Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Excitable Cells > Sleep & Circadian Rhythms > Flashcards

Sleep & Circadian Rhythms Flashcards

1
Q

What are biological rhythms?

A

Adaptations of organisms to 24-hour changes in their environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does the SCN (Suprachiasmatic Nucleus) consist of?

A

The SCN is a pair of nuclei

Core (ventrolateral SCN) and Shell (dorsomedial SCN)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the neuropeptides involved in the SCN’s function?

A

Neuropeptides are used by neurons to communicate with each other

  • VIP (vasointestinal polypeptide) in the core = receive input from the eyes (RHT)
  • AVP (arginine vasopressin) in the shell = sends output to other brain areas
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the primary function of the SCN?

A

Key biological pacemaker located in the hypothalamus
Receive input from melanopsin expressing retinal ganglion cells which travels through retinohypthalamic tract in the eyes (RHT) and send output to brain areas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does the molecular clock in the SCN generate?

A

Circadian expression of clock genes within SCN neurons generates circadian rhythms in neuronal function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is melatonin known as?

A

The hormone of sleep

it is secreted at night and inhibited by daylight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where is melatonin produced?

A

In the pineal gland

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Where else, besides the brain, is circadian expression of clock genes found?

A

Throughout the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the role of the circadian timing system?

A

Synchronises clocks across the body to adapt & optimise physiological changes in the environment

This is done by the SCN

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is chronopharmacology?

A

The study of
- the manner and extent to which the kinetics and dynamics of medication are affected by endogenous biological rhythms
- how the dosing time of medications affects biological timekeeping and features of biological rhythms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the impact of time of day on drug activity?

A

Time of day affects drug activity, and drugs can affect the biological clock

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the characteristic period of the mammalian circadian system?

A

Approximately 24 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the concept of chronotherapy in cancer treatment?

A

Maximises drug efficiency and minimises side effects by considering the time of day = time of best tolerability coincides with time of best efficiency

Conventional chemotherapy considers that the worst toxicity experienced by the patient = better the overall survival
But for chronotherapy, better survival rates are found among patients who don’t experience toxicity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is oxaliplatin known for in cancer treatment?

A

First cancer chronodrug approved for colorectal cancer

  • First anticancer drug to undergo chronotherapeutic development
  • When given at a constant rate = 10x higher incidence of neutropenia & distal paraesthesias (pins and needles in hands & feet) and 55% higher vomiting
  • Mean dose of oxaliplatin and its maximum tolerated dose could be increased by 15% if given in a circadian rhythm modulated rate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the stages of sleep and their characteristics?

A
  • Stage 1: NREM (light sleep), 1-7 min, 5% * Stage 2: NREM (deeper sleep), 10-25 min, 45% * Stage 3: NREM (deepest sleep), 20-40 min, 25% * Stage 4: REM (dreaming), 10-60 min, 25%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What external factors influence sleep?

A
  • Light * Jet lag * Shift work * Pain * Stress * Medical conditions * Medications * Other substances
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the problems associated with sleep deprivation?

A
  • Cognitive impairment * Performance impairment * Immune system impairment
18
Q

What is REM sleep also known as?

A

Rapid Eye Movement sleep

This is the dreaming stage

19
Q

What is NREM sleep?

A

Non-Rapid Eye Movement sleep

Stages 3 and 4 = slow wave sleep (deep sleep)

20
Q

What are the benefits of sufficient sleep?

A
  • Improved mood * Enhanced sleep efficiency
21
Q

What is the role of lithium in bipolar disorder treatment?

A

First-line treatment affecting circadian gene expression and rhythms

22
Q

What is the impact of lithium on circadian rhythms?

A

Affects expression of numerous circadian genes including the activation of clock transcription
Causes period lengthening and phase delay of sleep-wake and body temperature rhythms

23
Q

What are the physiological impacts of biological clocks?

A
  • Sleep/wake
  • Body temperature
  • Cardiac output
  • Memory
  • Energy metabolism
  • Eating behaviour
  • Immune response & detoxification
24
Q

What are the cellular impacts of biological clocks?

