Introduction to the Nervous System and Nervous Tissue – Study Notes

Chapter 11: Introduction to the Nervous System and Nervous Tissue

Overview of the Nervous System

The nervous system is a complex network responsible for coordinating body activities and responding to internal and external stimuli. It is essential for sensation, movement, cognition, and homeostasis.

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

• Major Components: Brain, spinal cord, nerves.

• Importance: Maintains communication between body systems and the environment.

Divisions of the Nervous System

Anatomical Divisions

The nervous system is divided into two main anatomical parts:

• Central Nervous System (CNS): Consists of the brain and spinal cord. Responsible for processing and integrating information.

• Peripheral Nervous System (PNS): Includes all neural tissue outside the CNS, such as nerves and ganglia. Connects the CNS to limbs and organs.

Functional Divisions

Functionally, the nervous system is divided into sensory and motor divisions:

• Sensory (Afferent) Division:

  • Somatic Sensory Division: Carries general sensory stimuli from muscles, bones, joints, and skin, as well as special sensory stimuli.

  • Visceral Sensory Division: Carries stimuli from internal organs (e.g., urinary bladder).

• Motor (Efferent) Division:

  • Somatic Motor Division: Carries stimuli to skeletal muscles for voluntary movement.

  • Autonomic Motor Division: Carries stimuli to cardiac muscle, smooth muscle, and glands for involuntary control.

Nervous Tissue

Neurons

Neurons are the functional cells of the nervous system, specialized for communication via electrical and chemical signals.

• Dendrites: Branch-like extensions that receive signals from other neurons.

• Cell Body (Soma): Contains the nucleus and organelles; integrates incoming signals.

• Axon: Long projection that transmits electrical impulses away from the cell body to other neurons or effectors.

• Axon Terminals: Release neurotransmitters to communicate with target cells.

Example:

A motor neuron receives input from the CNS and transmits signals to skeletal muscle, causing contraction.

Additional info:

Neurons are classified by structure (multipolar, bipolar, unipolar) and function (sensory, motor, interneuron).

Summary Table: Divisions of the Nervous System

Division	Anatomical Components	Functional Role
CNS	Brain, Spinal Cord	Integration, Processing
PNS	Nerves, Ganglia	Communication between CNS and body
Sensory (Afferent)	Somatic & Visceral Sensory Neurons	Transmit sensory information to CNS
Motor (Efferent)	Somatic & Autonomic Motor Neurons	Transmit motor commands from CNS

Key Terms

• Neuron: A nerve cell specialized for signal transmission.

• Dendrite: Receives incoming signals.

• Axon: Conducts impulses away from the cell body.

• CNS: Central Nervous System.

• PNS: Peripheral Nervous System.

• Afferent: Sensory input to CNS.

• Efferent: Motor output from CNS.

Equations and Scientific Principles

• Resting Membrane Potential: $V_m = V_{inside} - V_{outside}$ Where $V_m$ is the membrane potential.

• Action Potential Propagation: $I = g(V_m - E)$ Where $I$ is current, $g$ is conductance, $V_m$ is membrane potential, and $E$ is equilibrium potential.