Homeostasis and feedback Practice Questions
40 free Homeostasis and feedback practice questions for the Physiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Homeostasis is best defined as the ability of the body to:
- A Keep the size of each organ perfectly constant
- B Maintain a stable internal environment
- C Prevent every external change from occurring
- D Eliminate all variability in physiological processes
Correct answer: Maintain a stable internal environment
Homeostasis refers to maintaining internal conditions within narrow limits. This stability allows cells and organs to function optimally despite external changes.
The primary components of a homeostatic control system include:
- A Stimulus, circulating hormone, and target response
- B Receptor, control center, effector
- C Neuron, synapse, and contracting muscle
- D Input, output, and storage
Correct answer: Receptor, control center, effector
A homeostatic system detects changes via receptors, processes information in a control center, and corrects deviations through effectors. These components work together to restore balance.
Negative feedback differs from positive feedback because it:
- A Amplifies the initial stimulus
- B Has no control center
- C Opposes the initial change
- D Occurs only in disease states
Correct answer: Opposes the initial change
Negative feedback counteracts deviations from a set point. This mechanism promotes stability by reducing the original stimulus.
Which physiological process is primarily regulated by negative feedback?
- A Blood clotting
- B Childbirth
- C Regulation of blood glucose
- D Action potential generation
Correct answer: Regulation of blood glucose
Blood glucose regulation uses insulin and glucagon in a negative feedback loop. This maintains glucose levels within a narrow range.
Positive feedback is best exemplified by:
- A Thermoregulation
- B Blood pressure regulation
- C Blood clotting
- D Plasma osmolality regulation
Correct answer: Blood clotting
Blood clotting involves a cascade that amplifies the initial response. This positive feedback continues until the clot is formed.
The set point in a homeostatic system refers to:
- A The maximum value a variable can safely reach
- B The long-term average of environmental conditions
- C The desired value of a variable
- D The point at which the system fails completely
Correct answer: The desired value of a variable
The set point is the normal target value for a regulated variable. Deviations from this value trigger corrective responses.
Which variable is most tightly regulated by homeostatic mechanisms?
- A Total body weight
- B Blood glucose
- C Standing height in adulthood
- D Skin pigmentation and tanning response
Correct answer: Blood glucose
Blood glucose must be maintained within narrow limits to ensure cellular energy supply. Large deviations can be life-threatening.
Thermoregulation in humans primarily involves feedback from:
- A Muscle spindles
- B Baroreceptors
- C Thermoreceptors
- D Chemoreceptors
Correct answer: Thermoreceptors
Thermoreceptors detect changes in body and environmental temperature. Signals are integrated to maintain core body temperature.
Which organ acts as the main control center for thermoregulation?
- A Cerebellum
- B Medulla oblongata
- C Hypothalamus
- D Thalamus
Correct answer: Hypothalamus
The hypothalamus integrates thermal information and initiates appropriate responses. It is the primary temperature control center.
Homeostatic regulation of arterial blood pressure mainly involves:
- A Osmoreceptors
- B Baroreceptors
- C Photoreceptors
- D Mechanoreceptors in muscles
Correct answer: Baroreceptors
Baroreceptors sense changes in blood pressure. They trigger reflex adjustments in heart rate and vascular tone.
Failure of negative feedback mechanisms most commonly leads to:
- A Rapid recovery to normal
- B Exaggerated responses
- C Stable equilibrium
- D Reduced sensitivity of receptors
Correct answer: Exaggerated responses
Without negative feedback, deviations are not corrected. This can result in excessive or uncontrolled responses.
Which of the following best describes dynamic equilibrium?
- A No detectable change in any system variables
- B Continuous unregulated change in one direction
- C Small fluctuations around a set point
- D An irreversible, permanent change in the system state
Correct answer: Small fluctuations around a set point
Dynamic equilibrium involves constant minor fluctuations around a set point. This reflects ongoing regulation rather than absolute constancy.
In endocrine regulation, negative feedback typically occurs when:
- A A hormone stimulates its own continued secretion
- B Target gland hormones inhibit upstream release
- C Neural input ceases
- D Receptors become permanently and irreversibly activated
Correct answer: Target gland hormones inhibit upstream release
Target gland hormones feed back to inhibit hypothalamic or pituitary secretion. This stabilizes hormone levels.
Which feedback mechanism is most important for maintaining plasma calcium levels?
- A Positive feedback driven mainly by calcitonin secretion
- B Negative feedback via parathyroid hormone
- C Neural reflex arcs acting on their own
- D Renal autoregulation of blood flow alone
Correct answer: Negative feedback via parathyroid hormone
Parathyroid hormone is regulated by negative feedback from plasma calcium levels. This maintains calcium homeostasis.
