Normal Sleep Physiology — MCQs
Which of the following statements is MOST accurate regarding REM sleep?
The human body has rhythmic fluctuations in its function on a circadian cycle. Circadian rhythm is controlled by:
Berger waves (alpha waves) of EEG have a rhythm of how many Hz?
Which of the following is not true about sleep -
Which condition is associated with periodic discharges on EEG at 4-second intervals?
Which of the following neurotransmitters is primarily released from the sympathetic nervous system to increase heart rate in response to a DECREASE in blood pressure?
Caffeine impairs sleep by which of the following mechanisms?
A 7-year-old girl is reported by the parents as waking up in the night screaming, and she sits up in bed frightened. She does not respond to questions and after 2 or 3 minutes she goes back to sleep. She has no memory of these events the following morning. Which of the following is the most likely diagnosis?
Patient with obstructive sleep apnea-hypopnea syndrome is unlikely to have which of the following?
The sleep apnea syndrome is defined as -
Normal Sleep Physiology Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following statements is MOST accurate regarding REM sleep?
- A. Slow waves on EEG
- B. Low muscle tone (Correct Answer)
- C. Decrease in BP
- D. Dreams
Explanation: ***Low muscle tone*** - **Muscle atonia** (near-complete loss of skeletal muscle tone) is one of the **defining physiological characteristics** of **REM sleep**. - This **muscle paralysis** prevents individuals from acting out their dreams and is a consistent, measurable feature of REM sleep. - Along with rapid eye movements and desynchronized EEG, **muscle atonia** is one of the three hallmark features that define REM sleep. *Dreams* - While **vivid dreams** are commonly associated with **REM sleep** and dream recall is highest during this stage, not all REM periods result in recalled dreams. - Dream recall varies significantly between individuals and circumstances. - Dreams can also occur during **NREM sleep**, though they are typically less vivid and less frequently recalled. *Slow waves on EEG* - **Slow waves** are characteristic of **deep non-REM sleep (N3 stage)**, not REM sleep. - During REM sleep, the **EEG** shows a **low-voltage, mixed-frequency pattern** resembling wakefulness (desynchronized EEG). *Decrease in BP* - During **REM sleep**, blood pressure often **fluctuates** and can even **increase** due to autonomic instability, rather than consistently decreasing. - The cardiovascular system exhibits **irregularities** in both heart rate and blood pressure during REM sleep.
Question 2: The human body has rhythmic fluctuations in its function on a circadian cycle. Circadian rhythm is controlled by:
- A. Median eminence
- B. Suprachiasmatic nuclei (Correct Answer)
- C. Paramedian nuclei
- D. Supraoptic nuclei
Explanation: ***Suprachiasmatic nuclei*** - The **suprachiasmatic nuclei (SCN)**, located in the hypothalamus, are considered the primary **master clock** that regulates most **circadian rhythms** in the human body. - They receive light input directly from the retina, which helps to **synchronize** the internal clock with the external light-dark cycle. *Median eminence* - The median eminence is a structure at the base of the hypothalamus that serves as a **neurohemal organ**, where **hypothalamic releasing and inhibiting hormones** are secreted into the portal system to control anterior pituitary function. - It does not directly control circadian rhythm but plays a role in the **endocrine system's response** to circadian cues. *Paramedian nuclei* - The term "paramedian nuclei" can refer to various small nuclei located near the midline in different brain regions, such as the brainstem. - These nuclei are generally involved in various motor and sensory functions and do not serve as the **central pacemaker** for circadian rhythms. *Supraoptic nuclei* - The supraoptic nuclei are located in the hypothalamus and are primarily responsible for producing **vasopressin (ADH)** and **oxytocin**, which are then released from the posterior pituitary gland. - While they are important for fluid balance and social bonding, they are not directly involved in the **generation or regulation of circadian rhythms**.
Question 3: Berger waves (alpha waves) of EEG have a rhythm of how many Hz?
