MDS PREP
What is the role of leptin in the regulation of food intake?
1) It stimulates food intake
2) It inhibits food intake
3) It has no effect on food intake
4) It increases the absorption of nutrients in the intestine
Leptin plays a role in the regulation of food intake by inhibiting hunger, signaling to the brain that the body has enough energy stored.
What is the function of cholecystokinin (CCK) in the digestive system?
1) Stimulates the release of bile from the liver
2) Increases the secretion of water in the collecting tubules of the kidney
3) Relaxes the lower esophageal sphincter
4) Decreases the motility of the small intestine
Physiology
Answer: 3
Cholecystokinin is a hormone secreted by the mucosa of the upper intestine in response to the presence of food, particularly proteins and fats. One of its key functions is to stimulate the contraction of the gallbladder and relax the sphincter of Oddi, facilitating the release of bile and pancreatic enzymes into the duodenum to aid in digestion.
What type of aphasia is associated with lesions in the temporal lobe's auditory association area?
1) Broca's aphasia
2) Wernicke's aphasia
3) Global aphasia
4) Sensory aphasia
Wernicke's aphasia is associated with lesions in the temporal lobe's auditory association area, particularly Brodmann's area 22. It is characterized by fluent speech with impaired comprehension and repetition.
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.
What happens to lithocholic acid in the enterohepatic circulation?
1) It is reabsorbed in the terminal ileum and returned to the liver
2) It is metabolized into chenodeoxycholic acid
3) It is converted into deoxycholic acid
4) It is excreted in feces due to its insolubility
Lithocholic acid is excreted in feces due to its insolubility, as it is not efficiently reabsorbed in the enterohepatic circulation.
The glomerular filtration barrier consists of:
1) Endothelial cells
2) Basement membrane
3) Podocytes
4) All of the above
The glomerular filtration barrier is a three-layered structure composed of endothelial cells of the glomerular capillaries, the basement membrane, and the podocytes (visceral epithelial cells of Bowman's capsule). These layers work together to filter blood, allowing small molecules to pass into the nephron while retaining larger ones.
What is the primary mechanism by which the stomach protects itself from self-digestion by its own enzymes?
1) Mucus secretion by gastric mucosal cells
2) Presence of intrinsic factor in the gastric juice
3) High concentration of bicarbonate in gastric juice
4) Low pH of gastric juice inhibiting its own enzymes
E) The mucosal lining is impermeable to H+ ions
The stomach protects itself from the harsh acidic environment and its own digestive enzymes through the secretion of a thick layer of mucus by mucosal cells. This mucus barrier forms a physical and chemical barrier that shields the underlying tissue from the acid and pepsin. Additionally, the stomach lining has a high turnover rate and is continuously regenerated, and the enzymes in the gastric juice are inactive until they come into contact with food.
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, known as the first sensation of urgency, typically occurs when the bladder is about one-quarter full, which is around 150 ml. This is the point where an individual begins to become aware of the need to urinate.