Neurophysiology Health Article

Definition

Neurophysiology is the study of the functions of the nervous system. Clinical neurophysiology is the study of the functions of the nervous system in the clinical setting, for diagnostics, treatment, and intensive care purposes.

Description

Neurophysiology is a broad field of study because many different levels are involved in the overall functioning of the nervous system and its components. For example, the transmission of a nervous impulse across the synapses, or the cleft that connects nerve cells, involves chemical reactions at the cellular level of organization. Understanding how messages are relayed from the brain to the hand is best explained at the system level. This involves studying the relationship and pathways between the brain and the organs of the body and the nerves that connect them, both sensory, meaning nerves that receive input from sensors, and motor, meaning the nerves that activate muscle. Thus, neurophysiology studies nervous function ranging from individual nerve cells to the complex behaviors of the central nervous system. Additionally, the nervous system not only functions at the cell and system levels of organization, but also at a mechanistic level, that involves the study of the control or regulatory processes that occur.

The neurophysiology of systems

A branch of neurophysiology describes the function of the major system components of the nervous system of the human body at the system level. The overall nervous system of the body consists of the central nervous system (CNS), and the peripheral nervous system (PNS). The neurophysiology of the CNS studies the function of the brain and spinal cord while that of the PNS studies the function of all the nerves that connect the CNS with organs, muscles, blood vessels and glands. The neurophysiology of the PNS further subdivides into the somatic nervous system (SNS) and the autonomic nervous system (ANS), with the ANS being further divided by function into the sympathetic and parasympathetic systems.

KEY TERMS

Axon—The part of the nerve cell used to carry impulses away from the cell body.

Electroencephalography (EEG)—Recording of electrical impulses that reflect brain function, used to diagnose extensive variety of nervous system disorders.

Electromyography (EMG)—Electrical testing of nerves and muscles, used to diagnose nervous disorders.

Evoked potentials (EP)—Electrical signals of the nerves, spinal cord and brain in response to light stimulation of the eyes, or sound stimulation of the ears or mild electrical stimulation of the nerves in the arms or legs, used to diagnose nervous system disorders, such as multiple sclerosis, hearing loss, and various spinal cord disorders.

Microneurography—Technique used primarily for research purposes that enable recording of electrical activity of a single axon from the peripheral nerves of awake human subjects.

Nerve condition velocity (NCV)—Technique for studying nerve or muscle disorders, measuring the speed at which nerves transmit signals.

Neurophysiology—The study of the functions of the nervous system.

Polysomnography reduction—Technique used to monitor brain patterns, eye movements, muscle tension, air flow and respiratory effort, oxygen levels and heart beat during sleep to study sleep disorders.

PNS nerves are of two types: the sensory—or afferent—nerves that transmit information from the sensory organs, muscles, joints, internal organs and all other parts of the body to the CNS, and the motor—or efferent— nerves that transmit signals from the CNS to the body, for example, to the muscles or to internal organs.

The neurophysiology of nerve cells

Neurophysiology is also the study of the physiology, structure and function of nerve cells, or neurons, meaning how individual neurons receive and transmit information using chemical and electrical signals. The most important feature of neurons as compared to other cell types in the body is their high degree of electrical excitability. The transmission of nervous signals is based on changes in this electrical excitability, and neurophysiology studies these effects at the cellular level as well as the electrical properties of neurons. It also seeks to understand the differences between the excitability of muscle and nervous tissue. Examples are: the release of neurotransmitters, substances that are activated by the excitation of neurons; the specific chemical features of the various neurotransmitters; the study of the redistribution of charged ions inside and outside nervous cells, including the pumps used to transport them across cell membranes; and the properties of the various special channels used for this transport.