MDS PREP
What is the function of cholecystokinin (CCK) in the digestive system?
1) Stimulates the release of bile from the liver
2) Increases the secretion of water in the collecting tubules of the kidney
3) Relaxes the lower esophageal sphincter
4) Decreases the motility of the small intestine
Physiology
Answer: 3
Cholecystokinin is a hormone secreted by the mucosa of the upper intestine in response to the presence of food, particularly proteins and fats. One of its key functions is to stimulate the contraction of the gallbladder and relax the sphincter of Oddi, facilitating the release of bile and pancreatic enzymes into the duodenum to aid in digestion.
The glomerular filtration rate (GFR) is determined by which two factors?
1) Blood pressure and urine osmolarity
2) Blood flow rate and tubular reabsorption
3) Net filtration pressure and glomerular capillary filtration coefficient (Kf)
4) Hormonal levels and urine volume
The glomerular filtration rate (GFR) is determined by net filtration pressure and the glomerular capillary filtration coefficient (Kf), which are critical for kidney function.
What is the role of calbindin in calcium absorption in the intestine?
1) It sequesters calcium in the intestinal lumen
2) It transports calcium across the brush border membrane
3) It binds calcium and prevents it from affecting epithelial signaling
4) It stimulates the release of calcium from the intestinal cells into the bloodstream
Physiology
Answer: 3
Calbindin sequesters calcium within the intestinal epithelial cells to prevent it from interfering with calcium-dependent signaling processes, thereby facilitating efficient calcium absorption without disrupting normal cellular function.
What is the role of the vagus nerve in regulating heart rate?
1) Increases heart rate
2) Decreases heart rate
3) Has no effect on heart rate
4) Increases the force of heart contractions
E. Increases the conduction velocity of the cardiac impulse
The vagus nerve, a part of the parasympathetic nervous system, has a negative chronotropic effect on the heart, meaning it decreases the heart rate. It does this by releasing acetylcholine onto the sinoatrial (S1) node, which slows the SA node's pacemaker activity.
What is the role of intrinsic factor in vitamin B12 absorption?
1) It protects vitamin B12 from gastric digestion
2) It facilitates binding of vitamin B12 to intestinal receptors
3) It synthesizes vitamin B12 in the gastrointestinal tract
4) It increases the production of gastric acid
Physiology
Answer: 2
Intrinsic factor binds to vitamin B12 and protects it from digestion, allowing it to be absorbed in the ileum.
Which of the following statements about the neuronal circuit of the cerebellum is true?
1) Climbing fibers originate from the cerebral cortex and terminate on purkinje cells.
2) Mossy fibers establish excitatory synapses with interneurons in the molecular layer.
3) Stellate and basket cells are stimulated by inhibitory inputs from purkinje cells.
4) Golgi cells are inhibited by mossy fiber inputs.
E. All of the above.
Mossy fibers originate from various sources in the brain and spinal cord and terminate on granule cells in the granular layer of the cerebellum. The axons of granule cells, called parallel fibers, stimulate the purkinje cells and also synapse with interneurons such as stellate and basket cells in the molecular layer and Golgi cells in the granular layer. Climbing fibers originate from the inferior olivary nuclei and synapse directly on purkinje cells. The statement that stellate and basket cells are stimulated by inhibitory inputs from purkinje cells is incorrect; they are stimulated by parallel fibers and inhibit purkinje cells. Golgi cells are also stimulated by mossy fibers and help in the regulation of the overall output of the cerebellum.
What type of aphasia results from a lesion in Broca’s area?
1) Sensory aphasia
2) Motor aphasia
3) Global aphasia
4) Conduction aphasia
E. Wernicke’s aphasia
A lesion in Broca's area leads to motor aphasia, also known as Broca's aphasia or expressive aphasia. This type of aphasia is characterized by difficulty in producing speech, particularly with grammatical errors and reduced vocabulary. Understanding of language is usually preserved, but the ability to form coherent sentences is impaired.
What is the primary function of type A? fibers?
1) Proprioception and motor function in muscle spindles
2) Pain and temperature sensation
3) Touch and pressure sensation
4) Autonomic regulation of smooth muscles
Type A? fibers are thinly myelinated and conduct pain and temperature signals rapidly. They are involved in the transmission of the initial sharp pain sensation, often in response to noxious stimuli such as pinpricks or intense heat.