Flashcards in Physiology Block 3 Week 17 18 Sleep Deck (69)
What is sleep?
unconsciousness from which the person can be aroused by sensory or other stimuli.
An active process involving characteristic physiological changes in the organs of the body
Highly organized sequence of events that follow a regular, cyclic program each night.
Are sleep, anesthesia, or coma the same?
They do not exhibit the same brain wave patterns characteristic of true sleep
What does sleep deprivation cause in humans?
-dec cerebral glucose utilization and blood flow
Nonspecific neural and physiological symptoms
-changes in EEG
-increased sensitivity to painful stimuli
Proposed Functions of sleep
1. Restoration and recovery of body systems as well as replenish energy stores while repairing itself after periods of energy consumption
2. To conserve energy
--metabolic rate decreases during sleep
--"sleep = energy used per day'
3. REM needed for memory consolidation, reinforcement of learning, and clearing unneeded memories
4. Required for brain development and formation of brain synapses
--high REM in newborns
5. Discharge of emotions
--dreaming in REM may provide safe discharge of emotions
--muscular paralysis prevents acting out dreams
--regions that control emotions, decision making, and social interaction reduced = relief from stress?
Do species with greater sleep times have higher or lower metabolic rates?
In humans, do sleep time and metabolic rate stay constant?
No, both decrease with age
How does sleep affect ability to retain/recall information?
humans who get plenty of NREM sleep in the first half of the night and REM sleep in the second half improve their ability to perform spatial tasks and to retain/recall information obtained the previous day
How is arousal assessed?
Electrical activity reflecting activity of neuronal populations and not the activity of individual neurons
How is the electrical activity of awake state characterized?
alpha rhythm of 8 to 13 Hz
5-100 mv wave amplitude
How is the electrical activity of sleep state characterized?
High amplitude and low frequency (0.5 to 4Hz) during stage 3 and 4 sleep
Thought to reflect a slowing and synchronous discharge of neurons.
What is delta sleep?
Arousal is more difficult than stage 1 and 2, which have theta rhythm 4-7 Hz
During NREM sleep, are the muscles functional?During REM sleep?
NREM: Muscles are function, but activity is low
REM: skeletal muscle activity is absent, but heart, diaphragm, eye muscles, and smooth muscles remain functional
How is REM sleep characterized?
High frequency and low amplitude
Reflect high and desynchronized cortical activity
NREM: Somatic Activity
Few motor events
REM: Somatic Activity
-post synaptic inhibition of motorneurons
-hyperpolarization of motorneuron membranes
-rapid eye movements
NREM: CNS Activation
Mean discharge rate of neurons decreased
Cerebral glucose utilization decreased overall
REM: CNS Activation
Mean discharge rate of neurons INCREASED in many regions
-Rapid Eye movements
Cerebral glucose utilization increased
Cerebral blood flow greatly increased
Hypnogram: Young Adults
Five 90 minute cycles alternating between NREM and REM sleep with brief arousals
Deepest stage of NREM occur in first part of night
Episodes of REM becomes longer as night progresses
Tonic REM sleep
Periods of sustained postural muscle atonia + bursts of eye movements
Phasic REM sleep
Postural muscle twitches
When do dreams occur?
REM sleep aka paradoxical sleep
rhythm occurring within a period of less than 24 hours
Are sleep patterns of children and elderly the same as young adults?
No, they differ
What happens to total sleep time and percent REM sleep with increased age?
High percent of REM sleep
The predominance of REM in infants is thought to reflect synaptic and brain development that occur at these ages.
Fragmented and relatively reduced sleep time in elderly
The pattern in the elderly probably reflects a gradual deterioration with aging (as occurs in all organs) of sleep control mechanisms resulting in multiple sleep problems
What happens if sleep debt not paid? Can caffeine help?
Not meeting sleep needs still allows us to function, but motor and cognitive functions are impaired.
Caffeine cannot substitute for sleep because only counteract some of the effects of sleep deprivation.
-attenuates adenosine receptor activity promoting wakefullness
How is sleep regulated?
2 process model:
-the longer the organism is awake, the greater propensity to sleep
-oscillatory process that affects propensity for sleep and waking
Internal Biological Clock
26-hour period--makes us sleepy at night and awake during the day
10,000 neurouns in suprachiasmatic nucleus (SCN) of hypothalamus
-Regulates endogenous biological rhythms and is reset to match the day length by the environmental photoperiod
-mediated by photoreceptors in retina, sending signals to SCN
-pineal gland (SCN controlled) increases melatonin at night = promote sleep