extreme biology lecture 7 - humans (pressure)

Question 1

what is pressure?

Answer 1

-Pressure is the amount of force applied at right angles to the surface of an object per unit area.
-The symbol for it is “p” or P.

Question 2

what is the calculation for pressure?

Answer 2

pressure (Pa) = the force normal to a surface (n) / area of the surface (m2)

Question 3

what are the effects of pressure on the human body varying on?

Answer 3

-total pressure
-duration of exposure to pressure
-state of activity (resting or exercising)
-temperature
-drugs in the body
-gas mixtures inspired
-rate of decent/ascent

Question 4

what is partial pressure?

Answer 4

The pressure exerted by an individual gas in a mixture is known as its partial pressure

Question 5

what are martinis law?

Answer 5

-Reduced mental acuity
-Perception of time affected
-Perceptual narrowing
-Light-headedness
-Vomiting

Question 6

what are the bends?

Answer 6

• Decompression sickness (DCS)
• Retention of dissolved nitrogen on
  decompression
  -Causes bubbles

Symptoms:
Joint pain, Rashes, Paralysis, Death

Question 7

what happens above 8000m - the death zone

Answer 7

14 summits above 8000m
-Extreme hypoxia
- O2 used up faster than it can be
replenished
- No human can acclimatize
-Rapid deterioration of bodily
functions
-Loss of consciousness

Question 8

what happens during extreme oceanic pressures?

Answer 8

-ear and sinus pressure
-ruptured capillaries
-blackout
-inability to inspire gasses
-collapsed lungs
-the bends
-death
-nitrogen narcosis

Question 9

what happens under high altitudes?

Answer 9

-Density of air is not constant
-Altitude increase = non-linear air density decrease
- Air ‘gets thinner’

Question 10

how do human acclimatise to altitude

Answer 10

• Occur > 4 days at altitude
• Adaptation can be approximated by multiplying
  the altitude in kilometres by 11.4 days
  -Erythropoietin (EPO) produces more
  haemoglobin
• Increased ability to transport oxygen
  -Decreased plasma volume
• Increased capillarisation in skeletal muscle tissue
  -Increased muscle mitochondria
  -Right ventricular hypertrophy

Question 11

what are the effects of no pressure? such as space

Answer 11

• No gravity to move blood and
  other body fluids to legs – “puffy
  head, chicken legs”
• Reduced cardiac work – decreased
  CO
• Muscle wastage
• Reduction in bone density
• Dizziness

Question 12

what happens during acute exposure?

Answer 12

When humans are exposed to altitude >5500m
 Partial Pressure of Oxygen (PaO2) decreases with altitude
 1/3 of sea level POa2 at Everest summit (8848m)
 Arterial PO2 reduced
 Plasma volume decreases by ~20%
 Sensed by carotid body chemoreceptors:
 Increased respiratory rate
 Increased heart contractility and rate
 Increased urination
 Non-essential body functions suppressed