HESI A2 — All Questions

Which organelle is known as the 'powerhouse of the cell'?

• a.Nucleus
• b.Golgi apparatus
• c.Ribosome
• d.Mitochondrion✓

The mitochondrion produces most of the cell's energy in the form of ATP through cellular respiration. This role earns it the nickname powerhouse of the cell.

What is the basic structural and functional unit of all living organisms?

• a.The tissue
• b.The cell✓
• c.The atom
• d.The organ

The cell is the smallest unit that can carry out all life processes. All living organisms are made of one or more cells.

Which blood cells are primarily responsible for carrying oxygen?

• a.Red blood cells✓
• b.Plasma cells
• c.Platelets
• d.White blood cells

Red blood cells contain hemoglobin, a protein that binds oxygen. They transport oxygen from the lungs to the body's tissues.

At 25 degrees C, what is the pH of a neutral solution such as pure water?

• a.7✓
• b.1
• c.0
• d.14

At 25 degrees C the pH scale runs 0 to 14, with 7 neutral, values below 7 acidic, and values above 7 basic. Pure water is neutral at pH 7 at this temperature. Water stays neutral at other temperatures, but the neutral pH value shifts slightly because the ionization of water is temperature dependent.

Which system is responsible for pumping blood throughout the body?

• a.The respiratory system
• b.The digestive system
• c.The skeletal system
• d.The circulatory system✓

The circulatory system, centered on the heart and blood vessels, moves blood throughout the body. It delivers oxygen and nutrients and removes wastes.

What gas do humans breathe in that is essential for cellular respiration?

• a.Oxygen✓
• b.Helium
• c.Nitrogen
• d.Carbon dioxide

Cells use oxygen to break down glucose and release energy during cellular respiration. Humans inhale oxygen and exhale carbon dioxide as a waste product.

Which part of the cell contains the genetic material (DNA)?

• a.The nucleus✓
• b.The cytoplasm
• c.The cell membrane
• d.The vacuole

The nucleus houses the cell's DNA, which carries genetic instructions. It acts as the control center that directs cell activities.

What is the smallest unit of an element that retains its properties?

• a.A molecule
• b.A tissue
• c.A cell
• d.An atom✓

An atom is the smallest particle of an element that still has the properties of that element. Atoms combine to form molecules.

Which type of blood vessel carries blood away from the heart?

• a.Veins
• b.Venules
• c.Arteries✓
• d.Capillaries

Arteries carry blood away from the heart to the body's tissues. Veins, by contrast, return blood to the heart.

What is the largest organ of the human body?

• a.The heart
• b.The skin✓
• c.The liver
• d.The lungs

The skin is the body's largest organ by weight, making up roughly 16 percent of body mass. It protects the body, helps regulate temperature, and provides sensation.

Which nutrient is the body's primary source of quick energy?

• a.Carbohydrates✓
• b.Triglycerides
• c.Electrolytes
• d.Amino acids

Carbohydrates are broken down into glucose, which cells use for quick energy. They are the body's preferred and fastest energy source.

In chemistry, a substance that donates hydrogen ions and has a pH below 7 is called:

• a.An acid✓
• b.A base
• c.A salt
• d.A neutral

An acid releases hydrogen ions in solution and has a pH lower than 7. Bases, in contrast, have a pH above 7.

Which system includes bones, joints, and cartilage that support the body?

• a.The skeletal system✓
• b.The endocrine system
• c.The nervous system
• d.The muscular system

The skeletal system is made up of bones, joints, and cartilage. It provides structure, protects organs, and allows movement together with muscles.

What process do plants use to convert sunlight into chemical energy?

• a.Digestion
• b.Fermentation
• c.Respiration
• d.Photosynthesis✓

Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to make glucose and oxygen. It converts light energy into stored chemical energy.

Which organ filters waste from the blood and produces urine?

• a.The lungs
• b.The stomach
• c.The kidney✓
• d.The pancreas

The kidneys filter waste products and excess water from the blood, forming urine. This helps maintain the body's fluid and chemical balance.

What is the control center of the nervous system?

• a.The brain✓
• b.The heart
• c.The liver
• d.The lungs

The brain, along with the spinal cord, forms the central nervous system. The brain processes information and directs the body's responses.

Which of the following is a chemical change rather than a physical change?

• a.Ice melting
• b.Chopping wood
• c.Water boiling
• d.Iron rusting✓

A chemical change produces a new substance with different properties. Iron rusting forms iron oxide, whereas melting, boiling, and chopping only change form.

Which macromolecule is made of amino acids and builds body tissues?

• a.Nucleic acid
• b.Carbohydrate
• c.Protein✓
• d.Lipid

Proteins are built from chains of amino acids. They form the structural basis of muscles, enzymes, and many other body tissues.

How many chambers does the human heart have?

