The axon hillock is a region of the neuronal soma that________________?
Show answer Hide answer
Answer: B. Has no Nissl granules
Explanation
The axon hillock is characterized by the absence of Nissl granules, distinguishing it from the neuronal soma and dendrites. This specialized region of the cell body transitions into the initial segment of the axon where action potentials originate. The lack of rough endoplasmic reticulum in this specific area creates a paler appearance under microscopic examination. Neurons possess distinct structural compartments that facilitate the reception, integration, and transmission of electrochemical nerve signals. Nissl granules consist of dense clumps of rough endoplasmic reticulum and free ribosomes involved in high-rate protein synthesis. The axon hillock acts as a crucial summation zone where incoming graded potentials determine whether an action potential fires.
Neurons typically feature dense Nissl granules throughout their cytoplasm and dendrites, exactly where the axon hillock lacks them. Dendrites originate from different regions of the cell body and contain abundant Nissl substance near their bases. The shape of the axon hillock is typically conical rather than strictly round, serving as a transitional structural zone.
Related questions
Q1. All of the following clinical findings are typical of Cushing's syndrome except_______________?
Show answer Hide answer
Answer: C. Hypoglycemia
Excess cortisol stimulates gluconeogenesis and peripheral insulin resistance, raising blood glucose levels. Cushing's syndrome typically presents with fasting hyperglycemia rather than decreased blood sugar. Option C is...
Q2. All of the following hormones utilize cell surface receptors except_____________?
Show answer Hide answer
Answer: D. Thyroxine
Thyroxine is a hydrophobic amino acid-derived hormone bound to plasma carrier proteins in circulation. Its lipophilic nature enables it to diffuse passively across the target cell membrane. Once inside, it binds nuclear...
Q3. A pediatric patient falls below the third height percentile with normal growth velocity, where chronological age exceeds skeletal age. The most probable diagnosis is______________?
Show answer Hide answer
Answer: A. Constitutional delay in growth
Constitutional delay in growth presents with delayed skeletal bone age that closely matches height age. Patients maintain a normal growth velocity despite falling below standard height percentiles during childhood. Puber...
Q4. Aphasia is most frequently linked to a localized lesion within_______________?
Show answer Hide answer
Answer: A. Broca’s area
Broca’s area is located within the frontal lobe and controls motor aspects of speech. Damage to this critical language center results in expressive aphasia with impaired speech production. Option A is correct because aph...
Q5. What proportion of filtered glucose is reabsorbed within the proximal convoluted tubule_______________?
Show answer Hide answer
Answer: A. 100%
The proximal convoluted tubule possesses specialized transport proteins for active glucose reabsorption. Sodium-glucose cotransporters capture virtually all filtered glucose molecules from the tubular lumen. Consequently...
Q6. Bacterial pathogens are most frequently engulfed by _________________?
Show answer Hide answer
Answer: A. Neutrophilic leukocytes
Neutrophilic leukocytes are professional phagocytes equipped with specialized granules and surface receptors for pathogens. They migrate rapidly toward sites of infection to engulf and destroy invading bacterial microorg...