- A. 0-4 Hz
- B. 4-7 Hz
- C. 8-13 Hz (Correct Answer)
- D. 13-30 Hz
Explanation: ***8-13 Hz*** - **Berger waves**, also known as **alpha waves**, are defined by their frequency range of **8 to 13 Hz** in the electroencephalogram (EEG). - These waves are typically observed when a person is in a relaxed, awake state with their eyes closed. *0-4 Hz* - This frequency range corresponds to **delta waves**, which are characteristic of deep sleep and certain brain pathologies. - Delta waves are much slower and have higher amplitude compared to alpha waves. *4-7 Hz* - This frequency range is associated with **theta waves**, commonly seen during light sleep, drowsiness, and some meditative states. - Theta waves are slower than alpha waves and indicate a state of reduced alertness. *13-30 Hz* - This frequency range represents **beta waves**, which are associated with active thinking, problem-solving, and alertness with open eyes. - Beta waves are faster and typically have lower amplitude than alpha waves.
Question 4: Which of the following is not true about sleep -
- A. Dreams come in REM sleep
- B. REM sleep comes earlier than NREM sleep (Correct Answer)
- C. REM sleep is also called paradoxical sleep
- D. Sleep walking comes in NREM sleep
Explanation: ***REM sleep comes earlier than NREM sleep*** - This statement is **incorrect** because the sleep cycle typically begins with **NREM (non-rapid eye movement) sleep**, specifically NREM stage 1, before progressing to NREM stages 2 and 3, and then finally entering REM sleep. - NREM sleep accounts for about **75% of total sleep time** and occurs prior to REM sleep in a typical nocturnal sleep episode. *Dreams come in REM sleep* - This statement is **true** as **vivid, memorable dreams** are most commonly associated with **REM sleep**. - During REM sleep, brain activity significantly increases, mimicking the awake state, which facilitates complex dream formation. *REM sleep is also called paradoxical sleep* - This statement is **true** because **REM sleep** is characterized by **high brain activity** (similar to wakefulness) and rapid eye movements, yet the body experiences **muscle atonia**, leading to a state of profound relaxation. - This paradoxical combination of an active brain and a paralyzed body gives it the name **paradoxical sleep**. *Sleep walking comes in NREM sleep* - This statement is **true** as **sleepwalking (somnambulism)** typically occurs during **slow-wave sleep**, which is **NREM stage 3 (deep sleep)**. - During this stage, arousal thresholds are very high, and complex motor behaviors can occur while the individual remains in a sleep state.
Question 5: Which condition is associated with periodic discharges on EEG at 4-second intervals?
- A. SSPE (Correct Answer)
- B. Absence Seizure
- C. REM sleep disorder
- D. Focal epilepsy
Explanation: ***SSPE*** - **Subacute sclerosing panencephalitis (SSPE)** is a rare, fatal, progressive brain disorder characterized by inflammation and degeneration of the brain. - The distinctive EEG pattern consists of **periodic high-amplitude, slow-wave complexes** that recur every 4-15 seconds, often every 4-8 seconds, making 4-second intervals a key indicator. *Absence Seizure* - Absence seizures typically manifest as **brief staring spells** with impaired consciousness, lasting only a few seconds. - The EEG in absence seizures shows characteristic **generalized 3-Hz spike-and-wave discharges**, not 4-second interval periodic discharges. *REM sleep disorder* - **REM sleep behavior disorder** involves the acting out of vivid dreams due to the absence of normal muscle atonia during REM sleep [1]. - EEG in REM sleep behavior disorder shows normal sleep architecture but may include evidence of **muscle activity (EMG)** during REM sleep, not periodic discharges [1]. *Focal epilepsy* - **Focal epilepsy** originates in a specific area of the brain, causing seizures with symptoms dependent on the affected region [2]. - EEG findings in focal epilepsy typically show **interictal spikes or sharp waves** localized to the region of seizure onset, which are distinct from generalized periodic discharges [2].
Question 6: Which of the following neurotransmitters is primarily released from the sympathetic nervous system to increase heart rate in response to a DECREASE in blood pressure?
