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BIOL155 > The Stress Response > Flashcards

The Stress Response Flashcards

1
Q

What is stress

A

A physical or emotional situation that presents a threat to homeostasis

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2
Q

What is the stress response

A

A set of predictable changes that the body organizes to deal with any situation it classifies as stressful
- an adaptive, allostatic process preparing the body for an anticipated increase in energy expenditure
- there is an optimum stress level that actually allows the body to perform at its best

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3
Q

Trace the stress response briefly

A

The stress response begins in the brain
- components of the brain classify situations as stressful

Then passed on to the body via (neuro)endocrine systems
- causes ANS to react and causes release of hormones to counter the stress

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4
Q

What are the steps to the stress response

A
  1. The AMYGDALA reacts to the threat (brain)
    - starts in the brain
  2. The hypothalamus activates the SYMPATHETIC nervous system, release of adrenaline
    - hypothalamus activates adrenal medulla
    - adrenal medulla causes release of adrenaline
  3. The ADRENAL CORTEX releases cortisol for continued alertness
    - endocrine system
    - outside cortex of adrenal gland releases cortisol
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5
Q

What are the two main hormonal pathways activated by the stress response

A

The stress response activates one of two pathways:

  1. Stressful stimulus -> brain -> SYMPATHETIC nervous system -> ADRENAL MEDULLA -> EPINEPHRINE IN BLOOD
  2. Stressful stimulus -> brain -> HYPOTHALAMUS (CRH) -> ANTERIOR PITUITARY (ACTH) -> ADRENAL CORTEX -> CORTISOL
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6
Q

What are other non-hormonal components of the sympathetic ANS that are also activated by the stress response

A
  • increase of glucagon and decrease of insulin = FIGHT response is activated so there is an increased demand for glucose in the bloodstream
  • movement of muscles
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7
Q

Beta blockers are drugs that bind to and block adrenergic receptors for epinephrine and norepinephrine:

A beta blocker is agonist of adrenergic receptors (True or False)

A

FALSE

Beta blockers act on adrenergic receptors but it is not an AGONIST

It blocks the actions of epinephrine and norepinephrine = acts as an ANTAGONIST

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8
Q

Scenario: You have taken a beta blocker. Predict the effect on your heart rate (increase/no effect/decrease) in each of the following conditions compared to if you had not taken a beta blocker

A. Just waking up from a very restful sleep
B. Sitting in a boring lecture
C. In a stressful situation, like performing on stage

A

A. No effect
B. No effect
C. Decrease

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9
Q

What is the General Adaptation Syndrome model

A

A model that divides the stress response into three temporal phases
- phase 1: alarm reaction
- phase 2: resistance
- phase 3: exhaustion

  • describes the stress response in terms of the body’s ability to resist a stressful environment
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10
Q

Describe phase 1 (alarm reaction) of the General Adaptation Syndrome model

A

Phase 1: Alarm reaction
- realizes the need for increased energy
- mobilizes resources
- very brief (less than one hour)
- mid-low stress resistance
- immediate response to stress (epinephrine)

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11
Q

Describe phase 2 (resistance) of the General Adaptation Syndrome model

A

Phase 2: Resistance
- cope with stressor
- the body’s resistance to stress can only last so long before exhaustion sets in
- increased energy -> using energy stores
- maintain, deal with the stress enters resistance phase (glucocorticoids/cortisol)

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12
Q

Describe phase 3 (exhaustion) of the General Adaptation Syndrome model

A

Phase 3: Exhaustion
- reserves depleted
- cannot keep up with the demand for increased energy
- unbalanced, used up all the stored energy
- under conditions of severe and prolonged stress (weeks to months)
- nothing to restore energy stores
- mineral imbalances
- serious conditions

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13
Q

Which endocrine regulation is phase 1 (alarm phase) associated with

A
  • sympathetic stimulation

brain -> adrenal medulla -> NOREPINEPHRINE AND EPINEPHRINE

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14
Q

Which endocrine regulation is phase 2 (resistance/recovery phase) associated with

A
  • sympathetic stimulation

brain -> ACTH -> adrenal cortex -> glucocorticoids

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15
Q

What causes the rapid, brief alarm phase

A

The result of SYMPATHETIC activation - ganglia connected in a chain - getting a reaction

All ganglia of the sympathetic division of the ANS become highly active simultaneously

Sympathetic activity is known as the FIGHT OR FLIGHT RESPONSE

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16
Q

What are some effects of sympathetic activation/alarm phase

A

Endocrine release of NE/E contributes to increased physical activity and alertness
- initial burst of energy = alertness
- increased alertness
- feelings of energy and euphoria
- increased activity in the cardiovascular and respiratory centers
- increase in muscle tone
- mobilization of energy reserves

17
Q

What is the name of the cells in the adrenal medulla that secrete their hormones

A

Chromaffin cells

18
Q

What are the two major hormonal pathways activated by the stress response

A
  1. adrenal cortex -> increased cortisol
  2. adrenal medulla -> increased epinephrine in blood
19
Q

The HPA axis mediates which phase of the GAS model

A

HPA axis mediates the SLOWER RECOVERY - RESISTANCE phase of the acute stress response

