MDS PREP
The osmolarity of the tubular fluid in the medullary collecting duct is primarily controlled by which hormone?
1) Aldosterone
2) Atrial Natriuretic Peptide (ANP)
3) Antidiuretic Hormone (ADH)
4) Renin
The osmolarity of the tubular fluid in the medullary collecting duct is primarily controlled by Antidiuretic Hormone (ADH), which increases water reabsorption.
What is the typical pH of gastric chyme when it enters the duodenum?
1) 1.0-2.0 (very acidic)
2) 2.0-4.0 (slightly acidic)
3) 4.0-6.0 (weakly acidic)
4) 6.0-8.0 (slightly alkaline)
E) 8.0-10.0 (alkaline)
Gastric chyme, which is the mixture of food and gastric juice, is highly acidic due to the presence of hydrochloric acid secreted by parietal cells. The pH typically ranges from 1.0 to 2.0 when it enters the duodenum. This acidity helps to denature proteins and provides the optimal environment for pepsin activity. Once in the duodenum, the chyme is neutralized by the secretion of bicarbonate from the pancreas and bile from the liver.
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 significance of the intestinal phase of gastric acid secretion?
1) It is responsible for the majority of acid secretion
2) It is primarily responsible for the inhibition of acid secretion
3) It is only triggered by the thought of food
4) It is not a significant phase of gastric acid secretion
The intestinal phase of gastric acid secretion is primarily responsible for the inhibition of acid secretion, helping to regulate the digestive process after food enters the intestine.
What is the primary site of vitamin B12 absorption in the intestine?
1) Stomach
2) Duodenum
3) Jejunum
4) Ileum
Physiology
Answer: 4
The ileum is the primary site of vitamin B12 absorption, facilitated by intrinsic factor binding to specific receptors.
Which of the following is a characteristic of the absolute refractory period during an action potential?
1) The membrane is fully depolarized.
2) The membrane is fully repolarized.
3) The membrane is inexcitable regardless of the strength of the stimulus.
4) The membrane is hyperpolarized.
E. The membrane is depolarized.
The absolute refractory period occurs during the initial phase of repolarization after an action potential. During this period, the membrane is inactivated and cannot be depolarized to generate another action potential, regardless of the stimulus strength. This ensures that action potentials are unidirectional and do not propagate backward along the axon.
Which part of the autonomic nervous system is responsible for the regulation of the visceral organs during rest and digestion?
1) Sympathetic nervous system
2) Parasympathetic nervous system
3) Enteric nervous system
4) Sensory nervous system
The parasympathetic nervous system is involved in the regulation of the body's rest and digest functions. It operates to conserve energy and restore the body to a state of equilibrium. It acts on various visceral organs, such as the heart, gastrointestinal tract, and bladder, to slow down the heart rate, increase glandular secretions, and promote peristalsis for food assimilation.
What is the primary site of bilirubin deposition in tissues during jaundice?
1) The liver
2) The spleen
3) The skin and sclera
4) The pancreas
The primary site of bilirubin deposition in tissues during jaundice is the skin and sclera, leading to yellowing.