- A. Norepinephrine (Correct Answer)
- B. Dopamine
- C. Acetylcholine
- D. Epinephrine
Explanation: ***Norepinephrine*** - **Norepinephrine** is the primary neurotransmitter released by **postganglionic sympathetic neurons** directly onto the heart to increase heart rate and contractility in response to a drop in blood pressure. - It acts on **beta-1 adrenergic receptors** in the sinoatrial (SA) node, atria, and ventricles, leading to increased chronotropy (heart rate) and inotropy (contractility). *Dopamine* - While **dopamine** can have cardiovascular effects, particularly at high doses, it is not the primary neurotransmitter released by the sympathetic nervous system for direct heart rate regulation. - Dopamine is a precursor to norepinephrine and epinephrine, but its main physiological roles involve **renal blood flow regulation** and central nervous system functions. *Acetylcholine* - **Acetylcholine** is the primary neurotransmitter of the **parasympathetic nervous system**, which generally acts to **decrease heart rate** (bradycardia) through muscarinic receptors. - It is also released by **preganglionic sympathetic fibers**, but these do not directly innervate the heart to produce the desired effect of increasing heart rate. *Epinephrine* - **Epinephrine** (adrenaline) is primarily a **hormone** released from the **adrenal medulla** into the bloodstream, not directly from postganglionic sympathetic nerve terminals to the heart. - Although it has strong effects on beta-1 receptors in the heart, its release is more generalized and slower than the direct neuronal release of norepinephrine.
Question 7: Caffeine impairs sleep by which of the following mechanisms?
- A. Blocks adenosine action and promotes wakefulness (Correct Answer)
- B. Activates locus coeruleus & promotes wakefulness
- C. No role in maintaining wakefulness
- D. Activates histamine release and prevents sleep
- E. Inhibits phosphodiesterase and increases cAMP levels
Explanation: ***Blocks adenosine action and promotes wakefulness*** - Caffeine functions as a competitive **adenosine receptor antagonist**, primarily at A1 and A2A receptors in the brain. - By blocking adenosine, which is an endogenous sleep-promoting neurochemical, caffeine reduces its inhibitory effects on wakefulness centers, thus **promoting alertness** and delaying sleep onset. *Activates locus coeruleus & promotes wakefulness* - While caffeine indirectly influences brain regions that promote wakefulness, its primary mechanism is not direct activation of the **locus coeruleus**. - Its effects on wakefulness are mediated more broadly through antagonism of **adenosine receptors.** *No role in maintaining wakefulness* - This statement is incorrect; caffeine is well-known for its **psychoactive properties** and its ability to increase alertness and reduce fatigue. - Its widespread consumption is largely attributed to its role in **promoting wakefulness** and improving cognitive function. *Activates histamine release and prevents sleep* - Caffeine does not significantly activate **histamine release** as a primary mechanism for its wake-promoting effects. - The wake-promoting effects of histamine are mediated via H1 receptors, but this is a separate pathway not directly targeted by caffeine. *Inhibits phosphodiesterase and increases cAMP levels* - While caffeine does inhibit **phosphodiesterase enzymes** (particularly at higher concentrations), this is not the primary mechanism for its wake-promoting effects. - The concentrations required for significant phosphodiesterase inhibition are much higher than those achieved with typical caffeine consumption; **adenosine receptor antagonism** occurs at much lower doses and is the dominant mechanism for its effects on sleep and alertness.
Question 8: A 7-year-old girl is reported by the parents as waking up in the night screaming, and she sits up in bed frightened. She does not respond to questions and after 2 or 3 minutes she goes back to sleep. She has no memory of these events the following morning. Which of the following is the most likely diagnosis?
