Human Nervous System: Description, Development, Structure, Function, Diagram
The human nervous system is a complex network that controls and coordinates all body activities by transmitting electrical and chemical signals. It consists of the central nervous system and peripheral nervous system, ensuring communication between the brain and the rest of the body. This guide covers structure, neurons, functions, divisions, disorders, FAQs, and NEET-oriented MCQs.
This Story also Contains
- What Is the Nervous System?
- Structure of the Nervous System
- Central Nervous System (CNS)
- Peripheral Nervous System (PNS)
- Neurons – Structural and Functional Units
- Synapse and Neurotransmitters
- Functions of the Nervous System
- Disorders of the Nervous System
- Human Nervous System NEET MCQs (With Answers & Explanations)
- Recommended Video on the Human Nervous System
What Is the Nervous System?
The nervous system utilises a complicated web of nerves and cells that convey messages to and from the brain and spinal cord down to various parts of the body. It is responsible for nearly every operation going on in the human body and the maintenance of homeostasis by its reactions to internal and external stimuli.
Structure of the Nervous System
The nervous system is foremost divided into
Central Nervous System
Peripheral Nervous System
Central Nervous System (CNS)
The parts of Central Nervous System include:
Brain
The brain is that part of the nervous system which forms the central organ controlling various functions and processes as a whole.
Cerebrum
The cerebrum controls thinking, memory and intelligence. It is responsible for voluntary actions. The lobes of cerebrum are:
Frontal Lobe: It is related to decision-making, problem-solving, and planning.
Parietal Lobe: It processes sensory information like touch, temperature, pain, etc.
Temporal Lobe: Concerned with hearing processing and memory.
Occipital Lobe: It controls such visual processing.
Role and Importance
Each lobe has some special roles in the process of cognition, sensory processing, and motor control.
It regulates any vital life process: the brainstem controls heartbeat, breathing rate, sleeping, and waking up.
Cerebellum
It provides for smooth, coordinated muscle activity. It maintains posture and balance.
Brainstem / Medulla Oblongata
It controls involuntary movements like breathing, heartbeat, swallowing and sleep.
Spinal Cord
The spinal cord is another major component of the CNS and acts as a connecting link between the brain and the rest of the body. Moreover, it enables reflex actions to take place.
Structure of the Spinal Cord
Nerve fibres ensure that there are signals both toward and away from the brain.
A reflex arc includes sensory neurons, interneurons, and motor neurons that give rise to quick, involuntary responses to stimuli.
Peripheral Nervous System (PNS)
The Peripheral Nervous System is divided into two parts:
Somatic Nervous System
It controls voluntary movements by transmitting signals to skeletal muscles. The PNS relays information between the CNS and limbs/organ systems, so it's indispensable for the body's functioning and movements.
Structure and Function of Nerves
Nerves are bundles of axons that transmit signals between the CNS and the body.
Cranial Nerves: Twelve pairs of nerves arise directly from the brain, each with specific sensory or motor functions.
Spinal Nerves: Thirty-one pairs of nerves emerge from the spinal cord, transmitting signals to and from the body.
Autonomic Nervous System (ANS)
The ANS controls involuntary body functions, which it regulates with necessary physiological processes.
Sympathetic Nervous System
A help that turns on your body when under stress or during an emergency.
The sympathetic nervous system accelerates this rate of the heartbeat, dilates pupils, and inhibits digestion.
Parasympathetic Nervous System
Calms the body and saves energy after stress.
The parasympathetic nervous system will slow the heart rate, constrict the pupils, and prompt digestion.
Neurons – Structural and Functional Units
They are the basic units of the nervous system that convey information throughout the body.
Structure of a Neuron
Cell Body (Soma): It contains a nucleus surrounded by usual organelles.
Dendrites: The far ends of the dendrites receive signals from other neurons and conduct these towards the cell body.
Axon: The axon conducts electrical impulses away from the cell body.
Myelin Sheath: The sheath covering the axon that insulates it and increases the speed of transmission of the signal.
Classification of Neurons
Sensory Neurons: They carry information from sensory receptors to the CNS.
Motor Neurons: They carry commands from the CNS to muscles and glands.
Interneurons: These connect the sensory and motor neurons within the CNS.
