BackFundamentals of the Nervous System and Nervous Tissue – Study Notes
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Chapter 11: Fundamentals of the Nervous System and Nervous Tissue
Overview of the Nervous System
The nervous system is the master controlling and communicating system of the body. It is responsible for integrating sensory input, coordinating bodily functions, and facilitating rapid communication between different body regions.
Central Nervous System (CNS): Consists of the brain and spinal cord. It acts as the integration and command center.
Peripheral Nervous System (PNS): Composed of cranial nerves, spinal nerves, and ganglia. It connects the CNS to limbs and organs.
Example: The CNS processes information received from the PNS and sends out instructions to muscles and glands.
Structure of a Typical Neuron
Neurons are the basic functional units of the nervous system, specialized for the transmission of electrical signals.
Cell Body (Soma): Contains the nucleus and is the metabolic center of the neuron.
Dendrites: Branch-like extensions that receive signals from other neurons and convey them toward the cell body.
Axon: A long projection that transmits electrical impulses away from the cell body toward other neurons or effectors.
Axon Hillock: The cone-shaped region of the cell body where the axon originates; important in the initiation of action potentials.
Myelin Sheath: Insulating layer around many axons that increases the speed of impulse transmission.
Axon Terminals: The distal endings of the axon where neurotransmitters are released.
Example: Sensory neurons have long dendrites to receive signals from sensory receptors, while motor neurons have long axons to reach muscles.
CNS Versus PNS Terminology
Specific terms are used to describe similar structures in the CNS and PNS.
TERM | DEFINITION |
|---|---|
Nucleus | A collection of neuron cell bodies in the CNS |
Ganglion | A collection of neuron cell bodies in the PNS |
Tract | A bundle of axons in the CNS |
Nerve | A bundle of axons in the PNS |
Example: The optic nerve is a PNS structure, while the corticospinal tract is a CNS structure.
Functional Organization of the Nervous System
The nervous system is functionally divided into sensory (afferent) and motor (efferent) divisions.
Sensory (Afferent) Division: Transmits information from sensory receptors to the CNS.
Motor (Efferent) Division: Transmits commands from the CNS to effector organs (muscles and glands).
Example: Touching a hot surface activates sensory neurons, which send signals to the CNS; the CNS then sends motor commands to withdraw the hand.
Summary Table: CNS vs. PNS Structures
Structure | CNS | PNS |
|---|---|---|
Cell bodies | Nucleus | Ganglion |
Axon bundles | Tract | Nerve |
Key Terms and Definitions
Neuron: A nerve cell; the basic building block of the nervous system.
Neuroglia (Glial Cells): Supporting cells that provide structural and metabolic support to neurons.
Myelin: A fatty substance that surrounds axons, increasing the speed of nerve impulse conduction.
Synapse: The junction between two neurons or between a neuron and an effector cell.
Additional info:
These notes are based on the introductory content and figures from Chapter 11 of Marieb Human Anatomy & Physiology, focusing on the structure and terminology of the nervous system and neurons.
