Fundamentals of the Nervous System and Nervous Tissue: Chapter 11 Part A Study Notes

Fundamentals of the Nervous System and Nervous Tissue

Introduction

The nervous system is the master controlling and communicating system of the body. It utilizes both electrical and chemical signals to coordinate rapid and specific responses, ensuring immediate reactions to internal and external stimuli.

Functions of the Nervous System

Overview of Nervous System Functions

• Communication: The nervous system communicates via electrical impulses and chemical neurotransmitters.

• Speed and Specificity: Responses are rapid and highly specific, allowing for precise control of body functions.

• Immediate Response: Most nervous system actions result in almost instantaneous effects.

Three Overlapping Functions

• Sensory Input: Information is gathered by sensory receptors about changes occurring inside and outside the body.

• Integration: The nervous system processes and interprets sensory input, determining the appropriate response.

• Motor Output: Activation of effector organs (muscles and glands) produces a response to the integrated information.

Example: When you see a glass of water (sensory input), your brain processes this information (integration), and you reach out to grab it (motor output).

Organization of the Nervous System

Central Nervous System (CNS)

• Composed of the brain and spinal cord, located in the dorsal body cavity.

• Acts as the integration and control center, interpreting sensory input and dictating motor output.

Peripheral Nervous System (PNS)

• Consists of nerves that extend from the brain and spinal cord.

• Spinal nerves: Carry impulses to and from the spinal cord.

• Cranial nerves: Carry impulses to and from the brain.

Functional Divisions of the Peripheral Nervous System

Sensory (Afferent) Division

• Somatic sensory fibers: Transmit impulses from skin, skeletal muscles, and joints to the CNS.

• Visceral sensory fibers: Transmit impulses from visceral organs to the CNS.

Motor (Efferent) Division

• Transmits impulses from the CNS to effector organs (muscles and glands).

• Divided into:

  • Somatic Nervous System: Controls voluntary movements of skeletal muscles.

  • Autonomic Nervous System: Regulates involuntary functions of smooth muscle, cardiac muscle, and glands.

Somatic Nervous System

Characteristics

• Somatic motor nerve fibers conduct impulses from the CNS to skeletal muscles.

• Responsible for voluntary control of skeletal muscle activity.

Example: Deciding to move your arm is a function of the somatic nervous system.

Autonomic Nervous System (Additional info)

The autonomic nervous system (ANS) is further divided into the sympathetic and parasympathetic divisions, which typically have opposing effects on target organs. The sympathetic division prepares the body for 'fight or flight' responses, while the parasympathetic division promotes 'rest and digest' activities.

Summary Table: Organization of the Nervous System

Division	Main Components	Function
Central Nervous System (CNS)	Brain, Spinal Cord	Integration and control center
Peripheral Nervous System (PNS)	Spinal nerves, Cranial nerves	Communication lines between CNS and body
Sensory (Afferent) Division	Somatic and Visceral sensory fibers	Transmits sensory information to CNS
Motor (Efferent) Division	Somatic and Autonomic nervous systems	Transmits motor commands from CNS to effectors

Key Terms

• Neuron: The basic functional unit of the nervous system, specialized for transmitting electrical impulses.

• Effector: An organ (muscle or gland) that responds to a motor command.

• Integration: The process of interpreting sensory input and deciding on a response.

• Afferent: Carrying toward the CNS (sensory).

• Efferent: Carrying away from the CNS (motor).

Additional info: Understanding neurotransmitter function is crucial for recognizing how drugs and diseases can affect nervous system activity and overall health.