- A. Nightmare
- B. Sleep terrors (Correct Answer)
- C. Narcolepsy
- D. Nocturnal seizures
Explanation: ***Sleep terrors*** - **Sleep terrors** are characterized by abrupt awakenings, intense fear and screaming, autonomic arousal, and unresponsiveness, typically occurring during **NREM sleep** in the first third of the night. - The child will have **no memory** of the event the next morning, which is a key diagnostic feature, and they often return to sleep quickly afterward. *Nightmare* - **Nightmares** occur during **REM sleep**, usually in the latter half of the night, and the individual can often recall vivid and frightening details upon waking. - Unlike sleep terrors, individuals experiencing nightmares are typically **responsive to comfort** and fully alert after waking. *Narcolepsy* - **Narcolepsy** is a chronic neurological condition characterized by overwhelming daytime sleepiness and irresistible urges to sleep, often accompanied by **cataplexy**. - It does not involve nocturnal screaming episodes or unresponsiveness followed by a quick return to sleep with no memory. *Nocturnal seizures* - **Nocturnal seizures** can cause nocturnal awakenings with confusion or unusual behaviors, but they often involve **stereotyped movements**, sometimes with motor manifestations or post-ictal confusion that lasts longer than a few minutes. - While there might be no memory of the event, the screaming and frightened demeanor without typical seizure activity make sleep terrors a more likely diagnosis.
Question 9: Patient with obstructive sleep apnea-hypopnea syndrome is unlikely to have which of the following?
- A. Absence of snoring
- B. Bradycardia during sleep episodes (Correct Answer)
- C. Normal oxygen saturation throughout sleep
- D. Decreased neck circumference
Explanation: ***Bradycardia during sleep episodes*** - While patients with **obstructive sleep apnea (OSA)** commonly experience various cardiovascular complications, **bradycardia** during apneic episodes is *less typical* than **tachycardia**. - The body's initial response to apnea and **hypoxia** usually involves a sympathetic surge leading to tachycardia upon arousal, followed by bradycardia if the apnea is prolonged. However, the dominant pattern is often elevated heart rate variability. *Normal oxygen saturation throughout sleep* - Patients with OSA frequently experience intermittent **hypoxemia** due to repeated apneas and hypopneas, leading to significant drops in **oxygen saturation** [1]. - A *normal oxygen saturation throughout sleep* would effectively rule out significant OSA, as desaturation is a hallmark of the condition [1]. *Absence of snoring* - **Snoring** is a classic and highly prevalent symptom of OSA, caused by the vibration of upper airway tissues as air struggles to pass through an obstructed pharynx. - While not all snorers have OSA, the *absence of snoring* makes OSA less likely, although it can occur in some subsets of patients, particularly those with central sleep apnea or certain anatomical variations. *Decreased neck circumference* - A **large neck circumference** is a well-established anatomical risk factor for OSA, indicating increased soft tissue in the neck that can contribute to upper airway collapse. - A *decreased neck circumference* would generally be protective against OSA, making it less likely for an individual to have the condition.
Question 10: The sleep apnea syndrome is defined as -
- A. Apnea-Hypopnea Index (AHI) ≥ 5/hour (Correct Answer)
- B. Apnea-Hypopnea Index (AHI) ≥ 10/hour
- C. Apnea-Hypopnea Index (AHI) ≥ 30/hour
- D. Apnea-Hypopnea Index (AHI) ≥ 15/hour
Explanation: ***Apnea-Hypopnea Index (AHI) ≥ 5/hour*** - The definition of **sleep apnea syndrome** generally requires an **AHI of 5 or more events per hour**, often accompanied by symptoms like excessive daytime sleepiness or cardiovascular complications [1]. - This threshold identifies individuals with clinically significant sleep-disordered breathing that warrants further evaluation and potential treatment [1]. *Apnea-Hypopnea Index (AHI) ≥ 10/hour* - While an AHI of 10/hour indicates sleep apnea, it is a higher severity criterion and does not represent the **minimum threshold** for defining the syndrome [1]. - Patients with an AHI between 5 and 10 also have sleep apnea and can experience significant symptoms. *Apnea-Hypopnea Index (AHI) ≥ 30/hour* - An AHI of 30/hour or more signifies **severe sleep apnea**, which requires aggressive management. - This is far above the **general diagnostic threshold** for sleep apnea syndrome. *Apnea-Hypopnea Index (AHI) ≥ 15/hour* - An AHI of 15/hour is typically classified as **moderate sleep apnea**. - This value is higher than the **lowest AHI threshold** used to define the presence of sleep apnea syndrome.
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