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What is the lower temperature limit for ion channels function?

What is the lower temperature limit for ion channels function?


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What is the cold-block temperature of ion channels? (not of nerves or axons)


The lower temperature limit of ion channels likely is dependent on various factors, including the type of channel and the recording conditions (tissue type, medium etc.). Reports on the suppression of voltage spikes (i.e., the inhibition of action potential firing) range from 1 to -20oC in squid axons, dependent on the species (Leuchtag, 2008). I couldn't find information on specific channels.

Reference
- Leuchtag, Voltage-Sensitive Ion Channels: Biophysics of Molecular Excitability (2008)


What is the lower temperature limit for ion channels function? - Biology

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  1. Take a worm tray, add water, and let it freeze overnight.
  2. Once you are ready, prepare your worm for an experiment as you previously have by anesthetizing it in either 10% ethanol solution or carbonated water.
  3. Place the worm on the three wooden islands, with the red (channel 1) on the left island and the white (channel 2) and ground electrode on the right island, as indicated below:


Conclusions

The recent developments in understanding thermal sensation by TRPs and transcriptional regulation of metabolism suggest that there is a universal regulatory system that integrates body temperature and metabolism among vertebrates. Endothermic adaptive thermogenesis may result from the same regulatory pathways as ectothermic metabolic acclimation, and both could be considered as adaptive metabolic responses to temperature variation(Fig. 4). The functional similarity is that in both groups metabolism is adjusted to compensate for potentially negative thermodynamic effects resulting from environmental temperature variation. In mammals, the result is that body temperature remains stable because of increased heat production resulting from greater tissue metabolic rates and uncoupling of mitochondrial electron transport from oxidative phosphorylation. In ectotherms, the result is that thermodynamic effects on cellular reaction rates are counteracted by quantity adjustments of mitochondria and proteins.

Most knowledge of thermoregulation and metabolism stems from few mammalian model species. Nonetheless, pathways of energy metabolism, and the nervous system are highly conserved among vertebrates(Ghysen, 2003 Smith and Morowitz, 2004). It is unlikely, therefore, that different groups of vertebrates have evolved fundamentally different regulatory systems. The implication is that metabolic acclimation and thermogenesis are the result of the same evolutionary process,except that endotherms have also evolved high resting metabolic rates, higher metabolic capacities and regulated uncoupling of mitochondrial electron transport from oxidative phosphorylation(Lowell and Spiegelman, 2000). As dramatic as these differences may seem, they are quantitative and not qualitative evolutionary differences. Hence, endothermy does not require the evolution of de novo structures or pathways, and all of the components necessary for endothermy are also present in ectotherms. The challenge now lies in determining how vertebrates differ in their capacity to respond to thermal variability.


Dangers of Too Much Serotonin

Always ask your doctor before taking any medication or supplement to increase low serotonin. Certain medications and supplements can raise serotonin levels too much, which can lead to serotonin syndrome.  

The symptoms of serotonin syndrome range from unpleasant to life-threatening and can include sudden swings in blood pressure, seizures, and loss of consciousness.

Serious cases of serotonin syndrome can be fatal if left untreated. If you or a loved one is showing symptoms of serotonin syndrome, call 911 or go to the nearest emergency room.


Ion Channels and the Diffusion of Ions

Figure 2. An ion channel. Pictured is a cross section of a typical potassium ion channel that spans the lipid bilayer. Most ion channels are composed of multiple subunits. In this example, the potassium channel is composed of four identical subunits (only two are shown). Potassium ions (shown as green dots) can flow through this channel in either direction. Ion channels are very selective for the ions that pass through them. Amino acids in the region of the channel, referred to as the selective filter, interact with the ions, and in the case of a potassium ion channel, only permit potassium ions across the membrane.

As was described above, lipid bilayers are not permeable to charged ions nevertheless, the movement of ions in and out of a cell is critical for their normal activity. Ions do not pass through the plasma membrane by simple diffusion rather, their transport is mediated by protein-lined channels termed ion channels. Ion transport through these channels is an example of passive transport because energy is not required and the movement of ions is driven by their concentration gradient. Passive transport is also called facilitated diffusion, because the proteins make the solute movement across a membrane possible and movement of the solutes is down the electrochemical gradient.

