Central Nervous System: Description, Development, Structure, Function, Diagram

Edited By Irshad Anwar | Updated on Jul 02, 2025 06:46 PM IST

Definition Of Central Nervous System (CNS)

The central nervous system consists of the brain and spinal cord and serves as the main control centre of the body. It processes all sensory information, provides responses, and maintains homeostasis.

Components Of Central Nervous System

There are two prime parts of CNS. They include the brain and the spinal cord.

Brain

The brain is divided into three major parts:

Cerebrum

This is the largest part and is responsible for higher brain functions such as thought, action, and sensory processing.
Divided into lobes: frontal, parietal, temporal, occipital. Each lobe has well-defined functions, such as reasoning, perceiving sensations, and perceiving visions.

This Story also Contains

Definition Of Central Nervous System (CNS)
Components Of Central Nervous System
Cells Of The Central Nervous System
Function Of Central Nervous System
Protection Of The Central Nervous System
Disorders Of The CNS
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Central Nervous System: Description, Development, Structure, Function, Diagram

Cerebellum

It controls balance, coordination, and fine muscle control.
Coordinates involuntary motions and maintains posture.

Brainstem

Further divided into midbrain, pons, and medulla oblongata.
It regulates all vital activities, like the heartbeat, breathing, and sleep cycles.
Joins the brain with the spinal cord; it controls automatic functions.

Spinal Cord

Comprised of cervical, thoracic, lumbar, sacral, and coccygeal segments.
Carry information between the brain and the rest of the body, and mediate reflex actions.

Diagram: Central Nervous System

Cells Of The Central Nervous System

There are two kinds of cells within the central nervous system:

Neurons

Cell Body (Soma): Contains the nucleus and metabolic machinery.
Dendrites: Receive the signals from other neurons.
Axon: Conducts electrical impulses away from the cell body.

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Type Of Neurons

Sensory Neurons: Carry sensory information into the CNS
Motor Neurons: Carry signals from the CNS to muscles and glands.
Interneurons: Connect neurons, including other interneurons, within the CNS.

Glial Cells

The Types of glial cells are:

Astrocytes: Support and protection of neurons, maintenance of the blood-brain barrier.
Oligodendrocytes: Formation of myelin in the CNS
Microglia: Immune defence in the CNS
Ependymal Cells: Line ventricles.

Functions Of Glial Cells

To provide structural support, nourishment, and protection to neurons.

Function Of Central Nervous System

The functions of the CNS include:

Synaptic Transmission

A synapse includes the release of neurotransmitters by a presynaptic neuron, crossing the synaptic gap and binding to receptors of the postsynaptic neuron.
Chemical messengers, for example, dopamine, serotonin, and acetylcholine, modulate different CNS functions.

Reflex Actions

A reflex action tends to involve sensory input, integration in the spinal cord, and motor output without the inclusion of the brain.
Examples are the knee-jerk reflex and the withdrawal reflex to painful stimuli, both being of significance for rapid protective responses.

Protection Of The Central Nervous System

Dura Mater: Tough outer layer.
Arachnoid Mater: Middle web-like layer.
Pia Mater: Delicate inner layer adhering to the CNS surface.

Cerebrospinal Fluid (CSF)

Production, Circulation, and CSF Function.
Produced by the choroid plexus and flows through the ventricles and the subarachnoid space, cushioning the CNS, and removing waste.

Blood-Brain Barrier (BBB)

A selective barrier comprised of endothelial cells, astrocytes, and pericytes, which together protect the CNS from a wide range of injurious molecules.

Disorders Of The CNS

Multiple Sclerosis: Demyelination—causing such symptoms as muscle weakness or blindness.
Parkinson's Disease: Disruption in motor control due to the deficiency of dopamine; characterised by tremors and rigidity.
Alzheimer's Disease: From memory loss to the general cognitive decline of the patient.

The various disorders have characteristic symptoms and causes, with treatments ranging from medication for symptom management to physical therapy.

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Frequently Asked Questions (FAQs)

1. What is the function of the central nervous system?

The CNS processes and integrates sensory information and responses, and controls most activities of the body and mind.

2. How do neurons communicate within the CNS?

Neurons communicate by synapses, where neurotransmitters are released to carry on the signal across cells.

3. What are the symptoms of a spinal cord injury?

Symptoms might include the loss of movement, sensation, or function below the level of injury.

