IMAT - International Medical Admissions Human Anatomy and Physiology Questions and Answers — Questions and Answers
Question 1: Which of the following correctly sequences the path of a deoxygenated red blood cell returning from the systemic circulation to the lungs?
- Left atrium -> Left ventricle -> Aorta -> Lungs
- Vena cava -> Right atrium -> Right ventricle -> Pulmonary artery (Correct answer)
- Pulmonary vein -> Left atrium -> Left ventricle -> Pulmonary artery
- Vena cava -> Left atrium -> Right atrium -> Lungs
Correct answer: Vena cava -> Right atrium -> Right ventricle -> Pulmonary artery
Deoxygenated blood returns from the body via the vena cavae into the right atrium. It is then pumped into the right ventricle, which contracts to send the blood through the pulmonary artery to the lungs for oxygenation.
Question 2: A patient's blood glucose level rises significantly after a meal. Which of the following represents the correct physiological negative feedback response to this stimulus?
- The pancreas releases glucagon, stimulating the liver to release glucose.
- The adrenal gland releases adrenaline, causing a rapid breakdown of glycogen.
- The pancreas releases insulin, stimulating cells to take up glucose from the blood. (Correct answer)
- The pituitary gland releases growth hormone, promoting glucose synthesis.
Correct answer: The pancreas releases insulin, stimulating cells to take up glucose from the blood.
High blood glucose stimulates the beta cells of the pancreas to release insulin. Insulin promotes the uptake of glucose by cells and the storage of glucose as glycogen in the liver, which lowers blood glucose levels back to the normal range. This is a classic negative feedback mechanism.
Question 3: The chemical digestion of proteins begins in which organ, and by which primary enzyme?
- Small intestine, by trypsin
- Mouth, by amylase
- Stomach, by pepsin (Correct answer)
- Liver, by bile
Correct answer: Stomach, by pepsin
The highly acidic environment of the stomach denatures proteins, and the enzyme pepsin begins their chemical digestion by breaking them down into smaller polypeptides.
Question 4: In the sliding filament model of skeletal muscle contraction, what is the direct role of calcium ions (Ca2+)?
- To provide the energy for the power stroke.
- To bind to troponin, causing tropomyosin to move and expose actin binding sites. (Correct answer)
- To bind to myosin heads, causing them to detach from actin.
- To break down ATP into ADP and phosphate.
Correct answer: To bind to troponin, causing tropomyosin to move and expose actin binding sites.
When released from the sarcoplasmic reticulum, Ca2+ binds to troponin. This action causes a conformational change that moves tropomyosin away from the myosin-binding sites on the actin filament, allowing cross-bridges to form and contraction to occur.
Question 5: Following the repolarization phase of a neuron's action potential, what is the primary function of the Na+/K+ pump?
- To generate the initial depolarization stimulus for the next action potential.
- To close the voltage-gated K+ channels to prevent hyperpolarization.
- To open voltage-gated Na+ channels to initiate a new impulse.
- To restore the resting ion concentration gradients by moving Na+ out and K+ into the cell. (Correct answer)
Correct answer: To restore the resting ion concentration gradients by moving Na+ out and K+ into the cell.
After an action potential, the ion concentrations of Na+ and K+ are imbalanced. The Na+/K+ pump actively transports 3 Na+ ions out of the cell for every 2 K+ ions it transports in, re-establishing the original concentration gradients necessary for the resting membrane potential.
Question 6: In the human respiratory system, the net diffusion of oxygen from the alveoli into the pulmonary capillaries is primarily driven by:
- The higher partial pressure of oxygen in the alveolar air compared to the capillary blood. (Correct answer)
- Active transport mechanisms that pump oxygen across the respiratory membrane.
- The higher temperature of the blood, which increases oxygen's solubility.
- The binding affinity of carbon dioxide for hemoglobin.
Correct answer: The higher partial pressure of oxygen in the alveolar air compared to the capillary blood.
Gas exchange occurs via passive diffusion down a pressure gradient. The partial pressure of oxygen (PO2) is significantly higher in the alveoli (inhaled air) than in the deoxygenated blood arriving at the lungs. This pressure difference forces oxygen to move from the alveoli into the blood.
IMAT - International Medical Admissions Human Anatomy and Physiology Questions and Answers
Which of the following correctly sequences the path of a deoxygenated red blood cell returning from the systemic circulation to the lungs?