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Chapter 2

Health Sciences 1001A/B Chapter Notes - Chapter 2: Autonomic Nervous System, Hans Selye, Walter Bradford Cannon


Department
Health Sciences
Course Code
HS 1001A/B
Professor
Shauna Burke
Chapter
2

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What is Stress?
Stress refers to:
1. Situations that trigger physical and emotional reactions = STRESSOR
2. The reactions themselves = STRESS RESPONSE
STRESS: the general physical and emotional state that accompanies the stress response
Responses to Stressors
The primary determinant of the health consequences of stress is how the individual responds to
the stress (copes with the stress)
Responses to stressors include:
1) Physical Changes
2) Emotional and behavioural responses
Physical Responses to Stressors
Two control systems are responsible for the physical response to stressors:
1. Nervous system
2. Endocrine system
Physical Responses to Stressors
Nevous System
Autonomic Nervous System
o Part of the nervous system that is not under conscious supervision
o Consists of two divisions
1) Parasympathetic Division
In control when you are relaxed
Aids in digestion, storing energy, growth promotion
2) Sympathetic Division
Activated during arousal and emergency situations (pain, anger, fear)
Releases norepinephrine which commands body to mobilize energy resources to respond
to crisis and causes arousal (increases attention and alertness) when released in the brain
Norepinephrine is also called noradrenalin
Physical Responses to Stressors
Endocrine System
o The system of glands, tissues, and cells that help control body functions by releasing
hormones and other chemicals into the bloodstream
o Helps prepare the body to respond to a stressor
Physical Responses to Stressors
Nervous System and Endocrine System
BRAIN DETECTS THREAT:
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o Neurochemical message sent to HYPOTHALAMUS (hormone control system in brain) which
releases chemicals (chemical wakeup call) to PITUITARY GLAND which releases
adrenocorticotropic hormone (ACTH) into bloodstream
o ACTH reaches ADRENAL GLANDS which release CORTISOL and other key hormones into the
bloodstream (release of cortisol is related to health consequence, people who have higher
cortisol in their blood stream a lot, it later results in negative health consequences)
Physical Responses to Stressors
Nervous System + Endocrine System
SIMULTANEOUSLY:
o Sympathetic nerves instruct ADRENAL GLANDS to release the hormone EPINEPHRINE
(adrenaline) which triggers several bodily changes
o Examples: acute hearing and vision, increase heart rate, increase perspiration, etc.
o (stressor does not have to be real, if we imagine it or think about it, it can trigger all the
stress hormones)
Physical Responses to Stressors
Nervous System + Endocrine System = FIGHT- OR- FLIGHT REACTION
(Sir Walter Cannon)
**Physical changes vary in intensity but the same physical reactions occur in response to both
positive and negative stressors (e.g. positive stressors: graduation, sports)
Physical Responses to Stressors
Homeostasis
A state in which blood pressure, heart rate, hormone levels, and other vital functions are
maintained within a narrow range of normal
Once a stressful situation ends, the parasympathetic division of the ANS initiates adjustments
necessary to restore homeostasis (tries its best to reverse everything we feel when we are
under stress)
Physical Responses to Stressors
FIGHT-OR-FLIGHT REACTION IN MODERN LIFE
o A survival mechanism that is part of our biological heritage
o Not often necessarymany stressors we encounter do not require a physical reaction
o Fight-or-flight reaction prepares the body for physical action regardless of whether it is an
appropriate response
Emotional and Behavioural Responses to Stressors
TEND AND BEFRIEND
In addition to fight-or-flight, humans may respond to stress with social and nurturant behavior
Especially characteristic of females; female response to stress evolved to protect self and
offspring
May depend on underlying biological mechanisms (e.g. hormone oxytocin), there is no proof of
this (why women have an additional response to stress)
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