An ion channel provides a passage through which ions can traverse the membrane. However, an ion channel is not simply a "hole" in the membrane. An ion channel is extremely selective for the ion allowed through (i.e. distinct channels for each ion). A channel is composed of multiple subunits of integral membrane proteins that form a pore through the lipid bilayer (see Figure 2). In its simplest form, the ion channel is always open and the flow of ions is bidirectional. The specificity for a particular ion comes from the interactions between the ion and specific amino acids that form a ring inside the pore, which act as a selective filter (e.g. the potassium channel will only accommodate potassium ions). Ions pass through the pore in single-file and very rapidly (several thousand ions per millisecond). Many ion channels are gated, regulated to be in either the open or closed conformation. Gated ion channels will be described in greater detail in the tutorial entitled Membrane Potential, Ion Transport and Nerve Impulse, which focuses on the transport of ions and the function of nerve cells.

Movement through an ion channel is bidirectional and is determined, in part, by the concentration gradient. Ions will travel from the side of the membrane with the higher concentration to the side with the lower concentration. However, since ions are charged, the overall charge difference across the membrane must also be considered. It is thermodynamically favored for an ion to move across the membrane toward a solution of opposite charge. Therefore, when determining the deltaG of ion movement across a membrane, the ion concentration gradient and the charge differential across the membrane must be considered. The difference in charge across a membrane is referred to as the membrane electric potential, and it is measured in volts. The concentration gradient combined with the electric potential differences across a membrane is referred to as the electrochemical gradient. The deltaG of the movement for that ion across a membrane can be related to the electrochemical gradient of that ion. In the following equation, the deltaG for calcium moving into the cell is related to the electrochemical gradient of calcium:

R is the gas constant (1.987 cal/mol-K), T is the temperature in degrees K, [Ca 2+ ]in/[Ca 2+ ]out is the ratio of the calcium ion concentration inside the cell to the calcium ion concentration outside the cell, z is the charge of the ion (+2 for calcium), F is the Farady constant (23,062 cal/mol-V), and Vm is the plasma membrane electric potential, which is a unique property of each membrane. The plasma membrane electric potential, also called the membrane potential, for a typical animal cell is between -60 and -90 millivolts (mV). This indicates an accumulation of negative charge inside the cell, compared to outside the cell.

Similar to simple diffusion, ion channel transport is a thermodynamically spontaneous process that provides free energy available to the cell (i.e. a negative deltaG). The rate of ion channel transport at physiological ion concentrations normally found in the cell is proportional to the electrochemical gradient. For uncharged solutes, the electrochemical gradient is identical to the chemical gradient since the charge (z) is zero.


What are Proprioceptors?

Proprioceptors are a type of mechano-sensory neurons. They are usually present within muscles, tendons, and joints. There are different types of proprioceptors that are activated in different instances. It can be limb velocity and movement, limb load and limb limits. This is called proprioception or the sixth sense.

Proprioception is mainly mediated by the central nervous system and the stimuli such as vision and the vestibular system. Proprioceptors are distributed throughout the body. The three basic types of proprioceptors are muscle spindles, Golgi tendon organs, and Golgi tendons.

Figure 02: Proprioception

The activation of the proprioceptors takes place at the periphery. They are specific nerve endings that facilitate act on the proprioceptors. They are specific receptors for pressure, light, temperature, sound and other senses. These receptors are also mediated by ion gated channels. The proprioceptors also develop during embryonic development.


Vanilloid Receptors

CBD directly interacts with various ion channels to confer a therapeutic effect. CBD , for example, binds to TRPV1 receptors, which also function as ion channels. TRPV1 is known to mediate pain perception, inflammation and body temperature.

TRPV is the technical abbreviation for “transient receptor potential cation channel subfamily V.” TRPV1 is one of several dozen TRP (pronounced “trip”) receptor variants or subfamilies that mediate the effects of a wide range of medicinal herbs.

Scientists also refer to TRPV1 as a “vanilloid receptor,” named after the flavorful vanilla bean. Vanilla contains eugenol, an essential oil that has antiseptic and analgesic properties it also helps to unclog blood vessels. Historically, the vanilla bean has been used as a folk cure for headaches.

CBD binds to TRPV1 , which can influence pain perception.

Capsaicin—the pungent compound in hot chili peppers—activates the TRPV1 receptor. Anandamide, the endogenous cannabinoid, is also a TRPV1 agonist.


