Which of the following hormones increase the sensitivity of heart to epinephrine?

 # Which of the following hormones increase the sensitivity of heart to epinephrine?

A. Parathyroid

B. Insulin

C. Thyroid

D. Glucagon

The correct answer is:

C. Thyroid

Explanation:

Thyroid hormones (primarily T3 and T4) increase the sensitivity of the heart to catecholamines, including epinephrine. This effect is due to:

• Increased β-adrenergic receptor density: Thyroid hormones upregulate the expression of β-adrenergic receptors in the heart, enhancing responsiveness to epinephrine and norepinephrine.
• Increased myocardial contractility and heart rate: By amplifying the effects of catecholamines, thyroid hormones contribute to increased cardiac output and sympathetic tone.

Other options:

• A. Parathyroid hormone (PTH): This hormone regulates calcium and phosphate metabolism, with no direct role in cardiac sensitivity to epinephrine.
• B. Insulin: While insulin affects glucose metabolism and has some cardiovascular effects, it does not directly increase heart sensitivity to epinephrine.
• D. Glucagon: Glucagon has some inotropic and chronotropic effects on the heart, but it does not enhance the heart's sensitivity to epinephrine.

Thyroid hormones play a key role in modulating the cardiovascular system, particularly through their interaction with catecholamines.

Most common cause of multiple fetal anomalies is:

 # Most common cause of multiple fetal anomalies is:

A. Syphilis

B. Tetracycline

C. Rubella

D. Rubeola

The correct answer is C. Rubella.

The correct answer is:

C. Rubella

Explanation:

Rubella, especially when contracted during the first trimester of pregnancy, is a significant cause of multiple fetal anomalies. This is due to its teratogenic effects, which can result in congenital rubella syndrome (CRS). The anomalies caused by CRS can include:

• Cardiac defects (e.g., patent ductus arteriosus, pulmonary artery stenosis)
• Ocular defects (e.g., cataracts, retinopathy, glaucoma)
• Auditory defects (e.g., sensorineural hearing loss)
• Neurological defects (e.g., microcephaly, developmental delays)

Other options:

• A. Syphilis: Can cause congenital syphilis with specific anomalies (e.g., skeletal deformities, Hutchinson teeth), but it is not the most common cause of multiple fetal anomalies.
• B. Tetracycline: Causes specific anomalies, mainly involving dental staining and hypoplasia, not a wide range of fetal anomalies.
• D. Rubeola (measles): While it can cause complications in pregnancy, it is less associated with multiple fetal anomalies compared to rubella.

Rubella is particularly significant due to its potential to cause a broad spectrum of anomalies when maternal infection occurs early in pregnancy.

Mean diameter of inferior alveolar nerve is:

 # Mean diameter of inferior alveolar nerve is:

A. 10 mm

B. 4.7 mm

C. 8 mm

D. 1.7 mm

The correct answer is B. 4.7 mm.

The inferior alveolar nerve is a branch of the mandibular nerve (the third division of the trigeminal nerve), responsible for providing sensory innervation to the lower teeth, chin, and lower lip. Its diameter is significant in clinical practices like dental anesthesia, nerve preservation during surgeries, and implant placement.

• The mean diameter of 4.7 mm reflects the nerve's size as it travels through the mandibular canal.

Inferior Alveolar – exits the mental foramen as the mental nerve and continues as the incisive nerve.

● The nerve to mylohyoid is a motor and sensory branch of the inferior alveolar nerve

● The nerve to anterior belly of the digastric muscle is a motor branch of the inferior alveolar nerve

Molar relation in primary dentition is determined by:

 # Molar relation in primary dentition is determined by:

A. Mesiobuccal cusp of maxillary first molar

B. Buccal groove of mandibular first molar

C. Distal surface of maxillary and mandibular second molar

D. Distal surface of maxillary and mandibular first molar

The correct answer is:

C. Distal surface of maxillary and mandibular second molar

Explanation:

In primary dentition, the molar relationship is determined by the alignment of the distal surfaces of the maxillary and mandibular second molars. This is used to describe the primary occlusion as either:

Flush terminal plane: The distal surfaces of the second molars are aligned in a straight plane.

Mesial step: The mandibular second molar’s distal surface is mesial to the maxillary second molar’s distal surface.

Distal step: The mandibular second molar’s distal surface is distal to the maxillary second molar’s distal surface.

These relationships are important because they influence the development of the permanent molar occlusion.