BackModule 11.1: Overview of the Nervous System
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Overview of the Nervous System
Major Functions of the Nervous System
The nervous system is a complex network responsible for coordinating the body's activities. It enables rapid communication between different body parts and the environment, ensuring survival and homeostasis.
Sensory Input: Detects changes in the internal and external environment through sensory receptors.
Integration: Processes and interprets sensory input, making decisions about appropriate responses.
Motor Output: Initiates responses by activating muscles or glands (effectors).
Example: Touching a hot surface triggers sensory receptors in the skin, which send signals to the brain (integration), resulting in a rapid withdrawal of the hand (motor output).
Structures and Basic Functions of the Central and Peripheral Nervous Systems
The nervous system is divided into two main anatomical divisions: the central nervous system (CNS) and the peripheral nervous system (PNS).
Central Nervous System (CNS):
Brain: The control center for processing information, thought, memory, and decision-making.
Spinal Cord: Conducts signals to and from the brain; responsible for reflex actions.
Peripheral Nervous System (PNS):
Nerves: Bundles of axons that transmit signals between the CNS and the rest of the body.
Ganglia: Clusters of neuron cell bodies outside the CNS, involved in signal relay and processing.
Example: The optic nerve (PNS) carries visual information from the eye to the brain (CNS).
Major Differences Between the Two Functional Divisions of the Peripheral Nervous System
The PNS is functionally divided into the sensory (afferent) division and the motor (efferent) division.
Sensory (Afferent) Division: Transmits sensory information from receptors to the CNS.
Motor (Efferent) Division: Carries commands from the CNS to effectors (muscles and glands).
The motor division is further subdivided into:
Somatic Nervous System: Controls voluntary movements of skeletal muscles.
Autonomic Nervous System: Regulates involuntary functions (e.g., heart rate, digestion) and is further divided into sympathetic and parasympathetic branches.
Example: The sensory division detects a painful stimulus, while the somatic division initiates a voluntary withdrawal response.
