Human Physiology
Which hormone is primarily responsible for increasing blood glucose levels during the fight-or-flight response?
A
Epinephrine
B
Insulin
C
Glucagon
D
Thyroxine
Correct Answer:
A. Epinephrine
Epinephrine (adrenaline) is released by the adrenal medulla during stress and increases blood glucose by promoting glycogenolysis and inhibiting insulin secretion.
The countercurrent multiplier mechanism in the Loop of Henle allows the kidney to produce concentrated urine by:
A
Active transport of ions without water movement in ascending limb
B
Passive diffusion of all solutes
C
Random osmotic pressure changes
D
Continuous filtration at equal rates
Correct Answer:
A. Active transport of ions without water movement in ascending limb
The ascending limb actively transports Na+/K+/Cl- without water permeability, creating osmotic gradients that concentrate urine in the collecting duct.
A patient with nephrotic syndrome exhibits severe proteinuria. This occurs because:
A
Glomerular filtration rate is severely reduced
B
Increased permeability of glomerular filtration barrier
C
Decreased plasma colloid osmotic pressure
D
Increased glomerular hydrostatic pressure
Correct Answer:
B. Increased permeability of glomerular filtration barrier
Nephrotic syndrome involves damage to the glomerular filtration barrier (podocytes), increasing permeability to plasma proteins like albumin.
During an action potential in a neuron, the rapid depolarization phase is primarily due to:
A
Opening of K+ channels
B
Closing of Na+ channels
C
Opening of voltage-gated Na+ channels
D
Activation of Na+/K+ ATPase
Correct Answer:
C. Opening of voltage-gated Na+ channels
Depolarization occurs when voltage-gated Na+ channels open, allowing rapid Na+ influx that reverses membrane potential towards positive values.
A mutation affecting the dystrophin gene would primarily result in:
A
Hemophilia
B
Duchenne muscular dystrophy
C
Cystic fibrosis
D
Huntington's disease
Correct Answer:
B. Duchenne muscular dystrophy
Dystrophin protein deficiency causes Duchenne muscular dystrophy, an X-linked recessive disorder affecting muscle structure and function.
In the renal tubule, selective reabsorption of useful substances like glucose occurs primarily in:
A
Bowman's capsule
B
Proximal convoluted tubule
C
Loop of Henle
D
Distal convoluted tubule
Correct Answer:
B. Proximal convoluted tubule
The proximal convoluted tubule epithelial cells have numerous mitochondria and microvilli for active transport of glucose, amino acids, and ions.
Which of the following conditions results from deficiency of intrinsic factor?
A
Scurvy
B
Pernicious anemia
C
Beriberi
D
Pellagra
Correct Answer:
B. Pernicious anemia
Intrinsic factor is required for B12 absorption; its deficiency leads to pernicious anemia due to impaired vitamin B12 absorption.
A person experiences vasoconstriction and increased heart rate upon seeing a predator. This response is mediated by:
A
Parasympathetic nervous system
B
Sympathetic nervous system
C
Enteric nervous system
D
Somatic nervous system
Correct Answer:
B. Sympathetic nervous system
The fight-or-flight response involves sympathetic activation releasing epinephrine and norepinephrine causing vasoconstriction and tachycardia.
The resting membrane potential of a typical neuron is approximately:
A
-30 mV
B
-70 mV
C
-100 mV
D
+50 mV
Correct Answer:
B. -70 mV
The resting potential is maintained at -70 mV primarily by the Na+/K+ ATPase pump and differential ion permeability.
Which blood cells are responsible for producing antibodies?
A
Neutrophils
B
Plasma cells
C
Macrophages
D
Dendritic cells
Correct Answer:
B. Plasma cells
Plasma cells (differentiated B lymphocytes) produce and secrete specific antibodies in response to antigens.