  1. hypothalamus releases CRH after CRH neurons receive excitatory input from the amygdala
  2. CRH goes to the anterior pituitary’s corticotropes
  3. Corticotropes release ACTH
  4. ACTH travels to adrenal cortex which releases glucocorticoids
  5. Glucocorticoids act on target tissues/cells
20
Q

Where is cortisol/glucocorticoids secreted from

A

Cortisol and glucocorticoids are secreted from the cortex of the adrenal glands
- specifically secreted by the zona fasciculata

21
Q

Identify the true statements about glucocorticoids:

  1. Hydrophobic
  2. Stored in vesicles before release
  3. Associated with carrier proteins
  4. Associated with membrane bound receptors
A

TRUE = 1 and 3

  1. Hydrophobic - Class 3 hormones = lipid derivatives
  2. Stored in vesicles before release - FALSE
  3. Associated with carrier proteins - Because they are hydrophobic, they cannot travel through the blood by themselves so they need to attach to carrier proteins in order to travel through the blood
  4. Associated with membrane bound receptors - FALSE = they interact with INTRAcellular receptors instead because they are lipid-derivatives and can easily cross the membrane
22
Q

How do glucocorticoids affect metabolism

A

Affect metabolism through nutrient mobilization
- glucocorticoids tend to be glucose-sparing
- save glucose for the brain
- promote other cells to use lipids for energy instead of using glucose
- stimulates release of fatty acids from adipocytes (lipolysis in adipocytes)
- stimulates liver to make more glucose but save for the CNS (gluconeogenesis)
- enhance use of lipids from other cell types that are non-CNS (enhanced lipid uptake)

23
Q

The HPA wing of the stress response directs available nutrients and energy reserves to organs system that are needed for ____________

A

Short term survival

  • inhibits immune system activity
  • inhibits TSH, gonadotropins, GH
  • enhances vasoconstriction of specific regions such as the skin
  • decreases digestion
  • increases ventilation and heart rate (sympathetic activation)
  • opposes actions of insulin (need glucagon to increase the glucose in the bloodstream)
24
Q

When moderate stress is sustained over weeks to months, a chronic stress response is triggered:

How does response to acute stress differ during chronic stress

A

Normally, during stress you get a sympathetic response that is balanced out by a parasympathetic rebound

However, in chronic stress (because of the new factor introduced or the prolonged stress), the sympathetic response never gets balanced out by a parasympathetic rebound

  • changes to alarm phase response for new stressors
  • causes persistant hypercortisolaemia = excessive exposure to cortisol or glucocorticoids
25
Q

What is persistent hypercortisolaemia

A
  • excess tissue exposure to cortisol and/or other glucocorticoids
  • when a new factor comes in and changes the response to stress (chronic stress), the sympathetic response never gets balanced out by the parasympathetic response
26
Q

Name some of the negative effects that moderate/chronic stress can have on the body

A
  1. Depression
  2. Sleep disturbances
  3. Weight gain/loss
  4. Autoimmune disease
  5. Memory loss, lack of concentration
  6. Susceptibility to infection
  7. Osteoporosis
  8. Infertility
27
Q

Chronic stress affects neural tissues, what structure of the limbic system is especially affected in the brain

A

The HIPPOCAMPUS is affected by chronic stress/persistent hypoercortisolaemia

  • excessive stress results in fewer synapses in the hippocampus and loss of entire dendritic branches
  • memories are stored in the hippocampus… neural tissue will begin to change when exposed to prolonged stress
  • dendrites have a lot of spine in control mice, but when there is a lot of stress, the level of spines decreases (decreases synapses)
  • cannot form as many synapses which leads to shrinking or damage of specific neural tissue
28
Q

Effects of chronic hypercortisolemia on the hippocampus can lead to disruption of the HPA axis: Explain how

A

Stress damages hippocampus, suppressing its activities
- hippocampus normally inhibits CRH release while the amygdala enhances CRH release
- this results in an overall increase in CRH release
- which goes to the anterior pituitary and causes an increased release of ACTH
- goes to the adrenal cortex and causes an increased release of cortisol/glucocorticoids
- no negative feedback
- increased plasma CRH and ACTH levels

29
Q

Chronic stress can lead to shrinkage and reduced activity of hippocampal neurons:

Explain how these changes in the hippocampus lead to an overactive HPA axis

A
  • the hippocampus works to inhibit the release of CRH from the hypothalamus
  • chronic stress damages the hippocampus and its neural tissue
  • meanwhile, the amygdala enhances the release of CRH
  • so since there is no negative feedback stopping the release of CRH, there is a consistent release of CRH from the hypothalamus to the anterior pituitary
  • the pituitary releases ACTH
  • which travels to the adrenal cortex and releases cortisol and other glucocorticoids
  • cortisol normally works to inhibit ACTH, but it does not do that during chronic stress
  • in a positive feedback to continue the release of cortisol
30
Q

What kind of feedback loop is normally active in the HPA axis and how does it change during a chronic stress state

A

Normal = negative feedback

Chronic stress state = positive feedback, pushing body away from set points

BIOL155 (34 decks)

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