In a feedback loop, which component is the muscle, gland, or organ that changes its activity to counteract a change in the body?
Effector
✓
Receptor
Control center
Stimulus
Correct Answer
Effector
The effector carries out the response, such as sweat glands secreting fluid to cool the body. A receptor detects the change. The control center processes the signal and directs the response. The stimulus is the change that starts the loop.
Category: Feedback Loops
Question 2
Which component of a feedback loop detects a change in the internal or external environment and signals the control center?
Effector
Receptor
✓
Response
Set point
Correct Answer
Receptor
A receptor, also called a sensor, is a structure such as a nerve cell in the skin or brain that detects a change and sends that information on. An effector carries out the corrective action. The response is the result that feeds back on the stimulus. The set point is the target value the loop defends, not a structure that senses change.
Category: Feedback Loops
Question 3
In the negative feedback loop that regulates body temperature, which brain structure acts as the control center?
Cerebellum
Medulla oblongata
Hypothalamus
✓
Occipital lobe
Correct Answer
Hypothalamus
The hypothalamus contains the brain's temperature regulatory center, which compares body temperature with the set point and directs effectors such as sweat glands and skin blood vessels. The cerebellum coordinates movement and balance. The medulla oblongata controls breathing and heart rate. The occipital lobe processes vision.
Category: Temperature Regulation
Question 4
When body temperature falls below the set point, which response helps the body conserve heat?
Dilation of skin blood vessels
Increased sweat secretion
Relaxation of skeletal muscles
Constriction of skin blood vessels
✓
Correct Answer
Constriction of skin blood vessels
Narrowing the blood vessels in the skin reduces blood flow near the surface, so less heat is lost to the environment. Dilation of skin blood vessels releases heat and is a response to overheating. Increased sweat secretion cools the body through evaporation. Relaxation of skeletal muscles would not add heat, whereas shivering contractions do.
Category: Temperature Regulation
Question 5
Which body process is driven by a positive feedback loop?
Uterine contractions during childbirth
✓
Lowering of a high body temperature
Return of blood glucose to normal
Correction of a falling blood pressure
Correct Answer
Uterine contractions during childbirth
During labor, pressure on the cervix triggers oxytocin release, which strengthens contractions and increases pressure further until the baby is delivered, a self-amplifying cycle. Lowering of a high body temperature is a classic negative feedback response. Return of blood glucose to normal is controlled by negative feedback through insulin and glucagon. Correction of a falling blood pressure is also negative feedback, because the response opposes the change.
Category: Feedback Loops
Question 6
A cell is placed in a hypertonic solution. What happens to the cell?
It swells as water moves in
It shrinks as water moves out
✓
It stays the same size
It bursts as solutes rush in
Correct Answer
It shrinks as water moves out
A hypertonic solution has a higher tonicity than the cell's interior, so water leaves the cell by osmosis and the cell shrinks. Swelling as water moves in happens in a hypotonic solution. Staying the same size happens in an isotonic solution. Bursting as solutes rush in is wrong because tonicity moves water, and in this case water moves out.
Category: Osmolality and Tonicity
Question 7
Which term describes a solution whose tonicity matches the fluid inside a cell, so there is no net movement of water into or out of the cell?
Hypertonic
Hypotonic
Isotonic
✓
Hyperosmolar
Correct Answer
Isotonic
An isotonic solution has the same tonicity as the cell's interior, so water moves in and out equally and the cell keeps its size. A hypertonic solution pulls water out of the cell. A hypotonic solution lets water move into the cell. Hyperosmolar describes a higher than normal solute concentration; it draws water out of cells only when those solutes cannot cross the cell membrane.
Category: Osmolality and Tonicity
Question 8
Osmolality is expressed as the number of solute particles per what amount of solvent?
1 liter
1 milliliter
1 gram
1 kilogram
✓
Correct Answer
1 kilogram
Osmolality counts solute particles per kilogram of solvent and is used to assess the concentration of body fluids such as blood and urine. Per 1 liter is the basis of osmolarity, a related but different measure. Per 1 milliliter and per 1 gram are not the units used for either measure.
Category: Osmolality and Tonicity
Question 9
Which statement describes the ion movement carried out by the Na+K+ATPase pump?
Sodium out of the cell and potassium in
✓
Sodium into the cell and potassium out
Both sodium and potassium into the cell
Calcium out of the cell and chloride in
Correct Answer
Sodium out of the cell and potassium in
The Na+K+ATPase pump moves sodium out of the cell and potassium into the cell, each against its concentration gradient, which keeps sodium high outside cells and potassium high inside. Sodium into the cell and potassium out is the reverse of the pump's action. Both sodium and potassium into the cell is not how the pump works, because it exchanges the two ions in opposite directions. Calcium out of the cell and chloride in names ions this pump does not carry.
Category: Osmotic Equilibrium
Question 10
Which cation is present in the highest concentration in intracellular fluid?
Sodium
Potassium
✓
Calcium
Magnesium
Correct Answer
Potassium
Potassium is the major cation inside cells, kept high by the Na+K+ATPase pump. Sodium is the major cation of extracellular fluid. Calcium is found mainly outside cells and in bone. Magnesium is an important intracellular cation but is present in much lower concentration than potassium.
