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What is a Sensory System?

JoVE 10849

Sensory systems detect stimuli—such as light and sound waves—and transduce them into neural signals that can be interpreted by the nervous system. In addition to external stimuli detected by the senses, some sensory systems detect internal stimuli—such as the proprioceptors in muscles and tendons that send feedback about limb position.

Sensory systems include the visual, auditory, gustatory (taste), olfactory (smell), somatosensory (touch, pain, temperature, and proprioception), and vestibular (balance, spatial orientation) systems. All sensory systems have receptor cells that are specialized to detect a particular type of stimulus. For example, hair cells in the inner ear have cilia that move in the presence of sound waves, while olfactory receptor neurons in the nasal cavity have receptors that bind to odorant molecules. The presence of an appropriate stimulus triggers electrochemical changes in the nervous system. This stimulus typically changes the membrane potential of a sensory neuron, triggering an action potential. The information is then transmitted from the sensory organ to the spinal cord and then the brain, or directly to the brain (as in the visual system). The different types of sensory information—also called modalities—travel in different pathways through the central nervous system, but most

 Core: Biology

What is Gene Expression?

JoVE 10797

Gene expression is the process in which DNA directs the synthesis of functional products, such as proteins. Cells can regulate gene expression at various stages. It allows organisms to generate different cell types and enables cells to adapt to internal and external factors.

A gene is a stretch of DNA that serves as the blueprint for functional RNAs and proteins. Since DNA is made up of nucleotides and proteins consist of amino acids, a mediator is required to convert the information that is encoded in DNA into proteins. This mediator is the messenger RNA (mRNA). mRNA copies the blueprint from DNA by a process called transcription. In eukaryotes, transcription takes place in the nucleus by complementary base-pairing with the DNA template. The mRNA is then processed and transported into the cytoplasm where it serves as a template for protein synthesis during translation. In prokaryotes, which lack a nucleus, the processes of transcription and translation occur at the same location and almost simultaneously since the newly-formed mRNA is susceptible to rapid degradation. Every cell of an organism contains the same DNA, and consequently the same set of genes. However, not all genes in a cell are “turned on” or use to synthesize proteins. A gene is said to be “expressed” when the protein it encodes is produced by the cell. Gen

 Core: Biology

Positive Regulator Molecules

JoVE 10763

To consistently produce healthy cells, the cell cycle—the process that generates daughter cells—must be precisely regulated.

Internal regulatory checkpoints ensure that a cell’s size, energy reserves, and DNA quality and completeness are sufficient to advance through the cell cycle. At these checkpoints, positive and negative regulators promote or inhibit a cell’s continuation through the cell cycle. Positive regulators include two protein groups that allow cells to pass through regulatory checkpoints: cyclins and cyclin-dependent kinases (CDKs). These proteins are present in eukaryotes, ranging from yeast to humans. Cyclins can be categorized as G1, G1/S, S, or M cyclins based on the cell cycle phase or transition they are most involved in. Generally, levels of a given cyclin are low during most of the cell cycle but abruptly increase at the checkpoint they most contribute to (G1 cyclins are an exception, as they are required throughout the cell cycle). The cyclin is then degraded by enzymes in the cytoplasm and its levels decline. Meanwhile, cyclins needed for the next checkpoints accumulate. To regulate the cell cycle, cyclins must be bound to a Cyclin-dependent kinase (CDK)—a type of enzyme that attaches a phosphate group to modify the activity of a target protein.

 Core: Biology

Measuring Biodiversity- Concept

JoVE 10596

Diverse ecosystems are important for the health of the planet and our survival as humans; it is therefore incredibly important for us to understand and measure biodiversity, which is defined as the variability among living organisms in an ecosystem. Biodiversity can be measured at many different levels including genetic, species, community, and ecosystem. One way to measure biodiversity is to …

 Lab Bio

Stability of Floating Vessels

JoVE 10374

Source: Alexander S Rattner and Kevin Rao Li Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA


The objective of this experiment is to demonstrate the phenomenon of stability of floating vessels - the ability to self-right when rolled over to the side by some external force. Careful…

 Mechanical Engineering

Central Venous Access Device Dressing Change

JoVE 10311

Source: Madeline Lassche, MSNEd, RN and Katie Baraki, MSN, RN, College of Nursing, University of Utah, UT


Central venous access devices (CVAD), commonly known as central lines or central catheters, are large-bore intravenous (IV) catheters that are introduced into the central circulation. Typically, CVADs terminate in the superior vena…

 Nursing Skills

Preparing and Administering Secondary Intermittent Intravenous Medications

JoVE 10288

Source: Madeline Lassche, MSNEd, RN and Katie Baraki, MSN, RN, College of Nursing, University of Utah, UT


Secondary intravenous (IV) infusions are a way to administer smaller volume-controlled amounts of IV solution (25-250 mL). Secondary IV infusions are delivered over longer periods of time than IV push medications, which reduces the…

 Nursing Skills

Central Venous Catheter Insertion: Femoral Vein

JoVE 10240

Source: James W Bonz, MD, Emergency Medicine, Yale School of Medicine, New Haven, Connecticut, USA


Central venous access is necessary in a multitude of clinical situations, including vascular access, vasopressor and caustic medication delivery, central venous pressure monitoring, volume resuscitation, total parental nutrition,…

 Emergency Medicine and Critical Care

Common Lab Glassware and Uses

JoVE 10161

Source: Laboratory of Dr. Neal Abrams — SUNY College of Environmental Science and Forestry


Glassware is a regular appearance in the professional chemistry laboratory, because it has a relatively low cost, extreme durability, and specific levels of precision. While some labware is being supplemented with plastic or even everyday…

 General Chemistry
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