Psychendocrinology

Question 1

What are hormones?

Answer 1

Chemical messengers, generally synthesised by specialised glands, carried by the circulation to target tissues and organs

Question 2

What are the main endocrine glands where hormones are sysnthesised?

Answer 2

Hypothalamic – Pituitary – Thyroid axis (HPT axis) Hypothalamic – Pituitary – Adrenal axis (HPA axis) Hypothalamic – Pituitary – Gonadal axis (HPG axis) 

Question 3

What are some key differences between neural communication and endocrine/hormonal communication?

Answer 3

Neural communication - Signal travels to a specific location - Rapid - measured in ms - All or none Hormonal/endocrine communication - Signal travels everywhere (hormone molecules dispersed) - Slower - measured in seconds and minutes - Analogue messages - graded strength

Question 4

How do hormones work?

Answer 4

Hormones only affect cells that have the receptor protein that recognises the hormone to alter cell function The levels of most hormones vary rhythmically throughout the day (e.g. melatonin - pineal gland) Each hormone has multiple effects on different cells and behaviours 􏰀 - Additionally, a single type of behaviour can be affected by different hormones

Question 5

What was the first experiment involving behaviour endocrinology?

Answer 5

Conducted by Berthold (1849) - castrated cockerels 3 groups - control, completely castrated, one testis returned Control: combs, mounting behaviour, aggression, crowing behaviour Castrated - no comb, no mounting, no aggression, weak crowing One testis - normalised phenotype

Question 6

What was the significance of Berthold’s experiment?

Answer 6

Returning a testis reversed the phenotype change. However the re-implanted testis was in an abnormal body site, disconnected from neural innervation Thus reasoned that testes release a signal that has widespread effects throughout body -> hormone

Question 7

What are the types of hormones?

Answer 7

Peptide hormones - composed of strings of amino acids 􏰀 Steroid hormones – cholesterol derived hormones 􏰀 Amine hormones - composed of a single amino acid modified into a related molecule (molecule that acts as a hormone) 

Question 8

What are endocrine or neuroendocrine cells’ mechanism of functioning?

Answer 8

Simply release hormones into the bloodstream

Question 9

What are paracrine cells’ mechanism of functioning?

Answer 9

Paracrine hormones act locally on nearby cells

Question 10

What are autocrine cells’ mechanism of functioning?

Answer 10

Autocrine signals act directly on cell that released them; provide feedback to the cell from which they were released

Question 11

What are peptide and amine hormones’ mechanism of function?

Answer 11

Not lipid soluble (although a few amine hormones are). They bind with receptors on the cell membrane to exert effects. Second messenger systems

Question 12

What are steroid hormones’ mechanism of function?

Answer 12

Steroids are lipid soluble and can freely cross the phospholipid bi-layer. They bind to target receptors inside the target cell (intracellular).

Question 13

How do hormones alter cellular function?

Answer 13

By affecting the growth, proliferation, and differentiation of cells.

Question 14

What are the inputs controlling hormone secretion?

Answer 14

Changes in circulating concentrations of ions (e.g. Na+) or nutrients (e.g. glucose) Direct innervation from the nervous system

Question 15

What do direct innervation from the central nervous system do?

Answer 15

In the case of neurosecretary cells in the hypothalamus Receive direct inputs from other areas of brain (amygdala and hippocampus) Determine whether they should fire and release hormones

Question 16

An example of another hormone acting on the endocrine cell do?

Answer 16

HPT axis Hypothalamus –TRH—> anterior pituitary —TSH–> thyroid gland –thyroid hormone—> target cells

Question 17

What is negative feedback?

Answer 17

It plays an important role in regulation of most hormonal systems. An increase in a hormone produces feedback so the level substance is reduced (feedback switches the production off) Acts like a thermostat

Question 18

What is stress? And some examples?

Answer 18

Any circumstance that upsets the body’s balance (homeostasis) e.g. - exposure to extreme cod or heat, threatening psychological states

Question 19

When was the word stress first applied to physiology?

Answer 19

Walter B. Cannon Coined term ‘fight or flight’ Developed the concept of homeostasis

Question 20

Walter B. Cannon?

Answer 20

First used word ‘stress’ in physiology Coined term ‘fight or flight’ Developed the concept of homeostasis Demonstrated the role of epinephrine in the stress response

Question 21

What is a stressor?

Answer 21

Anything which disrupts physiological balance

Question 22

What is stress defined as?

Answer 22

The general state of stressors provoking a stress response

Question 23

What is a stress-response?

Answer 23

The body’s adaptations designed to reestablish the balance

Question 24

What are some types of stressors?

Answer 24

Acute stressful event (e.g. public speaking) Chronic stress (e.g. daily hassles) Both lead to HPA-axis and increase in SNS activation

Question 25

The physiological outcome of stress?

Answer 25

HPA-axis and increase in SNS activation

Question 26

Mechanism for action - HPA axis?

Answer 26

Question 27

HPA axis - mechanisms of action?

Answer 27

Hippocampus and amygdala in paraventricular nucleus -> corticotropin-releasing factor (CRF) in anterior pituitary -> Adrenocorticotropic hormone (ACTH) increased -> adrenal cortex -> glucocorticoids

Question 28

􏰀 Corticotropin-releasing factor (CRF) effects?

Answer 28

Causes ACTH production
􏰀 Suppresses appetite
􏰀 Increases subjective feelings of anxiety

Question 29

Adrenocorticotropic hormone (ACTH) effects?

Answer 29

Increases secretion of steroid hormone from the adrenal cortex

Question 30

Glucocorticoid (i.e. cortisol) effects?

Answer 30

􏰀 Gluconeogenesis

􏰀 Immunosuppression 􏰀

Negative feedback

High levels can kill neurons in the hippocampus

Question 31

What is the HPA-axis and SNS activation good for?

Answer 31

For acute physiological stress the HPA-axis and SNS provide excellent stress response

Question 32

What is the HPA-axis and SNS activation maladaptive for?

Answer 32

For chronic and psychosocial stress the response is maladaptive

Question 33

Normal vs crowded train study?

Answer 33

• Studied epinephrine levels
• In crowded train, there was 10% increase in the number of passesngers
  
  • Normal group: 20% increase in epinephrine levels compared to control
  • Crowded group: 65% increase in epinephrine levels compared to control

Question 34

Epinephrine and NE and exam stress?

Answer 34

Epinephrine and NE levels peak during exam. However they increase long before the exam.

Doubling of baseline epinephrine more than 2 weeks before exam

Aren’t adaptive to situation

Question 35

Trier Social Stress Test (TSST)

Answer 35

• TSST
  
  • Social stressors: Public talk
  • Count down backwards from 100 by 7s, angry panelists demand participants start again if wrong
• ACTH and cortisol responses
  
  • Activation of HPA-axis
  • Immediate increase in ACTH
  • Stronger, more sustanced cortisol release
  • Stress response is not advantageous

Question 36

What cells do chronic social stress impact on?

Answer 36

• Hippocampal pyramidal cells
  
  • Animal of low social status - social stress, far fewer cell bodies in hippocampus
  • Glucocorticoids lead to cell death in the hippocampus