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Sleep and Circadian Rythyms
N/A
36
Medical
Graduate
03/28/2012

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Cards

Term
What are some characteristics of sleep (Human)?
Definition
Recumbent posture, raised sensory thresholds, decreased motor output, dreaming
Term
What is polysomnography?
Definition

The simultaneous monitoring of physical activities during sleep.

 

EEG (brain waves), EKG (Heart activity)

EMG (Muscle activity), EOG (Eye activity)

Blood pressure and O2 level

Respiration

Term
Describe NREM sleep sensation and perception.
Definition
Dull/absent
Term
Describe Awake sensation/perception
Definition
Vivid, externally generated (input from eyes, mouth, ears)
Term
Describe REM sleep sensation and perception.
Definition
Vivid, internally generated (not input from sensory organs)
Term
What is the major difference between thought patterns in NREM + Awake behavior versus REM sleep?
Definition

NREM/Awake -> Logical

 

REM -> Illogical

Term
What are the thought states for each stage of arousal/sleep behavior
Definition

Awake -> logical/progressive

 

NREM -> Logical/repetitive

 

REM -> Illogical/bizarre

Term
What are the different movement command states for the different awake/sleep stages?
Definition

Awake -> Continuous, voluntary

 

NREM -> Episodic, involuntary

 

REM -> Commanded, but inhibited (except eyes)

Term
How many phases of NREM sleep are there?
Definition
4
Term
Characterize NREM sleep behavior.
Definition

Slow brain waves, no awareness of outside world

 

Increase sensory threshold

 

Decreased heart rate, blood pressure

 

Increased neuroendocrine activity, especially growth/sex hormones

Term
What is the first stage of NREM like?
Definition

slower EEG, low voltage, mixed frequencies.

 

Theta waves dominant

Term
Describe the shape of a theta wave
Definition

High frequency, low amplitude waves

 

looks like a buzz

Term
Describe what an alpha wave looks like.
Definition

An alpha wave consists of high frequency, and medium amplitude waves.

 

Looks like noise (correlates with an awake state)

Term
Describe the second stage of NREM
Definition
K-complexes and sleep spindles (12-14 hz)
Term
What is a K-complex?
Definition

Viewed in EEG, large biphasic amplitude modulation

 

Looks like QRS wave in EKG

Term
What is a sleep spindle?
Definition

higher frequency waveforms embedded on a lower frequencuy wave. Viewed easiest in Stage 2 of NREM sleep.

 

Looks like fused muscle tetany.

Term
Describe stage 3 + 4 of NREM sleep.
Definition

Low frequency, high amplitude delta waves (2 hz max) for both stages

 

Stage 3 has a smaller population of theta waves with the delta waves

 

Stage 4 is purely delta waves

Term
What are some characteristics of REM sleep?
Definition

Relaxed muscles (atonia)

Rapid Eye Movements

Loss of control of temperature and cardiopulmonary functions

 

vivid dreaming

Term
How much time is spent in REM sleep across young age, middle age, and elderly persons?
Definition

The same amount of time!

 

If you miss it, you must make it up.

Term
Describe the old wrong hypothesis of sleep.
Definition

Bremer: sleep is a reaction to the lack of sensory input.

 

He hypothesized this after decerberalizing cats: no sensory cortex went into a sleep like state.

Term
Describe the Hess theory of sleep.
Definition

Active process

 

Related to thalamocortical system

Term
What are the two mechanisms for regulating the sleep/wake cycle?
Definition

Circadian rythym (higher probability of falling asleep later in the day)

 

Homeostatic property (increases as you have not slept, adenosine in mamals? people who don't sleep die)

Term
What are the sequence of events in sleep?
Definition

1. Relax cortical waking mechanisms (slow EEG down)

 

2. Incomplete relaxation of areas controlling muscles (twitching)

 

3. Inhibit histimine producing hypothalamus (anti-histamines put you to sleep)

 

4. Early NREM - spindles created by interconnected corticothalamic activity, occasionally into burst mode

 

5. Late NREM -> spindle diminishes, hyperpolarized thalamocortical neurons, spontaneous delta waves. People are groggy when arising from this step.

Term
What are circadian rythyms?
Definition
Daily biological rythyms representing an adaptation to a light/dark cycle, but can operate independently of external cues.
Term
Why does the circadian rythym shift later over days in the absence of light/dark cues?
Definition
The rythym is a cycle slightly longer than 24 hours.
Term
What is the suprachiasmic nucleus' role in circadian rythyms?
Definition
Master pacemaker. If lesioned, the same amount of time is spent in both active/non-active phases, but completely arrythymic.
Term
How does information flow in the mammalian circadian rythym?
Definition
Retinal-hypothalamic tract -> suprachiasmic nucleus -> output pathways (everywhere)
Term
What does the intergeniculate nucleus do?
Definition
coordinates the influence of the circadian rythym
Term
Aside from the suprachiasmic nucleus, what are the targets of the intrinsically photosensitive retinal ganglion cells?
Definition
ventral LGN -> Intergeniculate leaflet -> olivary pretectal nucleus
Term
Describe the basic functioning of suprachiasmic nucleus cells.
Definition

If SCN is input/output cut, there is still circadian behavior

 

Separate SCN cells have individual, rythymic firing rates

 

Transplant SCN between animals, new animal inherits the other's circadian rythym.

Term
What is entrainment?
Definition
ability to alter circadian rythym using external cues (such as light)
Term
Describe the flow of action in the drosophilla circadian rythym.
Definition
1. Per and Tim proteins are synthesized
2. Per-Tim dimers form in cytoplasm, undimerized per is degraded by DBLTim protein
3. Per-Tim dimers migrate into nucleus, bind to Clk and Cyc on Tim and Per promoters, stopping production of Tim and Per
4. When activated by light, Cryptochrone in the nucleus degrades the Tim very quickly, and the DblTim degrades the Per slowly, slowly returning production of Tim and Per.
Term
What is the function of DblTim in the fly circadian cycle?
Definition
Degrades Per protein
Term
What is the function of Cryptochrome in the fly circadian cycle?
Definition
Activated by light, destroys the Tim proteins
Term
How does the circadian cycle work in mammmillian clock cells compared to a fly's clock cell?
Definition

Similar to drosophillia, but a few differences

 

clk-BMA1 promote transcription of Per and Cry (instead of Clk-Cyc promoting Per and Tim)

 

Per-Cry dimers form instead of Per-Tim

 

Casein Kinases Epsilon and delta take the role of Dbt and Sgg

Term
What are the major outputs and the functions of the suprachiasmatic nucleus?
Definition

Mainly to subparaventricular zone, sleep

 

Basal Forebrain, Thalamus -> memory, rewards

 

Paraventricular nucleus -> autonomic regulation

 

Preoptic, anterior hypothalamus areas -> thermoregulation, reproductive function

 

Posterior hypothalamus  areas -> sleep-wake cycle, prolactin, growth hormone.

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