• a.Four✓
• b.Two
• c.Three
• d.Five

The human heart has four chambers: two upper atria and two lower ventricles. This structure keeps oxygen-rich and oxygen-poor blood separated.

Which particle in an atom carries a negative electric charge?

• a.Nucleus
• b.Neutron
• c.Electron✓
• d.Proton

Electrons carry a negative charge and occupy orbitals, which are regions of space surrounding the nucleus where an electron is most likely to be found. Protons are positive and neutrons have no charge.

Which chamber of the heart pumps oxygen-rich blood out into the aorta?

• a.Right ventricle
• b.Left atrium
• c.Left ventricle✓
• d.Right atrium

The left ventricle has the thickest wall because it must drive blood through the entire systemic circuit by way of the aorta. The right ventricle pumps only as far as the lungs through the pulmonary trunk, and both atria are receiving chambers that move blood a few centimetres into the ventricle below them.

Blood moving from the right atrium into the right ventricle passes through which valve?

• a.The tricuspid valve✓
• b.The mitral (bicuspid) valve
• c.The pulmonary semilunar valve
• d.The aortic semilunar valve

The right atrioventricular valve has three cusps, which is what tricuspid means. The mitral valve sits on the left side between left atrium and left ventricle. The two semilunar valves guard the exits of the ventricles, not the openings between atrium and ventricle.

Which valve keeps blood from flowing backward from the aorta into the left ventricle?

• a.The pulmonary semilunar valve
• b.The mitral valve
• c.The aortic valve✓
• d.The tricuspid valve

The aortic semilunar valve snaps shut as the left ventricle relaxes, so blood already ejected cannot fall back in. The pulmonary valve does the same job at the exit of the right ventricle. The mitral and tricuspid valves lie between the atria and ventricles and have nothing to do with the aorta.

Which vessel carries oxygen-poor blood away from the heart toward the lungs?

• a.The pulmonary artery✓
• b.The pulmonary vein
• c.The aorta
• d.The superior vena cava

The pulmonary arteries are the one pair of arteries that carry deoxygenated blood, because arteries are defined by direction of flow rather than oxygen content. The pulmonary veins bring oxygenated blood back from the lungs, the aorta leaves the left ventricle, and the venae cavae return blood to the right atrium.

The pulmonary veins empty freshly oxygenated blood into which chamber?

• a.The right atrium
• b.The left ventricle
• c.The right ventricle
• d.The left atrium✓

Blood returning from the lungs enters the left atrium, drops through the mitral valve into the left ventricle, and is then ejected into the aorta. The right atrium receives deoxygenated blood from the venae cavae, and neither ventricle receives blood directly from a vein.

Which structure normally sets the rhythm of the heartbeat?

• a.The atrioventricular (AV) node
• b.The sinoatrial (SA) node✓
• c.The bundle of His
• d.The Purkinje fibers

The SA node in the wall of the right atrium depolarises fastest, so it acts as the pacemaker. The AV node, bundle of His and Purkinje fibers all conduct the impulse onward and can take over at a slower intrinsic rate if the SA node fails, but none of them normally sets the pace.

After the electrical impulse reaches the AV node, where does it travel next?

• a.Back up into the sinoatrial node to repeat
• b.Directly into the Purkinje fibers of the atrial walls
• c.Outward through the coronary arteries to the apex
• d.Into the bundle of His and its branches✓

The normal path is SA node, AV node, bundle of His, bundle branches, then Purkinje fibers in the ventricular walls. The impulse does not travel backward into the SA node, the Purkinje network lies in the ventricles rather than the atria, and coronary arteries carry blood, not electrical signals.

Which layer of the heart wall is the thick muscle that actually contracts?

• a.The endocardium
• b.The epicardium
• c.The myocardium✓
• d.The fibrous pericardium

Myo means muscle, so the myocardium is the contractile middle layer. The endocardium is the smooth inner lining in contact with blood, the epicardium is the thin outer surface layer, and the fibrous pericardium is the tough sac that surrounds the whole organ.

Which vessel returns oxygen-poor blood from the legs and abdomen to the heart?

• a.The superior vena cava
• b.The descending abdominal aorta
• c.The hepatic portal vein
• d.The inferior vena cava✓

The inferior vena cava drains everything below the diaphragm into the right atrium. The superior vena cava drains the head, neck and arms, the abdominal aorta carries blood away from the heart rather than toward it, and the hepatic portal vein runs from the intestines to the liver.

Where in the circulatory system does exchange of oxygen and nutrients with the tissues take place?

• a.In the arterioles
• b.In the large elastic arteries
• c.In the capillaries✓
• d.In the venules

Capillary walls are a single cell thick, which is what allows gases, nutrients and wastes to diffuse across. Arterioles and venules are resistance and collecting vessels with several layers in the wall, and large arteries are built for pressure, not for exchange.

In a blood pressure reading of 118/76, what does the 76 measure?

