REM Sleep

Ans. B. Brain is very active but muscles are virtually paralyzed

[REF: Check APPENDIX-11 for “Sleep physiology”]

Repeat from June 2010

Bruxism.

Ans:A-Dreams

• Normal sleep involves two states: REM sleep and non-REM sleep. REM sleep is often associated with dreaming.
• Non-REM sleep is a period of decreased physiologic and psychological activity and is further divided into stages 1, 2, 3, and 4 on the basis of visually scored EEG patterns.
• REM sleep is characterized by high-frequency; low-amplitude EEG and loss of muscle tone in the major antigravity muscles.
• REM sleep is a distinct state of sleep characterized by wake-pattern EEG, skeletal muscle paralysis, and rapid, conjugate eye movements.

During REM sleep brain is very active but muscles are virtually paralyzed. 

During REM sleep there is muscle atonia coupled with phasic muscle twitches. This phenomenon is regulated by the dorsolateral pons and ventrolateral medulla along with the local neurons within spinal cord. Glycinergic mechanisms are responsible for the control of muscle tone during REM sleep.

REM sleep is characterized by desynchronized, low amplitude EEG, complete loss of activity in the antigravity muscles, frequent bursts of eye movements, tonic hippocampal theta activity, increased metabolic rate, muscle twitches and ponto geniculo occipital waves. Other striking features are cardiovascular and respiratory irregularities, irregular sympathetic activity, increased parasympathetic tone, inhibited thermoregulatory responsiveness.

Based on EEG, EMG, EOG characteristics, REM sleep can be divided into two stages, tonic and phasic. Characteristics of the tonic stage include a desynchronized EEG, atonia of skeletal muscle groups, and suppression of monosynaptic and polysynaptic reflexes. Phasic REM sleep is characterized by rapid eye movements in all directions as well as transient swings in blood pressure, heart rate changes, irregular respiration, tongue movements, and myoclonic twitching of chin and limb muscles.

Sleep is made up of two physiological states: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. In NREM sleep, which is composed of stages 1 through 4, most physiological functions are markedly lower than in wakefulness. REM sleep is qualitatively different kind of sleep, characterized by a high level of brain activity and physiological activity levels similar to those in wakefulness. 

About 90 minutes after sleep onset, NREM yields to the first REM episode of the night. This REM latency of 90 minutes is a consistent finding in normal adults; shortening of REM latency frequently occurs with such disorders as dipressive disorders and narcolepsy.

Acetylcholine is the neurotransmitter of primary importance for the induction of REM sleep. Some of the other neurotransmitters do function in sleep, but REM sleep can occur in their absence.

During REM sleep, the brain is highly active and responsive, but the body is virtually paralyzed because of active inhibition of skeletal muscles by dedicated population of neurons in the brainstem. During REM sleep, the high amplitude slow waves seen in the EEG during sleep are periodically replaced by rapid, low voltage, EEG activity, which resembles that seen in the awake aroused state and in stage 1 sleep.  Another characteristic feature of REM sleep is the occurrence of pontogeniculo-occipital spikes.

B i.e. Beta

C i.e. Referred to as paradoxical sleep

A i.e. REM sleep

Ans. A: REM

Humans aroused at a time when they show the EEG characteristics of REM sleep generally report that they were dreaming, whereas individuals awakened from slow-wave sleep/ NREM do not. This observation and other evidence indicate that REM sleep and dreaming are closely associated. The tooth-grinding (bruxism) that occurs in some individuals is also associated with dreaming.

Ans. is ‘c’ i.e., REM sleep

REM sleep decreases the secretion of GH. Other three stimuli increase GH secretion.