turgor pressure

Examples of turgor pressure in the following topics:

• Osmoregulation

  • This inflow of water produces turgor pressure, which stiffens the cell walls of the plant.
  • In nonwoody plants, turgor pressure supports the plant.
  • Plants lose turgor pressure in this condition and wilt .
  • Without adequate water, the plant on the left has lost turgor pressure, visible in its wilting; the turgor pressure is restored by watering it (right).
  • The turgor pressure within a plant cell depends on the tonicity of the solution in which it is bathed.

• Pressure, Gravity, and Matric Potential

  • Pressure potential is also called turgor potential or turgor pressure and is represented by Ψp.
  • Positive pressure inside cells is contained by the cell wall, producing turgor pressure in a plant.
  • Turgor pressure ensures that a plant can maintain its shape.
  • A plant's leaves wilt when the turgor pressure decreases and revive when the plant has been watered .
  • When (b) the total water potential is higher outside the plant cells than inside, water moves into the cells, resulting in turgor pressure (Ψp), keeping the plant erect.

• Gas Pressure and Respiration

  • Gas pressures in the atmosphere and body determine gas exchange: both O2 and CO2 will flow from areas of high to low pressure.
  • Each gas component of that mixture exerts a pressure.
  • The pressure for an individual gas in the mixture is the partial pressure of that gas.
  • The pressure of the water vapor in the lung does not change the pressure of the air, but it must be included in the partial pressure equation.
  • For this calculation, the water pressure (47 mm Hg) is subtracted from the atmospheric pressure: 760 mm Hg 47 mm Hg = 713 mm Hg, and the partial pressure of oxygen is: (760 mm Hg 47 mm Hg) 0.21 = 150 mm Hg.

• Blood Pressure

  • Blood pressure is the pressure of blood against the blood vessel walls during the cardiac cycle; it is influenced by a variety of factors.
  • Blood pressure is the pressure of the fluid (blood) against the walls of the blood vessels.
  • Fluid will move from areas of high to low hydrostatic pressures.
  • The systolic pressure is defined as the peak pressure in the arteries during the cardiac cycle; the diastolic pressure is the lowest pressure at the resting phase of the cardiac cycle.
  • The blood pressure of the systole phase and the diastole phase gives the two readings for blood pressure .

• Basic Principles of Gas Exchange

  • Partial pressure (Px) is the pressure of a single type of gas in a mixture of gases.
  • For example, in the atmosphere, oxygen exerts a partial pressure, and nitrogen exerts another partial pressure, independent of the partial pressure of oxygen (Figure 1).
  • Total pressure is the sum of all the partial pressures of a gaseous mixture.
  • A gas will move from an area where its partial pressure is higher to an area where its partial pressure is lower.
  • The sum of the partial pressures of all the gases in a mixture equals the total pressure.

• The Mechanics of Human Breathing

  • The relationship between gas pressure and volume helps to explain the mechanics of breathing.
  • As volume decreases, pressure increases and vice versa .
  • Due to this increase in volume, the pressure is decreased, based on the principles of Boyle's Law.
  • This decrease of pressure in the thoracic cavity relative to the environment makes the cavity pressure less than the atmospheric pressure .
  • This increases the pressure within the thoracic cavity relative to the environment.

• Other Hormonal Controls for Osmoregulation

  • The renin-angiotensin-aldosterone system (RAAS) stabilizes blood pressure and volume via the kidneys, liver, and adrenal cortex.
  • Defective renin production can cause a continued decrease in blood pressure and cardiac output.
  • Thus, via the RAAS, the kidneys control blood pressure and volume directly.
  • Medically, blood pressure can be controlled by drugs that inhibit ACE (called ACE inhibitors).
  • The renin-angiotensin-aldosterone system increases blood pressure and volume.

• Gas Exchange across the Alveoli

  • Since this pressure gradient exists, oxygen can diffuse down its pressure gradient, moving out of the alveoli and entering the blood of the capillaries where O2 binds to hemoglobin.
  • Oxygen and carbon dioxide move independently of each other; they diffuse down their own pressure gradients.
  • This pressure gradient drives the diffusion of oxygen out of the capillaries and into the tissue cells.
  • The pressure gradient drives CO2 out of tissue cells and into the capillaries.
  • The partial pressures of oxygen and carbon dioxide change as blood moves through the body.

• Hormonal Regulation of the Excretory System

  • The reabsorption of Na+ also results in the osmotic reabsorption of water, which alters blood volume and blood pressure.
  • Aldosterone production can be stimulated by low blood pressure, which triggers a sequence of chemical release .
  • When blood pressure drops, the renin-angiotensin-aldosterone system (RAAS) is activated.
  • ADH and aldosterone increase blood pressure and volume.
  • This increases water retention and blood pressure.

• Somatosensory Receptors

  • They contain mechanically-gated ion channels whose gates open or close in response to pressure, touch, stretching, and sound.
  • Light touch, also known as discriminative touch, is a light pressure that allows the location of a stimulus to be pinpointed.
  • They respond to fine touch and pressure, but they also respond to low-frequency vibration or flutter.
  • Pacinian receptors detect pressure and vibration by being compressed which stimulates their internal dendrites.
  • Pacinian corpuscles detect transient pressure and high-frequency vibration.