Stress and Emotion - 8

Question 1

What is a definition of stress?

Answer 1

Definition from Hans Selve: “the non-specific response of the body to any demand for change”. Stress is part of everyday life. Can be due to direct external factors or from a behavioural expectation of a situation.

Question 2

What is the Hypothalamo-Pituitary Axis (HPA)?

Answer 2

Pituitary gland has 2 parts which have different functions:

1. Posterior = peptides released & go into the blood stream where they have remote effects. This is important in mating systems and sexual behaviour.
2. Anterior = nerve cells in the hypothalamus that when active release small peptides that run to the anterior pituitary gland (never get into blood circulation). These provoke release of hormones critical for the stress response. CRH is released in nerve endings which affect the functioning of the adrenal gland.

Question 3

What are the components of the physiological/hormonal response to stress?

Answer 3

1. CRH = small peptide hormone, made up of specific chain of amino acids. When active leads to the production of protein.
2. ATCH = affects the functioning of the adrenal gland.
3. Adrenalin & noradrenalin = monoamines: are synthesised within the body.
4. Glucocorticoids = e.g. cortisol and steroids. Release from adrenal gland under the influence of ACTH.

Combination of all of these which leads to physiological response. Two types of receptors (alpha and beta). Can design agonists which act only at alpha or beta receptors.

Question 4

How do receptors produce their effect on a cells functioning?

Answer 4

1. Neurotransmitter/hormone binds to a receptor and open ion channels (e.g. GABA receptors). Agonist binds to a specific receptor site. There is no channel opening, but causes an internal change of structure of receptor which allows it to produce another chemical. This chemical is referred to as a ‘second messenger’ which goes on to effect cell functioning. This process is particularly associated with steroid hormones. Because they are fat soluble, they can pass straight through the membrane when can change the genealogy of the cell. This is a way sex hormones can effect brain development early on.

Question 5

How does the fast stress response work?

Answer 5

Activation of the hypothalamus leads to activation down through the brain stem to the spinal cord to sympathetic nerves that stimulate the adrenal gland. Adrenal gland has 2 parts (adrenal cortex and adrenal medulla). Sympathetic nerves innervate the medulla which produce large amounts of adrenalin/noradrenalin - this produces shifts in metabolic functioning preparing you for fight or flight. There is also a parasympathetic innervation of the medulla which is associated with rest and digest (dampens monoamines).

Question 6

How does the slow stress response work?

Answer 6

Release of cortisol is triggered by ACTH from the pituitary. Some of the effects overlap those of the monoamines adrenalin and noradrenalin. They also enhance the ability to use fats and proteins in metabolism and a variety of other effects. The inability to produce glucocorticoids increases vulnerability to stress. Slower response depends on hormonal cascade. Its activation of cells in the hypothalamus acts as an integrator in stress response.

Question 7

What are the responses to stress & painful stimuli?

Answer 7

Acute stressors (including painful stimuli) include an ‘analgesic’ effect that involves suppression of incoming ‘nociceptive’ information. Stress is also involved in the modulation of pain responses. Acute stressor makes a person become much less responsive to pain stimuli. This process involves the release of endogenous opioid peptides and monoamines, among other neurochemical mechanisms.

Question 8

What are the effects of chronic stress?

Answer 8

Chronic exposure to stressors may be associated with the loss of the usual feedback control by cortisol on the production and release of CRH and ACTH. Long term effects are changed hippocampal function and structure, which is associated with depression.
Chronic stress problematic.

Question 9

What is the effect of stress on immune functioning?

Answer 9

Glucocorticoid release leads to suppression of inflammation and immune responses. Tissue damage leads to increased release of cytokines. Cytokines act at CNS receptors (hypothalamus and elsewhere) to produce behavioral effects (feelings of illness and lethargy). These responses may promote withdrawal from a dangerous environment, rest and recovery, and hence enhance biological fitness.