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Biology Hesi A2 Set

Question 1 of 35

Which valve lies between the left atrium and left ventricle?

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Biology Hesi A2 Set Practice Questions

Review these Biology Hesi A2 Set nursing practice questions with answer choices and explanations.

Question 1

Which valve lies between the left atrium and left ventricle?

  1. Tricuspid valve
  2. Pulmonary valve
  3. Aortic valve
  4. Mitral valve
View answer and explanation

Correct answer:

  1. Mitral valve

Explanation: The mitral, or bicuspid, valve controls flow from the left atrium to the left ventricle.

Question 2

Which valve lies between the right atrium and right ventricle?

  1. Mitral valve
  2. Pulmonary valve
  3. Aortic valve
  4. Tricuspid valve
View answer and explanation

Correct answer:

  1. Tricuspid valve

Explanation: The tricuspid valve helps prevent backflow into the right atrium.

Question 3

What is the heart's usual natural pacemaker?

  1. Mitral valve
  2. Aorta
  3. Left ventricular wall only
  4. Sinoatrial node
View answer and explanation

Correct answer:

  1. Sinoatrial node

Explanation: The sinoatrial node normally initiates the electrical impulses that set heart rhythm.

Question 4

What are coronary arteries mainly responsible for supplying?

  1. The air inside the lungs
  2. The contents of the stomach
  3. The heart muscle
  4. The kidney filtrate
View answer and explanation

Correct answer:

  1. The heart muscle

Explanation: Coronary arteries deliver oxygen and nutrients to the myocardium.

Question 5

What is systole in the cardiac cycle?

  1. A stage of DNA replication
  2. A phase of heart-muscle contraction
  3. A phase of bone growth
  4. A type of digestion
View answer and explanation

Correct answer:

  1. A phase of heart-muscle contraction

Explanation: Ventricular systole contracts the ventricles and ejects blood.

Question 6

What is diastole in the cardiac cycle?

  1. The removal of introns
  2. A contraction of skeletal muscle only
  3. A phase of heart-muscle relaxation
  4. The production of antibodies
View answer and explanation

Correct answer:

  1. A phase of heart-muscle relaxation

Explanation: During ventricular diastole, the ventricles relax and fill with blood.

Question 7

Why are alveolar walls thin?

  1. To make blood cells
  2. To prevent every gas molecule from crossing
  3. To shorten the diffusion distance for gases
  4. To store glycogen
View answer and explanation

Correct answer:

  1. To shorten the diffusion distance for gases

Explanation: Thin walls support rapid movement of oxygen and carbon dioxide between air and blood.

Question 8

What is pulmonary surfactant's main role?

  1. Reducing surface tension in alveoli
  2. Digesting starch
  3. Producing bile
  4. Carrying oxygen in red cells
View answer and explanation

Correct answer:

  1. Reducing surface tension in alveoli

Explanation: Surfactant helps keep alveoli from collapsing by lowering surface tension.

Question 9

Which gas movement normally occurs between tissues and systemic capillaries?

  1. Oxygen moves toward blood while carbon dioxide moves into tissues
  2. No gases cross capillary walls
  3. Oxygen moves toward tissues and carbon dioxide moves toward blood
  4. Oxygen and carbon dioxide both move only into tissues
View answer and explanation

Correct answer:

  1. Oxygen moves toward tissues and carbon dioxide moves toward blood

Explanation: Concentration and partial-pressure differences drive gas exchange in opposite directions.

Question 10

Where does blood filtration begin in a nephron?

  1. Urinary bladder
  2. Glomerulus
  3. Ureter
  4. Collecting duct outlet
View answer and explanation

Correct answer:

  1. Glomerulus

Explanation: Fluid passes from glomerular capillaries into the glomerular capsule.

Question 11

Which tubes carry urine from the kidneys to the bladder?

  1. Ureters
  2. Venae cavae
  3. Urethra
  4. Bronchi
View answer and explanation

Correct answer:

  1. Ureters

Explanation: Each ureter transports urine from a kidney to the urinary bladder.

Question 12

Which structure carries urine from the bladder to the exterior?

