Question 1

A PERSON WALKS FROM A WARM ROOM INTO FREEZING AIR AND STARTS TO SHIVER. WHICH DESCRIPTION FITS WHAT JUST HAPPENED?

Accepted Answer

A NEGATIVE FEEDBACK LOOP OPPOSING A DROP IN TEMPERATURE. Shivering generates heat to reverse the fall in core temperature, so the response opposes the original change. That is the signature of negative feedback, which the body uses to hold a variable near its set point.

Question 2

THIRTY MINUTES AFTER A LARGE PASTA MEAL, BLOOD GLUCOSE HAS RISEN SHARPLY. WHICH HORMONAL RESPONSE RESTORES IT TOWARD NORMAL?

Accepted Answer

INSULIN RISES TO MOVE GLUCOSE INTO CELLS. High blood glucose triggers insulin from the pancreas, which drives glucose uptake into liver and muscle and storage as glycogen. Glucagon does the opposite and would be suppressed here, while ADH and aldosterone regulate water and sodium, not glucose.

Question 3

A PATIENT STANDS UP QUICKLY AND BLOOD PRESSURE MOMENTARILY FALLS. WHAT DOES THE BARORECEPTOR REFLEX DO NEXT?

Accepted Answer

INCREASES HEART RATE AND CONSTRICTS VESSELS. Falling pressure unloads the baroreceptors, so they fire less. The brainstem responds by raising sympathetic drive, which speeds the heart and constricts vessels to push mean arterial pressure back up. Slowing the heart would make the drop worse.

Question 4

A RED BLOOD CELL IS DROPPED INTO A STRONGLY HYPERTONIC SALT SOLUTION. WHAT HAPPENS TO THE CELL?

Accepted Answer

IT SHRINKS AS WATER LEAVES. A hypertonic solution has more non-penetrating solute outside than inside, so water leaves the cell by osmosis and the cell shrinks. Water always moves toward the higher solute concentration across a selectively permeable membrane.

Question 5

WHICH OF THESE IS A TRUE POSITIVE FEEDBACK PROCESS RATHER THAN NEGATIVE FEEDBACK?

Accepted Answer

OXYTOCIN STRENGTHENING CONTRACTIONS DURING LABOR. During labor, cervical stretch releases oxytocin, which strengthens contractions and stretches the cervix further, amplifying the change until birth ends the loop. The other three all reverse a change to defend a set point, which is negative feedback.

Question 6

A HEART BEATS 80 TIMES PER MINUTE WITH A STROKE VOLUME OF 75 MILLILITERS. WHAT IS THE CARDIAC OUTPUT?

Accepted Answer

6.0 LITERS PER MINUTE. Cardiac output equals heart rate multiplied by stroke volume: 80 beats per minute times 75 milliliters equals 6,000 milliliters per minute, or 6.0 liters per minute. The other answers divide or add the two values instead of multiplying.

Question 7

A STIMULUS DEPOLARIZES A NEURON FROM MINUS 70 TO MINUS 60 MILLIVOLTS, BUT THRESHOLD IS MINUS 55. WHAT RESULT DO YOU PREDICT?

Accepted Answer

NO ACTION POTENTIAL FIRES. The membrane reached only minus 60, which is below the minus 55 threshold, so voltage-gated sodium channels do not open in force and no action potential fires. Action potentials are all-or-none: there is no half-sized version.

Question 8

VOLTAGE-GATED SODIUM CHANNELS SUDDENLY OPEN IN A RESTING NEURON. WHICH PHASE OF THE ACTION POTENTIAL DOES THIS PRODUCE?

Accepted Answer

DEPOLARIZATION. Sodium ions carry positive charge into the cell, making the inside less negative and driving voltage upward. That upstroke is depolarization. Repolarization comes afterward as potassium leaves and voltage falls back toward rest.

Question 9

AFTER HOURS OF HEAVY SWEATING WITHOUT DRINKING, BLOOD BECOMES TOO CONCENTRATED. WHAT DOES ADH DO TO THE URINE?

Accepted Answer

MAKES A SMALL VOLUME OF CONCENTRATED URINE. Concentrated blood raises ADH, which makes the kidney tubules reabsorb more water. The body conserves fluid, so the urine becomes small in volume and concentrated. Producing dilute urine here would worsen the dehydration.

Question 10

A SPRINTER PUSHES OFF THE BLOCKS AND THE SYMPATHETIC DIVISION ACTIVATES. WHICH COMBINATION OF EFFECTS FITS?

Accepted Answer

HEART RATE UP, AIRWAYS DILATED, BLOOD SHIFTED TO MUSCLES. The sympathetic fight-or-flight response prepares the body for exertion: it raises heart rate, widens the airways to move more air, and redirects blood toward working muscles. Slowing the heart and boosting digestion are parasympathetic, rest-and-digest actions.

Question 11

BLOOD PH DROPS TO 7.2 BECAUSE CARBON DIOXIDE IS BUILDING UP. WHICH RESPONSE HELPS CORRECT THE ACIDOSIS?

Accepted Answer

BREATHING SPEEDS UP TO BLOW OFF CARBON DIOXIDE. Excess carbon dioxide forms acid, so ventilation increases to exhale more carbon dioxide and pull pH back toward 7.4. Slowing breathing would trap more acid. The body does not simply reset its pH set point to the abnormal value.

Question 12

WHY IS OSMOSIS CLASSED AS A PASSIVE PROCESS EVEN THOUGH WATER CLEARLY MOVES?

Accepted Answer

IT NEEDS NO CELLULAR ENERGY, ONLY A SOLUTE DIFFERENCE. Osmosis is driven by the difference in solute concentration across the membrane, not by cellular energy, so it is passive. Active transport, by contrast, spends ATP to move a substance against its gradient.

Question 13

A PATIENT'S BLOOD PRESSURE READS 120 OVER 80 MILLIMETERS OF MERCURY. WHICH VALUE IS CLOSEST TO THEIR MEAN ARTERIAL PRESSURE?

Accepted Answer

93 MILLIMETERS OF MERCURY. Mean arterial pressure is roughly the diastolic pressure plus one third of the pulse pressure: 80 plus one third of 40 equals about 93. It is not the simple average of 120 and 80 because the heart spends more of each cycle in diastole.

Question 14

LOW BLOOD PRESSURE TRIGGERS ALDOSTERONE RELEASE. WHAT EFFECT ON SODIUM AND POTASSIUM DO YOU EXPECT?

Accepted Answer

SODIUM REABSORBED, POTASSIUM EXCRETED. Aldosterone makes the kidney reabsorb sodium, and water follows the sodium, which raises blood volume and pressure. It promotes potassium loss in exchange. So sodium is kept and potassium is excreted.

Question 15

IN THE LUNGS, OXYGEN'S PARTIAL PRESSURE IS HIGHER IN THE ALVEOLI THAN IN THE CAPILLARY BLOOD. WHICH WAY DOES OXYGEN MOVE, AND WHY?

Accepted Answer

FROM ALVEOLI TO BLOOD, DOWN ITS PARTIAL-PRESSURE GRADIENT. Gases diffuse from higher to lower partial pressure, so oxygen moves from the alveoli into the blood, no energy required. Osmosis refers to water, not gases, and active transport is not needed when a favorable gradient exists.

Question 16

SWEATING TO COOL A BODY THAT HAS BECOME TOO HOT IS AN EXAMPLE OF ___ FEEDBACK.

Accepted Answer

NEGATIVE. The response reverses the rise in temperature, moving it back toward the set point, so it is negative feedback. Positive feedback would instead push the temperature even higher.

Question 17

THE POSITIVELY CHARGED ION THAT RUSHES INTO A NEURON TO DRIVE THE DEPOLARIZATION UPSTROKE IS ___.

Accepted Answer

SODIUM. When voltage-gated sodium channels open, sodium floods in and makes the inside less negative, producing the rapid upstroke. Potassium leaving later brings the voltage back down during repolarization.

Question 18

WHEN BLOOD GLUCOSE FALLS BETWEEN MEALS, THE PANCREAS RELEASES ___ TO TELL THE LIVER TO FREE STORED GLUCOSE.

Accepted Answer

GLUCAGON. Glucagon opposes insulin: it raises blood sugar by prompting the liver to break down glycogen. This pairing lets the body defend blood glucose from both directions.

Question 19

THE MINIMUM MEMBRANE VOLTAGE A STIMULUS MUST REACH BEFORE AN ACTION POTENTIAL WILL FIRE IS CALLED THE ___.

Accepted Answer

THRESHOLD. Below threshold a stimulus produces only a small local change and no impulse; at or above it, a full all-or-none action potential always follows. In neurons it sits near minus 55 millivolts.

Question 20

THE FUNCTIONAL FILTERING UNIT OF THE KIDNEY THAT REGULATES FLUID AND ELECTROLYTES IS THE ___.

Accepted Answer

NEPHRON. Each nephron filters blood, then fine-tunes the filtrate by reabsorbing what the body needs and secreting wastes. Roughly a million per kidney let the organ balance water, salts, and pH.

Question 21

THE PASSIVE MOVEMENT OF WATER ACROSS A SELECTIVELY PERMEABLE MEMBRANE TOWARD THE SALTIER SIDE IS CALLED ___.

Accepted Answer

OSMOSIS. Water follows solutes it cannot equalize by crossing the membrane, moving toward the region of higher solute concentration. This is how tonicity decides whether a cell swells or shrinks.

Question 22

MOVING SODIUM OUT AND POTASSIUM IN AGAINST THEIR GRADIENTS IS ACTIVE TRANSPORT BECAUSE THE PUMP SPENDS ___ FOR ENERGY.

Accepted Answer

ATP. Because both ions are pushed uphill against their gradients, the cell must supply energy, and that energy is ATP. Passive processes like diffusion and osmosis need no ATP.

Question 23

THE BRAIN REGION THAT ACTS AS THE CONTROL CENTER FOR TEMPERATURE, THIRST, AND MANY OTHER SET POINTS IS THE ___.

Accepted Answer

HYPOTHALAMUS. The hypothalamus compares sensory input to set points and commands effectors through nerves and hormones. It is the integration hub for much of the body's homeostasis.

Question 24

WHEN YOU STAND UP AND PRESSURE FALLS, THE SENSORS THAT REPORT IT TO THE BRAINSTEM SO HEART RATE CAN RISE ARE THE ___.

Accepted Answer

BARORECEPTORS. Firing less when pressure drops, these sensors let the brainstem raise sympathetic drive and speed the heart. They are the input arm of the reflex that defends mean arterial pressure.

Question 25

CARDIAC OUTPUT EQUALS HEART RATE MULTIPLIED BY ___ VOLUME.

Accepted Answer

STROKE. Stroke volume is the blood ejected per beat, so multiplying it by beats per minute gives the total pumped per minute. Changing either factor changes how much oxygen the body can deliver.

Homeostasis and Body Systems