4. How can the CNS be prevented from damage?

Protective measures include helmets, avoiding smoking, a healthy diet, and keeping a regular level of exercise.

5. What is under development to treat disorders of the CNS?

Currently under development are studies on neuroplasticity, stem cell therapy, MRI technologies, and brain-computer interfaces.

6. What is the role of glial cells in the CNS?

Glial cells support and protect neurons in various ways. They provide structural support, supply nutrients, remove dead neurons, and some types (like oligodendrocytes) produce myelin. They also play a role in signal transmission and maintaining the blood-brain barrier.

7. What is neurogenesis, and does it occur in the adult CNS?

Neurogenesis is the process of forming new neurons. While most neurons are formed during embryonic development, neurogenesis does occur in specific regions of the adult CNS, such as the hippocampus and olfactory bulb, contributing to learning and memory.

8. How do neurotrophic factors influence CNS development and maintenance?

Neurotrophic factors are proteins that promote the growth, survival, and differentiation of neurons. In the CNS, they guide neuronal development, support synaptic plasticity, and help maintain neuronal health throughout life.

9. How do neurotransmitters function in the CNS?

Neurotransmitters are chemical messengers released by neurons to communicate with other neurons or target cells. In the CNS, they transmit signals across synapses, influencing various functions like mood, memory, and movement.

10. What is the function of the basal ganglia in the CNS?

The basal ganglia are a group of subcortical nuclei involved in motor control, learning, and executive functions. They play a crucial role in initiating and controlling voluntary movements, and are involved in reward-based learning and habit formation.

11. What is the role of the brainstem in the CNS?

The brainstem connects the brain to the spinal cord and controls vital functions such as breathing, heart rate, and blood pressure. It also regulates sleep cycles, attention, and arousal.

12. How does the spinal cord contribute to CNS function?

The spinal cord transmits signals between the brain and the rest of the body. It also contains neural circuits that can independently control certain reflexes and simple movement patterns without direct input from the brain.

13. What is the function of the corpus callosum in the CNS?

The corpus callosum is a large bundle of nerve fibers that connects the left and right hemispheres of the brain. It allows communication between the two hemispheres, enabling coordinated processing of information and integrated brain function.

14. What is the function of the cerebral cortex in the CNS?

The cerebral cortex is the outer layer of the brain responsible for higher-order functions such as thinking, reasoning, memory, and consciousness. It processes sensory information, controls voluntary movement, and is involved in language and decision-making.

15. How does the hypothalamus regulate homeostasis through the CNS?

The hypothalamus, part of the brain, regulates homeostasis by controlling the autonomic nervous system and endocrine system. It manages body temperature, hunger, thirst, sleep, and circadian rhythms by sending signals through the CNS and releasing hormones.

16. What is the central nervous system (CNS) and why is it called "central"?

The central nervous system (CNS) consists of the brain and spinal cord. It's called "central" because it acts as the main processing center for the entire nervous system, integrating information from all parts of the body and coordinating responses.

17. How does synaptic pruning contribute to CNS development?

Synaptic pruning is the process of eliminating unnecessary synaptic connections in the developing brain. It refines neural circuits, improving their efficiency and specificity. This process is crucial for cognitive development and continues through adolescence.

18. How does the CNS respond to injury or damage?

When the CNS is injured, it initiates an inflammatory response and activates glial cells to contain damage. Unlike the PNS, the CNS has limited regenerative capacity. Recovery often involves neuroplasticity, where undamaged areas take over functions of damaged regions.

19. How does neuroplasticity contribute to CNS function and recovery?

Neuroplasticity is the brain's ability to form new neural connections and reorganize existing ones. It allows the CNS to adapt to new experiences, learn, and recover from injuries by rerouting functions to undamaged areas.

20. How does the CNS process pain signals?

Pain processing in the CNS involves multiple areas. Nociceptive signals from the body are transmitted through the spinal cord to the thalamus and then to the somatosensory cortex. The limbic system and prefrontal cortex are involved in the emotional and cognitive aspects of pain perception.

21. How does the limbic system contribute to emotion processing in the CNS?

The limbic system, a group of interconnected structures in the brain, processes emotions and is involved in memory formation. It includes the amygdala, hippocampus, and parts of the thalamus, playing a crucial role in emotional responses and behavior.