  1. Esophagus
  2. Ureter
  3. Urethra
  4. Renal artery
View answer and explanation

Correct answer:

  1. Urethra

Explanation: The urethra provides the outlet for urine during urination.

Question 13

Which division of the nervous system includes the brain and spinal cord?

  1. Lymphatic system
  2. Central nervous system
  3. Peripheral nervous system
  4. Endocrine system
View answer and explanation

Correct answer:

  1. Central nervous system

Explanation: The central nervous system consists of the brain and spinal cord.

Question 14

Which nervous-system division generally supports the fight-or-flight response?

  1. Parasympathetic division
  2. Sympathetic division
  3. Enteric division only
  4. Somatic sensory division only
View answer and explanation

Correct answer:

  1. Sympathetic division

Explanation: Sympathetic activity prepares the body for increased demands, including a faster heart rate.

Question 15

Which nervous-system division generally supports rest-and-digest functions?

  1. Visual division
  2. Parasympathetic division
  3. Skeletal division
  4. Sympathetic division
View answer and explanation

Correct answer:

  1. Parasympathetic division

Explanation: Parasympathetic activity supports digestion and many resting functions.

Question 16

Which part of the brain is especially important for balance and coordination?

  1. Pituitary gland
  2. Cerebellum
  3. Retina
  4. Thyroid gland
View answer and explanation

Correct answer:

  1. Cerebellum

Explanation: The cerebellum helps coordinate movement, posture, and balance.

Question 17

What is the main role of myelin around many axons?

  1. Speeding electrical signal conduction
  2. Making antibodies
  3. Copying RNA
  4. Filtering blood
View answer and explanation

Correct answer:

  1. Speeding electrical signal conduction

Explanation: Myelin insulates axons and allows rapid conduction between gaps in the sheath.

Question 18

Which hormone is associated with increasing heart rate during an acute stress response?

  1. Melatonin
  2. Insulin
  3. Calcitonin
  4. Epinephrine
View answer and explanation

Correct answer:

  1. Epinephrine

Explanation: Epinephrine, also called adrenaline, supports the fight-or-flight response.

Question 19

Which gland produces melatonin, a hormone associated with daily sleep-wake timing?

  1. Pineal gland
  2. Thyroid gland
  3. Adrenal cortex
  4. Salivary gland
View answer and explanation

Correct answer:

  1. Pineal gland

Explanation: The pineal gland releases melatonin in relation to the light-dark cycle.

Question 20

Why are digestive enzymes generally ineffective at the wrong pH?

  1. They become new organs
  2. Changes in ionization and shape can reduce their activity
  3. pH always changes them into DNA
  4. Their amino acids disappear immediately
View answer and explanation

Correct answer:

  1. Changes in ionization and shape can reduce their activity

Explanation: Enzyme activity depends on conditions that preserve suitable structure and chemistry.

Question 21

Which nutrient is needed for synthesis of both hemoglobin's globin chains and antibodies?

  1. Protein supplying amino acids
  2. Sodium chloride alone
  3. Dietary cellulose only
  4. Water alone
View answer and explanation

Correct answer:

  1. Protein supplying amino acids

Explanation: Both globin and antibodies are proteins assembled from amino acids.

Question 22

Which statement about vitamins is correct?

  1. They are the body's main source of caloric energy
  2. They replace all dietary proteins
  3. They support physiological processes but do not directly provide food calories
  4. They are all made of amino acid chains
View answer and explanation

Correct answer:

  1. They support physiological processes but do not directly provide food calories

Explanation: Vitamins often act in regulation or as enzyme helpers, rather than providing energy like macronutrients.

Question 23

Why can dehydration affect circulation?

  1. Water loss instantly doubles red-cell production
  2. Dehydration creates new blood vessels
  3. Plasma contains no water
  4. Reduced body water can reduce plasma volume
View answer and explanation

Correct answer:

  1. Reduced body water can reduce plasma volume

Explanation: Plasma is largely water, so fluid loss can lower circulating volume.

Question 24

Which molecules are the immediate building blocks used to synthesize DNA and RNA?

  1. Nucleotides
  2. Cellulose fibers
  3. Calcium salts
  4. Cholesterol molecules
View answer and explanation

Correct answer:

  1. Nucleotides

Explanation: Nucleotides are the immediate building blocks used to assemble nucleic acids.

