concentric

Examples of concentric in the following topics:

• Principles of Electricity

  • Diffusion arises from the statistical tendency of particles to redistribute from regions where they are highly concentrated to regions where the concentration is low .
  • Differences in concentration of ions on opposite sides of a cellular membrane lead to a voltage called the membrane potential.
  • Many ions have a concentration gradient across the membrane, including potassium (K+), which is at a high inside and a low concentration outside the membrane.
  • Sodium (Na+) and chloride (Cl–) ions are at high concentrations in the extracellular region, and low concentrations in the intracellular regions.
  • These concentration gradients provide the potential energy to drive the formation of the membrane potential.

• Chemoreceptor Regulation of Breathing

  • Chemoreceptors detect the levels of carbon dioxide in the blood by monitoring the concentrations of hydrogen ions in the blood.
  • The respiratory chemoreceptors work by sensing the pH of their environment through the concentration of hydrogen ions.
  • Without that carbon dioxide, there will be less carbonic acid in blood, so the concentration of hydrogen ions decreases and the pH of the blood rises, causing alkalosis.
  • As bicarbonate levels decrease while hydrogen ion concentrations stays the same, blood pH will decrease (as bicarbonate is a buffer) and become more acidic.
  • In cases of acidosis, feedback will increase ventilation to remove more carbon dioxide to reduce the hydrogen ion concentration.

• Interactions of Hormones at Target Cells

  • The regulation of blood glucose concentration (through negative feedback) illustrates how the endocrine system maintains homeostasis by the action of antagonistic hormones.
  • These cells control blood glucose concentration by producing the antagonistic hormones insulin and glucagon.
  • When the concentration of blood glucose rises, such as after eating, beta cells secrete insulin into the blood.
  • In response, glucose concentration decreases in the blood, and insulin secretion discontinues through negative feedback from declining levels of glucose.
  • When the concentration of blood glucose drops, such as during exercise, alpha cells secrete glucagon into the blood.

• Body Fluid Composition

  • The concentrations of the other ions in cytosol or intracellular fluid are quite different from those in extracellular fluid.
  • In contrast to extracellular fluid, cytosol has a high concentration of potassium ions and a low concentration of sodium ions.
  • The reason for these specific sodium and potassium ion concentrations are Na+/K ATPase pumps, which facilitate the active transport of these ions.
  • These pumps transport ions against their concentration gradients to maintain cytosol fluid composition of ions.
  • Ocular fluid in the eyes contrasts cerebrospinal fluid by containing high concentrations of proteins, including antibodies.

• Types of Muscle Contractions: Isotonic and Isometric

  • Isotonic muscle contractions can be either concentric or eccentric.
  • A concentric contraction is a type of muscle contraction in which the muscles shorten while generating force, overcoming resistance.
  • For example, when lifting a heavy weight, a concentric contraction of the biceps would cause the arm to bend at the elbow, lifting the weight towards the shoulder.
  • For example, a voluntary eccentric contraction would be the controlled lowering of the heavy weight raised during the above concentric contraction.
  • An isotonic concentric contraction results in the muscle shortening, an isotonic eccentric contraction results in the muscle lengthening.

• Alkalosis

  • Alkalosis refers to a condition reducing hydrogen ion concentration of arterial blood plasma (alkalemia).
  • This is the result of decreased hydrogen ion concentration, leading to increased bicarbonate or alternatively a direct result of increased bicarbonate concentrations.
  • A Davenport Diagram, as shown, is a graphical tool developed by Allan Jones Davenport that allows a clinician or investigator to describe blood bicarbonate concentrations and blood pH following a respiratory and/or metabolic acid-base disturbance.

• Postabsorptive State

  • This phenomenon is due largely to greater lipid and lower carbohydrate availability, as plasma non-esterified fatty acid (NEFA) concentrations rise in response to lower insulin and higher counter-regulatory hormone concentrations.
  • However, there has not yet been any convincing evidence of the involvement of glucagon in post-absorptive plasma glucose concentration maintenance.
  • This indicates that there is support of post-absorptive plasma glucose concentrations from glucagon, when in concert with insulin.
  • Changes in plasma glucose concentrations also result from changes in glucose production, but not from glucose utilization.
  • Both scenarios result in much higher plasma glucose concentrations.

• Exercise-Induced Muscle Damage

  • Exercise damages muscles due to eccentric and concentric muscle loading and often results in delayed onset muscle soreness (DOMS).
  • Exercise damages muscles due to eccentric and concentric muscle loading.
  • Acute inflammation of the muscle cells, as understood in exercise physiology, can result after induced eccentric and concentric muscle training.
  • Damage to the sarcomeres causes aninflux of white blood cells, leading to inflammation, which is itself associated with increased plasma enzyme concentration, myoglobinemia, and abnormal muscle structure and histology.

• Dalton's Law of Partial Pressure

  • The air in the atmosphere is a mixture of many different gases, that vary in concentration.
  • Dalton's law also implies that the relative concentration of gasses (their partial pressures) does not change as the pressure and volume of the gas mixture changes, so that air inhaled into the lungs will have the same relative concentration of gasses as atmospheric air.
  • In the lungs, the relative concentration of gasses determines the rate at which each gas will diffuse across the alveolar membranes.
  • While inhaled air is similar to atmospheric air due to Dalton's law, exhaled air will have relative concentrations that are in between atmospheric and alveolar air due to the passive diffusion of gasses during gas exchange.

• Circumventricular Organs

  • Circumventricular organs are situated adjacent to the brain ventricles and sense concentrations of various compounds in the blood.
  • As a result, neurons located in circumventricular organs can directly sense the concentrations of various compounds, particularly peptide hormones, in the bloodstream without the need for specialized transport systems that move those compounds across the blood-brain barrier.