• a.Arterial pressure at the peak of ventricular contraction
• b.The number of heartbeats counted in one full minute
• c.The volume of blood ejected with each single beat
• d.Arterial pressure while the ventricles relax✓

The lower number is the diastolic pressure, the pressure remaining in the arteries while the ventricles fill. The upper number, 118, is the systolic peak during contraction. Heart rate is counted separately in beats per minute, and the blood ejected per beat is the stroke volume.

Which formed element of the blood is essential for clotting?

• a.Red blood cells
• b.White blood cells
• c.Lymphocytes
• d.Platelets✓

Platelets, also called thrombocytes, stick to a damaged vessel wall, plug the gap and release the chemicals that start the clotting cascade. Red cells carry oxygen, white cells defend against infection, and lymphocytes are simply one variety of white cell.

Which part of the blood is the straw-coloured liquid that carries cells, nutrients and hormones?

• a.Serum
• b.Plasma✓
• c.Lymph
• d.Interstitial fluid

Plasma is the liquid portion of circulating blood and makes up a little over half its volume. Serum is what is left after a sample clots, so it lacks the clotting factors plasma still contains. Lymph travels in lymphatic vessels and interstitial fluid sits between cells, neither of them inside blood vessels.

Hemoglobin cannot bind oxygen without which mineral at the centre of each heme group?

• a.Calcium
• b.Potassium
• c.Iron✓
• d.Magnesium

Each heme group holds one iron ion, and that iron is the site where oxygen attaches, which is why iron deficiency causes anemia. Calcium is needed for clotting and muscle contraction, potassium for nerve and cardiac conduction, and magnesium sits at the centre of chlorophyll in plants, not hemoglobin.

Type O negative red cells are called the universal donor type because they:

• a.carry neither the A, the B, nor the Rh antigen✓
• b.carry both the A and the B antigen on their surface
• c.contain no anti-A or anti-B antibodies in the cell
• d.are smaller and pass more easily through capillaries

With no A, B or Rh antigen on the membrane, the recipient's antibodies find nothing to attack. Carrying both A and B antigens describes type AB, the universal recipient. Antibodies circulate in plasma rather than inside red cells, and cell size has nothing to do with compatibility.

Which vessels have the thickest and most elastic walls to withstand the surge of each heartbeat?

• a.Arteries✓
• b.Veins
• c.Capillaries
• d.Venules

Arteries carry blood under the highest pressure, so their walls contain heavy layers of smooth muscle and elastic tissue. Veins carry low-pressure blood and rely on one-way valves instead, while capillaries and venules have very thin walls suited to exchange and collection.

Gas exchange between inhaled air and the blood takes place in which structures?

• a.The alveoli✓
• b.The bronchioles
• c.The trachea
• d.The pleural space

Alveoli are thin-walled air sacs wrapped in capillaries, so oxygen and carbon dioxide diffuse across in both directions. Bronchioles and the trachea are conducting passages that only move air, and the pleural space is a fluid-filled gap between the membranes covering the lung.

Which muscle does most of the work of a quiet inhalation?

• a.The internal intercostals
• b.The diaphragm✓
• c.The rectus abdominis
• d.The sternocleidomastoid

The diaphragm contracts and flattens, enlarging the chest cavity so air is drawn in. The internal intercostals assist with forced exhalation, the rectus abdominis pushes the diaphragm upward during forced exhalation, and the sternocleidomastoid is only an accessory muscle used in laboured breathing.

What happens inside the thoracic cavity during inhalation?

• a.Its volume decreases while the pressure inside rises sharply
• b.Its volume increases and the pressure inside falls✓
• c.Volume and pressure both increase at exactly the same rate
• d.Volume stays fixed while the lungs pull oxygen across actively

As the diaphragm and external intercostals contract, the cavity enlarges, so the pressure within it drops below atmospheric and air flows in down the gradient. Falling volume with rising pressure describes exhalation, and air moves passively down a pressure gradient rather than being actively pulled in.

What keeps food and liquid out of the airway during swallowing?

• a.The epiglottis covers the laryngeal opening✓
• b.The uvula swings down and seals the trachea
• c.The vocal cords open widely to let the food pass
• d.The diaphragm relaxes and pinches the airway shut

The epiglottis is a flap of cartilage that folds back over the entrance to the larynx each time a person swallows. The uvula helps close off the nasopharynx, not the trachea, opening the vocal cords would let food in rather than keep it out, and the diaphragm has no role in swallowing.

Which tube carries air from the larynx down to the two main bronchi?

• a.The esophagus
• b.The trachea✓
• c.The pharynx
• d.The bronchioles

The trachea is the cartilage-ringed windpipe that branches into the right and left primary bronchi. The esophagus carries food to the stomach, the pharynx is the shared throat passage above the larynx, and bronchioles are the small branches deep inside the lung.

Most carbon dioxide travels in the blood in which form?

