Nervous System Overview

Main Functions of the Nervous System

The nervous system is the master control and communication system in the body, responsible for integrating and responding to internal and external stimuli. It operates through three major overlapping functions:

• Sensory input: The process of receiving information from sensory receptors about changes in the environment.

• Integration: The interpretation and processing of sensory input, allowing the nervous system to make decisions.

• Motor output: The activation of effector organs (muscles and glands) in response to integrated sensory information.

Organization of the Nervous System

Divisions of the Nervous System

The nervous system is divided into two main parts:

• Central Nervous System (CNS): Consists of the brain and spinal cord. It is responsible for processing and integrating information and is crucial for higher functions such as thought and emotion.

• Peripheral Nervous System (PNS): Includes all nervous tissue outside the CNS. It connects the CNS to limbs and organs and is subdivided into:

  • Spinal nerves: Extend to and from the spinal cord.

  • Cranial nerves: Extend to and from the brain.

• The PNS has two functional divisions:

  • Sensory (afferent) division: Conveys impulses to the CNS from sensory receptors.

    • Somatic sensory fibers: Carry information from skin, skeletal muscles, and joints.

    • Visceral sensory fibers: Carry information from internal organs (lungs, heart, etc.).

  • Motor (efferent) division: Transmits impulses from the CNS to effector organs.

    • Somatic nervous system: Controls voluntary movements via skeletal muscles.

    • Autonomic nervous system: Regulates involuntary functions (smooth muscle, cardiac muscle, glands).

      • Includes sympathetic and parasympathetic divisions.

Nervous Tissue

Components of Nervous Tissue

Nervous tissue is composed of two main cell types:

• Neurons: Specialized cells that transmit electrical signals.

• Neuroglia (glial cells): Support neurons by nourishing, insulating, and protecting them.

Types and Functions of Neuroglia

There are six types of neuroglia, four in the CNS and two in the PNS:

• CNS neuroglia:

  • Astrocytes

  • Oligodendrocytes

  • Microglia

  • Ependymal cells

• PNS neuroglia:

  • Schwann cells

  • Satellite cells

Functions of neuroglia:

• Provide structural support for neurons

• Insulate neuronal processes

• Maintain the environment around neurons

• Assist in repair after injury

Neuron Structure and Function

Anatomy and Function of Neuron Components

• Cell Body (Soma):

  • Anatomy: Contains the nucleus and most organelles.

  • Function: Integrates incoming signals and generates outgoing signals to the axon.

• Dendrites:

  • Anatomy: Short, branched extensions from the cell body.

  • Function: Receive signals from other neurons and convey them to the cell body.

• Axon:

  • Anatomy: Long, slender projection from the cell body.

  • Function: Transmits electrical impulses away from the cell body to other neurons or effectors.

• Myelin Sheath:

  • Anatomy: Fatty layer covering the axon, formed by oligodendrocytes in the CNS and Schwann cells in the PNS.

  • Function: Insulates the axon and increases the speed of impulse transmission.

Functional Properties of Neurons

• Neurons are amitotic (do not divide after development).

• Require glucose as their sole energy source.

Application and Example Questions

Sample Multiple Choice and Analogy Questions

• When you reach for a beverage, the somatic nervous system is activated.

• The logical sequence of nervous system functions is: Sensory input, integration, motor output.

• Electrical wire is to electrical insulating tape as peripheral neurons are to Schwann cells.

Neuron Diagram Labeling and Analysis

• Signals are initiated at the axon hillock of the presynaptic cell.

• Signals travel down the axon to the axon terminal, where neurotransmitters are released into the synaptic cleft.

• Red dots in the synapse represent neurotransmitter molecules.

Table: Comparison of CNS and PNS Neuroglia

Key Equations and Concepts

• Resting membrane potential:

• Action potential propagation:

Additional info: The study notes above expand on the provided questions and diagrams, offering definitions, examples, and academic context for a comprehensive review of the nervous system suitable for Anatomy & Physiology students.