In a normal adult sitting with eyes closed EEG will show
Correct Answer: Alpha
Description: Ans. a (Alpha) (Ref. Ganong Physiology 22nd/pg. Chapter 11, Fig. 11-8).In a normal adult sitting with eyes closed EEG will show alpha waves. EEG with eyes open & mind wandering shows Beta waves.EEG wavesKey FactsAlpha# Happen between 8 and 13 times per second, or 8-13 Hertz (Hz).# Alpha represents a sort of "idle" state, or "ready but not doing much" state and is normally fairly large over the back third of the brain when the eyes are closed and when you are awake.# Alpha disappears when we either get mentally busy (e.g., open the eyes, start doing intense mental work even eyes closed) or when we become drowsy.# Thus the presence of alpha can show the presence of an awake, resting state,# If it is present at a fairly high voltage when the eyes are open, this would usually indicate an inattentive, daydreamy state.# In fact we often see this sign in adolescents and adults with attentional difficulties.Beta waves# The beta family of waves happen at frequencies from 16-40 Hz or higher.# When we get mentally busy and engaged, we should see alpha "block," or reduce significantly in size.# In its place we see mostly smaller, quicker "beta" waves.Delta and theta waves# Are relatively slow.# Delta is usually defined as waves occurring from 1-4 times per second (1-4 Hz).# Theta occurs at 4-7 Hz.# During drowsiness, first alpha disappears, then the size of theta waves begins to increase.# As sleep begins, theta waves get quite large, then become mixed with and eventually give way to slower delta waves.# The presence of delta and theta waves in the waking, eyes open EEG is normal, but only if the waves are fairly small.# High-amplitude slow waves can be signs of various neurological and psychological problems, ranging from epilepsy to ADHD. Educational points:# In a typical night of sleep, a young adult first enters NREM sleep, passes through stages 1 and 2, and spends 70-100 minutes in stages 3 and 4.# Sleep then lightens, and an REM period follows. This cycle is repeated at intervals of about 90 minutes throughout the night. The cycles are similar, though there is less stage 3 and 4 sleep and more REM sleep towards morning.# Thus, four to six REM periods occur per night. REM sleep occupies 80% of total sleep time in premature infants and 50% in full-term neonates.# Thereafter, proportion of REM sleep falls rapidly and plateaus at about 25% until it falls further in old age.# In REM, there occurs | and variable pulse, | and variable blood pressure, penile/clitoral tumescence. ACh is the principal neurotransmitter involved in REM sleep.# Children have more total sleep time and stage 4 sleep than adults.# Serotonergic predominance of raphe nucleus key to initiating sleep.# NE reduces REM sleep.# Extraocular movements during REM due to activity of PPRF (paramedian pontine reticular formation/conjugate gaze center).# Benzodiazepines shorten stage 4 sleep; thus useful for night terrors and sleepwalking# Imipramine is used to treat enuresis because it | stage 4 sleep.# Characteristic feature of NREM stage IV sleep is DELTA waves.FeatureStage of SleepCardiovascular activity in Sleep:Beta wavesAwake with eyes openNREM:BP |with less variability, CO |, vasodilation increases (|flow resistance).Alpha wavesAwake with closed eyesIheta wavesStage 1Tonic REM :BP stays the same, CO stays the same, muscles vasoconstriction.Sleep-SpindlesStage 2Delta wavesStage 3 & 4Phasic REM:BP variable, CO stays the same, whole body vasoconstriction.Beta wavesREM (same as Awake)Mnemonic: (BATS Drink Blood)
Category:
Physiology
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