• a.Bound to the iron of hemoglobin, exactly as oxygen is
• b.As visible bubbles of free gas within the plasma
• c.As bicarbonate ions dissolved in plasma✓
• d.Attached to the outer surface of circulating platelets

Roughly seventy percent of carbon dioxide is converted to bicarbonate in the red cells and carried in the plasma. A smaller share binds to the globin protein rather than the iron of hemoglobin, free gas bubbles in blood would be a dangerous embolism, and platelets carry no gases at all.

Which part of the brain sets the basic rhythm of breathing?

• a.The cerebellum
• b.The medulla oblongata✓
• c.The occipital lobe
• d.The anterior pituitary

Respiratory centres in the medulla of the brainstem generate the automatic breathing rhythm and respond to rising carbon dioxide. The cerebellum coordinates movement and balance, the occipital lobe processes vision, and the pituitary is an endocrine gland rather than a control centre for breathing.

What is the function of the mucus and cilia lining the airways?

• a.They exchange oxygen and carbon dioxide with the capillaries
• b.They produce the surfactant that keeps the alveoli open
• c.They add water vapour so that the lungs can absorb oxygen
• d.They trap particles and sweep them toward the throat✓

Sticky mucus captures dust and microbes and the beating cilia move the sheet upward to be swallowed or coughed out. Gas exchange happens in the alveoli, surfactant is made by type II alveolar cells, and although the airway does humidify air, that is not what the cilia are for.

Which pleural layer lies directly against the surface of the lung?

• a.The parietal pleura
• b.The visceral pleura✓
• c.The pericardium
• d.The peritoneum

Visceral refers to the organ itself, so the visceral pleura clings to the lung surface. The parietal pleura lines the chest wall, the pericardium surrounds the heart, and the peritoneum lines the abdominal cavity.

What does the term tidal volume describe?

• a.The largest volume that can be forced out after a maximal inhalation
• b.The air left in the lungs after the most forceful exhalation possible
• c.The air moved in or out during one normal breath✓
• d.The total volume the lungs can hold when completely filled with air

Tidal volume is the ordinary quiet breath, about 500 mL in an adult. The maximum that can be blown out after a full breath in is vital capacity, the air that always remains behind is residual volume, and the sum of everything is total lung capacity.

In which organ does the chemical digestion of protein begin?

• a.The mouth
• b.The duodenum
• c.The large intestine
• d.The stomach✓

Gastric juice supplies hydrochloric acid and pepsin, and pepsin is the first enzyme to break protein into shorter chains. The mouth begins starch digestion instead, the duodenum continues protein digestion but does not start it, and the large intestine performs no enzymatic digestion of protein at all.

Which enzyme in gastric juice begins breaking proteins into peptides?

• a.Amylase
• b.Pepsin✓
• c.Lipase
• d.Trypsin

Pepsinogen is secreted by chief cells and converted to active pepsin by the acid of the stomach. Amylase acts on starch, lipase on fats, and trypsin is a protein-splitting enzyme but it comes from the pancreas and works in the small intestine.

Where does most absorption of digested nutrients into the bloodstream occur?

• a.In the stomach
• b.In the large intestine
• c.In the small intestine✓
• d.In the esophagus

The small intestine is lined with villi and microvilli that give it an enormous absorptive surface. The stomach absorbs only a few substances such as alcohol and some drugs, the large intestine mainly reclaims water and electrolytes, and the esophagus is purely a passageway.

Which organ stores and concentrates the bile made by the liver?

• a.The pancreas
• b.The gallbladder✓
• c.The spleen
• d.The appendix

Bile is produced continuously by the liver and held in the gallbladder until fat entering the duodenum triggers its release. The pancreas makes enzymes and bicarbonate, the spleen filters blood and recycles old red cells, and the appendix has no digestive storage role.

What does bile actually do to fat in the small intestine?

• a.It emulsifies fat into small droplets✓
• b.It chemically splits fat into fatty acids and glycerol
• c.It neutralises the fat so that it can pass into the colon
• d.It converts fat directly into glucose for immediate energy

Bile salts are detergents, not enzymes: they break large fat globules into tiny droplets so lipase can reach more surface. The chemical splitting is done by pancreatic lipase, fat is absorbed in the small intestine rather than passed along, and fat is not converted into glucose by bile.

Salivary amylase begins the digestion of which nutrient?

• a.Protein
• b.Fat
• c.Vitamin C
• d.Starch✓

Amylase splits starch into shorter sugar chains while food is still being chewed. Protein digestion waits for the stomach, fat digestion mostly waits for pancreatic lipase in the small intestine, and vitamins are absorbed intact rather than digested.

Which structure is the first segment of the small intestine?

• a.The jejunum
• b.The duodenum✓
• c.The ileum
• d.The cecum

The duodenum receives chyme from the stomach along with bile and pancreatic juice. The jejunum and ileum are the second and third segments where most absorption finishes, and the cecum is the pouch at the beginning of the large intestine.