Feedforward control differs from feedback control because it:
- A Responds only after a disturbance has already occurred
- B Does not involve any sensory receptors
- C Anticipates changes before they occur
- D Always directly opposes the initial stimulus
Correct answer: Anticipates changes before they occur
Feedforward mechanisms act in anticipation of a change. They reduce the magnitude of disturbances before they affect homeostasis.
An example of feedforward regulation is:
- A Insulin release after glucose absorption
- B Sweating after body temperature rises
- C Increased heart rate before exercise
- D Vasoconstriction during blood loss
Correct answer: Increased heart rate before exercise
Heart rate increases at the onset of exercise before metabolic changes occur. This anticipatory response supports upcoming demands.
Which system plays the most rapid role in restoring homeostasis?
- A Endocrine system
- B Immune system
- C Nervous system
- D Renal system
Correct answer: Nervous system
The nervous system transmits signals quickly. This allows rapid corrective responses to disturbances.
Long-term homeostatic regulation of blood volume primarily depends on the:
- A Nervous system
- B Respiratory system
- C Renal system
- D Skeletal system
Correct answer: Renal system
The kidneys regulate water and sodium balance over the long term. This controls blood volume and pressure.
Which condition represents a breakdown of homeostasis?
- A Stable body temperature
- B Normal blood pH
- C Persistent hyperglycemia
- D Normal heart rate variability
Correct answer: Persistent hyperglycemia
Persistent hyperglycemia indicates failure of glucose regulatory mechanisms. This reflects disrupted homeostasis.
The ultimate goal of homeostatic regulation is to:
- A Eliminate all variability in the body
- B Maximize overall energy expenditure
- C Keep conditions optimal for cellular function
- D Prevent any adaptation to the environment
Correct answer: Keep conditions optimal for cellular function
Homeostasis ensures that cells operate in favorable conditions. This supports survival and normal physiological function.
Which component of a homeostatic control system is responsible for comparing the incoming signal with a set point?
- A Receptor
- B Effector
- C Control center
- D Afferent pathway
Correct answer: Control center
The integrating center (often the brain or an endocrine gland) receives information from sensors and compares it to the physiological set point to determine if a response is needed.
What is the primary difference between negative and positive feedback mechanisms?
- A Negative feedback moves a variable toward the set point; positive feedback moves it away.
- B Positive feedback is more common in healthy physiological states.
- C Negative feedback requires an energy-intensive effector, while positive feedback does not.
- D Negative feedback only occurs in the nervous system.
Correct answer: Negative feedback moves a variable toward the set point; positive feedback moves it away.
Negative feedback works to counteract a stimulus to return to a set point, whereas positive feedback reinforces the stimulus, driving the variable further from the initial state.
Which of the following is a classic example of a positive feedback loop in human physiology?
- A Regulation of blood glucose levels
- B The clotting of blood at a wound
- C Maintenance of body temperature
- D Control of arterial blood pressure
Correct answer: The clotting of blood at a wound
Blood clotting and childbirth (uterine contractions) are rare examples of positive feedback where the initial action triggers more of the same action until a final goal is reached.
In the regulation of body temperature, which of the following acts as the 'effector' when the body is too cold?
- A Thermoreceptors in the skin
- B The Hypothalamus
- C Skeletal muscle (shivering)
- D The cerebral cortex
Correct answer: Skeletal muscle (shivering)
Effectors are organs or tissues that carry out the response. Skeletal muscles act as effectors by shivering to generate heat when body temperature drops.
Feedforward control is best described as a mechanism that:
- A Responds after a variable has already changed.
- B Anticipates a change in a variable beforehand.
- C Always results in a positive feedback loop.
- D Only functions during pathological states.
Correct answer: Anticipates a change in a variable beforehand.
Feedforward control allows the body to anticipate changes, such as the secretion of digestive enzymes at the sight or smell of food before it is eaten.
What happens to the 'error signal' in a negative feedback loop as the variable returns to the set point?
- A It increases
- B It decreases
- C It remains constant
- D It becomes positive
Correct answer: It decreases
The error signal is the difference between the set point and the actual value. As the variable returns to the set point, this difference (the error) decreases.
Which physiological state is characterized by 'dynamic equilibrium'?
- A A state where variables never change.
- B A state where variables fluctuate within a narrow range.
- C A state where all metabolic processes have completely stopped.
- D A state of permanent positive feedback.
Correct answer: A state where variables fluctuate within a narrow range.
Homeostasis is not static; it is a dynamic equilibrium where internal conditions fluctuate slightly around a set point.