Effect of Pressure on the Solubility of Gases: Henry&rsquos Law

External pressure has very little effect on the solubility of liquids and solids. In contrast, the solubility of gases increases as the partial pressure of the gas above a solution increases. This point is illustrated in Figure (PageIndex<4>), which shows the effect of increased pressure on the dynamic equilibrium that is established between the dissolved gas molecules in solution and the molecules in the gas phase above the solution. Because the concentration of molecules in the gas phase increases with increasing pressure, the concentration of dissolved gas molecules in the solution at equilibrium is also higher at higher pressures.

Figure (PageIndex<4>): A Model Depicting Why the Solubility of a Gas Increases as the Partial Pressure Increases at Constant Temperature. (a) When a gas comes in contact with a pure liquid, some of the gas molecules (purple spheres) collide with the surface of the liquid and dissolve. When the concentration of dissolved gas molecules has increased so that the rate at which gas molecules escape into the gas phase is the same as the rate at which they dissolve, a dynamic equilibrium has been established, as depicted here. This equilibrium is entirely analogous to the one that maintains the vapor pressure of a liquid. (b) Increasing the pressure of the gas increases the number of molecules of gas per unit volume, which increases the rate at which gas molecules collide with the surface of the liquid and dissolve. (c) As additional gas molecules dissolve at the higher pressure, the concentration of dissolved gas increases until a new dynamic equilibrium is established. (CC BY-SA-NC anonymous)

The relationship between pressure and the solubility of a gas is described quantitatively by Henry&rsquos law, which is named for its discoverer, the English physician and chemist, William Henry (1775&ndash1836):

  • (C) is the concentration of dissolved gas at equilibrium,
  • (P) is the partial pressure of the gas, and
  • (k) is the Henry&rsquos law constant, which must be determined experimentally for each combination of gas, solvent, and temperature.

Although the gas concentration may be expressed in any convenient units, we will use molarity exclusively. The units of the Henry&rsquos law constant are therefore mol/(L·atm) = M/atm. Values of the Henry&rsquos law constants for solutions of several gases in water at 20°C are listed in Table (PageIndex<1>).

As the data in Table (PageIndex<1>) demonstrate, the concentration of a dissolved gas in water at a given pressure depends strongly on its physical properties. For a series of related substances, London dispersion forces increase as molecular mass increases. Thus among the Group 18 elements, the Henry&rsquos law constants increase smoothly from (ce) to (ce) to (ce).

Table (PageIndex<1>): Henry&rsquos Law Constants for Selected Gases in Water at 20°C
Gas Henry&rsquos Law Constant [mol/(L·atm)] × 10 &minus4
(ce) 3.9
(ce) 4.7
(ce) 15
(ce) 8.1
(ce) 7.1
(ce) 14
(ce) 392

Oxygen is Especially Soluble

Nitrogen and oxygen are the two most prominent gases in the Earth&rsquos atmosphere and they share many similar physical properties. However, as Table (PageIndex<1>) shows, (ce) is twice as soluble in water as (ce). Many factors contribute to solubility including the nature of the intermolecular forces at play. For a details discussion, see "The O2/N2 Ratio Gas Solubility Mystery" by Rubin Battino and Paul G. Seybold (J. Chem. Eng. Data 2011, 56, 5036&ndash5044),

