MDS PREP
What is the effect of acetylcholine on the heart's sinoatrial (S1) node?
1) It increases the heart rate
2) It decreases the heart rate
3) It has no effect on the SA node
4) It causes arrhythmias in the SA node
Acetylcholine, released by the vagus nerve, acts on the SA node to slow down the heart rate by hyperpolarizing the membranes of the SA node cells and decreasing their automaticity.
MCQ: The pancreas has which of the following cell types?
1) Alpha cells
2) Beta cells
3) Delta cells
4) All of the above
The pancreas has all of the following cell types: alpha cells (which produce glucagon), beta cells (which produce insulin), and delta cells (which produce somatostatin).
What are the two major functions of GH?
1) Stimulation of growth hormone-dependent lipolysis and glycogenolysis
2) Stimulation of gluconeogenesis and growth of the skeletal system
3) Stimulation of cortisol synthesis and thyroid hormone release
4) Regulation of insulin secretion and cardiovascular function
Answer: 2) The two major functions of GH are the growth of the skeletal system and metabolic effects, including gluconeogenesis.
What is the primary function of the enteric nervous system in the gastrointestinal tract?
1) Controlling digestive enzyme secretion
2) Regulating the absorption of nutrients
3) Coordinating muscular contractions and peristalsis
4) Secreting hormones that regulate digestion
E) Controlling blood flow to the GI tract
The enteric nervous system, also known as the gut-brain, is a network of neurons that controls the muscular activity of the gastrointestinal tract. It is capable of operating independently of the central nervous system but can be modulated by it. Its main function is to regulate motility and secretion within the GI tract, which includes coordinating peristaltic contractions that propel food and facilitate mixing and absorption.
What is the function of the cholinergic system in the regulation of gastric acid secretion?
1) Stimulates HCL secretion
2) Inhibits HCL secretion
3) Has no direct effect on HCL secretion
4) Stimulates the release of gastrin
The cholinergic system, which is part of the parasympathetic nervous system, stimulates the parietal cells in the stomach to release hydrochloric acid (HCL) through the activation of muscarinic M1 receptors. This is crucial for the digestion of food and the maintenance of gastric pH.
What is the primary effect of thyroid hormones on the peripheral vascular resistance during the fight-or-flight response?
1) Increases peripheral vascular resistance
2) Decreases peripheral vascular resistance
3) No effect on peripheral vascular resistance
4) Variable effect on peripheral vascular resistance
Answer: 2) Decreases peripheral vascular resistanceExplanation: Thyroid hormones cause vasodilatation in several vascular beds, which decreases peripheral vascular resistance. This, along with increased cardiac output, leads to an overall increase in systolic blood pressure despite the diastolic BP possibly decreasing due to reduced resistance.
What is the function of the macula densa in the regulation of the nephron's function?
1) It secretes ADH to regulate water reabsorption.
2) It monitors sodium chloride concentration in the tubular fluid.
3) It produces erythropoietin to stimulate RBC production.
4) It is involved in the conversion of vitamin D to its active form.
The macula densa monitors sodium chloride concentration in the tubular fluid, playing a crucial role in regulating kidney function.
All of the following promote activation of muscle contraction EXCEPT
1. Binding of myosin to actin.
2. Opening of the sarcoplasmic reticulum Ca channel.
3. Ca2+ binding to troponin C.
4. Opening of Na channels.
Physiology
Answer: 1
Activation of muscle contraction is promoted by :
Opening of the sarcoplasmic reticulum Ca channel.
Ca2+ binding to troponin C.
Opening of Na channels
Ca2+ binding to the Ca2+-ATPase