MDS PREP
What is the role of gastrin in the gastric phase of gastric acid secretion?
1) It directly stimulates the release of HCl from parietal cells.
2) It inhibits the release of HCl from parietal cells.
3) It activates the myenteric plexus to enhance intestinal motility.
4) It promotes the release of bicarbonate into the stomach lumen.
E) It is not involved in the gastric phase of acid secretion.
Gastrin is a hormone released by G cells in the gastric antrum in response to the presence of food, especially protein. It acts on parietal cells in the gastric glands, stimulating them to produce and secrete hydrochloric acid (HCl) and intrinsic factor, which is essential for vitamin B12 absorption. Gastrin is a critical component of the gastric phase, which is responsible for the bulk of gastric acid secretion.
What is the primary neurotransmitter responsible for the contraction of the pupillary sphincter muscle?
1) Acetylcholine
2) Norepinephrine
3) Epinephrine
4) GABA
Answer: 1) AcetylcholineExplanation: The pupillary sphincter muscle is innervated by the parasympathetic nervous system, which uses acetylcholine as its primary neurotransmitter. Contraction of this muscle leads to pupil constriction, or miosis, which occurs in low-light conditions or when focusing on near objects.
What is the significance of the transport maximum for substances like glucose and phosphate?
1) It indicates the maximum amount that can be filtered by the glomerulus
2) It represents the maximum amount that can be actively reabsorbed by the tubules
3) It is the point at which the substance begins to be excreted in the urine
4) It is the point at which the substance becomes toxic to the body
The transport maximum for substances like glucose and phosphate represents the maximum amount that can be actively reabsorbed by the tubules before reaching saturation and being excreted in urine.
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).
The regulation of sodium reabsorption in the kidney tubules involves which of the following?
1) Tubulo-glomerular feedback
2) Glomerulo-tubular feedback
3) Both A and B
4) Neither A nor B
Tubulo-glomerular feedback (TGF) and glomerulo-tubular feedback (GTF) are both important in regulating sodium reabsorption in the kidney tubules. TGF involves the macula densa sensing the sodium chloride concentration in the tubular fluid and adjusting the glomerular filtration rate accordingly, while GTF is the adjustment of tubular sodium reabsorption in response to changes in glomerular filtration rate.
Diabetic insipidus is due to the lack of
1 Insulin
2 Angiotensin.
3 Aldosterone.
4 A.D.H.
Physiology
Answer: 4
Diabetic insipidus is due to the lack of 4. A.D.H. (Antidiuretic hormone).
Explanation:
Diabetic insipidus (DI) is a condition characterized by the production of large
volumes of dilute urine due to the lack of the antidiuretic hormone (ADH) or the
body's inability to respond to it. It is different from diabetes mellitus, which
involves problems with insulin and blood sugar regulation.
1. Insulin: Insulin is a hormone produced by the pancreas that plays a critical
role in regulating blood sugar levels. A deficiency or resistance to insulin
leads to diabetes mellitus, not diabetic insipidus. Diabetes mellitus is
characterized by hyperglycemia (high blood sugar) and increased thirst and urine
production due to the inability of the kidneys to reabsorb glucose properly.
2. Angiotensin: Angiotensin is a hormone system that plays a role in the
regulation of blood pressure and fluid balance. It is involved in the
renin-angiotensin-aldosterone system (RAAS). While it is crucial for maintaining
blood pressure, it is not directly related to the pathophysiology of diabetic
insipidus.
3. Aldosterone: Aldosterone is a mineralocorticoid hormone produced by the
adrenal glands. It helps regulate sodium and potassium levels in the body, which
in turn affects fluid and blood volume. While it is essential for electrolyte
and fluid balance, it does not cause diabetic insipidus when lacking.
4. Antidiuretic hormone (ADH): ADH is a hormone produced by the hypothalamus and
stored in the posterior pituitary gland. It acts on the kidneys to increase
water reabsorption, which leads to the production of concentrated urine. In
diabetic insipidus, there is either a deficiency of ADH or the kidneys fail to
respond to it adequately. This results in the kidneys being unable to reabsorb
enough water, leading to the production of large volumes of dilute urine and
increased thirst.
There are two main types of diabetic insipidus: central and nephrogenic. Central
DI occurs when the pituitary gland does not produce enough ADH, while
nephrogenic DI results from the kidneys' inability to respond to ADH. Both types
lead to an imbalance in water regulation and can cause symptoms such as polyuria
(excessive urine production), polydipsia (excessive thirst), and dehydration if
not managed properly.
To treat diabetic insipidus, the underlying cause must be addressed. If it is
central DI, synthetic ADH (desmopressin) is administered to replace the missing
hormone. If it is nephrogenic DI, the treatment focuses on addressing the
kidney's response to ADH and managing symptoms such as maintaining fluid intake
and sometimes medications to reduce urine output.
What is the function of titin in muscle contraction?
1) It provides the structural framework for the sarcomere
2) It acts as a bridge between actin and myosin filaments
3) It is the primary contractile protein in muscle fibers
4) It regulates muscle length during contraction and relaxation
Titin acts as a scaffold that supports the alignment of the thick and thin myofilaments in muscle cells, maintaining the integrity of the sarcomere structure during contraction.
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.