The answer lies in the body’s incredibly intricate network of cells and tissues that coordinate and control its functions, known as the nervous system. It plays a crucial role in regulating everything from our movements and sensations to thought processes and emotions. Let’s explore the key components of the nervous system and their functions.
Basics of the Nervous System:
Neurons
The basic unit of the nervous system is the nerve cell, or neuron. Neurons typically consist of four main parts:
- Dendrites
- Cell body/Cyton/Soma
- Axon/Conductive part
- Axon terminals/Transmissive part
There are three types of neurons:
- Sensory Neurons – These convey impulses (messages) from the sense organs to the brain or spinal cord.
- Motor Neurons – These transmit impulses from the brain or spinal cord to the muscles or glands (also known as effector organs).
- Association Neurons – Located in the brain and spinal cord, these neurons interconnect sensory and motor neurons.
The human brain contains approximately 100 billion neurons, while the octopus brain has around 300 million.
H3 Nerves
Nerves are like cables, carrying electrical impulses between the brain and the rest of the body. A single nerve is a bundle of nerve fibres (axons) from multiple neurons, enclosed in a protective sheath.
There are three types of nerves:
- Sensory nerves – Containing only sensory fibres, they carry impulses from the sense organs to the spinal cord or brain.
- Motor nerves – Containing only motor fibres, these transmit impulses from the brain or spinal cord to muscles or glands.
- Mixed nerves – These contain both sensory and motor fibres.
H3- Synapse
A synapse is the site where nerve impulses are transmitted between two neurons or between a neuron and a gland or muscle cell. This chemical process occurs when an impulse reaches the terminal end of an axon, releasing a neurotransmitter called acetylcholine. Acetylcholine triggers a new impulse in the dendrites of the next neuron, after which it is broken down by an enzyme to reset the synapse for the next transmission.
Components of the Nervous System:
Central Nervous System (CNS)
The CNS is composed of the brain and the spinal cord.
Brain
The brain is the central organ of the nervous system, responsible for coordinating and controlling various body functions. It is divided into three main parts: the cerebrum, cerebellum, and medulla oblongata (brain stem).
Spinal Cord
The spinal cord is a vital part of the nervous system, acting as a communication pathway between the brain and the rest of the body. It is a long, tubular structure made of nervous tissue that extends from the medulla of the brain to the lumbar region of the vertebral column, protected by the vertebrae. The spinal cord’s three primary functions are reflex control, signal transmission, and movement coordination.
On average, the spinal cord stops growing around four to five years of age.
Peripheral Nervous System (PNS)
The PNS connects the central nervous system to the rest of the body and consists of nerves and ganglia (clusters of nerve cell bodies). It is divided into:
Somatic Nervous System
The somatic nervous system consists of two sets of nerves: cranial and spinal.
- Cranial nerves emerge from the brain in twelve pairs and include sensory, motor, and mixed nerves.
- Spinal nerves, in 31 pairs, emerge from the spinal cord and are categorised into cervical, thoracic, lumbar, sacral, and coccygeal regions.
Autonomic Nervous System (ANS)
The ANS controls involuntary body functions, such as heart rate, digestion, respiration, and blood pressure. It has two main divisions:
- Sympathetic Nervous System – Often referred to as the “fight or flight system,” it prepares the body for emergency situations, increasing heart and respiratory rates while inhibiting digestion.
- Parasympathetic Nervous System – Known as the “rest and digest system,” it helps the body relax after stress by lowering heart and respiratory rates and stimulating digestion.
There is also the enteric nervous system, which independently controls gastrointestinal functions but communicates with the sympathetic and parasympathetic systems.
Our brain has a built-in social media-like function, allowing us to “like” and “share” others’ emotions. For example, when someone cracks a joke, our brain may trigger the “ha-ha” response even if we don’t fully understand it.
Reflexes
A reflex is an automatic, involuntary action in response to a stimulus (e.g., heat, pain, or pressure). Reflexes are classified as voluntary (performed consciously) or involuntary (performed unconsciously).
Reflex Action Mechanism
- Detection of stimulus – Specialised receptors, such as photoreceptors, detect stimuli like heat or pressure.
- Transmission of signal – Sensory neurons transmit the signal to the spinal cord.
- Processing of signal – The spinal cord or brain processes the signal.
- Initiation of response – A motor neuron sends a signal to the muscle or gland.
- Execution of response – The muscle or gland carries out the response, such as pulling your hand away from a hot surface.
Functions of the Nervous System
- Keeps us informed about our environment.
- Enables thinking, memory, and reasoning.
- Controls voluntary and involuntary actions.
Our brain has an impressive memory capacity—like a well-organised library—which is why we easily remember the lyrics of 90s songs!
Conclusion
The nervous system underpins nearly every aspect of our daily life. It’s important to nurture it through healthy lifestyle choices, mental exercises, and medical care. Stay curious, stay informed, and appreciate the incredible work of the nervous system!
Also Read: Essential Brain Facts That Every Parent Should Know About Their Baby’s Brain
