N Flashcards
Na+/K+ ATPase
An ion transporter that expels 3 Na+ out of a cell and imports 2 K+, driven by the energy of ATP hydrolysis.
NaCaX
Sodium-calcium exchanger; a type of ion exchanger.
Nares
Nostrils.
Natriuretic
Leading to the appearance of sodium in the urine.
Natural Killer Cells
A type of lymphocyte that is part of the innate immune system of vertebrates that is capable of killing tumors or cells infected with viruses without prior stimulation by the immune system.
Near-Equilibrium Reaction
A reaction in which the products and substrates in vivo are near the concentrations that would arise if the enzymatic reaction were to reach equilibrium. The reaction is regulated by changes in the concentrations of substrates and products.
Negative Feedback Loop
A regulatory mechanism whereby a step late in a pathway causes a decrease in the activity of a step earlier in the pathway to reduce the flow through the pathway.
Negative Feedback Regulation
see negative feedback loop
A type of regulation in which the output of a pathway tends to decrease the activity of earlier steps in the pathway.
Negative Work
Work that arises when the muscle is lengthening.
Nematocyst
The stinging cell of cnidarians.
Nephridium
A primitive type of kidney tubule found in some invertebrates, such as annelids and mollusks; can also refer to the embryonic kidney of vertebrates.
Nephron
The multicellular unit of the kidney, consisting of the tubule and the vasculature that serves it, typically a glomerulus.
Nernst Equation
An expression that describes the ion concentration gradient across a permeable membrane in relation to the voltage when the system is at equilibrium.
Nerve
A cordlike structure composed of a collection of neuronal axons grouped together by connective tissues.
Nerve Net
Description of the structure of the nervous system of cnidarians.
Nervous System
Network of neurons and their supporting cells.
Net Energy
The proportion of metabolizable energy that is retained by the body, excluding that lost to specific dynamic action.
Neurogenic
A contraction that occurs in response to a nervous stimulus.
Neurogenic Muscle
A muscle that is activated by neuronal stimulation.