Gases that react chemically with water, such as (ce) and the other hydrogen halides, (ce), and (ce), do not obey Henry&rsquos law all of these gases are much more soluble than predicted by Henry&rsquos law. For example, (ce) reacts with water to give (ce(aq)>) and (ce(aq)>), not dissolved (ce) molecules, and its dissociation into ions results in a much higher solubility than expected for a neutral molecule. Gases that react with water do not obey Henry&rsquos law. Henry&rsquos law has important applications. For example, bubbles of (ce) form as soon as a carbonated beverage is opened because the drink was bottled under (ce) at a pressure greater than 1 atm. When the bottle is opened, the pressure of (ce) above the solution drops rapidly, and some of the dissolved gas escapes from the solution as bubbles. Henry&rsquos law also explains why scuba divers have to be careful to ascend to the surface slowly after a dive if they are breathing compressed air. At the higher pressures under water, more N2 from the air dissolves in the diver&rsquos internal fluids. If the diver ascends too quickly, the rapid pressure change causes small bubbles of (ce) to form throughout the body, a condition known as &ldquothe bends.&rdquo These bubbles can block the flow of blood through the small blood vessels, causing great pain and even proving fatal in some cases. Due to the low Henry&rsquos law constant for (ce) in water, the levels of dissolved oxygen in water are too low to support the energy needs of multicellular organisms, including humans. To increase the (ce) concentration in internal fluids, organisms synthesize highly soluble carrier molecules that bind (ce) reversibly. For example, human red blood cells contain a protein called hemoglobin that specifically binds (ce) and facilitates its transport from the lungs to the tissues, where it is used to oxidize food molecules to provide energy. The concentration of hemoglobin in normal blood is about 2.2 mM, and each hemoglobin molecule can bind four (ce) molecules. Although the concentration of dissolved (ce) in blood serum at 37°C (normal body temperature) is only 0.010 mM, the total dissolved (ce) concentration is 8.8 mM, almost a thousand times greater than would be possible without hemoglobin. Synthetic oxygen carriers based on fluorinated alkanes have been developed for use as an emergency replacement for whole blood. Unlike donated blood, these &ldquoblood substitutes&rdquo do not require refrigeration and have a long shelf life. Their very high Henry&rsquos law constants for (ce) result in dissolved oxygen concentrations comparable to those in normal blood. The Henry&rsquos law constant for (ce) in water at 25°C is (1.27 imes 10^ M/atm), and the mole fraction of (ce) in the atmosphere is 0.21. Calculate the solubility of (ce) in water at 25°C at an atmospheric pressure of 1.00 atm. Given: Henry&rsquos law constant, mole fraction of (ce), and pressure Asked for: solubility Use Dalton&rsquos law of partial pressures to calculate the partial pressure of oxygen. (For more information about Dalton&rsquos law of partial pressures) Use Henry&rsquos law to calculate the solubility, expressed as the concentration of dissolved gas. A According to Dalton&rsquos law, the partial pressure of (ce) is proportional to the mole fraction of (ce): B From Henry&rsquos law, the concentration of dissolved oxygen under these conditions is To understand why soft drinks &ldquofizz&rdquo and then go &ldquoflat&rdquo after being opened, calculate the concentration of dissolved (ce) in a soft drink: bottled under a pressure of 5.0 atm of (ce) in equilibrium with the normal partial pressure of (ce) in the atmosphere (approximately (3 imes 10^ atm)). The Henry&rsquos law constant for (ce) in water at 25°C is (3.4 imes 10^ M/atm). Interactive resources for schools

Home / Homeostasis - blood sugar and temperature

Core temperature

The temperature in the core of the body not at the surface of the skin

Blood sugar

The sugar (glucose) dissolved in the blood the normal range is 4.0 - 7.8 mmol/l

Homeostasis

The maintenance of a constant internal environment in the body

Glucagon

A hormone produced by the pancreas. It causes the liver to convert glycogen back to glucose and to release glucose into the bloodstream.

Glossary

A list of often difficult or specialised words with their definitions.

Insulin

A hormone produced by the pancreas. It allows cells in the body to take in and store glucose.

Enzyme

Reusable protein molecules which act as biological catalysts, changing the rate of chemical reactions in the body without being affected themselves

Puberty

The time of gradual development of the secondary sexual characteristics and sexual maturity.

Glucose

A type of sugar: a mono saccharide with 6 carbon atoms (a hexose sugar).

The basic unit from which all living organisms are built up, consisting of a cell membrane surrounding cytoplasm and a nucleus.

Homeostasis - Sugar balance and temperature control

Homeostasis describes the functions of your body which work to keep your internal environment constant within a very narrow range. Two important aspects of homeostasis are balancing the blood sugar levels and maintaining the body temperature.

Your body is made up of millions of cells which need the conditions inside your body to be as constant as possible so they can work properly. However everything you do tends to change your internal conditions.

You take millions of new molecules into your body when you eat and digest food. Your blood sugar levels soar after you have a meal - but your cells use up the glucose fast when you exercise hard. You release heat energy every time you move about, the amount of water you take into and lose from your body varies all the time and your cells are constantly producing poisonous waste (see Homeostasis - the kidneys and water balance.)

The blood sugar levels in your body are coordinated by hormones, chemicals which regulate and balance the working of organs and cells. Hormones are made in endocrine glands and are carried around the body to their target organs in the blood stream.

Some hormones have long term effects, for example, the hormones that control how you grow and the changes that happen at puberty. Other hormones have shorter term effects. The hormones insulin and glucagon which control your blood sugar levels are like this.

It is important that the core temperature of your body stays within a very small range for the enzymes in the cells of your body to work properly. Your skin is one of the most important organs in the control of body temperature.



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