Fundamentals of the Nervous System and Nervous Tissue – Study Notes

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.

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

• Example: Touching a hot object triggers sensory neurons to send signals to the CNS, which processes the information and sends motor commands to withdraw the hand.

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 organelles; the metabolic center of the neuron.

• Dendrites: Short, branched processes that receive signals from other neurons and convey them toward the cell body.

• Axon: A long, singular process 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: A fatty insulating layer that increases the speed of impulse transmission along the axon.

• Axon Terminals: The distal endings of the axon where neurotransmitters are released to communicate with other cells.

• Example: Motor neurons have long axons to transmit signals from the spinal cord to 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

• Key Point: The same structural features are named differently depending on their location in the nervous system.

Additional info:

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

• Myelination: Oligodendrocytes myelinate axons in the CNS, while Schwann cells myelinate axons in the PNS. Myelination increases the speed of nerve impulse conduction.