Stress and Circadian Rythms Flashcards

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1
Q

Cortisol

A

Stress hormone released by adrenal cortex

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2
Q

Diurnal cortisol

A

Daily rhythm of cortisol (12 hours)

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3
Q

What is the differences between circadian rhythm and diurnal rhythm?

A

Circadian rhythm = 24 hours

Diurnal rhythm = 12 hours

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4
Q

Neuroendocrine system

A

Is the central nervous system and endocrine system

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5
Q

Endocrine system

A

Is the system that produce and release hormones

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6
Q

Function of neuroendocrine system

A
  • is how brain communicates with the rest of the body.

- maintain regular functioning of organs

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7
Q

What are the glands in the brain that are part of the neuroendocrine system ?

A

Pituitary gland

Pineal gland

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8
Q

Pineal gland

A

Secretes melatonin (sleep hormone)

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9
Q

HPA axis

A

Hypothalamic pituitary adrenal axis. It is the body’s response to stress.

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10
Q

Hypothalamus

A

Is made up of clusters of nuclei

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11
Q

What is the function of hypothalamus?

A

Controls bodily functions e.g. sleep, mood, appetite, stress response.

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12
Q

What is the hpa?

A

It is the interaction between the hypothalamus, pituitary gland and adrenal cortex.

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13
Q

CRH

A

Corticotrophin-releasing hormone.

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14
Q

How is the hypothalamus and pituitary gland connected?

A

The hypothalamus and pituitary Gland are connected by a structure called infundibulum.

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15
Q

What is the blood supply in hypothalamus

A

Hypothalamus has a blood supply called portal blood supply.

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16
Q

CRH

A

corticotrophin releasing hormone is released by the paraventricular nucleus in the hypothalamus and travels in the portal blood stream to the pituitary gland. CRH stimulates the anterior pituitary gland to release ACTH.

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17
Q

Explain the HPA

A

The paraventricular nucleus in the hypothalamus releases CRH, which goes into the portal blood stream to the pituitary gland. CRH stimulates the release of ACTH from the anterior pituitary gland. The ACTH goes into the general blood stream and is detected by the adrenal cortex which produces cortisol

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18
Q

What does Adrenal gland consist of?

A

Adrenal gland consist of adrenal medulla (centre) and adrenal cortex (outer part)

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19
Q

ACTH

A

adrenocorticotropic hormone is produced by the anterior pituitary gland and it stimulates the production and release of cortisol from the adrenal cortex

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20
Q

Adrenal medulla

A

Inner part of adrenal gland. Adrenal medulla secretes Adrenaline.

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21
Q

Adrenal cortex

A

Outer part of adrenal gland. Adrenal cortex secretes cortisol when stimulated by ACTH

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22
Q

What does the HPA axis do?

A

The hypothalamic pituitary adrenal axis secretes cortisol and plays an important role in the stress response

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23
Q

What happens when stress occurs?

A

Stress activates brain monoamines, which stimulates the paraventricular nucleus in the hypothalamus to secrete CRH. The CRH goes through the portal blood supply to the the anterior pituitary gland. The anterior pituitary gland secretes ACTH. ACTH goes into the general blood supply and is detected by the adrenal cortex which releases cortisol. Cortisol goes everywhere.

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24
Q

Why is cortisol important?

A

Cortisol is necessary for survival. But too much or too little leads to problems.

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25
Q

What occurs when you are chronically stressed?

A

excessive cortisol secretion and enlarged adrenal glands.

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26
Q

Cortisol awakening response

A

Cortisol levels are highest in the morning and decreases during the day.

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27
Q

Differences between Adrenalin and cortisol.

A

Cortisol takes 15-20 minutes to be released. Whereas Adrenalin is released straight away.

28
Q

How can cortisol be measured?

A

Cortisol can be measured in saliva by salivette. Simple to do and non-invasive. Saliva measurement can be done at home.

29
Q

Circadian rhythm

A

Is a 24 hour rhythm that tells the body when to wake up, eat, sleep ect.

30
Q

Cortisol circadian rhythm

A

Cortisol follows a circadian rhythm as cortisol levels vary throughout the day. Highest in the morning after 30 mins waking up and decreases during the day.

31
Q

Examples of circadian rhythms

A

Sleep wake cycle, body temperature, Frequency of eating and drinking ect.

32
Q

What happens when you cross time zones?

A

Your circadian rhythm changes and jet lag occurs to adjust to the external cues (light)

33
Q

Why is circadian rhythm adaptive

A

Circadian rhythm is adaptive and allows us to adapt to new time zones.

34
Q

How does cortisol vary?

A

Cortisol is highest in the morning, decreases during the day and lowest at night.

35
Q

How does melatonin vary?

A

There is no melatonin during the day and is highest at night which helps you sleep .

