PS263 Lec 14: Stress

Endocrine System

network of glands and organs that produce and release hormones

Hormones

long range, chemical signaling in the body

How do hormones move through the body and cause effects?

they are released from glands and travel through the circulatory system (blood vessels) and act by binding to receptors 

Steroid Hormones 

a class of hormones derived from cholesterol that can easily pass through cell membranes and bind to intracellular receptors, influencing gene expression. 

• made out of lipids

Peptide Hormones

a class of hormones made up of chains of amino acids that bind to surface receptors on target cells, triggering signaling pathways. 

• made up of proteins 

are steroid receptors intracellular?

yes they are, stereoids usually pass through the lipid bilayer

What determines how a hormone affects a target cell?

Receptors — hormones must bind to specific receptors on or inside the cell.

Why is the hypothalamus called the “master gland”?

Because it controls the pituitary gland, which then regulates many other endocrine glands.

2 divisions for pituitary gland

1. anterior - most hormones released from here 

2. posterior 

Pituitary Gland

controls many other endocrine glands in the body by releasing hormones.

Acute stress responses are managed by

sympathetic nervous system

Chronic stress responses are managed by

Endocrine system

What is Stress?

a physiological response that can prepare an animal to avoid or respond to a punisher 

• may decrease activity in hippocampus and PFC 

  • these are the areas that handle long-term planning and reminiscing, etc 

• may increase activity in sensory and motor regions 

  • these are areas that handle attention and behavioural response 

• overall, increases the sympathetic nervous system (fight or flight)

Hypothalamic-pituitary-adrenal (HPA) activation

is the body’s central stress-response system. When activated:

1. autonomic

   1. hormones: adrenaline, norepinephrine

   2. fight-or-flight, increased heart rate, high bp, short term adaptation

2. endocrine

   1. hormones: glucocorticoids

   2. long term adaption

Glucocorticoids 

steroid hormones that are released in response to HPA activation. these receptors are expressed in nearly every cell in the body 

main glucocorticoid

cortisol

what does high, excess, glucocorticoids do?

too much can cause receptors to shut off areas of hippocampus, PFC and ventral striatum leading to cognitive deficits, mood changes, disrupted memory, less able to inhibit prepotent responses and understand value of rewards.

• + decrease in immune system activity making you more susceptible to illness

can chronic stress make you sick?

yes in 2 main ways

• changes in cardiovascular system

  • stronger more rigid vessels which would lead to higher BP, increased risk of heart attack

• changes in metabolic system 

  • more bad cholesterol, changes in insulin sensitivity, changes to stomach chemical concentrations → increased risk of diabetes and heart attack 

    • difference in stomach acid can let bad bacteria grow and stay causing ulcers  

Which type of stress increases immune responses

acute stress

Which type of stress decreases immune responses

prolonged stress releases glucocorticoids which would deactivate immune responses 

Learned Helplessness

A mental state where an individual believes they have no control over the outcome of a situation, often resulting from repeated exposure to stressful events. This belief can lead to anxiety, depression, and a lack of motivation.

• this means that people do not get out of their symptoms or seek help, perpetuating their distress and SHOWS signs of depression

How can acute stress improve memory?

by temporarily increasing neuromodulators  → better attention + learning

• low levels of glucocorticoids → highly sensitive receptors → more plasticity 

How can high and chronic stress can damage memory?

damage depends on amygdala activity AND high levels of glucocorticoids

• high levels of glucocorticoids → less sensitive receptors → less plasticity 

How does controllability affect stress?

Being able to control a stressor (or the environment generally) can reduce stress, because having control makes the situation feel less threatening.

How does social support affect stress?

can buffer stress, possibly because it increases feelings of predictability and controllability of the environment.

How does predictability affect stress?

Being able to predict a stressor (or the environment generally) can reduce stress, because uncertainty increases stress responses.

How does the expectation that things will improve affect stress?

Expecting that situations will get better reduces stress, whereas expecting things to worsen increases stress.