resistance

Examples of resistance in the following topics:

• Factors Affecting Pulmonary Ventilation: Airway Resistance

  • Airway resistance refers to resistance in the respiratory tract to airflow.
  • Airway resistance can change over time, especially during an asthma attack when the airways constricts causing an increase in airway resistance.
  • Below is the equation for calculating airway resistance (R).
  • Therefore the resistance to air in the bronchi is greater than the resistance to air in the trachea.
  • Laminar flow (a) has orderly layers and low resistance.

• Introduction to Blood Flow, Pressure, and Resistance

  • Resistance to flow must be overcome to push blood through the circulatory system.
  • If resistance increases, either pressure must increase to maintain flow, or flow rate must reduce to maintain pressure.
  • Numerous factors can alter resistance, but the three most important are vessel length, vessel radius, and blood viscosity.
  • With increasing length, increasing viscosity, and decreasing radius, resistance is increased.
  • The resistance offered by peripheral circulation is known as systemic vascular resistance (SVR), while the resistance offered by the vasculature of the lungs is known as pulmonary vascular resistance (PVR).

• The Resistance Reaction

  • Resistance is the second stage of the general adaptation syndrome, where the body has an increased capacity to respond to the stressor.
  • The organism's resistance to the stressor drops temporarily below the normal range and some level of shock (e.g., circulatory shock) may be experienced.
  • Resistance is the second stage and the increased secretion of glucocorticoids plays a major role by intensifying the systemic response.
  • Resistance reaction is the second stage of the general adaptation syndrome and is characterized by a heightened resistance to a stressor.
  • Explain how the endocrine system reacts to stress in the resistance stage

• Muscular Arteries

  • Distributing arteries are medium-sized arteries that draw blood from an elastic artery and branch into resistance vessels.
  • Muscular or distributing arteries are medium-sized arteries that draw blood from an elastic artery and branch into resistance vessels, including small arteries and arterioles.

• Velocity of Blood Flow

  • At its simplest, imagine a perfect, rigid tube with no resistance and with a homogeneous liquid flowing through in a perpendicular manner.
  • Resistance is the force that must be overcome by pressure in order for flow to occur, and is a factor of vessel length, diameter, surface composition, and the viscosity of the liquid flowing through.
  • As resistance increases the difference in pressure which influences velocity decreases, which in turn reduces flow.
  • However, pathological changes in blood vessels that result in narrowing or an increase in surface resistance can lead to a reduction in pressure, velocity, and thus flow, which can in turn lead to tissue damage.
  • Increases in viscosity such as reduced water content lead to increases in resistance and thus reduction in flow.

• Exhaustion

  • The organism's resistance to the stressor drops temporarily below the normal range and some level of shock may be experienced.
  • Resistance is the second stage.

• Metabolic Changes

  • Protein and carbohydrate metabolism are affected during pregnancy and maternal insulin resistance can lead to gestational diabetes.
  • Maternal insulin resistance can lead to gestational diabetes.

• Principles of Electricity

  • The amount of charge that moves between two points depends on two factors: voltage and resistance.  
  • Resistance is the hindrance to the flow of charge.
  • Some substances with high resistance are insulators, like the myelin sheath.

• Antimicrobial Proteins

  • Bacteria can develop resistance to antimicrobial peptides (as well as separate resistances to antibiotics and other antimicriobials).
  • Bacteria like staphylococcus aureas, which forms the highly resistant MRSA strain, can reduce the negativity of the charge of its cell membrane by bringing amino acids from the cytoplasm into its cell membrane so antimicrobial peptides won't bind to it.
  • Other forms of antimicrobial resistance include producing enzymes that inhibit the antimicrobial peptides, altering the hydrophobic forces on the cell membrane, and capturing antimicrobial peptides in vesicles on the cell membrane to remove them from the bacterium.
  • Additionally, commensal bacteria have developed antimicrobial resistance to peptides , but they are normal flora of the body.

• Hypertension

  • In most people with established essential (primary) hypertension, increased resistance to blood flow (total peripheral resistance) accounts for the high pressure while cardiac output remains normal.
  • This increased peripheral resistance is mainly attributable to structural narrowing of small arteries and arterioles, although a reduction in the number or density of capillaries may also contribute.