The 'internal environment' of the body, which homeostatic mechanisms work to protect, refers specifically to:
- A Intracellular fluid
- B Extracellular fluid
- C The cytoplasm
- D The digestive tract contents
Correct answer: Extracellular fluid
Claude Bernard defined the 'milieu intérieur' as the extracellular fluid (plasma and interstitial fluid) that bathes the cells.
Which system provides the fastest homeostatic responses in the body?
- A Endocrine system
- B Renal system
- C Cardiovascular system
- D Nervous system
Correct answer: Nervous system
The nervous system uses electrical impulses to provide near-instantaneous responses, whereas the endocrine system relies on blood-borne hormones which are slower.
During childbirth, the hormone oxytocin causes uterine contractions, which then trigger more oxytocin release. This is an example of:
- A Negative feedback
- B Feedforward inhibition
- C Positive feedback
- D Redundancy
Correct answer: Positive feedback
Because the response (contractions) increases the stimulus (oxytocin release), it is a positive feedback loop that continues until delivery.
Which of the following is an example of an extrinsic homeostatic regulatory mechanism?
- A Local blood flow auto-regulation in a muscle
- B Chemical changes within a cell regulating its own metabolism
- C A tissue releasing nitric oxide to dilate its own vessels
- D The heart rate increasing via sympathetic nervous activity
Correct answer: The heart rate increasing via sympathetic nervous activity
Extrinsic regulation involves control originating outside of the organ or tissue, usually via the nervous or endocrine systems.
A rise in plasma glucose levels triggers the release of insulin, which acts to lower glucose. This is a:
- A Positive feedback loop
- B Feedforward response
- C Non-homeostatic event
- D Negative feedback loop
Correct answer: Negative feedback loop
The response (lowering glucose) opposes the initial stimulus (high glucose), making it a negative feedback loop.
The 'set point' for a physiological variable can be adjusted. An example of this is:
- A A fever during an infection
- B Death due to hypothermia
- C The resting heart rate
- D A sudden drop in blood pressure
Correct answer: A fever during an infection
During a fever, the hypothalamus increases the body's temperature set point to help fight infection.
If a homeostatic mechanism fails and a variable moves significantly outside the normal range, the result is typically:
- A Enhanced health
- B Acclimatization
- C Disease or death
- D A new, adjusted set point
Correct answer: Disease or death
Homeostatic imbalance is the fundamental cause of most diseases; if the body cannot restore balance, pathophysiology or death occurs.
Which organ is primarily responsible for the homeostatic regulation of blood pH and ion concentration over the long term?
- A Lungs
- B Liver
- C Kidneys
- D Pancreas
Correct answer: Kidneys
While lungs manage CO2 (and thus pH) quickly, the kidneys provide long-term regulation of pH and electrolyte balance through excretion and reabsorption.
Which pathway carries information from the receptor to the integrating center?
- A Afferent pathway
- B Efferent pathway
- C Effector pathway
- D Motor pathway
Correct answer: Afferent pathway
The afferent pathway (think 'A' for 'Approaching' the center) carries sensory information to the control center.
Which of the following describes the concept of 'redundancy' in homeostasis?
- A Multiple mechanisms exist to regulate the same variable.
- B One system is enough to control all variables.
- C The body stops regulating a variable if it's too difficult.
- D Positive feedback takes over when negative feedback fails.
Correct answer: Multiple mechanisms exist to regulate the same variable.
Redundancy ensures that if one mechanism fails, others (like sweating and vasodilation for cooling) can still maintain balance.
In the baroreceptor reflex, when blood pressure rises, the heart rate is decreased. In this arc, the baroreceptor is the:
- A Effector
- B Integrating center
- C Stimulus
- D Sensor/Receptor
Correct answer: Sensor/Receptor
Baroreceptors are specialized pressure-sensitive nerve endings that act as the sensors to detect changes in blood pressure.
Which of the following is NOT a regulated variable in the human body?
- A Blood glucose
- B Body temperature
- C Plasma osmolarity
- D Hair or eye color
Correct answer: Hair or eye color
Regulated variables are those maintained by active homeostatic loops (glucose, temperature, osmolarity). Hair and eye color are fixed genetic traits, not actively regulated by the body.
Acclimatization refers to:
- A The body's improved homeostatic response to stress over time.
- B A permanent, inherited genetic change within a population over generations.
- C A failure of the body's negative feedback control mechanisms.
- D The use of positive feedback loops to adapt to cold weather conditions.
Correct answer: The body's improved homeostatic response to stress over time.
Acclimatization is a reversible physiological adjustment, such as producing more red blood cells after staying at high altitudes for several weeks.