Nervous System: Structure, Function, and Cellular Components (Chapter 11 Study Notes)

Nervous System: Structure, Function, and Cellular Components

Overview

The nervous system is a major organ system responsible for rapid communication, coordination, and control throughout the body. It is divided into structural and functional components, each with specialized roles in maintaining homeostasis and responding to internal and external stimuli.

Major Divisions of the Nervous System

Central Nervous System (CNS)

• Components: Brain and spinal cord

• Function: Integrates, processes, and coordinates sensory data and motor commands

Peripheral Nervous System (PNS)

• Components: All neural tissue outside the CNS, including cranial nerves (12 pairs), spinal nerves (31 pairs), ganglia (collections of neuron cell bodies), and sensory receptors

• Function: Relays information between the CNS and the rest of the body

• Types of Sensory Receptors:

  • Touch receptors (skin)

  • Photoreceptors (eye)

  • Olfactory receptors (nose)

Functional Divisions of the Nervous System

Sensory (Afferent) Division

• Function: Receives sensory information from receptors and transmits it to the CNS

• Somatic Sensory System: Detects stimuli we consciously perceive (e.g., touch, vision)

• Visceral Sensory System: Detects stimuli we typically do not perceive (e.g., signals from internal organs)

Motor (Efferent) Division

• Function: Initiates motor output and transmits it from the CNS to effectors

• Somatic Motor System: Sends voluntary signals to skeletal muscles

• Autonomic Motor System (ANS): Sends involuntary commands to heart, smooth muscle, and glands

  • Sympathetic Division: Prepares the body for 'fight or flight' responses

  • Parasympathetic Division: Promotes 'rest and digest' activities

Cells of the Nervous System

Neurons

• Definition: Cells that send and receive signals via electrical impulses known as action potentials

• Functions: Communication, information processing, and control

Neuroglia (Glial Cells)

• Definition: Supportive cells that protect, nourish, and insulate neurons

• Functions: Maintain homeostasis, form myelin, and provide support and protection for neurons

Structure of a Multipolar Neuron

Multipolar neurons are the most common type of neuron in the CNS. They have several key structural features:

• Cell Body (Soma): Contains the nucleus and organelles; responsible for metabolic activities

• Dendrites: Short, branched extensions that receive information from other neurons and conduct impulses toward the cell body

• Axon: A long, single extension that carries electrical signals (action potentials) away from the cell body to target cells

• Perikaryon: The cytoplasm surrounding the nucleus in the cell body

• Telodendria: Fine extensions at the end of the axon, forming synaptic terminals

Example:

Motor neurons controlling skeletal muscles are typically multipolar neurons, with many dendrites and a single long axon.

Summary Table: Divisions and Functions of the Nervous System

Division	Main Components	Primary Function
Central Nervous System (CNS)	Brain, Spinal Cord	Integration, processing, coordination
Peripheral Nervous System (PNS)	Cranial nerves, Spinal nerves, Ganglia, Sensory receptors	Communication between CNS and body
Sensory (Afferent) Division	Somatic and Visceral sensory neurons	Transmit sensory input to CNS
Motor (Efferent) Division	Somatic and Autonomic motor neurons	Transmit motor output from CNS to effectors

Key Terms

• Neuron: The functional unit of the nervous system, specialized for communication

• Neuroglia (Glial Cells): Supportive cells in the nervous system

• Action Potential: A rapid, temporary change in a membrane potential that travels along the axon

• Ganglia: Clusters of neuron cell bodies in the PNS

• Receptor: Specialized cell or structure that detects stimuli

Additional info:

• Further sections of this chapter would likely cover the physiology of neurons, synaptic transmission, and the roles of different types of neuroglia in more detail.