What is the main job of the large intestine?

• a.Absorbing water and electrolytes✓
• b.Absorbing most amino acids and simple sugars
• c.Producing the enzymes that finish digesting starch
• d.Storing bile until a fatty meal is eaten

The colon reclaims water and salts, which is what turns liquid chyme into formed stool. Amino acids and sugars are absorbed upstream in the small intestine, digestive enzymes come from the pancreas and intestinal lining, and bile is stored in the gallbladder.

What is peristalsis?

• a.Wavelike smooth muscle contractions that move contents along✓
• b.The churning of food with acid inside the stomach only
• c.The chemical breakdown of nutrients by digestive enzymes
• d.The passive sliding of food downward under its own weight

Rings of smooth muscle contract behind the bolus and relax ahead of it, pushing contents through the whole tract. Churning is one action of the stomach rather than the definition of peristalsis, enzymatic breakdown is chemical digestion, and swallowing works even lying down, so gravity is not the mechanism.

Which structures give the small intestine its huge absorptive surface area?

• a.Villi and microvilli✓
• b.Rugae
• c.Alveoli
• d.Nephrons

Finger-like villi, each cell covered with microvilli, multiply the lining surface many times over. Rugae are the folds of the stomach wall, alveoli belong to the lungs, and nephrons are the filtering units of the kidney.

Which of these is a function of the liver?

• a.Secreting insulin into the bloodstream
• b.Detoxifying drugs and storing glycogen✓
• c.Absorbing the bulk of dietary protein
• d.Producing hydrochloric acid for digestion

The liver processes everything absorbed from the intestines, neutralising toxins and banking glucose as glycogen. Insulin comes from the pancreas, protein is absorbed by the small intestine, and hydrochloric acid is secreted by parietal cells of the stomach.

Which two structures make up the central nervous system?

• a.The brain and the cranial nerves
• b.The brain and the spinal cord✓
• c.The spinal cord and the spinal nerves
• d.The sensory and the motor neurons

The central nervous system is only the brain and spinal cord; everything else is peripheral. Cranial and spinal nerves belong to the peripheral nervous system, and individual sensory and motor neurons are cell types found in both divisions.

Which part of the brain coordinates balance, posture and smooth movement?

• a.The cerebellum✓
• b.The cerebrum
• c.The medulla oblongata
• d.The thalamus

The cerebellum fine-tunes motor commands so movement is coordinated and balance is kept. The cerebrum plans voluntary movement and handles thought, the medulla runs vital automatic functions such as heart rate, and the thalamus relays incoming sensory traffic.

Which brain structure regulates body temperature, hunger and thirst and links the nervous system to the endocrine system?

• a.The hippocampus
• b.The hypothalamus✓
• c.The pons
• d.The corpus callosum

The hypothalamus is the body's homeostatic thermostat and it controls the pituitary gland directly below it. The hippocampus forms memories, the pons relays signals between brainstem and cerebellum, and the corpus callosum is the bridge of fibres joining the two hemispheres.

Which part of a neuron receives incoming signals from other neurons?

• a.The axon
• b.The axon terminal
• c.The dendrites✓
• d.The myelin sheath

Dendrites are the branching extensions that collect input and carry it toward the cell body. The axon conducts the impulse away, the axon terminal releases neurotransmitter onto the next cell, and the myelin sheath is insulation rather than a receiving structure.

What does the myelin sheath do for a nerve fibre?

• a.It speeds up conduction of the impulse✓
• b.It supplies the neuron with oxygen and glucose
• c.It manufactures and stores the neurotransmitters
• d.It connects one neuron directly to the next neuron

Myelin insulates the axon so the impulse leaps between the gaps in the sheath rather than creeping along the whole membrane. Nutrients arrive from capillaries, neurotransmitters are made and stored in the axon terminal, and neurons stay separated by a synapse rather than joining.

What is the tiny gap between one neuron and the next cell called?

• a.The node of Ranvier
• b.The synapse✓
• c.The neuromuscular plate
• d.The ganglion

The impulse crosses the synaptic cleft as chemical neurotransmitter released from the terminal. Nodes of Ranvier are the gaps in the myelin along one axon, a ganglion is a cluster of nerve cell bodies, and the motor end plate is one specific kind of synapse, not the general term.

Why is a reflex such as the knee-jerk faster than a deliberate movement?

• a.The sensory neuron carries the impulse in both directions at once
• b.Reflex impulses travel through the bloodstream instead of nerves
• c.The signal is processed in the spinal cord, not the brain✓
• d.Reflexes use only one neuron running from the skin to the muscle

In a spinal reflex the sensory neuron synapses in the cord and a motor neuron responds immediately, with the brain only informed afterward. A neuron conducts in one direction, nerve signals are electrical rather than carried in blood, and a reflex arc always involves at least a sensory and a motor neuron.

Stimulating the sympathetic nervous system produces which effect?

• a.A slower heart rate and increased digestion
• b.A faster heart rate and dilated pupils✓
• c.Narrowed airways and heavier salivary flow
• d.Reduced blood flow to the skeletal muscles

The sympathetic division drives the fight-or-flight response, raising heart rate, opening the pupils and shunting blood to the muscles. Slowing the heart and boosting digestion are parasympathetic effects, and the sympathetic division widens rather than narrows the airways.

Which lobe of the cerebrum processes visual information?

• a.The temporal lobe
• b.The parietal lobe
• c.The frontal lobe
• d.The occipital lobe✓

The primary visual cortex sits at the back of the brain in the occipital lobe. The temporal lobe handles hearing and some memory, the parietal lobe interprets touch and body position, and the frontal lobe governs planning, judgement and voluntary movement.

Damage to the frontal lobe would most likely affect which ability?

• a.Hearing spoken words
• b.Feeling touch on the hand
• c.Seeing colour and shape
• d.Planning and judgement✓

The frontal lobe houses executive functions such as reasoning, judgement and voluntary motor control. Hearing is a temporal lobe function, touch is interpreted in the parietal lobe, and vision belongs to the occipital lobe.

Which cranial nerve carries impulses from the retina to the brain?

• a.The olfactory nerve
• b.The oculomotor nerve
• c.The optic nerve✓
• d.The trigeminal nerve

The optic nerve is cranial nerve II and carries only vision. The olfactory nerve carries smell, the oculomotor nerve moves most of the eye muscles without carrying sight, and the trigeminal nerve supplies sensation to the face and the muscles of chewing.

Which is the tough outermost membrane covering the brain and spinal cord?

• a.The pia mater
• b.The arachnoid mater
• c.The dura mater✓
• d.The periosteum

From the outside in the meninges run dura, arachnoid, then pia. The pia mater is the delicate innermost layer hugging the brain surface, the arachnoid lies between the two, and the periosteum covers the outer surface of bone rather than nervous tissue.

The peripheral nervous system is made up of which structures?

• a.The brain, the spinal cord and the meninges together
• b.Only the twelve pairs of cranial nerves in the head
• c.All nerves outside the brain and spinal cord✓
• d.The sensory organs such as the eye, ear and skin

Everything outside the central nervous system, cranial and spinal nerves alike, is peripheral. The brain, cord and their coverings are central, cranial nerves are only part of the peripheral system, and sense organs are organs rather than nerves.

Which part of the brainstem controls heart rate, blood pressure and the cough reflex?

• a.The cerebellum
• b.The thalamus
• c.The pituitary gland
• d.The medulla oblongata✓

The medulla holds the cardiac, vasomotor and respiratory centres, along with reflex centres for coughing, sneezing and vomiting. The cerebellum coordinates movement, the thalamus relays sensation, and the pituitary secretes hormones.

Which fluid cushions the brain and spinal cord and circulates in the ventricles?

• a.Lymph
• b.Cerebrospinal fluid✓
• c.Plasma
• d.Synovial fluid

Cerebrospinal fluid is produced in the ventricles and surrounds the central nervous system as a shock absorber. Lymph drains tissue spaces, plasma is the liquid part of blood, and synovial fluid lubricates joint cavities.

How many bones make up the normal adult human skeleton?

• a.300
• b.186
• c.254
• d.206✓

An adult skeleton has 206 bones, made up of 80 axial and 126 appendicular bones. A newborn starts with roughly 300 separate bones, many of which fuse during growth, so the higher figure describes an infant rather than an adult, and the other counts match no stage of development.

Which is the longest and strongest bone in the human body?

• a.The tibia
• b.The humerus
• c.The femur✓
• d.The sternum

The femur, or thigh bone, runs from hip to knee and bears the greatest load. The tibia is the larger of the two lower leg bones but is shorter, the humerus is the single bone of the upper arm, and the sternum is the flat breastbone at the front of the chest.

Which cells build new bone tissue by laying down matrix?

• a.Osteoclasts
• b.Chondrocytes
• c.Osteoblasts✓
• d.Erythrocytes

Osteoblasts deposit bone matrix, and when they become trapped within it they mature into osteocytes. Osteoclasts do the opposite work of breaking bone down, chondrocytes maintain cartilage, and erythrocytes are red blood cells.

The elbow permits bending and straightening in one plane only. What type of joint is it?

• a.A ball-and-socket joint
• b.A pivot joint
• c.A hinge joint✓
• d.A saddle joint

Hinge joints such as the elbow and knee move in a single plane like a door. Ball-and-socket joints at the hip and shoulder move in every direction, pivot joints allow rotation as at the top of the neck, and the saddle joint of the thumb allows two planes of motion.

Which structure attaches a skeletal muscle to a bone?

• a.A ligament
• b.A fascia sheet
• c.A bursa
• d.A tendon✓

Tendons are dense cords of connective tissue joining muscle to bone so contraction produces movement. Ligaments join bone to bone at a joint, fascia wraps and separates muscle groups, and a bursa is a small fluid sac that reduces friction.

Which two protein filaments slide past each other when a muscle contracts?

• a.Collagen and elastin
• b.Actin and myosin✓
• c.Keratin and albumin
• d.Fibrin and globulin

Calcium released inside the muscle fibre lets myosin heads grip actin and pull, shortening the sarcomere. Collagen and elastin are connective tissue proteins, keratin and albumin belong to skin and plasma, and fibrin and globulin are blood proteins involved in clotting and immunity.

Which hormone lowers blood glucose by moving sugar into the cells?

• a.Glucagon
• b.Insulin✓
• c.Cortisol
• d.Epinephrine

Insulin from the beta cells of the pancreas opens the cells to glucose, dropping the blood level. Glucagon from the alpha cells does the reverse by releasing stored glycogen, and both cortisol and epinephrine tend to raise blood glucose during stress.

Which gland secretes the hormones that set the body's overall metabolic rate?

• a.The thyroid gland✓
• b.The adrenal cortex
• c.The parathyroid glands
• d.The pineal gland

Thyroxine from the thyroid, which needs dietary iodine, governs the speed of metabolism throughout the body. The adrenal cortex makes cortisol and aldosterone, the parathyroids control calcium, and the pineal gland secretes melatonin for the sleep cycle.

Parathyroid hormone has what effect on the blood?

• a.It lowers the blood calcium level
• b.It raises the blood calcium level✓
• c.It raises the blood glucose level
• d.It lowers the blood sodium level

Parathyroid hormone pulls calcium out of bone and increases its absorption and retention, so blood calcium climbs. Calcitonin from the thyroid is the hormone that lowers it, glucose is controlled by insulin and glucagon, and sodium balance is regulated mainly by aldosterone.

Antidiuretic hormone (ADH) acts on the kidney to do what?

• a.Return more water to the bloodstream✓
• b.Increase the amount of urine produced
• c.Excrete more sodium into the urine
• d.Filter more protein out of the blood

ADH makes the collecting ducts permeable so water is reabsorbed, producing a smaller volume of concentrated urine. Increasing urine output is what a diuretic does, sodium excretion is controlled by aldosterone, and healthy kidneys keep protein in the blood rather than filtering it out.

Which gland releases epinephrine during a sudden fright?

• a.The adrenal cortex
• b.The posterior pituitary
• c.The thymus
• d.The adrenal medulla✓

The inner medulla of the adrenal gland pours epinephrine and norepinephrine into the blood, reinforcing the sympathetic response. The outer cortex secretes steroid hormones such as cortisol, the posterior pituitary stores ADH and oxytocin, and the thymus matures T lymphocytes.

What is the functional filtering unit of the kidney?

• a.The alveolus
• b.The renal pelvis
• c.The nephron✓
• d.The ureter

Each kidney holds about a million nephrons, and every one filters blood and fine-tunes the filtrate. The alveolus is the gas-exchange unit of the lung, the renal pelvis is the collecting basin inside the kidney, and the ureter is simply the tube draining to the bladder.

In which part of the nephron is blood first filtered?

• a.The glomerulus✓
• b.The loop of Henle
• c.The collecting duct
• d.The distal convoluted tubule

Blood pressure forces water and small solutes out of the glomerular capillaries into the surrounding Bowman capsule. The loop of Henle concentrates the filtrate, and the distal tubule and collecting duct make the final adjustments to water and salt before urine leaves.

Which sequence correctly traces urine leaving the body?

• a.Kidney, ureter, bladder, urethra✓
• b.Kidney, urethra, bladder, ureter
• c.Bladder, kidney, ureter, urethra
• d.Ureter, kidney, urethra, bladder

Urine forms in the kidney, travels down a ureter to be stored in the bladder, and leaves through the single urethra. The other orders reverse the ureter and urethra or begin at the bladder, which stores urine rather than producing it.

Which cells produce the antibodies that mark a specific invader for destruction?

• a.Red blood cells
• b.Neutrophils
• c.Platelets
• d.B lymphocytes✓

B lymphocytes mature into plasma cells that secrete antibodies against one specific antigen. Red cells carry oxygen, neutrophils are phagocytes that swallow bacteria without making antibodies, and platelets belong to the clotting system.

Why does a vaccine produce active immunity?

• a.The body makes its own antibodies and memory cells✓
• b.It supplies ready-made antibodies from a donor
• c.It kills any organism the person later encounters
• d.It raises the body temperature to destroy microbes

A vaccine presents a harmless form of the antigen so the immune system responds and keeps memory cells for later. Receiving ready-made antibodies is passive immunity, a vaccine does not itself kill later invaders, and fever is a general inflammatory response, not how vaccination works.

