MDS PREP
MCQ: The first sensation of bladder filling occurs at approximately:
1) 150 ml
2) 250 ml
3) 450 ml
4) 750 ml
The first sensation of bladder filling occurs at approximately 150 ml, signaling the need to void.
Most of the pre ganglionic sympathetic fibres are
1 A fibres
2 B fibres
3 C Fibres
4 None of the above
Physiology
Answer: 2
- A fibres are myelinated fibres having fastest rate of conduction
Which of the following is NOT a clinical consequence of defective bile acid absorption?
1) Fat malabsorption
2) Steatorrhea
3) Hemolytic anemia
4) Vitamin K deficiency
Physiology
Answer: 3
Defective bile acid absorption primarily leads to fat malabsorption and vitamin deficiencies, including vitamin K, but not directly to hemolytic anemia.
What is the role of gastrin in the gastric phase of acid secretion?
1) It is released by the pancreas and stimulates acid secretion in the stomach
2) It is released by the duodenum and inhibits acid secretion
3) It is released by the stomach and stimulates acid secretion in response to food
4) It has no role in gastric acid secretion
Gastrin is released by the stomach and stimulates acid secretion in response to food, playing a key role in the gastric phase of digestion.
An unstable membrane potential that will spontaneously depolarize is a property of which type of muscle?
1. Cardiac only
2. Cardiac and smooth
3. Skeletal and smooth
4. Skeletal and cardiac
Physiology
Answer: 1
The type of muscle that exhibits an unstable membrane potential that will
spontaneously depolarize is cardiac muscle.
Cardiac muscle cells, which are responsible for the contraction of the heart,
have an intrinsic ability to contract rhythmically without the need for external
stimulation. This is due to their unique property of automaticity, which is
mediated by the presence of the sinoatrial (SA) node and the subsequent
propagation of electrical impulses throughout the heart via the conduction
system. The SA node, often referred to as the "natural pacemaker" of the heart,
generates action potentials spontaneously and sets the heart rate.
The cardiac action potential involves a series of ionic currents across the cell
membrane that result in the depolarization and repolarization of the membrane.
During the resting phase, the membrane potential is maintained at a negative
value (around -90 mV) primarily due to the efflux of potassium ions (K+). When
the SA node initiates an action potential, voltage-gated sodium (Na+) channels
open, allowing an influx of sodium ions that leads to depolarization. Following
this, calcium (Ca2+) and more sodium ions enter the cell through voltage-gated
calcium (CaV) and sodium (Nav) channels, while potassium ions efflux through
various types of potassium (K+) channels, contributing to the plateau phase and
repolarization of the membrane.
The spontaneous depolarization of cardiac muscle cells is essential for the
coordinated contraction of the heart, which is critical for maintaining blood
circulation in the body. This property is not typically found in skeletal
muscles, which require an external signal from motor neurons to contract, nor in
smooth muscles, which are controlled by the autonomic nervous system and
hormones.
MCQ: The epithelial cells of the villi in the small intestine are responsible for:
1) Secreting gastric acid
2) Synthesizing bile
3) Final stage of digestion and nutrient absorption
4) All of the above
The epithelial cells of the villi in the small intestine are responsible for the final stage of digestion and nutrient absorption, playing a crucial role in the digestive process.
What is the function of the hypothalamus in the regulation of spermatogenesis?
1) It produces gonadotropin-releasing hormone (GnRH) which stimulates the release of LH and FSH from the pituitary
2) It produces androgens such as testosterone
3) It directly controls the maturation of spermatids
4) It has no role in spermatogenesis
Physiology
Answer: 1
The hypothalamus produces GnRH, which stimulates the anterior pituitary to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH is essential for the maturation of spermatogonia into primary spermatocytes, while LH acts on Leydig cells to produce testosterone, which is critical for the later stages of spermatogenesis and sperm maturation.
Which of the following substances does NOT directly depolarize taste cells during the sensation of bitter taste?
1) Increased intracellular calcium (Ca+) concentration
2) Activation of amiloride-sensitive Na+ channels
3) Closure of K+ channels
4) Release of neuronal glutamic acid
Bitter taste is mediated by the activation of bitter receptors, which are G protein-coupled and result in an increase in intracellular Ca+2 and subsequent neurotransmitter release, not by the activation of sodium channels as seen in salty taste transduction.