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Glossary of Physiology Terms
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Definition:
A rectangular signal waveform used in physiological studies to perturb (i.e., challenge) the system under study. The response of the system to the pulse is then studied carefully to learn about how the system responds to challenges.

Examples include pulses of voltage or current in electrophysiological experiments. Other examples include pulses of light, pressure, temperature, ligand, etc.

A square-wave pulse is defined by the amplitude and duration of the pulse, as well as by the frequency at which the pulse is applied to the system under study.

See also:
Neuronal Action Potential - Introduction

Other resources:
Square wave (Wikipedia)



Definition:
Proposed model for the inactivation of some voltage-gated ion channels. According to this model, after channel opening, the pore of the open channel is plugged by a globular cytoplasmic portion of the channel protein. The globular portion (ball of amino acids) is tethered to the rest of the protein by a linker part (chain of amino acids).

Related glossary terms/phrases:
Channel inactivation

See also:
Neuronal Action Potential - Important Features of the Neuronal Action Potential



Definition:
The one-way valve between the left atrium and left ventricle of the heart. It is also known as the left atrioventricular valve or mitral valve.

The direction of blood flow through the bicuspid valve is from the left atrium to the left ventricle.

Related glossary terms/phrases:
Left atrioventricular valve
Mitral valve



Definition:
An endogenous, tissue-specific molecule that functions to inhibit mitosis (cell division) in the very tissue releasing the molecule.



Definition:
Electrophysiology is the study of the electrical properties of biological macromolecules, cells, tissues, and organs. Electrical signals such as voltage and/or current are generally measured. Examples include measuring changes in the membrane voltage of excitable cells (e.g., neurons, muscle cells, and some endocrine cells) during an action potential. The current carrried by ions as they permeate the pore of ion channels can also be measured - both at the single-channel level (single-channel current), as well as the macroscopic current resulting from the activity of a population of channels. As another example, electrical measurements may involve recording voltage changes at the surface of the skin that result from the activity of skeletal muscles (electromyogram, EMG), cardiac myocytes (electrocardiogram, ECG), or neurons in the brain (electroencephalogram, EEG).



Definition:
The Hodgkin cycle represents a positive feedback loop in neurons, where an initial membrane depolarization from the resting value (∼ −70 mV) to the threshold value (∼ −50 mV) leads to rapid depolarization of the membrane potential to approach the equilibrium potential for Na+ (VNa ≈ +60 mV). The voltage-gated Na+ channels of neurons are responsible for the Hodgkin cycle.

See the figure depicting the Hodgkin cycle.

See also:
Important Features of the Neuronal Action Potential



Definition:
The one-way valve between the left atrium and left ventricle of the heart. It is also known as the bicuspid valve or mitral valve.

The direction of blood flow through the left atrioventricular valve is from the left atrium to the left ventricle.

Related glossary terms/phrases:
Bicuspid valve
Mitral valve



Definition:
Lidocaine is a local anesthetic and an antiarrhythmic drug. It is a commonly used local anesthetic for minor surgery and in dental procedures. Lidocaine is also used topically to relieve itching, burning, and pain from skin inflammations.

Lidocaine's mechanism of action is to block fast voltage-gated Na+ channels of neurons and cardiac myocytes.

Other names used for lidocaine are xylocaine and lignocaine.

See also:
Pharmacological Inhibition of Na+ and K+ Channels

Other resources:
Lidocaine (Wikipedia)



Definition:
The one-way valve between the left atrium and left ventricle of the heart. It is also known as the left atrioventricular valve or bicuspid valve.

The direction of blood flow through the mitral valve is from the left atrium to the left ventricle.

Related glossary terms/phrases:
Left atrioventricular valve
Bicuspid valve



Definition:
Neurotoxins are chemical molecules that have an adverse effect on neuron function and, thus, disrupt the normal function of the nervous system. Neurotoxins could be small molecules or peptides and can be derived from a variety of invertebrate and vertebrate animals, as well as plant species.

The following is a short list of some examples of neurotoxins:

α-Bungarotoxin: A peptide neurotoxin that inhibits the nicotinic acetylcholine receptor.

Chlorotoxin: A peptide neurotoxin that inhibits chloride channels.

α-Conotoxin: A peptide neurotoxin that inhibits the nicotinic acetylcholine receptor.

δ-Conotoxin: A peptide neurotoxin that inhibits voltage-gated sodium channels.

w-Conotoxin: A peptide neurotoxin that inhibits N-type voltage-gated calcium channels.

Picrotoxin: Inhibits GABAA receptor chloride channels.

Tetrodotoxin: Inhibitor of neuronal voltage-gated sodium channels.



Definition:
A local topical anesthetic.

Procaine's mechanism of action is to block fast voltage-gated Na+ channels of neurons.

See also:
Pharmacological Inhibition of Na+ and K+ Channels

Other resources:
Procaine (Wikipedia)



Definition:
The one-way valve between the right atrium and right ventricle of the heart. It is also known as the tricuspid valve.

The direction of blood flow through the right atrioventricular valve is from the right atrium to the right ventricle.

Related glossary terms/phrases:
Tricuspid valve



Definition:
Synaptic pathology. Any pathophysiological condition that leads to abnormal function of synapses within the nervous system. The pathology may be due to pre-synaptic and/or post-synaptic mechanisms, or may involve glial cells surrounding synapses.



Definition:
Tastants are taste-provoking chemical molecules that are dissolved in ingested liquids or saliva.

Tastants stimulate the sense of taste. It can also be said that tastants elicit gustatory excitation.

A tastant is the appropriate ligand for receptor proteins located on the plasma membrane of taste receptor cells.



Abbreviation:
TEA

Definition:
An inhibitor of voltage-gated potassium (K+) channels.

TEA is a quaternary ammonium cation (positively charged ion). It is also commonly used as a cation replacement for sodium (Na+) in physiological buffers used in ion replacement experiments.

See also:
Pharmacological Inhibition of Na+ and K+ Channels



Abbreviation:
TTX

Definition:
Inhibitor of fast voltage-gated sodium (Na+) channels of neurons and muscle cells. It is an extremely potent and toxic neurotoxin.

See also:
Pharmacological Inhibition of Na+ and K+ Channels

Other resources:
Tetrodotoxin (Wikipedia)



Definition:
The membrane voltage that must be reached in an excitable cell (e.g., neuron or muscle cell) during a depolarization in order to generate an action potential. At the threshold voltage, voltage-gated channels become activated. Threshold is approximately −50 to −40 mV in most excitable cells.

Related glossary terms/phrases:
Sub-threshold
Supra-threshold

See also:
Neuronal Action Potential - Introduction



Definition:
The one-way valve between the right atrium and right ventricle of the heart. It is also known as the right atrioventricular valve.

The direction of blood flow through the tricuspid valve is from the right atrium to the right ventricle.

Related glossary terms/phrases:
Tricuspid valve









Posted: Sunday, March 31, 2013
Last updated: Friday, August 28, 2015