Which hormone surge indicates the fertile period in females?
Maximum duration of time is spent in NREM stage:
Which of the following is true about NREM sleep?
Hypothalamus increases release of all hormones from the pituitary except ?
What primarily causes vasoconstriction in skin?
NEET-PG 2012 - Physiology NEET-PG Practice Questions and MCQs
Question 91: Which hormone surge indicates the fertile period in females?
- A. LH (Correct Answer)
- B. FSH
- C. Estrogen
- D. Oxytocin
Explanation: ***LH*** - The **luteinizing hormone (LH) surge** triggers **ovulation**, releasing a mature egg from the follicle. - This surge is a key indicator of the **fertile window** in a woman's menstrual cycle. *FSH* - **Follicle-stimulating hormone (FSH)** primarily stimulates the growth and development of **ovarian follicles** early in the menstrual cycle, prior to the fertile period. - While essential for follicle maturation, it does not directly signal the immediate fertile window or ovulation. *Estrogen* - **Estrogen levels peak** just before the LH surge, playing a role in triggering the surge itself through positive feedback. - However, estrogen itself does not directly indicate the onset of the fertile period; rather, the subsequent LH surge does. *Oxytocin* - **Oxytocin** is largely involved in processes like **uterine contractions during childbirth** and **milk ejection during lactation**. - It has no direct role in indicating a female's fertile period or timing of ovulation.
Question 92: Maximum duration of time is spent in NREM stage:
- A. I
- B. III
- C. IV
- D. II (Correct Answer)
Explanation: ***II*** - **NREM Stage II** constitutes the largest percentage of total sleep time, typically accounting for about 45-55% of an adult's sleep. - This stage is characterized by the presence of **sleep spindles** and **K-complexes** on an EEG, and it is a relatively stable period of sleep. *I* - **NREM Stage I** is the lightest stage of sleep, representing the transition from wakefulness to sleep. - It is the shortest stage, lasting only a few minutes, and is characterized by slow eye movements and a decrease in muscle tone. *III* - **NREM Stage III** (along with Stage IV in older classifications) is considered **slow-wave sleep** or deep sleep. - While crucial for restorative processes, Stage III does not account for the majority of total sleep time, typically being less than Stage II. *IV* - **NREM Stage IV** is the deepest stage of sleep, now often combined with Stage III as part of **slow-wave sleep**. - It involves the lowest brain wave activity and is difficult to awaken from, but its duration is significantly less than Stage II.
Question 93: Which of the following is true about NREM sleep?
- A. Narcolepsy
- B. Teeth grinding (Correct Answer)
- C. Nightmares
- D. Sleep paralysis
Explanation: ***Teeth grinding*** - **Bruxism** (teeth grinding) commonly occurs during **NREM sleep stages**, particularly stage N2. - It is an **involuntary motor activity** that can lead to dental issues and jaw pain. *Narcolepsy* - Narcolepsy is a neurological condition characterized by overwhelming daytime sleepiness and involves dysregulation of **REM sleep**. - Patients often experience **sudden REM sleep onset** during waking hours, not typically an NREM sleep phenomenon. *Nightmares* - Nightmares are generally vivid, disturbing dreams that occur during **REM sleep**. - While other sleep disturbances can occur in NREM, classic nightmares are a **REM-related parasomnia**. *Sleep paralysis* - Sleep paralysis is a temporary inability to move or speak that occurs when waking up or falling asleep, often associated with **REM sleep**. - It involves the persistence of **REM atonia** into the waking state.
Question 94: Hypothalamus increases release of all hormones from the pituitary except ?
- A. ACTH
- B. TSH
- C. FSH
- D. Prolactin (Correct Answer)
Explanation: ***Prolactin*** - The hypothalamus primarily **inhibits prolactin release** from the anterior pituitary via **dopamine** (prolactin-inhibiting hormone). - All other hormones listed (ACTH, TSH, FSH/LH, GH) are stimulated by their respective hypothalamic releasing hormones. *ACTH* - The hypothalamus **increases ACTH release** by secreting **corticotropin-releasing hormone (CRH)**, which acts on the anterior pituitary. - CRH stimulates corticotrophs to synthesize and release ACTH, which then acts on the adrenal glands. *TSH* - The hypothalamus **increases TSH release** by secreting **thyrotropin-releasing hormone (TRH)**, which stimulates thyrotrophs in the anterior pituitary. - TRH also has a minor stimulatory effect on prolactin release, but its primary role is TSH stimulation. *FSH* - The hypothalamus **increases FSH release** (along with LH) by secreting **gonadotropin-releasing hormone (GnRH)** in a pulsatile manner. - GnRH stimulates gonadotrophs in the anterior pituitary to produce and secrete both FSH and LH.
Question 95: What primarily causes vasoconstriction in skin?
- A. Warm climate
- B. Wheal and flare
- C. Sympathetic (Correct Answer)
- D. Parasympathetic
Explanation: ***Sympathetic*** - The **sympathetic nervous system** primarily controls vasoconstriction in the skin via **adrenergic receptors** on vascular smooth muscle. - Activation of these nerves releases **norepinephrine**, leading to the contraction of smooth muscle and thus narrowing of blood vessels. *Warm climate* - A warm climate typically causes **vasodilation** in the skin, allowing for increased blood flow to the surface to facilitate heat loss. - This is a physiological response to prevent **overheating**, not to vasoconstrict. *Wheal and flare* - A **wheal and flare reaction** is a localized immune response, often to allergens, characterized by histamine release causing **vasodilation** (flare) and edema (wheal). - This reaction involves localized vasodilation, not systemic or primary vasoconstriction. *Parasympathetic* - The **parasympathetic nervous system** generally has minimal direct control over cutaneous vascular tone, especially regarding vasoconstriction. - Its primary role in the skin is related to **glandular secretions**, such as sweat production.