Topic 2.2: Physiology of the Neuron

Overview

This topic explores the structure and function of neurons, the fundamental units of the nervous system. It covers the regions of the neuron, the basis of electrical activity, propagation of action potentials, and mechanisms of synaptic transmission.

Neuronal Structure and Functional Regions

Special Properties of Neurons

• Extreme Longevity: Neurons can survive for over 100 years if adequately nourished.

• Amitotic: Most neurons do not undergo mitosis after maturation, meaning lost neurons are generally not replaced. Additional info: This is why neural injuries can be permanent.

• High Metabolic Rate: Neurons require continuous supply of oxygen and glucose to function.

Structural Features

• Cell Body (Soma): Contains the nucleus and is the biosynthetic center of the neuron. It has extensive rough endoplasmic reticulum (Nissl bodies), Golgi apparatus, and mitochondria.

• Processes: Extensions from the cell body, including dendrites and axons.

Functional Regions of the Neuron

• Receptive Region: Includes dendrites and cell body; receives incoming signals.

• Conducting Region: The axon; propagates electrical impulses away from the cell body.

• Secretory Region: Axon terminals; release neurotransmitters to communicate with other cells.

Neuronal Connectivity

Neuronal Numbers and Interconnections

• The human brain contains approximately 100 billion neurons.

• The number of possible interconnections between neurons exceeds the number of atoms in the universe.

Key Terms and Definitions

• Nucleus (CNS): Cluster of neuron cell bodies in the central nervous system.

• Ganglion (PNS): Cluster of neuron cell bodies in the peripheral nervous system.

• Tract: Bundle of nerve processes in the CNS.

• Nerve: Bundle of nerve processes in the PNS.

Summary Table: Neuron Regions and Functions

Example

• Motor Neuron: Receives input via dendrites, conducts action potential along the axon, and releases neurotransmitter at the neuromuscular junction to stimulate muscle contraction.

Additional info: These notes are based on slides and textbook references (pp. 391-397, 400-409, 409-412, 412-420) and are suitable for college-level Anatomy & Physiology students.