22. What is the function of the corpus striatum in the CNS?

The corpus striatum, part of the basal ganglia, plays a crucial role in motor planning, decision-making, and reward-based learning. It receives input from the cerebral cortex and helps coordinate smooth, purposeful movements.

23. What are neurons, and how do they function in the CNS?

Neurons are specialized cells in the nervous system that transmit electrical and chemical signals. In the CNS, neurons process and relay information, forming complex networks that enable perception, thought, and control of body functions.

24. What is gray matter in the CNS, and what is its function?

Gray matter is tissue in the CNS composed mainly of neuronal cell bodies, dendrites, and unmyelinated axons. It's involved in processing information, controlling muscles, and regulating sensory perception.

25. How does white matter differ from gray matter in the CNS?

White matter consists primarily of myelinated axons, which appear white due to the myelin sheath. It functions to transmit signals between different areas of gray matter within the CNS, enabling communication between different brain regions.

26. How does the process of myelination affect CNS function?

Myelination is the formation of a fatty sheath around axons, which increases the speed and efficiency of signal transmission. In the CNS, myelination continues from infancy through adolescence, improving cognitive and motor functions as it progresses.

27. What are the three primary stages of CNS development?

The three main stages of CNS development are: 1) Neurulation, where the neural tube forms; 2) Proliferation and migration of neurons; and 3) Differentiation and synapse formation, where neurons specialize and form connections.

28. How does the blood-brain barrier protect the CNS?

The blood-brain barrier is a selective membrane that separates the brain from circulating blood. It protects the CNS by preventing many potentially harmful substances from entering the brain while allowing essential nutrients to pass through.

29. What is cerebrospinal fluid (CSF), and what are its functions in the CNS?

Cerebrospinal fluid is a clear, colorless liquid that surrounds the brain and spinal cord. It cushions the CNS, removes waste products, and helps maintain proper chemical balance. CSF also plays a role in the brain's immune system.

30. How do the meninges protect the CNS?

The meninges are three layers of protective tissue (dura mater, arachnoid mater, and pia mater) that surround the brain and spinal cord. They provide physical protection, contain cerebrospinal fluid, and help regulate blood flow to the CNS.

31. How does the CNS differ from the peripheral nervous system (PNS)?

The CNS (brain and spinal cord) processes and integrates information, while the PNS (nerves outside the brain and spinal cord) carries signals between the CNS and the rest of the body. The CNS is encased in bone for protection, while the PNS is more widely distributed throughout the body.

32. What is the role of astrocytes in the CNS?

Astrocytes are star-shaped glial cells that perform various supportive functions in the CNS. They provide nutrients to neurons, maintain ion balance, form the blood-brain barrier, and play a role in synaptic transmission and repair after injury.

33. What is the role of the cerebellum in CNS function?

The cerebellum, located at the back of the brain, coordinates voluntary movements, maintains balance and posture, and is involved in motor learning. It receives input from sensory systems and other parts of the brain to fine-tune motor activity.

34. What is the role of the thalamus in the CNS?

The thalamus acts as a relay station for sensory and motor signals going to the cerebral cortex. It plays a crucial role in regulating consciousness, sleep, and alertness, and is involved in processing and integrating various types of information.

35. How does the reticular activating system (RAS) function in the CNS?

The reticular activating system is a network of neurons extending from the brainstem to the cerebral cortex. It plays a crucial role in regulating arousal, sleep-wake transitions, and filtering incoming sensory information to maintain attention and consciousness.

36. How does the CNS regulate the sleep-wake cycle?

The CNS regulates the sleep-wake cycle through interactions between the hypothalamus, brainstem, and thalamus. The suprachiasmatic nucleus in the hypothalamus acts as a "biological clock," while neurotransmitters like serotonin and norepinephrine influence arousal states.

37. What is the role of oligodendrocytes in the CNS?

Oligodendrocytes are glial cells responsible for producing myelin in the CNS. They wrap around axons, forming the myelin sheath, which increases the speed and efficiency of electrical signal transmission along neurons.

38. How does the CNS process visual information?

Visual processing in the CNS begins when signals from the retina travel through the optic nerve to the lateral geniculate nucleus of the thalamus, and then to the primary visual cortex. Higher-order visual areas then process specific aspects of the visual scene, such as color, motion, and form.

