The Nervous System: Structure and Function
The nervous system is a complex network of specialized cells and tissues that coordinates and regulates body functions through electrical and chemical signals, consisting of two main divisions: the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves throughout the body). 1
Central Nervous System (CNS)
The central nervous system comprises:
Brain: The command center that processes and integrates information
- Cerebral cortex: Responsible for higher cognitive functions
- Limbic system: Involved in emotional processing and memory
- Brainstem: Controls basic vital functions
- Cerebellum: Coordinates movement and balance
Spinal Cord: The main pathway for information traveling between the brain and peripheral nervous system
- Transmits sensory information to the brain
- Carries motor commands from the brain to muscles and glands
- Contains reflex pathways that can process some information without brain involvement
Peripheral Nervous System (PNS)
The peripheral nervous system extends throughout the body and is divided into:
Somatic Nervous System
- Controls voluntary movements via motor neurons
- Transmits sensory information from the body to the CNS
- Includes sensory receptors that detect stimuli such as touch, temperature, and pain 1
Autonomic Nervous System
- Regulates involuntary bodily functions
- Divided into two complementary branches:
Enteric Nervous System
- Sometimes called the "second brain"
- Controls gastrointestinal functions
- Can operate independently of the CNS 3
Neural Communication
Neural communication occurs through:
Neurons: Specialized cells that transmit information
- Cell body (soma)
- Dendrites: Receive signals
- Axons: Transmit signals
- Synaptic terminals: Release neurotransmitters
Synapses: Junctions between neurons where information is transferred
- Chemical synapses: Use neurotransmitters
- Electrical synapses: Direct electrical coupling between cells
Neurotransmitters: Chemical messengers that transmit signals across synapses
- Examples: serotonin, dopamine, glutamate, GABA
Functional Integration
The nervous system integrates with other body systems through:
- Neuroendocrine interactions: Communication with the endocrine system through hormones 3
- Neurovascular control: Regulation of blood vessels and circulation
- Neuroimmune connections: Bidirectional communication with the immune system
- Brain-gut axis: Communication between the CNS and digestive system, including gut microbiota 3
Sensory Processing
The nervous system processes various types of sensory information:
- Nociception: Detection of potentially harmful stimuli, which may lead to pain perception 1
- Proprioception: Awareness of body position and movement
- Interoception: Sensing internal bodily states
- Exteroception: Processing information from the external environment
Development and Evolution
The human nervous system:
- Develops from neural tube and neural crest cells during embryogenesis
- Shows significant evolutionary specializations compared to other primates 4
- Exhibits remarkable plasticity throughout life, allowing for learning and adaptation
Clinical Significance
Understanding the nervous system is crucial for:
- Diagnosing and treating neurological disorders
- Developing targeted therapies for conditions affecting neural function
- Creating neural interfaces for prosthetics and assistive technologies 1, 5
- Understanding mechanisms of pain and developing appropriate analgesic strategies 1
The nervous system's complexity and integration with all body systems make it fundamental to human physiology, cognition, and behavior. Its hierarchical organization allows for both automatic regulation of basic functions and sophisticated cognitive processes that define human experience.