Lecture 16: stress Flashcards
What are the 2 types of stress responses
Fast and slow response
Fast –> sympathetic nervous system
Slow –> HPA axis
Schematically describe the slow-acting response to stress. Include the hormones secreted and the part of the brain/organ secreting these hormones and negative feedback.
- the hypothalamus receives the stress signal from the amygdala –> releases CRH
- pituitary receives signal from CRH –> releases ACTH
- adrenal gland receives signal from ACTH –> releases cortisol
- cortisol responsible for the main stress response in the body
- negative feedback: hypothalamus receives signal from cortisol –> stops releasing CRH –> stops the cycle
What is the function of the negative feedback?
To stop the stress response / stop production of cortisol
What would happen if the negative feedback were blocked? How could it be blocked?
- the hypothalamus would not respond to cortisol signals telling it to stop producing CRH, so the axis would not shut off
- chronically high cortisol levels
- can lead to disease (heart disease, immune system suppressed, stroke, etc)
- can be blocked if…
–> the receptors on the hypothalamus are insensitive to cortisol
–> tumor in pituitary/adrenal –> cortisol w/o stress –> Cushing syndrome
How do the amygdala and hippocampus affect the hypothalamic response to stress?
- amygdala triggers the hypothalamic response to stress
–> amygdala processes a stimuli as a threat/demand –> triggers hypothalamus - hippocampus is another part of the negative feedback system
- it receives signals from cortisol levels and sends signals to the hypothalamus to shut off the HPA axis and stop producing CRH
What does it mean that stress is a non-specific response of the body to a demand?
Regardless of the stressor, whether it’s good or bad, your body responds the same way
Demand: something that is a threat (physical or psychological)
How does the tend-and-befriend explain the stress response?
Fight or flight doesn’t explain the challenges faced by females, especially those with babies, because it puts the babies at risk.
Instead, stress increases social behavior and empathy. Joint protection and comfort
- Strength in numbers
- Comfort offspring
- Controlled by oxytocin (estrogen/endogenous opioids)
What do we learn about the etiology of depression by knowing that people with Cushing’s disease suffer from depression?
Cushing’s disease is caused by a tumor in the pituitary or adrenal glands that results in increased cortisol levels in the absence of stress. This shows a connection between depression and cortisol levels.
Carlos works as an air traffic controller. He has been in the job for 3 years and he is starting to notice that his memory is not what it used to be. What you think is happening to him? Explain your answer (the answer is not that he is getting older)
- Air traffic controllers are a very high stress job, because they’re constantly making life or death decisions for pilots and passengers
- Chronic high stress = chronic high cortisol
- Chronic high cortisol is neurotoxic for hippocampus, which is super important for memory
- When the hippocampus is damaged, memory is damaged too
What happens in general when cortisol levels are high chronically? Why does chronic stress affect memory?
- cortisol is neurotoxic for hippocampal neurons, chronic high cortisol levels starts to kill them!!
–> hippocampus is super important for memory
other things: - lots of things that cortisol inhibits are chronically inhibited, like growth hormones, immune system and reproductive functions
- hyperglycemia –> excess energy to cope with stress
Why does chronic stress cause an increase in strokes?
- chronic stress increases blood pressure and heart rate –> hyper-working the heart
- increased fat deposits in blood vessels
- arteriosclerosis
- blood vessels blocked by fat deposits
- blood vessels blocked in…
–> heart = heart attack
–> brain = stroke
I have noticed that people tend to get sick during exams. Based on what we learned could you explain the reason for the spike in health-related issues during exams?
- cortisol levels increase in response to stress
- exams are stressful
- cortisol inhibits things not required to deal with stressor, especially the immune system
- inhibited immune system = sick
The diathesis-stress hypothesis of anxiety states that early life stress plays a role on anxiety disorders later in life. Explain how that happens.
- chronic high cortisol levels in early life make cortisol receptors in hypothalamus insensitive to cortisol
- baby ignores cortisol levels
- negative feedback doesn’t work properly, HPA system doesn’t stop b/c hypothalamus never shuts it down
The antiabortion drug Mifepristone (RU-486) has been shown to have potential therapeutic in the treatment of depression. How could you explain that? (You will need to search the mechanism of action of RU-486)
- blocks cortisol (glucocorticoid) receptors on hypothalamus that are responsible for stopping the production of cortisol
- by blocking them, it increases cortisol levels
- this treats depression that is caused by low cortisol levels
If RU-486 were to be used in the treatment of depression. Would it be more effective in the treatment of atypical or melancholic depression? Explain your answer
- more effective for atypical depression
- atypical depression is caused by hypo-cortisol levels (too low)
- it is a result of exaggerated negative feedback
- when mifepristone blocks the receptors, it will decrease the negative feedback, and increase the cortisol levels