Category: Ions and Electrolytes
Question 11
Which of these electrolytes is an anion?
Sodium
Potassium
Chloride
✓
Calcium
Correct Answer
Chloride
Chloride carries a negative charge because it has more electrons than protons, which makes it an anion. Sodium is a cation with a single positive charge. Potassium is also a cation with a single positive charge. Calcium is a cation with a double positive charge.
Category: Ions and Electrolytes
Question 12
Fluid in the pleural cavity, the peritoneal cavity, and the joint spaces belongs to which fluid compartment?
Intracellular
Interstitial
Intravascular
Transcellular
✓
Correct Answer
Transcellular
The transcellular compartment is a small volume of fluid in body cavities and structures such as the pleural and peritoneal cavities and joints. Intracellular fluid is inside cells. Interstitial fluid surrounds tissue cells. Intravascular fluid is within the blood vessels.
Category: Fluid Compartments
Question 13
Which force pushes fluid out of the capillaries and into the surrounding tissue?
Hydrostatic pressure
✓
Oncotic pressure
Osmotic equilibrium
Active transport
Correct Answer
Hydrostatic pressure
Hydrostatic pressure is the pressure of fluid confined in a space, and in capillaries it pushes fluid outward into the interstitial space. Oncotic pressure works in the opposite direction, pulling fluid back into the capillaries. Osmotic equilibrium is a balanced state, not a force. Active transport moves specific molecules across cell membranes using energy rather than pushing bulk fluid out of vessels.
Category: Osmotic Equilibrium
Question 14
Which age-related change makes older adults more likely to drink too little fluid?
Increased muscle mass
Reduced thirst sensation
✓
Higher metabolic rate
Improved kidney function
Correct Answer
Reduced thirst sensation
Older adults often feel less thirsty, so they may not drink enough and become dehydrated. Increased muscle mass is not typical of aging; muscle mass usually declines. Higher metabolic rate is a reason children need more water, not an aging change. Improved kidney function is wrong because kidney function tends to decline with age.
Category: Special Populations
Question 15
Which condition is a common cause of hyperosmolality of the blood?
Excessive water intake
Hypotonic fluid overload
Dehydration
✓
Low plasma sodium
Correct Answer
Dehydration
Losing water without losing solute concentrates the blood, so dehydration raises its osmolality. Excessive water intake dilutes body fluids and causes hypoosmolality. Hypotonic fluid overload also dilutes the blood. Low plasma sodium usually lowers osmolality, because sodium is the main contributor to it.
Category: Osmolality and Tonicity
Question 16
The movement of water across a semipermeable membrane from an area of higher water concentration to an area of lower water concentration is called what?
Active transport
Filtration
Facilitated diffusion
Osmosis
✓
Correct Answer
Osmosis
Osmosis is the passive movement of water across a semipermeable membrane toward the side with more solute. Active transport moves substances against their gradients using energy. Filtration is the movement of fluid driven by pressure, as in the kidney's glomerulus. Facilitated diffusion is the carrier-assisted passive movement of solutes, not water moving toward a higher solute concentration.
Category: Fluid Compartments
Question 17
Because it moves ions against their concentration gradients using energy from ATP, the Na+K+ATPase pump is an example of which process?
Active transport
✓
Osmosis
Simple diffusion
Filtration
Correct Answer
Active transport
Active transport uses cellular energy to move substances against their concentration gradients, which is exactly what this pump does. Osmosis is the passive movement of water. Simple diffusion moves substances down their concentration gradients without energy. Filtration moves fluid under pressure.
Category: Osmotic Equilibrium
Question 18
Electrolyte balance requires each fluid compartment to hold balanced numbers of cations and anions. What overall charge state does this produce in each compartment?
Strongly positive
Electrically neutral
✓
Strongly negative
Free of all ions
Correct Answer
Electrically neutral
Each compartment keeps the total positive and negative charges equal, so it remains electrically neutral. A strongly positive or strongly negative compartment would mean the balance had failed. Free of all ions is wrong because every body fluid compartment contains electrolytes.
Category: Ions and Electrolytes
Question 19
Severe abnormal osmolality of the blood, whether too high or too low, commonly produces which type of signs?
Skin rashes and itching
Joint pain and stiffness
Neurologic changes such as seizures
✓
Hearing loss and ringing
Correct Answer
Neurologic changes such as seizures
Brain cells are very sensitive to water shifts, so both high and low osmolality can cause irritability, seizures, and coma if not corrected. Skin rashes and itching suggest an allergic or skin problem. Joint pain and stiffness suggest a musculoskeletal problem. Hearing loss and ringing suggest an ear problem, not an osmolality disorder.
Category: Osmolality and Tonicity
Question 20
The fluid portion of the cytoplasm, in which the organelles are suspended, is called what?
Plasma
Interstitial fluid
Lymph
Cytosol
✓
Correct Answer
Cytosol
Cytosol is the fluid portion of the cytoplasm and makes up most of the intracellular fluid. Plasma is the liquid portion of blood. Interstitial fluid surrounds tissue cells outside the blood vessels. Lymph is fluid carried in lymphatic vessels.
Category: Fluid Compartments