39. What is the function of the hippocampus in the CNS?

The hippocampus, part of the limbic system, plays a crucial role in forming, organizing, and storing memories. It's particularly important for converting short-term memories to long-term memories and for spatial navigation.

40. How does the CNS control voluntary movement?

Voluntary movement control involves multiple CNS areas. The motor cortex initiates movement, the basal ganglia refine it, the cerebellum coordinates it, and the spinal cord executes it. This process involves complex interactions between these regions and feedback from sensory systems.

41. What is the role of microglia in the CNS?

Microglia are the primary immune cells of the CNS. They constantly survey their environment, respond to injury or infection by engulfing pathogens or cellular debris, and release inflammatory mediators. They also play a role in synaptic pruning during development.

42. How does the CNS regulate autonomic functions?

The CNS regulates autonomic functions through the hypothalamus and brainstem. These structures control the autonomic nervous system, which manages involuntary processes like heart rate, digestion, and respiration, maintaining homeostasis.

43. What is the function of the pineal gland in the CNS?

The pineal gland, located in the epithalamus, produces melatonin, a hormone that regulates the sleep-wake cycle. It responds to light information received from the eyes, helping to synchronize circadian rhythms with the external environment.

44. What is the role of the prefrontal cortex in the CNS?

The prefrontal cortex, located in the frontal lobes, is responsible for executive functions such as planning, decision-making, and impulse control. It's also involved in personality expression, moderating social behavior, and processing complex cognitive information.

45. How does the CNS process auditory information?

Auditory processing in the CNS begins when sound waves are converted to electrical signals in the cochlea. These signals travel through the auditory nerve to the brainstem, then to the thalamus, and finally to the auditory cortex where different aspects of sound are processed.

46. What is the function of the pons in the CNS?

The pons, part of the brainstem, serves as a relay station between the cerebral cortex and the cerebellum. It's involved in sleep, arousal, respiratory control, and plays a role in several cranial nerve functions.

47. How does the CNS maintain its energy supply?

The CNS relies heavily on glucose for energy. The blood-brain barrier allows glucose to enter the brain, where it's primarily metabolized through aerobic respiration. Astrocytes play a crucial role in providing energy substrates to neurons and regulating blood flow.

48. What is the role of the amygdala in the CNS?

The amygdala, part of the limbic system, plays a central role in processing emotions, particularly fear and anxiety. It's involved in emotional learning, memory consolidation, and influences decision-making based on emotional context.

49. How does the CNS process olfactory information?

Olfactory processing begins when odorants bind to receptors in the nasal epithelium. Signals then travel directly to the olfactory bulb in the forebrain, bypassing the thalamus. From there, information is sent to the piriform cortex and other brain areas for further processing and integration with other sensory inputs.

50. What is the function of the substantia nigra in the CNS?

The substantia nigra, part of the basal ganglia, plays a crucial role in movement control, reward, and learning. Its dopamine-producing neurons project to the striatum, and their degeneration is associated with Parkinson's disease.

51. How does the CNS regulate body temperature?

The CNS regulates body temperature primarily through the hypothalamus. It receives information from temperature sensors throughout the body and initiates responses such as sweating or shivering to maintain a stable core temperature.

52. What is the role of the cerebral ventricles in the CNS?

The cerebral ventricles are interconnected cavities within the brain that produce and circulate cerebrospinal fluid (CSF). They help protect the brain, remove waste products, and maintain proper chemical balance in the CNS.

53. How does the CNS process taste information?

Taste information is detected by taste buds and transmitted through cranial nerves to the brainstem. From there, signals are sent to the thalamus and then to the gustatory cortex. The CNS integrates taste with other sensory information to create the overall perception of flavor.

54. What is the function of the medulla oblongata in the CNS?

The medulla oblongata, the lowest part of the brainstem, controls vital autonomic functions such as heart rate, blood pressure, breathing, and digestion. It also serves as a relay station for various sensory and motor pathways between the brain and spinal cord.

55. How does the CNS contribute to learning and memory formation?

Learning and memory formation in the CNS involve multiple regions, including the hippocampus, amygdala, and prefrontal cortex. These processes rely on synaptic plasticity, where connections between neurons are strengthened or weakened based on experience. Long-term potentiation in the hippocampus is particularly important for forming new memories.