A

These generate physiological rhythms

  • Cell cycle progression
  • DNA damage repair
  • Cellular energy metabolism
  • Cell detoxification
  • Neuronal excitability
25
How are biological clocks associated with disease?
Affective disorders (bipolar, depression) Sleep disorders Neurodegenerative disease (Alzheimer’s) Obesity/metabolic syndrome Inflammation (asthma, COPD) Cancer
26
How do modern lifestyles oppose natural rhythms?
Chronic shift work Sleep deprivation Altered eating habits Social jet lag These can lead to health problems, road incidents and industrial accidents
27
How can shift work influence health?
- Mental health issues (e.g. stress, anxiety, depression etc) - Cardiovascular disorders (40% increase of risk) - Increased cancer (breast cancer and colorectal cancer) - GI disorders (e.g. heartburn, abdominal pain etc) - Disruption to circadian rhythms - Reproductive effects - Brain effects (sleep loss, fatigue etc)
28
Different types of biological rhythms
- Circadian (daily) = last 20-28 hours - Ultradian (seconds, minutes or hours) = last less than 20 hours - Infradian = last over 28 hours
29
What is bright light therapy and what does it target?
Involves high intensity blue light exposure early in the day —> blue light is the most effective to synchronise the biological clock Targets conditions such as mood disorders (seasonal affective disorders, unipolar & bipolar depression, antepartum depression etc) and also in elderly, AD, jet lag, insomnia etc
30
What are the benefits of bright light therapy?
Improves mood and enhances sleep efficiency Can take a few weeks to show benefit
31
Why is sleep necessary?
It is a basic homeostatic need & is important for learning and memory and growth and repair Problems associated with sleep deprivation - cognitive impairment - performance impairment —> increased errors, poor vigilance, poor memory, reduced mental & physical reaction times and reduced motivation - immune system impairment —> more susceptible to illness - also contributes to diabetes, obesity and hypertension
32
How long does each sleep cycle last?
70-90 minutes
33
Describe the stages of sleep
**Stage 1** - NREM (N1) = light sleep - lasts 1-7 minutes - accounts for 5% of total sleep time - muscle tone is present and breathing is regular **Stage 2** - NREM (N2) = deeper sleep - lasts 10-25 minutes - accounts for 45% of total sleep time - heart rate and body temperature drops **Stage 3** - NREM (N3, slow wave sleep/delta sleep) = deepest sleep - hard to wake up in this stage - lasts 20-40 minutes - accounts for 25% of total sleep time - body repairs & regrows tissues, builds bone & muscle and strengthens the immune system **Stage 4** - REM = dreaming - lasts 10-60 minutes - accounts for 25% of total sleep time - muscles don’t move (except eyes) and breathing becomes irregular
34
How is sleep regulated?
1. Brain areas controlling sleep 2. The drive to sleep and the circadian clock 3. External factors that influence sleep I.e. light, coffee, travelling
35
What is Encephalitis lethargica?
- disease where individuals slept for over 20 hours a day - epidemic affected millions of people in Europe and North America after WW1 - only 1/3rd of patients made recovery - cause unidentified - last case reported in the 1920s - patients had lesions at the junction of the midbrain and the Diencephalon - Von Economo proposed the existence of an arousal system
36
How is the brain involved in control of sleep?
In circadian rhythms - SCN - SPZ (subparaventricular) - DMH (dorsomedial) - all located in the hypothalamus In sleep - VLPO (ventrolateral preoptic, lateral, tuberomammilary) - also in the hypothalamus When awake - LDT (laterodorsal tegmental) - PPT (pedunculopontine) - Raphe (dorsal raphe) - LC (locus coeruleus) - all located in the Pons - LHA (lateral hypothalamic area) - located in the hypothalamus
37
What is the flip-flop switch model?
Orexin inhibits activity of brain areas controlling awakeness to keep the individual asleep
38
Describe circadian control of sleep
- SCN sends signals to the SPZ which goes on to signal the DMH - Lesions of the DMH attenuate or eliminate circadian rhythms of sleep-wake - Wakefulness & feeding —> DMH sends signals to the LHA - Sleep —> sends signals to the VLPO - Thermoregulation —> sends signals to the MPO (controls body temperature)
39
What signals sleep drive?
Interaction between the homeostatic drive to sleep and the circadian alerting signal governs sleep and wakefulness = increased melatonin and lower core temperature
40
External factors that influence sleep
- Light (main one) - Sleep environment - Medication and other substance e.g. coffee - Pain, stress & medical conditions (allow brief episodes of sleep = more REM sleep) - Jet lag or shift work (excessive sleeping or insomnia)
41
What is narcolepsy?
- Chronic disorder —> suffer profound daytime sleepiness (causes sleeping at inappropriate times) - Caused by disruption to brain’s orexin pathways - Orexin (also known as hypocretin) is a neuropeptide produced by a small number of neurons in the hypothalamus - Acts on G protein coupled receptor Hcrtr2 in its target tissues - Autoimmune attack on orexin producing neurons in narcolepsy results in their destruction - Also occurs in dogs & can be inherited —> results in premature stop codon in the Hcrtr2 receptor = receptor is non-functional

Excitable Cells (22 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions