Science Task 1 2025 - Disease Flashcards
(9 cards)
Define homeostasis
A state of balance among all the body systems needed for the body to survive and function correctly.
Define a negative feedback mechanism
A negative feedback loop is a biological mechanism in which a system responds to a change by reducing or counteracting it, maintaining stability or homeostasis. It works by detecting deviations from a set point and triggering responses that restore balance.
How does negative feedback work?
(What are the steps?}
Negative feedback involves the following three steps:
1. A change in the body is detected (e.g. a change in temperature or glucose level)
2. A message is sent to a gland or organ
3. A response is initiated. The response returns the body to its normal state.
How is negative feedback involved in the maintenance of blood sugar level?
The hormone insulin is released by the pancreas when an increase in blood sugar levels is detected. Insulin causes cells, including those of muscles and the liver, to take up glucose, thereby returning blood sugar levels to normal. When blood sugar levels are lower than normal the hormone glucagon, which has the opposite effect to insulin, is released.
What is an example of negative feedback?
The kidneys filter blood to remove waste and regulate water and salt balance through negative feedback.
As the fluid moves through the tubule, useful substances and water are reabsorbed, and salt levels are adjusted. The body controls how much water and salt is excreted based on needs. For example, on a hot day or after exercise, less water is lost to prevent dehydration.
Define a positive feedback loop
Positive feedback is when a change from the normal state triggers a reaction that results in the change being amplified.
What is an example of positive feedback?
During labour, positive feedback helps intensify contractions. As the baby moves into the cervix, stretch receptors send signals that trigger the release of oxytocin. This hormone causes stronger contractions, pushing the baby further down and activating more stretch receptors.
What is the ADH?
The hormone ADH (anti-diuretic hormone) plays a key role in regulating water balance in the body through negative feedback. It controls how much water the kidneys reabsorb, ensuring the body maintains the right water levels.
What is the balanced chemical equation for respiration and photosynthesis?
Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
