Effects of acceleratory forces on the body in aviation and space physiology

Effects of acceleratory forces on the body in aviation and space physiology

• Because of rapid changes in velocity and direction of motion in airplanes or spacecraft, several types of acceleratory forces affect the body during flight

• Centrifugal Acceleratory Forces F= (mv2)/r

Measurement of acceleratory force—“G”

• Weight of aviator on his seat due to gravity - intensity of this force is said to be +1 G

• If this force increase – Positive G• If this force increase – Negative G

Positive G

• blood centrifuge to lower extremities• Venous pooling, decreased cardiac output• Effects on the Vertebrae- causes fracture • “Black out” • Unconsciousness followed by death

Negative G

• causing intense momentary hyperemia of the head

• cerebral blood pressure reaches 300 to 400 mm Hg,

• “red-out” due to hyperemia in eye

Protection of the body against centrifugal acceleratory forces.

• Tightening abdominal muscles and leans forward prevents venous pooling

• “Anti- G suits” compress legs & abdomen to prevents venous pooling

Effects of linear acceleratory forces on the body

Deceleratory forces associated with parachute jumps.parachuting aviator leaves the airplane, his velocity of fall is at

first• exactly 0 ft/sec• 32 ft/sec • 64 ft/sec• At 12th sec 110 miles/hr reaching terminal velocity• “Opening shock load” up to 1200 pounds occur when

parachute is opened

• the speed of landing is about 20 ft/Sec cause damage to body resulting in fracture of his pelvis, vertebrae or leg.

• the trained parachutist strikes the earth with knees bent but muscles taut to cushion the shock of landing.

“Artificial Climate” in the Sealed Spacecraft

• there is no atmosphere in outer space• an artificial atmosphere and climate must be

produced in a spacecraft• Atmosp pressure 760mmHg• Prolong space travel: needs recycle of oxygen

Weightlessness in Space

• near-zero G force - microgravity

Physiologic problems of weightlessness (Microgravity).

• motion sickness during the first few days of travel

• translocation of fluids within the body because of failure of gravity to cause normal hydrostatic pressures

• diminished physical activity because no strength of muscle contraction is required to oppose the force of gravity

Effects of prolonged stay in space

• decrease in blood volume• decrease in red blood cell mass• decrease in muscle strength and work capacity• decrease in maximum cardiac output• loss of calcium and phosphate from the bones, as

well as loss of bone mass

Cardiovascular, muscle, and bone “Deconditioning” duringprolonged exposure to weightlessness.

• decreased work capacity, reduced blood volume, impaired baroreceptor reflexes, and reduced orthostatic tolerance

• Susceptible to bone fractures• Artificial gravity

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