is the pia mater.
Work:The spinal cord is crucial in coordinating and controlling simple actions between various body parts, aided by afferent nerves. Its principal function is to transmit neural signals between the brain and the peripheral nervous system.
Peripheral Nervous System
The peripheral nervous system (PNS) comprises all the nerves that extend from the central nervous system (CNS). It includes 12 cranial nerves from the brain and 31 pairs of spinal nerves originating from the spinal cord. The PNS responds to various internal and external stimuli in the human body and facilitates communication with the CNS.
The neurons, or nerve cells, within the peripheral nervous system come in different types and communicate with one another using electrical signals and neurotransmitters. For example, if a mosquito lands on your skin, the peripheral nervous system transmits that sensory information to the central nervous system (the brain) to trigger a response to swat it away. Conversely, the PNS also sends signals from the CNS to enable you to take action.
Additionally, the peripheral nervous system plays a vital role in managing external functions, such as digestion and temperature regulation, which are controlled by the central nervous system.
This is also of two types:
Automatic Nervous System
The nerves that control the involuntary muscles of the animal body are known as the autonomic nervous system. The autonomic nervous system is divided into two parts:
Sympathetic nervous system
Parasympathetic nervous system:
Work: The sympathetic nervous system increases heart rate, dilates airway passages, decreases motility of the large intestine, constricts blood vessels, increases involuntary contractions in the esophagus, enhances pulmonary expansion and sweating, and sometimes raises blood pressure.
Somatic Nervous System
The somatic nervous system is a component of the peripheral nervous system that works in conjunction with the central nervous system. It creates a network of connections between the brain and spinal cord to various organs, explicitly linking to the skin of the human body. This system transmits sensations from the sensory organs—such as the eyes, ears, nose, and skin—to the cerebral cortex. Additionally, it conveys information about both positive and negative stimuli related to visual and auditory sensations and experiences of taste and smell to the central nervous system.
Nerve signals can be categorized into three types:
Afferent Nerves:These nerves carry sensory information from receptor cells to the central nervous system. Due to their function, they are also known as sensory nerves. Examples include the optic nerve (for vision), the olfactory nerve (for smell), and the auditory nerve (for hearing).
Efferent Nerves:These nerves transmit signals from the central nervous system to effector cells, which act in response to these signals. Composed of motor neurons, these nerves are referred to as motor nerves. Notable examples include the third cranial nerve (oculomotor nerve) and the sixth cranial nerve (abducens nerve).
The somatic nervous system is vital in processing sensory information and enabling motor responses.
How the Nervous System Works
The nervous system is a complex network of nerves that coordinates actions and sensory information throughout the body. It consists of two main parts: the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which comprises nerves that connect to all parts of the body.
The CNS processes information inside and outside the body, while the PNS gathers data from sensory receptors and transmits signals to muscles, glands, and other organs. Additionally, the nervous system includes non-neuronal cells called glia. These cells play crucial roles in supporting neurons, creating insulation, repairing neurons, and regulating neurotransmitters.
The primary function of the nervous system is to send messages between various body parts and the brain. This communication controls numerous functions, including thoughts, movements, sensory perception, wound healing, sleep patterns, heartbeat regulation, breathing patterns, responses to stress, digestion, puberty, aging, and conditions such as meningitis, cancer, brain tumors, and multiple sclerosis.
The Structure of the Nervous System
The nervous system is complex and consists of two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS includes the brain and spinal cord and processes information from the body while regulating voluntary movements. Conversely, the PNS encompasses nerves and ganglia that handle sensory information and control involuntary movements.
Functionally, the nervous system can be divided into sensation, integration, and response or somatic and autonomic control. Additionally, a specific region of the PNS known as the enteric nervous system is responsible for functions related to the gastrointestinal system.
Functions of the Nervous System
The nervous system is a complex network of nerve cells and fibers that transmits signals throughout the body, facilitating communication, coordination, and control of various bodily functions. It is divided into two main parts: the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which comprises the nerves that branch out from the spinal cord.
The CNS processes sensory information and generates responses, while the PNS regulates involuntary functions such as heart rate, digestion, and breathing. Additionally, the nervous system contains non-neuron cells called glia, which support and protect neurons.
The nervous system has four main functions: receiving general sensory information, perceiving exceptional sensations, integrating sensory information from different body parts, and generating responses.
Fun Facts about the Nervous System
The nervous system is a complex and fascinating human body part that controls and coordinates various bodily functions. It consists of two main components: the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS), which encompasses sensory neurons, ganglia, and nerves. The CNS processes information and sends signals to the PNS, which then transmits those signals to various organs throughout the body.
Neuroscience is a rapidly growing field focused on understanding how the nervous system operates and how this knowledge can be applied to treat or prevent disorders such as addiction, dementia, Down syndrome, epilepsy, multiple sclerosis, Parkinson’s disease, and schizophrenia. By studying the nervous system, researchers aim to improve the health and well-being of people worldwide.
Summary
Neurological diseases kill 9.8 million people worldwide each year and leave 250.7 million people disabled.