Synapse and Neurotransmitters
Synapse is the junction between two neurons. The ending of one neuron releases neurotransmitters, which carry the signal. It ensures unidirectional flow of information.
Functions of the Nervous System
The nervous system has important functions, including:
Sensory Input
Sense changes in the environment with the help of sensory receptors.
Integration
Process and interpret sensory information to make decisions.
Motor Output
Generate responses by activating muscles and glands.
Disorders of the Nervous System
Several disorders may occur within the nervous system and may trigger critical health concerns.
Alzheimer's Disease
Memory loss, confusion, and cognitive decline.
Deposits of amyloid plaques and neurofibrillary tangles within the brain.
Medications to alleviate symptoms, and supportive care.
Parkinson's Disease
Tremors, rigidity, and problems with balance and coordination
Prospective loss of dopamine-producing neurons in the brain
Medications aimed at increasing dopamine levels; physical therapy.
Epilepsy
Recurrent seizures of variable intensity and type
Abnormal electrical activity within the brain.
Anti-seizure medications; surgery in some cases.
Multiple Sclerosis
Fatigue, muscle weakness, coordination and balance difficulty
Immune system attacking the myelin sheath of neurons.
Immunosuppressive drugs, physical therapy.
Human Nervous System NEET MCQs (With Answers & Explanations)
Important questions asked in NEET from this topic are:
Nervous system and its components (CNS & PNS)
Functions of Nervous System
Practice Questions for NEET
Q1. The somatic neural system
is the site of information processing and control
relays impulses from the CNS to skeletal muscles
is further classified into the sympathetic neural system and parasympathetic neural system
transmits impulses from the CNS to the involuntary organs and smooth muscles of the body
Correct answer: 2) relays impulses from the CNS to skeletal muscles
Explanation:
The PNS is divided into two divisions called the somatic neural system and the autonomic neural system. The somatic neural system relays impulses from the CNS to skeletal muscles. The autonomic neural system transmits impulses from the CNS to the involuntary organs and smooth muscles of the body. The autonomic neural system is further classified into the sympathetic neural system and parasympathetic neural system. The somatic neural system relays impulses from the CNS to skeletal muscles.
Hence, the correct answer is option 2) relays impulses from the CNS to skeletal muscles.
Q2. Myelinated nerve fibres are found in
Spinal nerves
Cranial nerves
Autonomic nervous system
Both a and b
Correct answer: 4) Both a and b
Explanation:
There are two types of axons, namely, myelinated and unmyelinated. The myelinated nerve fibers are enveloped with Schwann cells, which form a myelin sheath around the axon. The gaps between two adjacent myelin sheaths are called nodes of Ranvier. Myelinated nerve fibers are found in spinal and cranial nerves. Unmyelinated nerve fiber is enclosed by a Schwann cell that does not form a myelin sheath around the axon and is commonly found in autonomous and somatic neural systems.
Hence, the correct answer is option 4) Both a and b.
Q3. The basic unit of the neural system is called
Axon
Dendrites
Neurons
Myelin cell
Correct answer: 3) Neurons
Explanation:
The basic unit of the nervous system is the neuron. Neurons are specialized cells that send electrical and chemical signals around the body. They have the role of transmitting messages from the brain, spinal cord, and the rest of the body parts. There are three primary parts in a neuron, namely, the cell body containing the nucleus, dendrites which receive signals from other neurons, and axons, which carry electrical impulses to other neurons or muscles.
Hence, the correct answer is option 3) Neurons.
Also Read:
Recommended Video on the Human Nervous System
Frequently Asked Questions (FAQs)
This system detects and processes sensory input and it produces motor output that controls muscle and gland activity in the coordination of the activity of the body.
Neurons communicate via electrical impulses and chemical signalling. An action potential will travel down the axon to the synapse; there, neurotransmitters are released into the synapse and transmit this signal across to the following neuron.
The brain and the spinal column comprise the central nervous system. It interprets nerve impulses and processes the information.
The ANS controls involuntary activities, as in the case of heartbeats and digestion. Further, it is divided into the Sympathetic System, responsible for the 'fight or flight' responses, and the Parasympathetic System, responsible for 'rest and digest' activities.
The common diseases treated in this area include Alzheimer's, Parkinson's disease, epilepsy, and multiple sclerosis. Treatments usually involve medication, physical therapy, and schemes of supportive care to help the patient with his/her symptoms.