User:Cwelsh3/sandbox

What is already there:

A receptor potential, also known as a generator potential, a type of graded potential, is the transmembrane potential difference produced by activation of a sensory receptor.

A receptor potential is often produced by sensory transduction. It is generally a depolarizing event resulting from inward current flow. The influx of current will often bring the membrane potential of the sensory receptor towards the threshold for triggering an action potential.

An example of a receptor potential is in a taste bud, where taste is converted into an electrical signal sent to the brain. When stimulated, the taste bud triggers the release of neurotransmitter through exocytosis of synaptic vesicles from the presynaptic membrane. The neurotransmitter molecules diffuse across the synaptic cleft to the postsynaptic membrane of the primary sensory neuron, where they elicit an action potential.

My Version

Receptor Potential

Receptor potential is a type of change in the potential difference across a membrane. Receptor potentials occur in the sensory neurons of the central nervous system, at the peripheral ends. When a sensory neuron receives a stimulus, it must transfer this information into a form the body can comprehend and use to make the correct response; a process known as sensory transduction. Sensory receptors most commonly function by controlling ion channels, allowing the influx or removal of charged molecules. The control of ion channels allows the neuron to allow certain ions to come in, or stay out. By allowing ions to flow in or out, the neuron is able to create a charged gradient across the membrane. Receptor potential can work to trigger an action potential either within the same neuron or on an adjacent cell. Within the same neuron, a receptor potential can cause local current to flow to a region capable of generating an action potential and open voltage gated channels. A receptor potential can cause the release of neurotransmitters from one cell that will act on another cell, generating an action potential in the second cell. The magnitude of the receptor potential determines the frequency with which action potentials are generated, and is controlled by adaption, stimulus strength, and temporal summation of sucessive receptor potentials. Receptor potential relies on receptor sensitivity and can adapt slowly, resulting in a slowly decaying receptor potential or rapidly, resulting in a quickly generated but short lasting receptor potential.

Examples in the Human Body

End Plate Potential

Temperature

Sensory neurons in the body called thermoreceptors use a proteins called transient receptor potential proteins (TRP) to generate receptor potentials. The TRP protein serves as a nonspecific cation channel and when activated by different ranges of temperatures allows an inward flux of sodium ions that depolarizes the cell. This receptor potential then creates an action potential along the afferent neurons leading to the brain. A receptor potential can also be generated with TRP proteins bind to different chemicals, such as ethanol or capsaicin, providing the body with the feeling of either being hot or cold.

Gustation

Two of the the three types of gustation receptor cells, types II and III, generate receptor potentials in response to chemicals. Cell type II, which responds to the chemicals of bitter, sweet, and umami tastes, creates a receptor potential through the use of G-protein coupled receptors . When activated, the G-protein coupled receptors initiate a second messenger cascade that releases calcium from intracellular stores which then acts to open monovalent cation channel TRMP5. Upon depolarization, the cell releases a neurotransmitter that will generate an action potential in an afferent neuron. Type III taste cells respond to acids associated with sour tastes and uses a nonselective cation channel called PKD2L1 to depolarize the cell. Additionally, the hydrogen ions block K+ channels in the cell, minimizing K+ leak and aiding in the cell's depolarization.

Description

This site is run by Clayton Welsh.

The article I am editing is "Receptor Potential." We have covered receptor potential in class which should be helpful. The article is very limited and offers a poor definition of what receptor potential is. I plan to expand on the definition, talk about how receptor potential fits into the signal transduction pathway, and then talk about how receptor potential can be altered and changed by some of the common mechanisms in the body such as Na+ and Cl- channels.

Posted above is the current draft of my wikipedia article.

I have now changed my topic to Respiratory Quotient. The lead to the article needs a great deal more explaining, as does the applications.

Respiratory Quotient

Lead

The respiratory quotient (or RQ or respiratory coefficient), is a dimensionless number used in calculations of basal metabolic rate (BMR) when estimated from carbon dioxide production. It is calculated from the ratio of carbon dioxide produced by the body to oxygen consumed by the body. Such measurements, like measurements of oxygen uptake, are forms of indirect calorimetry. It is measured using a respirometer. The Respiratory Quotient value indicates which macronutrients are being metabolized, as different energy pathways are used for fats, carbohydrates, and proteins. A value of 0.7 indicates that lipids are being metabolized, 0.8 for proteins, and 1.0 for carbohydrates. The approximate respiratory quotient of a mixed diet is 0.8.

It can be used in the alveolar gas equation.

Clinical Uses

Respiratory Quotient can be used as an indicator of over or underfeeding. Underfeeding, which forces the body to utilize fat stores, will lower the respiratory quotient while overfeeding, which causes lipogenesis, will increase it. Underfeeding is marked by a respiratory quotient below 0.85, while a respiratory quotient greater than 1.0 indicates overfeeding. This is particularly important in patients with compromised respiratory systems, as an increased respiratory quotient significantly corresponds to increased respiratory rate and decreased tidal volume, placing compromised patients at a significant risk.

Because of its role in metabolism, respiratory quotient can be used in analysis of liver function and diagnosis of liver disease. In patients suffering from liver cirrhosis, non-protein respiratory quotient (npRQ) values act as good indicators in the prediction of overall survival rate. Patients having a npRQ < 0.85 show considerably lower survival rates as compared to patients with a npRQ > 0.85. A decrease in npRQ corresponds to a decrease in glycogen storage by the liver. Similar research indicates that non-alcholic fatty liver dieases is also accompanied by a low respiratory quotient value, and the non protein respiratory quotient value was a good indication of disease sevarity.

Affects of L-Caratine

Numerous studies show that an increase in dietary caratine leads to a decrease in the respiratory quotient, indicating an

From the Textbook

Notes

The amount of oxygen body cells consume and the amount of carbon dioxide produced are not identical and depend upon what nutrients are broken down for energy. The respiratory quotient gives the ratio of carbon dioxide produced to oxygen consumes. The approximate respiratory quotient of a mixed diet is 0.8.

Sources

Supplementation of L-Carnitine in Athletes: Does It Make Sense?

Feedback

Hi, great job on starting to add information for receptor potential, especially about the different sensory systems such as gustation. For the temperature section, if there is information about the receptor potential involvement in feedback systems such as feedforward regulation I would suggest briefly mentioning after "...being hot or cold." Also, you could elaborate on which afferent neuron the taste receptor(s) trigger. Hope this helps. C.q20n.17 (talk) 16:16, 1 March 2017 (UTC)