Definition & Core Concepts
What is homeostasis?
Maintenance of a stable internal environment despite external changes
What type of feedback reduces a change?
Negative feedback
What is normal body temperature?
Approximately 37°C
Which system uses electrical signals?
Nervous system
What happens to body temperature during exercise?
It increases
What is meant by “internal environment”?
The conditions inside the body (e.g. temperature, pH, blood glucose)
Give one example of negative feedback in the body
Body temperature regulation or blood glucose control
What happens to blood vessels when you are hot?
Vasodilation (widening of blood vessels)
Which system uses hormones?
Endocrine system
What happens to heart rate during exercise?
It increases
What is a set point?
The normal value or target range for a physiological variable
What is positive feedback?
A mechanism that increases or amplifies a change
What happens to blood vessels when you are cold?
Vasoconstriction (narrowing of blood vessels)
Which system responds faster?
Nervous system
Why does sweating increase during exercise?
To enhance heat loss via evaporation
What type of feedback is most common in homeostasis?
Negative feedback
Give an example of positive feedback in the human body
Childbirth (oxytocin release) or blood clotting
What is sweating’s role in thermoregulation?
Evaporative cooling to reduce body temperature
Which system has longer-lasting effects?
Endocrine system
What happens to blood flow during exercise?
Blood is redistributed to active muscles and skin
What is a stimulus in homeostasis?
A detectable change in the internal or external environment
What happens if feedback mechanisms fail?
Internal conditions move further from the set point, potentially causing illness or death
What is vasodilation?
Widening of blood vessels to increase heat loss
What is a hormone?
A chemical messenger released by glands that affects target cells
How is oxygen delivery maintained?
Increased heart rate and ventilation improve oxygen delivery
What is a receptor?
A structure that detects a change (stimulus)
What role does the brain play in feedback loops?
The brain (especially hypothalamus) acts as the control centre to process information and initiate responses
What is vasoconstriction?
Narrowing of blood vessels to conserve heat
How are hormones transported in the body?
Via the bloodstream
What happens to metabolic rate during exercise?
It increases to meet energy demands
What is an effector?
A structure that produces a response to restore balance
How do receptors detect change?
By detecting deviations from the set point through specialised sensory cells
Which part of the brain controls temperature?
The hypothalamus
What is the role of the hypothalamus?
Acts as the control centre for homeostasis, regulating temperature, thirst, heart rate, etc.
Why is fluid balance important in exercise?
To maintain plasma volume and prevent dehydration
What is the difference between negative and positive feedback?
Negative feedback reverses change; positive feedback amplifies change
Why is negative feedback more common than positive feedback?
Because it promotes stability and prevents extreme deviations
How does evaporation cool the body?
Sweat absorbs heat and evaporates, removing heat from the body
Compare nervous vs endocrine response speed and duration
Nervous = fast, short-lasting; endocrine = slow, long-lasting
Explain how the body maintains blood pressure during exercise
Increased heart rate and vasoconstriction in non-essential areas help maintain blood pressure
Why is homeostasis important during exercise?
It ensures optimal enzyme function and performance during increased physiological stress
Explain a full negative feedback loop using temperature regulation
Increase in temperature → thermoreceptors detect change → hypothalamus activated → sweating + vasodilation → temperature decreases
Explain how the body responds to overheating during exercise
Increased temperature → hypothalamus activates sweating + vasodilation → increased heat loss → return to set point
Explain how both systems work together in homeostasis
Nervous system detects rapid changes; endocrine system provides sustained regulation (e.g. hormones during prolonged exercise)
Analyse the role of the cardiovascular system in homeostasis during exercise
The cardiovascular system increases cardiac output and redistributes blood to maintain oxygen delivery and temperature regulation
Explain how multiple systems interact to maintain homeostasis
The nervous and endocrine systems coordinate responses via receptors, control centres, and effectors to maintain equilibrium
Evaluate why positive feedback is rare but necessary in some cases
Positive feedback is rare because it can destabilise systems, but is essential for rapid completion of processes (e.g. childbirth)
Analyse how thermoregulation may be impaired in extreme environments
Extreme heat/humidity reduces evaporation efficiency; dehydration reduces sweating → impaired thermoregulation and risk of hyperthermia
Evaluate the advantages and limitations of each system in maintaining homeostasis
Nervous system allows rapid response but is short-lived; endocrine system is slower but provides prolonged, widespread effects—both are essential for full regulation
Evaluate how failure of homeostasis affects performance (e.g. dehydration, hyperthermia)
Failure leads to fatigue, dehydration, hyperthermia, reduced performance, and potential collapse