Overview of the Nervous System – Study Guide

Overview of the Nervous System

Major Functions of the Nervous System

The nervous system is a complex network responsible for regulating and coordinating body activities. It enables organisms to perceive, interpret, and respond to internal and external stimuli.

• Sensory Function: Detects changes in the environment (internal and external) through sensory receptors and transmits this information to the central nervous system (CNS).

• Integrative Function: Processes and interprets sensory input, making decisions about appropriate responses.

• Motor Function: Initiates responses by activating effectors such as muscles and glands.

• Homeostasis: Maintains internal balance by regulating physiological processes.

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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, responsible for thought, memory, emotion, and coordination of body functions.

  • Spinal Cord: Conducts signals between the brain and the rest of the body; also responsible for reflex actions.

• Peripheral Nervous System (PNS):

  • Cranial Nerves: Emerge from the brain and primarily serve the head and neck region.

  • Spinal Nerves: Emerge from the spinal cord and serve the rest of the body.

  • Ganglia: Clusters of neuron cell bodies located outside the CNS.

  • Plexuses: Networks of nerves that serve specific body regions.

  • Sensory Receptors: Specialized cells that detect stimuli and send information to the CNS.

Functional Divisions of the Peripheral Nervous System

The PNS is further divided into functional subdivisions based on the direction of information flow and the type of effectors they control.

• Sensory (Afferent) Division: Transmits sensory information from receptors to the CNS.

• Motor (Efferent) Division: Transmits commands from the CNS to effectors (muscles and glands).

The motor division is further subdivided into:

• Somatic Nervous System (SNS): Controls voluntary movements by innervating skeletal muscles.

• Autonomic Nervous System (ANS): Controls involuntary functions by innervating smooth muscle, cardiac muscle, and glands. The ANS is further divided into the sympathetic and parasympathetic divisions.

Division	Function	Effectors
Sensory (Afferent)	Transmits sensory input to CNS	Sensory receptors
Somatic Motor	Voluntary control of movements	Skeletal muscles
Autonomic Motor	Involuntary control of body functions	Smooth muscle, cardiac muscle, glands

Example: When you touch a hot object, sensory receptors in your skin send a signal through the sensory division to the CNS. The CNS processes this information and sends a command through the motor division to your muscles to withdraw your hand.

Additional info: The autonomic nervous system (ANS) is further divided into the sympathetic ("fight or flight") and parasympathetic ("rest and digest") divisions, which have opposing effects on target organs to maintain homeostasis.