15 - Stress response

Question 1

stress response (2)

Answer 1

1. coordinated by brain regions such as the hypothalamus
2. signals stress to the body via autonomic and endocrine routes

Question 2

low arousal

Answer 2

low activation of nervous system characterised by fatigue, cognitive dullness and sleepiness

Question 3

high arousal

Answer 3

heightened activation of the nervous system, leading to anxiety and stress

Question 4

moderate arousal

Answer 4

may include some level of stress, can benefit performance

Question 5

allostasis

Answer 5

change in set point of one/more physiological variables outside normal homeostatic range (can involve physiological and/or behavioural changes)

Question 6

why is allostasis important?

Answer 6

allows organisms to respond adaptively to change in internal/external conditions

Question 7

acute stress (3)

Answer 7

1. lasts for short period of time
2. sympathetic activation due to stressor, fades quickly
3. parasympathetic dominance restored

Question 8

chronic stress (2)

Answer 8

1. occurs if stress response becomes elevated over prolonged period
2. sympathetic activation maintained long after initial stressor

Question 9

allostatic load

Answer 9

with chronic stress, homeostatic regulation cannot return to set point, set point remains elevated

Question 10

2 main systems that coordinate physiological stress responses (2)

Answer 10

1. sympathetic nervous system
2. hypothalamic-pituitary-adrenal

Question 11

sympathetic nervous system stress response (3)

Answer 11

1. fast stress response
2. mediated by autonomic sympathetic nervous system
3. including by specialised direct neuroendocrine route via adrenal medulla (the sympatho-adrenomedullary axis)

Question 12

hypothalamic-pituitary-adrenal stress response (2)

Answer 12

1. slower stress response
2. mediated by endocrine interactions between the hypothalamus, pituitary gland and adrenal cortex

Question 13

how does the sympatho-adrenomedullary axis trigger a fast stress response? (3)

Answer 13

1. stress signals from brain sent directly via sympathetic preganglionic neurons
2. these pass through spinal cord and thoracic splanchnic nerves to adrenal medulla
3. release acetylcholine in adrenal medulla to activate chromaffin cells

Question 14

role of chromaffin cells in adrenal medulla

Answer 14

release adrenaline and noradrenaline to trigger effector organs

Question 15

adrenaline and noradrenaline (3)

Answer 15

1. catecholamines
2. synthesised from tyrosine by chromaffin cells in adrenal medulla
3. chromaffin cells mainly release adrenaline (80%)

Question 16

how does adrenaline exert itself on multiple organs?

Answer 16

via alpha and beta adrenergic receptors on organs

Question 17

adrenaline effect on heart

Answer 17

increases heart rate and force of contraction

Question 18

adrenaline effect on lungs

Answer 18

increases bronchodilation (relaxes muscles in bronchi to widen airways)

Question 19

adrenaline effect on liver

Answer 19

increases glycogenolysis to increase blood glucose level

Question 20

adrenaline effect on digestive system

Answer 20

triggers vasoconstriction to reduce blood flow to gut

Question 21

most common cause of adrenaline overproduction

Answer 21

tumour in adrenal medulla

Question 22

corticotropin-releasing hormone (CRH)

Answer 22

hormone that activates stress response as part of the hypothalamic-pituitary adrenal (HPA) axis

Question 23

components of HPA axis (4)

Answer 23

1. hypothalamus
2. anterior pituitary gland
3. adrenal glands
4. adrenal cortex

Question 24

hypothalamus role in HPA axis (2)

Answer 24

1. neurosecretory cells in paraventricular nucleus (PVN) secrete corticotropin-releasing hormone (CRH)
2. diffuses via portal vein to trigger anterior pituitary gland

Question 25

anterior pituitary gland role in HPA axis

Answer 25

binding of CRH triggers release of adrenocorticotropic hormone (ACTH) from endocrine cells

Question 26

adrenal glands role in HPA axis

Answer 26

located on top of each kidnet and are made up of adrenal medulla (inner) and adrenal cortex (outer)

Question 27

adrenal cortex role in HPA axis (2)

Answer 27

1. ACTH (adrenocorticotropin hormone) binding triggers release of cortisol from cells in adrenal cortex 2. cortisol triggers stress response via effector organs (e.g. heart, lungs)

Question 28

negative feedback mechanisms in HPA axis (2)

Answer 28

1. ACTH secreted by anterior pituitary -> inhibits CRH release 2. cortisol secreted by adrenal cortex -> inhibits both ACTH and CRH release

Question 29

how can chronic stress effect HPA axis?

Answer 29

can cause sensitisation of neural responses -> leading to HPA axis hyperactivation

Question 30

cortisol (3)

Answer 30

1. glucocorticoid hormone (form of steroid hormone) 2. lipid soluble (like all steroid hormones) - can cross plasma membranes 3. synthesised from cholesterol in adrenal cortex

Question 31

endocrine effect of cortisol (3)

Answer 31

1. lipid soluble - can cross plasma membrane of target cells to bind to intracellular receptor 2. cortisol receptor complex enters nucleus 3. acts as transcription factor, altering gene expression

Question 32

cortisol effect on liver

Answer 32

increases gluconeogenesis and glycogenolysis

Question 33

cortisol effect on pancreas

Answer 33

decreases insulin secretion

Question 34

cortisol effect on adipose tissue

Answer 34

increases lipolysis in peripheral fat stores to yield fatty acids

Question 35

cortisol effects on skeletal muscle (2)

Answer 35

1. increases breakdown of muscle proteins (proteolysis) to yield amino acids 2. also has numerous other effects e.g. increasing blood pressure by enhancing vasoconstriction caused by adrenaline/noradrenaline