Which of the following is the correct sequence that describes the excitation and contraction of a skeletal muscle fiber?

A. Tropomyosin shifts and unblocks the cross-bridge binding sites.

B. Calcium is released and binds to the troponin complex.

C. Transverse tubules depolarize the sarcoplasmic reticulum.

D. The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using energy from ATP.

E. An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane.

TLS Online TPP Program

#Question id: 12060

#Unit 7. System Physiology – Animal

 Eating a meal leads to a large increase in gastric acid secretion that peaks within about 5 min and returns to normal about 4 hr after a meal is taken. How long after a meal does the pH of the gastric contents reach its lowest level (in hours)?

TLS Online TPP Program

#Question id: 12061

#Unit 7. System Physiology – Animal

Cystic fibrosis (CF) is an inherited disorder of the exocrine glands, affecting children and young people. Mucus in the exocrine glands becomes thick and sticky and eventually blocks the ducts of these glands (especially in the pancreas, lungs, and liver), forming cysts. A primary disruption in the transfer of which ion across cell membranes occurs in CF leading to decreased secretion of fluid?

TLS Online TPP Program

#Question id: 12062

#Unit 7. System Physiology – Animal

Mass movements are often stimulated after a meal by distention of the stomach (gastrocolic reflex) and distention of the duodenum (duodenocolic reflex). Mass movements often lead to which of the following?

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#Question id: 12211

#Unit 7. System Physiology – Animal

A 57-year-old man is admitted as an emergency for upper GI bleeding. Endoscopy reveals multiple ulcers in the duodenum. Serum gastrin levels are eight-fold higher compared to normal. Zollinger-Ellison syndrome (ZES, gastrinoma) is suspected. Administration of which of the following substances is useful in confirming the diagnosis?

TLS Online TPP Program

#Question id: 12212

#Unit 7. System Physiology – Animal

 A 71-year-old man with upper abdominal pain and blood in the stool takes NSAIDS for the pain and washes it down with whiskey. Pentagastrin administration produced lower than predicted levels of gastric acid secretion. Secretion of which of the following substances is most likely to be diminished in this patient with gastritis?

TLS Online TPP Program

#Question id: 12213

#Unit 7. System Physiology – Animal

The gastric phase of gastric secretion accounts for about 60% of the acid response to a meal. Which of the following can virtually eliminate the secretion of acid during the gastric phase?