Question 25

What does antigen specificity mean for an antibody?

  1. It binds only ATP
  2. It binds particular molecular features of an antigen
  3. It cannot interact with proteins
  4. It destroys every kind of cell equally
View answer and explanation

Correct answer:

  1. It binds particular molecular features of an antigen

Explanation: Antibody binding sites recognize particular antigenic structures, called epitopes.

Question 26

What is a major function of helper T cells?

  1. Forming blood clots
  2. Producing bile
  3. Coordinating responses of other immune cells
  4. Transporting oxygen
View answer and explanation

Correct answer:

  1. Coordinating responses of other immune cells

Explanation: Helper T cells release signals and support activation of other immune-system components.

Question 27

Which immune organ filters blood and helps respond to blood-borne antigens?

  1. Thymus
  2. Urinary bladder
  3. Pancreas
  4. Spleen
View answer and explanation

Correct answer:

  1. Spleen

Explanation: The spleen screens blood and participates in immune responses and removal of old blood cells.

Question 28

What is an autoimmune condition?

  1. An immune response directed against the body's own tissues
  2. A normal response to every food
  3. An infection affecting only bacteria
  4. Any inherited dominant trait
View answer and explanation

Correct answer:

  1. An immune response directed against the body's own tissues

Explanation: Autoimmunity results when self-tolerance fails and immune mechanisms target self.

Question 29

How does natural killer cell activity differ from a typical antigen-specific T-cell response?

  1. It produces pollen
  2. It requires red blood cells to make antibodies
  3. It occurs only in plants
  4. It belongs to innate defense and can target abnormal cells without prior antigen-specific sensitization
View answer and explanation

Correct answer:

  1. It belongs to innate defense and can target abnormal cells without prior antigen-specific sensitization

Explanation: Natural killer cells contribute to early defense against certain infected or abnormal cells.

Question 30

What is an epitope?

  1. An enzyme that digests starch
  2. A particular antigen region recognized by an antibody or immune receptor
  3. A complete chromosome set
  4. The liquid component of blood
View answer and explanation

Correct answer:

  1. A particular antigen region recognized by an antibody or immune receptor

Explanation: An antigen may contain multiple epitopes recognized by different immune receptors.

Question 31

A father passes a Y chromosome to a child in typical human inheritance. Which sex-chromosome combination is expected if the egg contributes X?

  1. XY
  2. YY
  3. XXX
  4. XX
View answer and explanation

Correct answer:

  1. XY

Explanation: A typical egg supplies X; X combined with a sperm's Y produces XY.

Question 32

Which chromosome combination is normally present in a typical human somatic cell?

  1. 46 pairs of sex chromosomes
  2. One chromosome only
  3. 22 pairs of autosomes and one pair of sex chromosomes
  4. 23 unpaired autosomes only
View answer and explanation

Correct answer:

  1. 22 pairs of autosomes and one pair of sex chromosomes

Explanation: Most human body cells contain 46 chromosomes arranged in 23 pairs.

Question 33

For an autosomal recessive condition, an aa parent and an AA parent have children. Which outcome is expected in the simple model?

  1. All children are unaffected carriers
  2. All children are affected
  3. Half are affected and half are AA
  4. No child inherits a recessive allele
View answer and explanation

Correct answer:

  1. All children are unaffected carriers

Explanation: Each child receives a from one parent and A from the other, producing Aa.

Question 34

What does penetrance describe in genetics?

  1. The movement of oxygen across a membrane
  2. The total ATP produced by a cell
  3. The length of a chromosome in millimeters
  4. The proportion of individuals with a genotype who show its associated phenotype
View answer and explanation

Correct answer:

  1. The proportion of individuals with a genotype who show its associated phenotype

Explanation: Penetrance measures how often an associated trait is expressed among people carrying a particular genotype.

Question 35

What is the usual purpose of mitosis in human tissues?

  1. Making new bacterial species
  2. Halving chromosome number for gametes
  3. Growth and replacement of cells
  4. Producing pollen
View answer and explanation

Correct answer:

  1. Growth and replacement of cells

Explanation: Mitosis preserves chromosome number while supporting growth, maintenance, and repair.