H Flashcards
H Zone
The central region of a sarcomere corresponding to the location of the thick filaments where there is no overlap with thin filaments; the H zone reduces in size upon contraction.
Habituation
A process by which repeated stimulation of a neuron results in a decreased response.
Hair Cell
Ciliated sensory cells of vertebrates that react to mechanical stimuli (particularly to vibrations). They are the basis of the senses of hearing and balance, and of the lateral line systems of fishes and amphibians.
Haldane Effect
The effect of oxygen on hemoglobin–carbon dioxide binding.
Half-Life
A period of time required for half of a population of molecules to be converted to another form; often applied to radioactive decay.
Heart
A muscular pumping structure.
Heart Rate
The number of times the heart beats in a given period of time; typically measured as beats per minute.
Heat
The kinetic energy associated with the movement of atoms and molecules.
Heat Capacity
The amount of thermal energy required to increase the temperature of 1 g of a substance by 1°C.
Heat of Vaporization
The heat needed to cause a liquid to become gaseous, expressed per unit mass.
Heat Shock Proteins
A class of molecular chaperones that increase in abundance in response to elevated temperature; the term includes members of genetically related proteins that are constitutive and do not increase in expression in response to thermal stress.
Heater Tissues
A general term for tissues that serve to elevate regional or systemic temperature of an animal, such as the heater organ of billfish.
Helicobacter pyloric
A bacterium that infects gastric pits, creating conditions that can lead to a gastric ulcer.
Hematocrit
The proportion of whole blood that is occupied by red blood cells.
Heme
A metal-binding porphyrin derivative that is incorporated into enzymes (e.g., cytochromes) and non-enzyme proteins (e.g., hemoglobin).
Hemerythrin
An iron-containing respiratory pigment found in sipunculids, priapulids, brachiopods, and annelids; lacks heme.
Hemimetabolous Insect
see also holometabolous insect
Type of insect that possesses immature stages (nymphs) that resemble the adults, except in lacking fully formed wings.
Hemocoel
Collective name for the sinuses in the open circulatory systems of many invertebrates.
Hemocyanin
A respiratory pigment found in arthropods and mollusks consisting of one or more protein molecules complexed directly to copper molecules.
Hemocytes
Generalized term for blood cells. Most commonly used for the blood cells of invertebrates.
Hemoglobin
A respiratory pigment consisting of a globin protein complexed to an ironcontaining porphyrin molecule called heme.
Hemolymph
The circulatory fluid of arthropods.
Hemopoietic Factor
A regulatory protein that induces the synthesis of red blood cells; erythropoietin, for example.
Henderson-Hasselbalch Equation
The mass action equation for the dissociation of carbonic acid (H2CO3) to bicarbonate (HCO3−) and hydrogen ions (H+); important in respiratory physiology.
Henry’s Law
One of the ideal gas laws; describes the dissolution of a gas in a liquid, stating that the amount of gas dissolved in a liquid is related to the partial pressure and the solubility of that gas.
Hepatocyte
The dominant cell type in a liver.
Hepatopancreas
An invertebrate tissue that serves the same roles as the vertebrate liver and pancreas.
Hering-Breuer Inflation Reflex
A respiratory reflex that reduces breathing in response to overinflation of the lungs; involved in the termination of a breath.
Hermaphrodite
An animal that possesses both male and female reproductive tissues either simultaneously or sequentially.
Hertz
A frequency of 1 per second (1 Hz = 1 sec−1).
Heterodimer
A quaternary structure of two dissimilar monomers
Heterothermy
A thermal strategy in which the body temperature (TB) varies either spatially or temporally.
Hexose
A general name for monosaccharides with six carbons; includes glucose and fructose.
