MDS PREP
What is the role of the sodium-calcium exchanger (NCX) in calcium homeostasis?
1) It transports calcium into cells
2) It transports sodium into cells and calcium out of cells
3) It transports sodium out of cells and calcium into cells
4) It has no role in calcium homeostasis
Physiology
Answer: 3
The sodium-calcium exchanger (NCX) is involved in the regulation of calcium levels in cells. It exchanges three sodium ions (Na+) for one calcium ion (Ca2+), thereby helping to maintain intracellular calcium homeostasis.
What type of aphasia is associated with lesions in the temporal lobe's auditory association area?
1) Broca's aphasia
2) Wernicke's aphasia
3) Global aphasia
4) Sensory aphasia
Wernicke's aphasia is associated with lesions in the temporal lobe's auditory association area, particularly Brodmann's area 22. It is characterized by fluent speech with impaired comprehension and repetition.
What is the threshold for phosphate excretion in the urine?
1) 0.10 mM
2) 0.50 mM
3) 1.00 mM
4) 2.00 mM
Physiology
Answer: 2
The threshold for phosphate excretion is when the plasma phosphate concentration reaches approximately 0.50 mM, causing some to be filtered into the urine.
MCQ: The epithelial cells of the villi in the small intestine are responsible for:
1) Secreting gastric acid
2) Synthesizing bile
3) Final stage of digestion and nutrient absorption
4) All of the above
The epithelial cells of the villi in the small intestine are responsible for the final stage of digestion and nutrient absorption, playing a crucial role in the digestive process.
Which type of autonomic nerve fibers are primarily involved in the pupillary light reflex?
1) Muscarinic
2) Adrenergic
3) Nicotinic
4) GABAergic
The pupillary light reflex is mediated by the parasympathetic nervous system, which uses acetylcholine as its neurotransmitter and acts on muscarinic receptors. The contraction of the sphincter pupillae muscle, which is innervated by the parasympathetic system, results in pupil constriction (miosis) in response to light.
What is the primary mechanism of H+ secretion by parietal cells?
1) Active transport via the sodium-hydrogen exchanger (NHE3)
2) Secretion through H+-K+ ATPase pump
3) Secretion through a chloride-bicarbonate antiporter
4) Secretion through a sodium-bicarbonate cotransporter
E) Secretion through a sodium-hydrogen antiporter
The primary mechanism of H+ secretion by parietal cells is through the action of the H+-K+ ATPase pump, also known as the proton pump. This enzyme is responsible for actively transporting H+ ions into the gastric lumen while moving K+ ions into the cells, thereby acidifying the gastric content.
Which cranial nerve is involved in the parasympathetic innervation of the lacrimal gland and pupillary constriction?
1) Cranial nerve III (Oculomotor)
2) Cranial nerve VII (Facial)
3) Cranial nerve X (Vagus)
4) Cranial nerve V (Trigeminal)
The vagus nerve, also known as the tenth cranial nerve, provides the parasympathetic innervation to various organs, including the lacrimal gland for tear production and pupillary constriction via the ciliary ganglia.
What is the primary role of the cephalic phase of gastric acid secretion?
1) Stimulation of gastrin release in the stomach
2) Secretion of gastric juices in response to the thought or smell of food
3) Increase in gastric motility
4) Secretion of gastric juices in response to food entering the duodenum
Physiology
Answer: 2
The cephalic phase of gastric acid secretion is initiated by the parasympathetic system and is triggered by the sight, smell, or thought of food. It accounts for approximately 20% of total acid secretion and prepares the stomach for digestion even before food arrives.