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8. Discuss two effects of the environment on physiological processes

Physiology: Branch of biology that deals with the normal functions of organisms and their parts. How your body reacts.

Environment: Stress + Jetlag

What is stress?
1. An internal automatic bodily/biological reaction to external stimuli
2. Our emotional and physiological reactions to situations in which we feel in conflict or threatened beyond our capacity to cope or endure.
3. An interaction between stimulus and response that depends on cognitive appraisal of the situation. Again, depends on our perception of our ability to cope.
If we feel that something is beyond our control and we are unable to cope with it, then we start to feel the symptoms of stress, such as pressure, emotion, and physical effects. E.g. Heart races.

How we know we have stress

  1. Experience an external stimuli
  2. Then use cognitive appraisal to evaluate the outcome
  3. If we cannot cope or overcome external stimuli, we have stress

Summary: Stress is “A pattern of negative physiological states and psychological responses occurring in situations where people perceive threats to their well being which they may be unable to meet” Lazarus and Folkman (1984)

[Stressor stimuli] ——> [Cognitive appraisal] ——> [Stress response]
Demanding -ve              perceive a mismatch           physiological and psychological
e.g. work, pollution       concludes out of control      e.g lack of sleep / depression

Body’s response to stress

  1. Stressful stimuli
  2. Hypothalamus stimulates pituitary gland
  3. Gland secretes hormones
  4. This stimulates adrenal gland
  5. This produces other hormones such as adrenaline
  6. Stimulates sympathetic nervous system
  7. Results in body’s internal physiological changes e.g. increase heart rate

Short term stress: Adrenaline - Adrenal glands and cortisol and it increases heart rate. This makes you very focus and the ability to get what you need to get done shoots up. Secretion of hormones makes him stiff and there is blood rush to the brain so you can think faster. Positive response to stress.

Long term stress: High blood pressure, hard to sleep, affects one’s life negatively

Stress can be useful: To increase performance levels (in Short Term)

Emotional feelings associated with stress: Pissed off, sad, irritated
Cognitions: Ability to think fast, effects autonomic system, affect all glands and organs
affects hypothalamus, CRF, stimulates pituitary gland, releases hormones.
Physical effects (physiological): grind teeth more, poor sleep patterns, tension in muscles, poor decisions that affect negatively in body. More likely to get sick.

Cognitive response: According to Yerkes-Dodson Law - relationship between our levels of arousal and ability to function effectively.
1. As arousal increases, performance on tasks of moderate difficulty first rise but then eventually decline.
2. If you are too laid back your performance also declines.

What is the physiological impact of stress
1. Ulcers
2. Coronary Heart Disease
3. Cancer
4. Immune system
Illness, link to an environmental stressor, relevant evidence, evaluation points

immune system and stress:
Physiological effects - associated illnesses

  • Headaches (Gannon et al., 1987)
  • Asthma (Miller and Strunk, 1979)
  • Colds (Stone et al., 1987)
  • Stomach ulcers (Brady, 1958)
  • Cancer (Jacobs and Charles, 1980)

Reduced resistance to infection — Long term stress can affect the immune system as corticosteroids suppress its activity and thereby increasing vulnerability to infection.

Cohen et al. (1993) - If participants experience higher levels of stress along with negative emotions within the previous year, they would develop more colds.

Heart and circulatory disorders — Stress triggers the release of glucose or fatty acids into the blood stream that may deteriorate and block the vessels, therefore resulting in the increase in cardiovascular disorder.
Stress-induced negative affect and behaviour — Stress indirectly causes illness and negative emotions and behaviour. (e.g. not enough sleep, lack of exercise etc.)

Psychological effects (emotional)

  • Anger and frustration
  • Depression and helplessness
  • Anxiety

Other research/experiments:

  • Haynes and Feinleib (1980)
  • Marmot et al. (1997)



  • The hormone melatonin controls our circadian rhythm (approx 24 hours long)
  • more melatonin, we feel more sleepy

How melatonin is controlled:

  • Light enters eyes
  • signal transmitted by the optic nerve to the Suprachiasmatic Nucleus (SCN)
  • SCN sends signal to pineal gland, where melatonin is created
  • melatonin production is adjusted according to light levels
  • more melatonin when it is dark

What is Jet Lag?
It is the mismatch of old circadian rhythm and zeitgebers (external environmental factors) such as mealtimes, light levels
- happens when you cross multiple time zones

Experiments to examine how the effects of jet lag on the circadian rhythm can differ in severity according to variables: Waterhouse et al. and Block and Davidson
*** the results of Waterhouse et al and Block and Davidson contradict… read Waterhouse et al. fully to find out…….

- Another variable that affects the severity of jet lag that we feel is the direction of travel
- Some suggest that traveling from east to west will affect a person less than traveling from west to east.
- This is because:
- traveling from east to west, you GAIN time [phase delay]
- traveling from west to east, you LOSE time [phase advance]
- our body’s circadian rhythm tends to lengthen more so than shorten
- Siffre’s Cave Study showed that in the absence of external environmental factors (i.e the length of a day), the body’s circadian rhythm will lengthen to about 25 hours long
- Siffre’s cave study
                - spent 6 months in a cave
                - no external zeitgebers
                - no times cues, no telephone contact
                - artificial lights were switched on/off when he woke up and fell asleep
                - natural body rhythm lengthened to 25 hours
- therefore it is easier for us to lengthen the amount of time we stay awake, than to force ourselves to sleep earlier than we usually do

- environmental factors such as stress from work and jet lag from the mismatch of circadian rhythm and zeitgebers can affect our health
- often these effects are negative
- A lot of variables come to play in deciding how severe the effects are
- however prolonged periods of our health being negatively affected by environmental factors can lead to serious complication

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