1. The T wave on an ECG corresponds to:

A. Atrial depolarization
B. Ventricular depolarization
C. Atrial repolarization
D. Ventricular repolarization

Correct answer: D

Rationale: The T wave on an ECG corresponds to ventricular repolarization. During this phase, the ventricles are resetting electrically after contraction, preparing for the next heartbeat. Atrial depolarization is represented by the P wave, ventricular depolarization by the QRS complex, and atrial repolarization is typically hidden within the QRS complex. Therefore, option D, 'Ventricular repolarization,' is the correct choice when identifying the electrical activity represented by the T wave on an ECG.

2. The tiny contractile units within muscle cells are called:

A. Myocytes
B. Myofibrils
C. Sarcomeres
D. Tendons

Correct answer: C

Rationale: The correct answer is C: Sarcomeres. Sarcomeres are the basic contractile units within muscle cells. They are made up of overlapping filaments of actin and myosin proteins, which slide past each other during muscle contraction, resulting in muscle movement. Myocytes (A) are muscle cells, myofibrils (B) are cylindrical structures within muscle fibers composed of sarcomeres, and tendons (D) are tough bands of connective tissue that connect muscle to bone. Therefore, sarcomeres are specifically responsible for muscle contraction within muscle cells.

3. In a neutral atom, the number of electrons:

A. Must be equal to the number of protons.
B. Must be less than the number of protons.
C. Must be greater than the number of neutrons.
D. Can vary depending on the atom's temperature.

Correct answer: A

Rationale: Must be equal to the number of protons - For electrical neutrality, the positive charge of protons must be balanced by the negative charge of an equal number of electrons.

4. During gas exchange in the alveoli, what happens to oxygen?

A. Oxygen is released from the bloodstream into the alveoli.
B. Oxygen is absorbed from the alveoli into the bloodstream.
C. Oxygen is converted into carbon dioxide.
D. Oxygen is stored in the alveoli for later use.

Correct answer: B

Rationale: During gas exchange in the alveoli, oxygen is absorbed from the alveoli into the bloodstream. In the alveoli, oxygen diffuses across the thin walls of the alveoli and into the surrounding capillaries where it binds to hemoglobin in red blood cells. This oxygen-rich blood is then transported to the body's tissues for cellular respiration. Therefore, option B is correct as it accurately describes the direction of oxygen movement during the process of gas exchange in the lungs.

5. The process of a fertilized egg attaching itself to the uterine lining is called:

A. Ovulation
B. Implantation
C. Parturition
D. Menstruation

Correct answer: B

Rationale: The correct answer is B: Implantation. Implantation is the process where the fertilized egg, known as a zygote, attaches itself to the uterine lining to begin developing into an embryo. Ovulation is the release of an egg from the ovary, not the attachment process. Parturition refers to the process of giving birth, while menstruation is the shedding of the uterine lining if fertilization does not occur. Therefore, in the context of pregnancy, the process described is specifically referred to as implantation.

6. What is the medical term for a urinary tract infection (UTI)?

A. Nephritis
B. Cystitis
C. Urethritis
D. All of the above

Correct answer: D

Rationale: The correct answer is D, 'All of the above.' A urinary tract infection (UTI) can affect different parts of the urinary system. Nephritis refers to inflammation of the kidneys, cystitis refers to inflammation of the bladder, and urethritis refers to inflammation of the urethra. Therefore, all of these terms can be used to describe a UTI depending on which part of the urinary tract is affected. It's important to differentiate between these terms to accurately diagnose and treat UTIs.