Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

SGUL - Physiology 2 > Sleep & Circadian Rhythms > Flashcards

Sleep & Circadian Rhythms Flashcards

1
Q

What are Brain Rhythms?

A

Refer to distinct patterns of neuronal activity that are associated with specific behaviours, arousal level and sleep rate

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

List some environmental rhythms

A

The earth has a rhythmic environment that can vary with the seasons
- Temperature
- Precipitation
- Daylight

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

What must an animal do in order to survive and compete efficiently?

A
  • In order to compete effectively and survive, an animals behaviour must oscillate with its environment
  • The brain has evolved a variety of systems for thymine control such as sleep/wake cycle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What does an electroencephalogram (EEG) do?

A

It’s a measurement of electrical activity generated by the brain and recorded from the scalp

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

What does an electroencephalogram involve?

A
  • Involves non invasive electrodes placed on standard positions on the head
  • Connected to amplifiers and a recording device
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Briefly describe how an electroencephalogram works (PART 1)

A
  • EEG measures the combined activity of a large number (1000s) of similarly orientated neurons
  • Requires synchronous activity across groups of cells
  • EEG reflects summed post synaptic activity of large cell ensembles
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Briefly describe how an electroencephalogram works (PART 2)

A
  • The amplitude of an EEG signal depends upon how synchronous the activity of a group of cells is
  • When a group of cells are excited and synchronous, the tiny signals sum to generate a large surface signal
  • However, timing is everything, the same amount excitation can occur at irregular intervals and result in a small summed signal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How can the EEG rhythms be categorised?

A

By their frequency range:
- A high frequency low amplitude associated with alertness and waking
- A low frequency high amplitude aaaociated with non dreaming sleep

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

What is the electroencephalogram used for today?

A

Primarily used to help diagnose certain neurological disorders (Seizures in epilepsy)

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

What are the 2 types of synchronous base rhythms?

A
  • Pacemaker: Synchronous rhythms can be led by a central clock or pacemaker (e.g. thalamus)
  • Collective behaviour: Synchronous rhythms can arise from the collective behaviour of cortical neurons themselves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the thalamic pacemakers

A
  • The thalamus can act as a pacemaker with its vast input to the cerebral cortex
  • Synaptic connections between excitatory and inhibitory thalamic neurons force each individual neurons to conform to the rhythm of the group
  • Co-ordinated rhythms are then passed to the cortex by thalamuocrotical axons
  • Therefore a relatively small group of centralised thalamic neurons can compel a much larger group of cortical neurons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the collective behaviour of cortical neurons

A
  • Some rhythms of the cerebral cortex do not depend on a thalamic pacemaker
  • Instes they rely on collective interactions of cortical neurons themselves
  • Excitatory and inhibitory interconnections of neurons result in a coordinated synchronous pattern of activity
  • This can remain localised or spread to encompass larger regions of the cerebral cortex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the functions of brain rhythms?

A
  • One hypothesis is that most brain rhythms have no direct function but are by products instead
  • Brain rhythms are strongly interconnected with various forms of excitatory feedback
  • Rhythms must be an unavoidable consequence of such circuitry
  • However even if brain rhythms don’t have a function, they provide us with a convenient window on the functional states of the brain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Define sleep

A

A readily reversible state of reduced responsiveness and interaction with the environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Do we really need sleep?

A
  • Prolonged sleep deprivation can be devastating to proper functioning
  • However we can starve off sleep but not for long
  • Longest record without sleep was 264.4 hours by Randy Gardner
  • Sleep is be universal amongst all animals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the 3 functional states of the brain?

A
  • Wakefulness
  • Non REM sleep: Body capable of involuntary movement, rarely accompanied by vivid, detailed dreams
  • REM sleep: Body immobilised, accompanied by vivid, detailed dreams
17
Q

List some features of Non REM sleep

A
  • Decreased temperature
  • Decreased heart rate
  • Decreased breathing
  • Brain energy consumption
18
Q

List some features of REM sleep

A
  • Decreased temperature
  • Decreased irregular heart rate
  • Decreased irregular breathing
  • Increased brain energy consumption
19
Q

Describe the sleep cycle

A
  • EEG rhythms can be divided to indicate depth of sleep (Stages 1-4)
  • Each night begins with a period of non REM sleep
  • Sleep stages are then cycled throughout the night repeating approximately every 90 minutes
  • As night progresses, there is a shift from non REM to REM sleep
20
Q

Why do we sleep?

