Rhythms Flashcards

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1
Q

Biological Rhythms

A
  • Recurring patterns of behaviour in the body’s systems (eg. endocrine, immune)
  • In humans, evolutionary pressure on these rhythms included avoiding predators and repair/recovery/growth
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2
Q

Circadian Rhythms

A
  • Latin term meaning a pattern or cycle that lasts around (circa) a day (dies)
  • Biological clock responds to sunlight
  • Melatonin levels vary depend on time of day
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3
Q

Light & Rhythms

A
  • Rods and cones in eye use chemicals called opsins to detect light
  • We have a third photoreceptor cell called ipRCGs - contain melanopsin, a non-visual opsin to detect intensity and wavelength of light
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3
Q

Role of Suprachiasmatic Nucleus (SCN)

A
  • The body’s ‘master circadian clock’ - located in hypothalamus
  • Contains neurons that fire in synchronised pattern
  • These neurons communicate with other pacemakers all over the body
  • All pacemakers keep time but SCN sets them - regulation of circadian rhythm
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4
Q

Role of Pineal Gland

A
  • Receives signals from SCN to produce melatonin according to light levels
  • Melatonin derived from serotonin - inhibitory NT
  • Inhibits many ares of brain that are responsible for wakefulness
  • Inhibition of these areas leads to sleep
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5
Q

Endogenous Pacemaker

A

Internal body clocks that allow us to keep pace with changing cycles in the environment - eg. SCN, pineal gland

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6
Q

Exogenous Zeitgeber

A

External cues that are responsible for entraining internal biological clock of an organism - eg. light, social cues

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6
Q

Ralph (199) - SCN as main endogenous pacemaker

A
  • Tau mutation hamsters have 20 hr circadian rhythm compared with 24 hrs in normal hamsters
  • SCN from normal hamsters transplanted into Tau mutants - Tau mutants gained 24 hr circadian rhythm
  • Normal hamster given Tau SCN gain 20 hr circadian rhythm
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7
Q

Steps of the Circadian Rhythm

A

1) SCN receives info from optic nerve about light levels (even if eyes are shut)
2) SCN sends impulses to pineal gland
3) Pineal gland release/inhibits melatonin production depending on light levels
4) Melatonin induces sleep by inhibiting brain activities that promote wakefulness

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8
Q

Social Cues: Aschoff et al (1971)

A

Individuals are able to compensate for absence of zeitgebers such as natural light by responding to social zeitgebers instead

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9
Q

Social Cues - Klein & Wegmann (1974)

A
  • Circadian rhythms of air travellers adjusted more quickly if they went outside at their destination
  • Exposed to social cues of their timezone (eg, when people go home for the night)
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10
Q

Ultradian Rhythms

A

Span a period of less than one day

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11
Q

Infradian Rhythms

A

Span a period longer than a day

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12
Q

90 Minute Sleep Stages - Ultradian

A

1&2) Light sleep, brainwave patterns slower and more rhythmic - alpha to theta waves
3&4) Deep sleep, slow wave sleep, difficult to wake someone up, slower delta waves
5) REM (or dream) sleep, body is paralysed to prevent acting out the dream, brain activity resembles that of someone who is awake
* A person can experience up to 5 full cycles per night

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12
Q

Weekly Testosterone Rhythms - Infradian

A
  • Testosterone levels higher at weeekends
  • Young couples reported more sexual activity at the weekend than in the week
  • Little evidence, many other possible variables
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12
Q

90 Minute Basic Rest Activity Cycle (BRAC) - Ultradian, Kleitman (1969)

A
  • Referred to sleep cycle as BRAC but suggested it happens when awake too
  • We move through stages of alertness rather than sleep
  • Human mind can focus for up to 90 minutes before the body begins to run out of resources - loss of concentration, fatigue, hunger
  • Can be seen through 10.30 coffee breaks and cat naps in the afternoon
12
Q

Refinetti (2006)

Menstrual Cycle - Infradian

A

1) Follicle Stimulating Hormone (FSH) causes maturation of egg in ovary
2) Luteinising Hormone (LH) stimulates release of egg
3) Oestrogen involved in repairing and thickening uterus lining
4) Progesterone maintains uterus lining
* Refinetti (2006) - there can be considerable variations in length of cycle

13
Q

Russell et al (1980): Menstrual Cycle

A
  • Menstrual cycle controlled by endogenous system (hormones from pituitary), but can also be controlled by exogenous cues
  • Daily sweat samples taken from one group of women and rubbed onto upper lips of women in second group
  • Groups kept separate
  • Menstrual cycles became synchronised with their odour donor