Introduction to the Nervous System

Overview

The nervous system is the master control and communication system of the body. It regulates every thought, action, and emotion by using electrical impulses to communicate. This system is responsible for monitoring changes inside and outside the body, processing and interpreting sensory input, and causing responses by activating muscles and glands.

• Key Functions: Sensory input, integration, and motor output.

• Key Terms: Stimulus (change detected), Sensory input (gathered information), Integration (processing and decision-making), Response (activation of effectors).

Organization of the Nervous System

Structural Classification

The nervous system is divided into two main subdivisions based on structure:

• Central Nervous System (CNS): Consists of the brain and spinal cord. It is the integration and command center.

• Peripheral Nervous System (PNS): Includes all neural elements outside the CNS, such as cranial and spinal nerves. It connects the CNS to limbs and organs.

Functional Classification

Functionally, the nervous system is divided into:

• Sensory (Afferent) Division: Carries impulses from sensory receptors to the CNS. Keeps the CNS informed of changes.

• Motor (Efferent) Division: Transmits impulses from the CNS to effector organs (muscles and glands).

The motor division is further subdivided into:

• Somatic Nervous System: Voluntary control of skeletal muscles.

• Autonomic Nervous System (ANS): Involuntary control of smooth muscle, cardiac muscle, and glands. The ANS is divided into:

  • Sympathetic Division: Prepares the body for stress-related activities ("fight or flight").

  • Parasympathetic Division: Conserves energy and promotes "rest and digest" functions.

Example: Functional Pathway

Touching a hot object activates sensory receptors (afferent), the CNS processes the information, and the motor division (efferent) causes muscle contraction to withdraw the hand.

Nervous Tissue

Neuroglia and Neurons

Nervous tissue consists of two main cell types: neuroglia and neurons.

• Neuroglia (Glial Cells): Support, insulate, and protect neurons. Types include astrocytes, microglia, oligodendrocytes (CNS), and Schwann cells, satellite cells (PNS).

• Neurons (Nerve Cells): Specialized for transmitting electrical impulses. Each neuron has a cell body (with nucleus), and processes (fibers) called dendrites (carry impulses toward cell body) and axons (carry impulses away from cell body).

• Axon Hillock: Region where the axon arises from the cell body.

• Axon Terminals: Branches at the end of the axon, forming synapses with other cells.

Structural and Functional Classification of Neurons

• Sensory (Afferent) Neurons: Carry impulses from receptors to the CNS.

• Motor (Efferent) Neurons: Carry impulses from the CNS to effectors.

• Interneurons (Association Neurons): Connect sensory and motor neurons within the CNS.

Major Topics and Learning Objectives

• Describe the functions and organization of the nervous system.

• Explain the roles of neuroglia and neurons.

• Classify neurons structurally and functionally.

• Outline the steps in generating and conducting a nerve impulse.

• Identify the anatomy and functions of the brain and spinal cord.

• Describe the structure of nerves and the autonomic nervous system.

• Distinguish between sympathetic and parasympathetic divisions.

• Recognize homeostatic imbalances (e.g., multiple sclerosis, hydrocephalus, concussion, CVA, paralysis, cerebral palsy, spina bifida).

• Describe the anatomy and physiology of the special senses (eye, ear, taste, smell).

• Identify homeostatic imbalances of the special senses (e.g., conjunctivitis, night blindness, color blindness, glaucoma, otitis media, deafness, Meniere's syndrome, strabismus, presbyopia).

HTML Table: Nervous System Divisions and Functions

Key Equations and Concepts

• Resting Membrane Potential: The difference in electrical charge across the neuron's membrane at rest.

• Action Potential: Rapid change in membrane potential that travels along the axon.

Study Tips

• Keep track of vocabulary words and their definitions.

• Take good notes in preparation for quizzes and exams.

• Use flashcards for key terms and concepts.

• Review diagrams and flowcharts for system organization.

Additional info: This study guide is based on a syllabus/lesson plan outlining the major topics, objectives, and structure for a college-level Anatomy & Physiology course focused on the nervous system and special senses. For detailed explanations, refer to chapters 7 and 8 of the recommended textbook.