The nervous system is one of the most complex and vital systems in the human body. It is responsible for perceiving stimuli, processing information, and coordinating responses that help organisms adapt and survive. In neuroscience, understanding the structure and function of the nervous system is essential to understanding how the brain, spinal cord, and nerves communicate with each other.
Excitation and conductivity
Excitability and conductivity are two key properties of living protoplasm through which all living organisms respond to environmental changes. The changes that stimulate living organisms are called stimuli, while the actions or reactions that occur in response are called reactions.
In simple organisms such as amoebas, the undifferentiated protoplasm itself performs the functions of receiving and transmitting stimuli. However, in multicellular organisms, specialized receptors and effectors have evolved to perform these roles efficiently.
Neurons and the reflex arc
In complex organisms, the nervous system consists of a series of receptors, neurons and effectors, which together form a reflex arc .
- A sensory (afferent) neuron carries impulses from receptors to the central nervous system (CNS).
- A motor (efferent) neuron carries responses from the central nervous system to effectors such as muscles or glands.
- In some cases, interneurons connect sensory and motor neurons, forming a multi-synaptic reflex arc .
The point of contact between neurons is called a synapse – a microscopic gap where impulses are transmitted chemically and electrically.
central and peripheral nervous system
The central nervous system (CNS) includes the brain and spinal cord, while the peripheral nervous system (PNS) includes all the other nerves and ganglia that connect the CNS to the rest of the body.
- Sensory nerve cells are grouped in ganglia located outside the central nervous system.
- Their dendrons enter the central nervous system through dorsal (afferent) roots, while motor axons exit through ventral (efferent) roots.
Evolutionarily, the concentration of sensory input— especially from the visual and auditory organs-led to the considerable expansion of the anterior neural region , forming the brain , while the remainder evolved into the spinal cord .
Coordination and integration of nervous system impulses
The nervous system does more than simply transmit signals; it coordinates, integrates, and synthesizes signals to produce appropriate responses. This is possible because of the dense network of synapses and neural connections in the central nervous system, which enables effective communication between different areas of the brain and spinal cord. Normally, dendrons carry impulses toward the cell body, while axons carry them away from it — although in some sensory neurons, dendrons can be so long that they resemble axons.
Conclusion
The nervous system is the body’s ultimate control and coordination mechanism. It controls everything from involuntary reactions to complex thought processes through the intricate interactions of neurons, receptors, and effectors. In neuroscience, understanding this system lays the foundation for the diagnosis and treatment of neurological disorders.
FAQs about the nervous system
The nervous system is divided into the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves and ganglia).
The reflex arc is the pathway followed by nerve impulses that produce an automatic response, involving sensory neurons, interneurons, and motor neurons.
Nerve cells or neurons have excitability (the ability to respond to stimuli) and conductivity (the ability to transmit impulses).
It coordinates body functions by integrating impulses through the brain and spinal cord and sending appropriate responses to effectors such as muscles and glands.