INTBUS 6 Lecture Notes - Lecture 11: Hans Selye, Adrenal Medulla, Sympathetic Nervous System
6 Oct 2020
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PBL CASE 3
Nervous system:
Hans Selye, Bernstein (1979) defined stress as the nonspecific response of the body to any
demand upon it.
General adaption syndrome: Any threat to the body, in addition to its specific effects, activated a
generalised response to stress.
Initial stage-Alarm: Characterised by increased activity of the sympathetic nervous system,
readying the body for brief emergency activity. (“flight or fight response”), adrenal medulla releases
adrenaline, and endorphins are also released.
Secondary stage-Resistance: Sympathetic response declines, but adrenal cortex secretes cortisol
and other hormones that enable the body to maintain prolonged alertness, fight infection and heal
wounds.
Third stage-Exhaustion: After intense prolonged
stress, individual is tired, inactive and vulnerable
due to nervous system and immune system no
longer have the energy to sustain heightened
responses.
Stress activates two body systems, sympathetic
nervous system (“fight or flight”) and the other is
the HPA axis, hypothalamus, pituitary gland and
adrenal cortex, more in long term stress.
Short term stress Sympathomedullary pathway
(SAM) (symphatic)
Sudden and severe stress generally produces:
• Increase in heart rate
• Increase in breathing (lungs dilate)
• Decrease in digestive activity (don’t feel hungry)
• Liver released glucose for energy
1. Body judges a situation and decides whether or not it is stressful. Decision is made based on
sensory input and processing and also stored memories.
2. If situation is judged as being stressful, hypothalamus is activated.
3. When stress response is triggered, it sends signals to two other structures: the pituitary gland
and the adrenal medulla, so called “The fight or flight response”, via the Sympathomedullary
Pathway (SAM).
4. Adrenal medulla secretes the hormone adrenaline, which includes increased heart rate,
decreased digestion and increases sweating and increased pulse.
5. Once threat is over the parasympathetic branch takes control and bring body back into a
balanced state.
Long term stress regulated by Hypothalamic Pituitary Adrenal system (HPA) (parasymphatic)
• Stressor activates the hypothalamic pituitary axis
• Hypothalamus stimulates the pituitary gland
• Pituitary gland secretes adrenocorticotropic hormone (ACTH)
• ACTH stimulates the adrenal glands to produce the hormone corticosteroid
• Cortisol enables the body to maintain steady supplies of blood sugar
• Adequate and steady blood sugar levels help person to cope with prolonged stressor, and helps
the body to return to normal.
• Immune system is suppressed while this happens.
• Reacts more slowly but becomes more dominant after a period.
Document Summary
Hans selye, bernstein (1979) defined stress as the nonspecific response of the body to any demand upon it. General adaption syndrome: any threat to the body, in addition to its specific effects, activated a generalised response to stress. Initial stage-alarm: characterised by increased activity of the sympathetic nervous system, readying the body for brief emergency activity. ( flight or fight response ), adrenal medulla releases adrenaline, and endorphins are also released. Secondary stage-resistance: sympathetic response declines, but adrenal cortex secretes cortisol and other hormones that enable the body to maintain prolonged alertness, fight infection and heal wounds. Third stage-exhaustion: after intense prolonged stress, individual is tired, inactive and vulnerable due to nervous system and immune system no longer have the energy to sustain heightened responses. Stress activates two body systems, sympathetic nervous system ( fight or flight ) and the other is the hpa axis, hypothalamus, pituitary gland and adrenal cortex, more in long term stress.
