Cortical states Flashcards
What is a circadian rythm?
A 24 hour cycle that induces physical, mental, and behavioral changes.
What are external cues that help your body form it’s circadian rythm?
Light and absence of light and daily routines such as meal times and social interaction.
How is the cycle kept to 24 hours?
Our internal biological clock that works as homeostatic regulation with temperature and levels of hormones and operates even in the absence of external information.
What part of the brain regulates these cyclical changes?
Hypothalamus.
What is the pathway that allows light to regulate the circadian rhythm?
Absence of light -> Intrinsically photosensitive ganglion (melanopsin) stop being inhibited -> retinohypothalamic tract -> suprachiasmatic nucleus (master clock) -> Paraventricular nucleus -> spinal chord intermediolateral cells -> superior cervical ganglion -> Pineal gland –> synthesis of melatonin
How does the cyrcadian affect learning and mood?
Light also signals directly to the thalamic perihabenular nucleus, which sends signals to N. Accumbens and medial Prefrontal Cortex which regulate mood.
What is sleep behaviorally?
- reversible state of disengagement from and unresponsiveness to the outside environment
- postural recumbence, behavioral quiescence and closed eyes
- a normal suspension of consciousness
What is sleep electrophysiologically?
Specific brain waves - specific patterns of electrical activity.
Why do we sleep?
- To conserve energy by replenishing brain glycogen levels and decreasing the metabolism
- Sleep allows us to restore ourselves while it is dark and our primary sensory system (visual) is not very
effective - To consolidate memory as it has been shown that sleeping soon after learning increases recall and that
sleep closes the gap between short term and long term memory stores - To clear the brain of metabolic waste by an increase in the flow of cerebral spinal fluid.
What are the 4 stages of sleep?
N1: - drowsiness/transition to sleep
- Waves start to have lower frequency and higher amplitude
N2: - Periodic bursts of activity of about 10-12 Hz that last 1-2 seconds and are called sleep spindles
- Even lower frequency and higher amplitude
N3: - Number of sleep spindles decreases
- slow-wave sleep
REM: - EEG similar to an awake state
What are the physiological changes that happen in the N1 stage of sleep?
- low arousal threshold
- slow rolling eye movements
- the start of a decrease in muscle tone, body movements, heart rate, blood pressure, metabolic rate and temperature
What are the physiological changes that occur in the N2 stage of sleep?
- more intense stimuli required to produce arousal
- stimuli that might have produced arousal in N1 now produce a sleep spindle
- the presence of K complexes
- progression of the decrease in muscle tone, body movements, heart rate, blood pressure, metabolic rate, and temperature
What are the physiological changes present in stage n3 of sleep?
- Highest arousal threshold
- muscle tone, body movements, heart rate, blood pressure, metabolic rate, and temperature reach their lowest values
What are the physiological changes present in the rem stage of sleep?
- rapid ballistic eye movement
- increase in muscle tone, body movements, heart rate, blood pressure, metabolic rate, and temperature
- pupillary constriction
- paralysis of large muscle groups and twitching of small muscle groups
- spontaneous penile erection
- greater prevalence of dreaming
When do dreams occur?
Both in rem and non rem sleep,
What is the difference between rem and non rem dreams?
Rem dreams tend to be longer, somewhat emotional, and disconected from the dreamers current life while non rem dreams tend to be shorter, less emotional and more conceptual and somewhat connected to the dreamers current life
How does sleep change over the course of a life?
You need much less sleep as you get older with a marked drop in rem sleep in the transition out of infancy.
What part of the brain when electrically stimulated causes wakefulness and arousal?
the midbrain pons junction
What part of the brain when stimulated with what kind of electrical stimulation causes slow wave sleep?
Low frequency stimulation to the thalamus.
What are 2 features of the neural circuits of sleep?
- A patterened interaction between the brainstem (reticular activating system), the thalamus and the cortex
- regulated by the hippocampus
What is the REM Saccades circuit?
The pontine reticular formation (brainstem) signals to the superior colliulus which sends input to the paramedian pontine reticular formation which sends input to the rostral interstitial nucleus which generates eye movements
What are the Pontine geniculate occipital (PGO) waves?
A phasic bursts of action potentials occur throughout the borebrain in association with rapid eye movements that are regulated by the pontine reticular formation.
What is the circuit of the hyperpolarization of spinal cord motor neurons?
Pontine inhibitory area sends inhibitory inputs through the medulla to the spinal cord in order that we do not make large movements in our sleep.
What is the reticular activation system?
A group of nuclei in the brainstem that operate with distinct neurotransmitters that project to thalamocortical neurons. Responsible for activating the cortex.