36
Q

Why is there no melatonin during the daytime?

A

Melatonin production is stopped by light exposure.

37
Q

What influences circadian rhythms?

A

Circadian rhythm is self regulating but Light is required to reset the circadian rhythm.

38
Q

How is light detected?

A

Light is detected by the retina and sent to the suprachiasmatic nucleus in the hypothalamus by the retino- hypothalamic tract.

39
Q

Where is the suprachiasmatic nucleus located?

A

Suprachiasmatic nucleus is located in the hypothalamus above the optic chiasm which is where the optic nerves cross

40
Q

Suprachiasmatic nucleus

A
  • is the central pacemaker it tells the body what time it is (master).
  • and is the central oscillator as it goes back and forward with the cells in the peripheral circadian system and tells them what time it is.
41
Q

What cells does the suprachiasmatic nucleus communicate with?

A

Suprachiasmatic nucleus is a central oscillator as it communicates with cells in the peripheral circadian system about what time it is

42
Q

What is required to reset circadian rhythm?

A

Circadian is reset by external cues like Light is required to reset circadian rhythm but circadian rhythm is self regulating.

43
Q

How long is the circadian rhythm in humans?

A

Circadian rhythm is 24 hours and a half, this allows for flexibility allows body to adapt to new time zones.

44
Q

Zeitgeber

A

Exogenous (external) cues that reset the biological clock e.g. light, meals, social interactions, temperature ect.

45
Q

What nuclei are important for the regulation of cortisol levels?

A
  1. Paraventricular nucleus = part of the HPA axis and is in the hypothalamus. It produces CRH which stimulates the
    production of ACTH from pituitary gland.
  2. Suprachiasmatic nucleus = is located above the optic chiasm in the hypothalamus. Suprachiasmatic nucleus is the central pacemaker and is the central oscillator. It tells the cells in the peripheral circadian system what time it is. Suprachiasmtic nucleus controls our sleep wake cycle
46
Q

Circadian system model

A

Circadian system model consist of input, oscillator and output

47
Q

What is the input in the circadian system model?

A

Exogenous zeitgeber like light which resets the biological clock.

48
Q

What is the oscillator in the circadian system model?

A

The oscillator is the Suprachiasmatic nucleus which is the central pacemaker that generates oscillation which means it goes back and forward communicating with cells. Oscillation determines the output

49
Q

What is the output in the circadian system model?

A

The output translates the oscillation into behavioural and physiological rhythms.

50
Q

What is the difference between nerve and tract?

A

Nerve is outside the central nervous system and tract is inside the central nervous system.

51
Q

Endogenous pacemaker

A

Is our internal body clock that controls our circadian rhythms. An example of an endogenous pacemaker is suprachiasmatic nucleus this controls our sleep wake cycle.

52
Q

What type of rhythm does cortisol follow?

A

Cortisol follows a diurnal rhythm (12 hours)

53
Q

Endogenous

A

Internal

54
Q

Exogenous

A

External

55
Q

CAR

A

Cortisol awakening response = rapid increase in cortisol levels within an hour of waking up.

56
Q

Aqua phase

A

Is the highest point in cortisol circadian rhythm which is 30-40 minutes after waking up.

57
Q

When will you have a larger CAR?

A

Cortisol awakening response will be larger if you wake up in bright light so in the morning compared if you wake up in the afternoon as cortisol awakening response is light sensitive.

58
Q

Factors influencing CAR

A

Light, prior day experiences, time we wake up, ovulation

59
Q

Boost hypothesis

A

Is the theory that Cortisol Awakening Response is what boast you in the morning.

60
Q

How do endogenous pacemaker and exogenous zeitgebers work together?

A

Endogenous pacemaker and exogenous zeitgebers interact with each other to control circadian rhythms.
For example suprachaismatic nucleus receives information about light from the retina. The suprachiasmatic nucleus sends this information to the pineal gland to release melatonin which helps a person sleep.

61
Q

What are circadian rhythms affected by?

A

Circadian rhythms are endogenous but exogenous zeitgebers affect the circadian rhythm.

Endogenous pacemaker like suprachiasmatic nucleus and pineal gland work together but are affected by exogenous zeitgebers like light.

62
Q

Where is the SCN in terms of pathways?

A

Suprachiasmatic nucleus is between the visual and neuroendocrine system (CNS and endocrine system)

63
Q

RGCs

A

Melanopsin containing retinal ganglion cells = are specialised cells (photoreceptors) found in the retina that detect light.

64
Q

Melanopsin

A

Melanopsin is a chemical released from melanopsin retinal ganglion cells and the chemical travels down the retino-hypothalamic tract to the suprachiasmatic nucleus which communicates with the cells.

65
Q

Retino-hypothalamic tract

A

Is where melanopsin (light information) travels down to the suprachiasmatic nucleus