MDS PREP
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 primary function of the reticular activating system during wakefulness?
1) It initiates REM sleep
2) It suppresses sensory input
3) It filters and modulates sensory information
4) It maintains the overall level of arousal and alertness
The reticular activating system (RAS) is involved in the regulation of wakefulness and arousal by modulating the transmission of sensory information to the thalamus and cortex and by influencing the release of neurotransmitters that promote alertness.
What is the mechanism of action of umami taste substances?
1) Activation of sodium-dependent glucose transporters
2) Stimulation of bitter G-protein coupled receptors
3) Activation of amiloride-sensitive sodium channels
4) Activation of glutamate taste sensors (glutamate receptors)
Umami taste is triggered by the activation of glutamate receptors present in taste cells, which leads to the perception of savoriness.
What happens when the estrogen level crosses a certain threshold during the menstrual cycle?
1) It inhibits the release of LH and FSH
2) It stimulates the release of LH and FSH
3) It has no effect on pituitary hormone secretion
4) It triggers ovulation
Physiology
Answer: 4
Around day 11 of the menstrual cycle, the rising estrogen level reaches a threshold that has a positive feedback effect on LH secretion, leading to the LH surge. This LH surge is essential for ovulation to occur.
What is the role of the acrosome in sperm?
1) Provides energy for sperm motility
2) Contains enzymes that help in the penetration of the ovum
3) Protects the sperm DNA
4) Involved in the fertilization process by fusing with the egg membrane
Physiology
Answer: 2
The acrosome is a cap-like structure located on the head of a spermatozoon. It contains lysosome-like organelles rich in enzymes that are essential for penetrating the egg's outer layers during fertilization.
What is the most common cause of vitamin D deficiency?
1) Inadequate sunlight exposure
2) Poor dietary intake of vitamin D
3) Impaired liver function
4) Impaired kidney function
Physiology
Answer: 1
Vitamin D deficiency is most commonly due to insufficient exposure to sunlight, as the skin synthesizes vitamin D when exposed to UVB radiation. Other factors include poor dietary intake and impaired conversion or absorption in the liver and kidneys.
What is the typical rate of gastric emptying in healthy individuals?
1) 0.5-1.5 liters per hour
2) 1-2 liters per hour
3) 2-4 liters per hour
4) 4-6 liters per hour
E) It varies with the type and amount of food consumed
The rate of gastric emptying is influenced by the type and amount of food consumed. In healthy individuals, it typically takes 1-4 hours for the stomach to empty its contents into the duodenum. The rate of emptying can be slower with high-fiber or high-fat meals and faster with liquids. Factors such as gastric motility, the presence of gastric emptying hormones, and the presence of food in the intestine also play a role in this process.
What is the primary inhibitory neurotransmitter in the central nervous system?
1) Dopamine
2) GABA (gamma-aminobutyric acid)
3) Glutamate
4) Acetylcholine
GABA is the main inhibitory neurotransmitter in the central nervous system, playing a crucial role in reducing the excitability of neurons and contributing to the regulation of neural circuits and synaptic plasticity.