Lecture two - Mood, Food, and Brain

Question 1

How is stress defined in the lecture?

Answer 1

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.

Question 2

When a stressful event is accompanied by a real or perceived total lack of control, how is it experienced?

Answer 2

Very negatively. Our level of control in a situation is a key modulator of how negatively we experience an event.

Question 3

How is ACUTE STRESS defined in the lecture?

Answer 3

Acute stress represents a single event that leads to increased “flight or fight” response raising levels of arousal.

Question 4

What is episodic acute stress?

Answer 4

Repeated (but independent) acute stress, such as excessive worry about normal life events.

What are some other examples?

Question 5

How is CHRONIC STRESS defined?

Answer 5

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.

Question 6

What are the two main stress response systems in acute stress?

Answer 6

1. HPA axis - Hypothalamic - Pituitary - Adrenal axis - release of CORTISOL.
2. Activation of the sympathetic nervous system.

Question 7

Which stress-modulating system is faster, the HPA axis or the Sympathetic Nervous System?

Answer 7

The sympathetic nervous system, as this involves neurotransmitters, whereas the HPA axis involves CORTISOL (a hormone that circulates through the bloodstream).

Question 8

What are some of the physiological responses/effects of acute stress?

Answer 8

1. Increased heart rate.
2. Bladder or sphincter relaxation.
3. Tunnel vision.
   4.Shaking.
4. Dilated pupils;.
5. Flushed face.
6. Dry mouth.
7. Decreased digestion.
8. Hearing loss (or focusing only sound associated with the threat).

Question 9

Which brain area detects threat before we are consciously aware of the threat?

Answer 9

The AMYGDALA.

Question 10

What is the role of the AMYGDALA?

Answer 10

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.

Question 11

Is the pituitary gland a hormone-producing gland?

Answer 11

Yes.

Question 12

Where is the pituitary gland located?

Answer 12

Next to the hypothalamus.

Question 13

What hormone does the hypothalamus release that acts on the pituitary gland to release ACTH (adrenocorticotropic hormone)?

Answer 13

Corticotropin-releasing hormone (CRH).

Question 14

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?

Answer 14

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.

Question 15

What part of the adrenal glands secretes cortisol?

Answer 15

The adrenal cortex (which is the outer layer of the adrenal glands).

Question 16

What do high levels of cortisol in the bloodstream cause the hypothalamus to do?

Answer 16

Decrease or stop the production of corticotropin-releasing hormone (CRH).

Question 17

What is the adrenal medulla?

Answer 17

The inner part of the adrenals.

Question 18

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?

Answer 18

Cortisol.

Adrenaline and noradrenaline.

Question 19

Is noradrenaline a neurotransmitter and a hormone?

Answer 19

Yes.

Question 20

What is the inverted U model of acute stress that describes the relationship between acute stress levels and performance?

Answer 20

Some acute stress allows us to function optimally.

Question 21

Do high levels of acute stress lead to the decrease in function of the prefrontal cortex?

Answer 21

Yes.

Question 22

What part of the brain is highly involved in habitual behaviours?

Answer 22

The basal ganglia.

Question 23

What is the relationship between the amygdala and the prefrontal cortex in:
1. Mild stress.
2. Extreme stress.

Answer 23

1. 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.
2. 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.

Question 24

What are some of the changes that take place in the brain and body under chronic stress?

Answer 24

1. Number and strength of neural connects from and within the amygdala increases, due to constant, repetitive use. Increases sensitivity and reactive strength?
2. Number and strength of neural connections decreases in the hippocampus. More cell death and less neurogenesis, leading to reduced volume.
3. Number and strength of connections in the PFC decreases, due to lack of use. Reduced volume

Question 25

What is one of the only places in brain that continues to undergo neurogenesis after the rest of the brain stops (around mid-20s)?

Answer 25

The hippocampus.

Question 26

Chronic stress leads to increased emotional reactivity and decreased rational thinking. What are some of the reasons for this?

Answer 26

1. Decreased number and strenghth of neural connections in the prefrontal cortex leads to decreased capacity for emotional connection.
2. Increased number and strength of neural connections in the amygdala leads to increased stress sensitivity and reactivity.

Question 27

Under stress we turn to habitual ways of thinking and behaving. Why?

Answer 27

Amygdala downregulates the prefrontal cortex and upregulates the basal ganglia and other areas of the brain that are highly involved in habitual behaviour. We go into survival and survival does often requires a lot of reliance on habitual behaviours - less energy consuming.

Question 28

In a study looking at the effects of stress on the body’s immune system in train drivers after a train accident, what did they find?

Answer 28

Train drivers were more likely to get sick/ill a few months after the event.
Stress compromises the immune system.

Question 29

What are some of the effects of stress when acute and chronic?

Answer 29

Acute stress leads to increased energy availability in the muscles and brain via cortisol. Allows us to respond to the stressor that is present.

Chronic stress leads to dysregulated immune function, high blood pressure, and reduced fertility.

Question 30

What is one of the evolutionary arguments for why the body allows us to be chronically stressed, despite the negative health effects of this state?

Answer 30

If we have been exposed to recurrent stressors or even just one or two major stressors, especially early on in life, it may be that the body thinks it is wiser to stay hypervigilent and ‘over-cautious’ than to be naiive. There are negative health effects of this state, yes, but survival is more important to the body. Negative health effects only matter if you are still alive.

Question 31

What are some psychiatric disorders associated with stress?

Answer 31

1. Depression.
2. Bipolar and schizophrenia.
3. Alzheimers.

Question 32

What are the roles of ghrelin and leptin?

Answer 32

Ghrelin is produced in the stomach and indicates to the brain that we need to eat/we are hungry/increases appetite.

Leptin is produced in adipose tissue and indicates to the brain that we are full/satiated.

Question 33

Where is insulin produced?

Answer 33

Insulin is produced in the pancreas in response to elevated glucose in the blood.

Question 34

What are some characteristic levels of ghrelin and leptin seen in anorexia nervosa?

Answer 34

Higher than average levels of ghrelin. Likely due to prolonged lack of adequate caloric intake.

Lower than average levels of leptin. Likely due to the fact that those with anorexia nervosa have very small fat cells/very low amounts of adipose tissue. This means there is less capacity to produce leptin.