Lecture two - Mood, Food, and Brain Flashcards
How is stress defined in the lecture?
Stress is a response to a PERCEIVED aversive or threatening situation.
Stress can be positive or negative.
The experience of stress is coloured by the real or perceived lack of control over the stressor.
When a stressful event is accompanied by a real or perceived total lack of control, how is it experienced?
Very negatively. Our level of control in a situation is a key modulator of how negatively we experience an event.
How is ACUTE STRESS defined in the lecture?
Acute stress represents a single event that leads to increased “flight or fight” response raising levels of arousal.
What is episodic acute stress?
Repeated (but independent) acute stress, such as excessive worry about normal life events.
What are some other examples?
How is CHRONIC STRESS defined?
Chronic stress is uncontrollable and seemingly endless.
Some examples are:
-being exposed to domestic violence as a child.
-living in a war zone.
-severe financial stress, e.g. poverty.
-if you’re a first responder, such as a paramedic.
What are the two main stress response systems in acute stress?
- HPA axis - Hypothalamic - Pituitary - Adrenal axis - release of CORTISOL.
- Activation of the sympathetic nervous system.
Which stress-modulating system is faster, the HPA axis or the Sympathetic Nervous System?
The sympathetic nervous system, as this involves neurotransmitters, whereas the HPA axis involves CORTISOL (a hormone that circulates through the bloodstream).
What are some of the physiological responses/effects of acute stress?
- Increased heart rate.
- Bladder or sphincter relaxation.
- Tunnel vision.
4.Shaking. - Dilated pupils;.
- Flushed face.
- Dry mouth.
- Decreased digestion.
- Hearing loss (or focusing only sound associated with the threat).
Which brain area detects threat before we are consciously aware of the threat?
The AMYGDALA.
What is the role of the AMYGDALA?
The amygdala receives sensory information about the environment and determines it’s threat level. If it detects threat then it activates the HPA axis and the sympathetic nervous system response (the sympathetico-adrenal-medullary pathway). This happens before we are even consciously aware of the threat.
Is the pituitary gland a hormone-producing gland?
Yes.
Where is the pituitary gland located?
Next to the hypothalamus.
What hormone does the hypothalamus release that acts on the pituitary gland to release ACTH (adrenocorticotropic hormone)?
Corticotropin-releasing hormone (CRH).
What hormone does the pituitary gland release in response to stress (aka being acted upone by corticotropin-releasing hormone from the hypothalamus)?
Where is this hormone released to?
When corticotropin-releasing hormone is released from the hypothalamus and binds to receptors on the pituitary gland, adrenocorticotropic hormone (ACTH) is released into the bloodstream and makes its way to the adrenal glands (more specifically the adrenal cortex). It binds to receptors there, which leads to the release of cortisol into the bloodstream.
Cortisol is a glucocorticoid, which means it increases the metabolism of glucose.
What part of the adrenal glands secretes cortisol?
The adrenal cortex (which is the outer layer of the adrenal glands).
What do high levels of cortisol in the bloodstream cause the hypothalamus to do?
Decrease or stop the production of corticotropin-releasing hormone (CRH).
What is the adrenal medulla?
The inner part of the adrenals.
What hormone is released from the adrenal cortex in response to ACTH from pituitary gland?
What hormone is released from the adrenal medulla in response to messages from the neurons of the sympathetic nervous system?
Cortisol.
Adrenaline and noradrenaline.
Is noradrenaline a neurotransmitter and a hormone?
Yes.
What is the inverted U model of acute stress that describes the relationship between acute stress levels and performance?
Some acute stress allows us to function optimally.
Do high levels of acute stress lead to the decrease in function of the prefrontal cortex?
Yes.
What part of the brain is highly involved in habitual behaviours?
The basal ganglia.
What is the relationship between the amygdala and the prefrontal cortex in:
1. Mild stress.
2. Extreme stress.
- Amygdala causes the activation of certain brain areas, such as raphe and LC, that tell the prefrontal cortex to downregulate the amygdala. The PFC is in control. This is what allows us to function optimally under mild stress.
- The amygdala activates the same brain areas but to greater extent and this leads to the downregulation of the PFC. The amygdala and basal ganglia are in control and survival behaviours kick in, e.g. flight or fight.
What are some of the changes that take place in the brain and body under chronic stress?
- Number and strength of neural connects from and within the amygdala increases, due to constant, repetitive use. Increases sensitivity and reactive strength?
- Number and strength of neural connections decreases in the hippocampus. More cell death and less neurogenesis, leading to reduced volume.
- Number and strength of connections in the PFC decreases, due to lack of use. Reduced volume