A

No single theory of the function of sleep is widely accepted although most reasonable ideas fall into two categories
- Restoration: We sleep to rest and recover to prepare to be awake again
- Adaptation: We sleep to protect ourselves and to conserve energy

21
Q

What are the Neural mechanisms of wakefulness?

A
  • During wakefulness, there is an increase in brain stem activity
  • Several sets of neurons increase the rate of firing in anticipation of wakening and enhance the wake state
  • Collectively, these neurons synapse direct brain regions including the thalamus and cerebral cortex
  • Increase in excitatory activity suppresses rhythmic forms of firing in the thalamus and cortex present during sleep
22
Q

What are the Neural mechanisms of sleep? (PART 1)

A
  • During sleep, there is a decrease in brain stem activity
  • Several sets of neurons decrease rate of firing during sleep
  • However cholinerguc neurons in pons shown to increase rate of firing to induce REM sleep: linked with dreaming
23
Q

What are the Neural mechanisms of sleep? (PART 2)

A
  • Rhythmic forms of firing in the thalamus shown to block the flow of sensory information up to the cortex
  • However other sleep promoting factors also involved in promoting sleep
24
Q

List the 2 sleep promoting factors

A
  • Adenosine
  • Nitric Oxide
  • Inflammatory factors
  • Melatonin
25
Q

Describe adenosine as a sleep promoting factor

A
  • Adenosine is a building block for DNA, RNA and ATP
  • Adenosine receptor activation decreases heart rate, respiratory rate and smooth muscle tone (decreasing blood pressure)
  • Inhibitory effect on ACh, norepinephrine and 5-HT which promote wakefulness
  • Adenosine receptor antagonists promote wakefulness
26
Q

Describe Nitric Oxide as a sleep promoting factor

A
  • Nitric Oxide is a potent vasodilator
  • Decreases smooth muscle tone (Decreasing blood pressure)
  • Nitric Oxide also stimulates adenosine release
27
Q

Describe inflammatory factors as sleep promoting factors

A
  • Sleepiness is a familiar consequence of infection
  • Cytokines stimulate the immune system to fight infections
  • Interleukin 1 levels shown to promote non REM sleep, evidence for adaptation theory
28
Q

Describe Melatonin as a sleep promoting factor

A
  • Melatonin is a hormone secreted by the pineal gland at night
  • Shown to initiate and maintain sleep
  • Over the counter medication for symptoms of insomnia and jet lag
29
Q

What is a circadian rhythm?

A

Refers to any rhythm with a period of approximately 24 hours

30
Q

Describe circadian rhythms

A
  • Almost all land animals coordinate behaviour according to circadian rhythms: Daily cycles of daylight and darkness
  • Most physiological processes also rise and fall with daily rhythms
31
Q

What happens to the circadian rhythm, if daylight and darkness are removed from an animals environment ?

A
  • Circadian rhythms continue
  • Primary clocks for circadian rhythms are biological (Brain clocks)
32
Q

What is meant by the term brain clocks?

A

Environmental time cues (light-dark, temperature, humidity) are collectively termed Zeitgebers

33
Q

What is the problem with Brain clocks?

A
  • It is quite difficult to separate a human from all possible Zeitgebers, even in a lab
  • Isolation studies are therefore best conducted in deep caves
  • If humans are separated from all Zeitgebers, they’re said to be in a free running state, internal biological clocks of approximately 24.5 hours-25.5 hours
34
Q

What is the Suprachiasmatic nucleus (SCN)?

A

A small nucleus of the hypothalamus that receives retinal inner action and synchronises circadian rhythms with the daily light dark cycle

35
Q

How do neurons in the SCN regulate circadian rhythmicity?

A
  • SCN clock genes produce proteins that send feedback to the SCN
  • This inhibits further protein production over a period of 24 hours
  • Light information from the retina serves to rest the SCN neuron clocks each day
  • SCN has control over circadian clocks throughout the body

SGUL - Physiology 2 (37 decks)

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