MDS PREP
What is the primary effect of norepinephrine on the pupillary dilator muscle?
1) Contraction
2) Relaxation
3) No effect
4) It depends on the presence of other neurotransmitters
Answer: 1) ContractionExplanation: Norepinephrine acts on alpha-adrenergic receptors on the pupillary dilator muscle, causing its contraction and pupil dilatation (mydriasis). This is part of the sympathetic nervous system's response to stress and increased alertness during the fight-or-flight response.
What is the effect of vitamin E deficiency on cell membranes?
1) Increased fluidity
2) Decreased fluidity
3) No change in fluidity
4) Unknown
Physiology
Answer: 2
Vitamin E is an important antioxidant that protects unsaturated fats in cell membranes from oxidation. Without vitamin E, these fats can become oxidized, leading to decreased fluidity and altered function of membranes.
What is the primary effect of insulin on the skeletal muscles?
1) Stimulation of protein synthesis
2) Increased glycolysis
3) Increased glucose uptake and glycogen synthesis
4) Stimulation of muscle contraction
Answer: 3) Increased glucose uptake and glycogen synthesisExplanation: Insulin stimulates glucose uptake by muscle cells and promotes glycogen synthesis. It does so by increasing the number of glucose transporters on the muscle cell membrane and facilitating the transport of glucose into the cells.
What happens when the transport maximum for glucose is exceeded?
1) All excess glucose is reabsorbed
2) Some glucose is reabsorbed and some is excreted
3) All excess glucose is excreted in the urine
4) No glucose is excreted regardless of the amount
When the transport maximum for glucose is exceeded, some glucose is reabsorbed and some is excreted in the urine, leading to glucosuria.
What happens to the skin color in dark-skinned patients with high serum bilirubin levels?
1) It turns yellow.
2) It turns green.
3) It remains unaffected.
4) It turns blue.
In dark-skinned patients with high serum bilirubin levels, the skin turns yellow due to the accumulation of bilirubin.
What is the main mechanism by which the intestinal phase inhibits gastric acid secretion?
1) By releasing hormones that inhibit gastrin release
2) By promoting the release of somatostatin
3) By reducing vagal input to the stomach
4) By increasing the pH of gastric contents
E) By reducing the activity of the myenteric plexus
The intestinal phase of gastric acid secretion is mainly responsible for inhibiting gastric secretion. This is primarily achieved through the release of hormones like secretin and cholecystokinin (CCK) in response to the presence of acidic chyme in the duodenum. These hormones act on D cells in the stomach to reduce gastrin secretion, which in turn decreases acid production by parietal cells. Additionally, the presence of food in the intestine triggers an enterogastric reflex that inhibits the vagal nerve's excitatory effects on the stomach.
The reticular formation gives rise to which of the following extrapyramidal tracts?
1) Corticospinal tract
2) Reticulospinal tract
3) Vestibulospinal tract
4) Rubrospinal tract
E. Tectospinal tract
The reticulospinal tract arises from neurons in the reticular formation of the brainstem and projects to the spinal cord. It influences both voluntary and involuntary motor activities, modulating the excitability of motor neurons. The corticospinal tract arises from the cerebral cortex, the vestibulospinal tract from the vestibular nuclei, the rubrospinal tract from the red nucleus, and the tectospinal tract from the superior colliculus.
Which of the following statements is true about the regulation of the sympathetic nervous system?
1) The sympathetic nervous system is primarily regulated by the parasympathetic nervous system.
2) The sympathetic nervous system is mainly controlled by the hypothalamus.
3) The sympathetic nervous system is regulated by the spinal cord through the sympathetic chain ganglia.
4) The sympathetic nervous system is primarily regulated by the sympathetic chain ganglia.
Answer: 3) The sympathetic nervous system is regulated by the spinal cord through the sympathetic chain ganglia, which receive input from the hypothalamus and other higher centers.