Structure of the Nervous System
The nervous system is divided into two primary structural components:
- Central Nervous System (CNS): Comprises the brain and spinal cord. It acts as the integration centre for processing and commands.
- Peripheral Nervous System (PNS): Includes all nerves branching from the spinal cord to the organs, limbs, and skin.
Key Cellular Components
1. Neurons
The primary functional units responsible for transmitting electrical impulses (action potentials).
2. Glial Cells (Glia)
Non-neuronal cells providing vital support, nutrition, and insulation (myelin) to neurons.
Functional Divisions of the PNS
- Somatic Nervous System: Governs voluntary movements of skeletal muscles.
- Autonomic Nervous System: Regulates involuntary functions like digestion and heart rate.
- Sympathetic: "Fight-or-flight" (prepares for activity).
- Parasympathetic: "Rest-and-digest" (calms the body).
Core Properties
- Speed: Signals can exceed 100 metres per second.
- Plasticity: The ability to adapt, form new pathways, and learn.
- Electrochemical Signaling: Uses electrical impulses and chemical neurotransmitters.
- Fragility: Highly susceptible to trauma, infection, or toxicity.
Primary Functions
- Sensory Input: Detecting stimuli inside and outside the body.
- Integration: Processing and storing information to make decisions.
- Motor Output: Activating muscles and glands for appropriate responses.
- Regulation: Maintaining homeostasis (temperature, sleep cycles).
- Cognition: Managing high-level thinking, learning, and emotion.