Dendrite Definition Dendrites are projections of a neuron (nerve cell) that receive signals (information) from other neurons. The transfer of information from one neuron to another is achieved through chemical signals and electric impulses, that is, electrochemical signals.  The information transfer is usually received at the dendrites through chemical signals, then it travels to the … Read more

Hypotonic Solution Definition A hypotonic solution is a solution that has a lower solute concentration compared to another solution. A solution cannot be hypotonic, isotonic or hypertonic without a solution for comparison. Hypotonic is a description of the solute content of one solution in relation to another solution.  It is used in biology to help … Read more

Pyloric Sphincter Definition The pyloric sphincter is a small piece of smooth visceral muscle that acts as a valve and regulates the flow of partially digested food from the stomach to the duodenum. The opening and closing of the sphincter is controlled by peristaltic waves produced by the stomach during the digestion process.  At rest, … Read more

Gel Electrophoresis Definition Gel electrophoresis is a procedure used to separate biological molecules by size. The separation of these molecules is achieved by placing them in a gel with small pores and creating an electric field across the gel. The molecules will move faster or slower based on their size and electric charge. Gel Electrophoresis … Read more

Definition The spindle fiber is a microscopic protein structure that divides genetic material during cell division and organizes the components of a cell. A centrosome, also known as a microtubule-organizing center, or MTOC, forms spindle fibers. Overview Spindle fibers are formed from microtubules with many accessory proteins which help guide the process of genetic division. … Read more

Organ Definition An organ is a self-contained group of tissues that performs a specific function in the body. The heart, liver, and stomach are examples of organs in humans. The word organ comes from the Latin organum, which means “instrument”.  This in turn comes from the Greek word ὄργανον (órganon), which refers to a musical … Read more

Definition Codominance occurs when two different versions – a.k.a. “alleles” – of the same gene are present in a living thing, and both alleles are expressed separately in different parts of an organism. Instead of one trait being dominant over the other, both traits appear. Overview Codominance is easy to spot in plants and animals … Read more

Notochord Definition A notochord provides rigid support to Chordate organisms by acting as an elastic rod. Among the more derived Chordates, the Vertebrates, the notochord is replaced by the vertebral column and becomes cartilaginous between vertebrae. Below is an image of a lancelet showing the notochord. Chordates with Lancelets are among the simplest. Muscles attach … Read more

Calmodulin Definition All eukaryotic cells contain calcium-modulated protein, or calcium-modulated protein. It acts as a regulator or effector molecule in a wide variety of cellular functions, interacting with other proteins in the cell. Regulation of the cell cycle, intracellular signaling, fertilization, and muscle contraction are among these functions.  Among the calcium-binding proteins involved in muscle … Read more