Which is the outermost layer of the skin?

• a.The dermis
• b.The subcutaneous layer
• c.The epidermis✓
• d.The stratum basale

The epidermis is the thin surface layer of stratified cells with no blood vessels of its own. The dermis beneath it holds blood vessels, nerves and glands, the subcutaneous layer is the fatty layer deeper still, and the stratum basale is the deepest layer within the epidermis rather than its surface.

Melanin produced by melanocytes serves what protective purpose?

• a.It waterproofs the surface of the skin
• b.It absorbs ultraviolet radiation✓
• c.It insulates the body against heat loss
• d.It kills bacteria on contact with the skin

Melanin is the pigment that shields deeper cells from ultraviolet damage. Waterproofing is the work of keratin and sebum, insulation comes from subcutaneous fat, and antibacterial defence on the skin comes from sebum, sweat and an intact barrier rather than from pigment.

Where does fertilization of an ovum normally take place?

• a.In the uterus
• b.In the ovary
• c.In the cervix
• d.In the fallopian tube✓

Sperm usually meet the egg in the upper portion of the fallopian tube, and the fertilised egg then travels down to implant. The uterus is where implantation occurs, the ovary releases the egg, and the cervix is only the passage between vagina and uterus.

Which plane divides the body into right and left portions?

• a.The frontal plane
• b.The sagittal plane✓
• c.The transverse plane
• d.The oblique plane

A sagittal cut runs front to back and separates right from left. The frontal or coronal plane separates front from back, the transverse plane separates upper from lower, and an oblique plane is any angled cut.

Which statement uses directional terms correctly?

• a.The wrist is proximal to the elbow
• b.The knee is superior to the hip joint
• c.The nose is lateral to the ear on the head
• d.The wrist is distal to the elbow✓

Distal means farther from the point of attachment to the trunk, and the wrist is farther down the arm than the elbow. Proximal would mean closer to the trunk, the knee lies below and therefore inferior to the hip, and the nose is medial to the ear rather than lateral.

Which structure separates the thoracic cavity from the abdominal cavity?

• a.The pleura
• b.The peritoneum
• c.The diaphragm✓
• d.The mediastinum

The dome-shaped diaphragm forms the floor of the chest and the roof of the abdomen. The pleura lines the lungs and chest wall, the peritoneum lines the abdominal cavity, and the mediastinum is the central space of the thorax that contains the heart.

Homeostasis is best described as:

• a.keeping internal conditions within a narrow range✓
• b.holding every internal condition at one fixed value
• c.the steady growth of an organism over its lifetime
• d.the ability of cells to divide and replace themselves

Homeostasis is dynamic: values such as temperature and glucose fluctuate slightly and negative feedback pulls them back toward a set point. Nothing in the body holds perfectly still, growth is a separate process, and cell replacement is regeneration rather than homeostasis.

Which organelle assembles amino acids into proteins?

• a.The lysosome
• b.The Golgi apparatus
• c.The mitochondrion
• d.The ribosome✓

Ribosomes read messenger RNA and link amino acids into a chain. Lysosomes contain digestive enzymes that break material down, the Golgi apparatus packages and ships proteins after they are made, and mitochondria generate ATP.

How does meiosis differ from mitosis?

• a.It produces four cells with half the chromosome number✓
• b.It produces two cells identical to the parent cell
• c.It happens only in cells that line the skin and gut
• d.It copies the DNA twice before the cell divides once

Meiosis halves the chromosome number and yields four genetically varied gametes. Two identical daughter cells describe mitosis, meiosis occurs in the testes and ovaries rather than the skin and gut, and the DNA is copied once while the cell divides twice.

In a DNA molecule, adenine always pairs with which base?

• a.Thymine✓
• b.Guanine
• c.Cytosine
• d.Uracil

The complementary pairs in DNA are adenine with thymine and guanine with cytosine. Guanine and cytosine pair with each other rather than with adenine, and uracil replaces thymine only in RNA, which is single stranded.

The atomic number of an element tells you the number of:

• a.neutrons in the nucleus
• b.protons plus neutrons together
• c.protons in the nucleus✓
• d.electron shells around the nucleus

Atomic number is the proton count, and it is what defines the element. The number of neutrons varies between isotopes of the same element, protons plus neutrons give the mass number, and the shells simply hold the electrons that balance the protons.

An ionic bond forms when:

• a.two atoms share a pair of electrons equally
• b.two molecules are attracted by hydrogen bonding
• c.one atom transfers an electron to another✓
• d.a proton moves from the nucleus of one atom

Losing and gaining electrons leaves oppositely charged ions that attract each other, as sodium and chloride do in table salt. Shared electrons make a covalent bond, hydrogen bonding is a weak attraction between molecules, and protons never move out of a nucleus in ordinary chemistry.