Environmental and Psychological stress factors (chapt. 3) Flashcards
motion stressor
high frequency vibration, low frequency vibration,motion sickness
vibrations
whole body vibration, hand and arm vibration,vibration measurement. Vibration is simple or complex oscillatory motion. Human vibration exposure is measures by its properties magnitude of acceleration, frequency,direction, and exposure time
physiological effect of vibration
each part of the human body has its own resonance frequency, therefore, it reacts differently to different frequencies. It can manifest itself as increased pulse rate or respiratory rate or more seriously as aliments of spinal muscle, and-rectal or gastro-intestinal systems.
physiological effect of vibration
The human responses to vibration depend also on which part of the body is affected there are 2 major types of human exposure to vibration: vibration transmitted to the whole body and applied to a part of the body.
Whole-body and segmental are the two major types of human exposure to vibration.
vibration measurement
vibration is simple or complex oscillatory motion. Human vibration exposure is measured by its properties:magnitude of acceleration,frequency,direction, and exposure time
vibration and performance
performance effects on eye-hand coordination, visual tasks,reading,precision tasks, low frequency vibration and motion sickness decoupling between the visual and vestibular inputs ship, airplanes, and closed cab: military tanks
vibration reduction
source control, path control, receiver control
thermal stressors
cold, heat, air quality
comfortable heat
most people feel comfortable when the air temperature is between 20 degrees C and 27 degrees C when relative humidity ranges from 35 to 60%
Thermal balance
heat exchange between the person and the environment
S=M+C+R+K+E
storage rate-is the cumulative effect of the other factors and the indicator of risk for hyperthermia
metabolic rate- is largely driven by the amount of external work performed
convection-is the net flow of heat between the skin and air, some of which may occur through clothing
radiation-is the net rate of heat flow between the person and the solid surroundings caused by infrared radiation
conduction (k)-occurs when there is direct contact between the person and a solid surface in the workplace. The contact can occur through some clothing.
evaporative cooling-is the loss of her due to evaporation of swear from the skin.
Heat stress
is the net (overall) heat burden on the body from the combination of the body heat generated while working environmental sources (air temperature, humidity, air movement, radiation from these or hot surfaces/sources) and clothing requirements.
in door, outdoor, high humidity
cold stress
hypothermia is a condition marked by abnormally low internal body temperature. it develops when body heat is lost to a cool or cold environment faster that it can be replaced.
thermal comfort
work environment climate, work demand,clothing
Factors affecting thermal comfort air temperature, humidity,thermal radiation, air movement
heat
indirect affecting the efficiency of information processing long term effects dehydration, heat stork and exhaustion
cold
indirect effect disruption of coordinated motor performance coordinated by hands and fingers
psychosocial stressors
perceived threat of harm loss of esteem
cognitive appraisal
fail to perceive the circumstance of risk, fail to understand the risk, overconfidence,more in control of the situation rather than the soother agents are in control
Level of arousal
stressful circumstances of anxiety and danger produce an increase in physiological arousal such as heart rate, pupil diameter, hormonal chemistry,
arousal
the concept of arousal has been a major aspect of many learning theories and is closely related to other important concepts such as anxiety, attention, attention,a nd motivation
York’s Dodson Law
predicts a reverse u-shaped function between arousal motivation and performance. Across a broad range of experimental settings, it has been shown that both low and high levels of arousal produce minimum performance whereas a moderate level of arousal results in maximum performance in a test. This suggest that too little or too much stimulation tends to be ignored by individuals.
normal distribution
Performance and over-arousal
perceptual or attentional narrowing or tunneling the tendency to restrict the range or breathe of attention, to concentrate very hard on only one things and to ignore surrounding information sources.
working memory loss
under stress people appears to be less capable using working memory to store or rehears new material or to perform computation an other attention demanding mental activities.
strategic shifts
tendency to do something now speed accuracy trade off
workload and stress
stress can be imposed by having too much to do in too little time.
Timeline model
ratio of the time required (to do task) to the time available (to do them in) time required/time available
Timeline
hypothetical relationship between workload imposed by task, measured by TR/AD and workload experienced and performances
Vigilance and under arousal
cause of the vigilance decrement time longer duration greater misses, event salience: Lout Bright Intermittent, Signal rate: Relatively low rate-detection reduce. Vigilance remediation not to be too long vigil tasks. fairly frequent break, more salient signals,detecting signal through payoffs
Fatigue and Steep Disruption
sleep deprivation or sleep loss:Less than 7 to 9 hours of sleep per night
circadian rhythms
are physical, mental and behavioral changes that follow a roughly 24hr cycle, responding primarily to light and darkness in an organisms environment
What disrupt the circadian rhythms
- jet lag
- shift work
