Homeostasis, thermoregulation and excretion Flashcards
(34 cards)
What is homeostasis?
maintenance of a stable internal environment within restricted limits in organisms ensuring cells function normally despite environmental change
Why is homeostasis important?
- keeps internal environment constant for metabolic reactions
- ensures cells function properly and avoid damage
- helps organisms respond + adapt to external change
What is the role of a receptor in homeostasis?
sensory receptors = detect stimuli sending signals to the brain about changes in the environment (e.g blood pH and temp)
What is the role of a coordinator in homeostasis?
receives and interprets information from receptors and sends instructions to an appropriate effector
What is the role of an effector in homeostasis?
effectors = muscles or glands that act on signals from the brain and cause responses to regain equilibrium (e.g sweating)
What is a negative feedback system?
coordination between receptors and effectors to maintain optimum conditions
How does negative feedback work?
- receptors detect a change in direction (e.g rising BG)
- signals trigger effectors to produce responses that reverse the initial change (e.g releasing insulin)
- conditions return to their set range
Why is maintaing blood glucose concentration important and how is it achieved?
Important = glucose is needed for respiration but too much can affect water potential in blood cells
Achieved = insulin and glucagon adjust BG concentration to maintain a healthy glucose supply
Why is maintaining blood PH important and how is it achieved?
Important = changes in PH can impair enzyme action
Achieved = adjustments are made to the acid-base balance in the blood to maintain optimum pH
Why is maintaining water regulation important and how is it achieved?
Important = too much or little water in the blood and cells can cause cells to burst or shrink via osmosis
Achieved = water removed or reabsorbed from blood or tissue fluid to maintain optimum water potential
Why is maintaining temperature important and how is it achieved?
Important = changes in temp can impair enzyme action
Achieved = adjustments made by sweating or shivering to maintain optimum
What is a positive feedback system?
amplifies changes rather than reversing them a deviation from an optimum results in an even greater deviation from the optimum
How does positive feedback work?
- initial change occurs (e.g release of clotting factors after injury)
- effectors are stimulated and enhance the change (e.g more clotting factors being released)
- change continues until an endpoint is met (e.g a fully formed clot)
what are 2 examples of positive feedback?
Blood clotting = clotting factors activate further clotting
Childbirth = oxytocin stimulates more uterus contractions
What is cell signalling?
process which cells communicate
can occur between adjacent cells or between distant cells
How does cell signalling occur between distant cells?
- communicate by releasing hormones
- these hormones travel in the blood and signal to target cells
- cell-surface receptors enable cells to recognise and respond to hormones
What is thermoregulation?
process of maintaining a relatively constant core body temperature important to maintain optimum enzyme activity
What are ectotherms and give an example?
animals that use their surroundings to regulate body temp through behavioural changes like surrounding change
e.g reptiles and fish
What are endotherms and give an example?
animals relying on their metabolic internal processes to control body temp
e.g mammals and birds
How does thermoregulation reduce body temperature when it’s too high?
Sweating = effector sweat glands produce more sweat to promote evaporative cooling
Flattening hair = effector pili muscles relax flattening hairs to reduce insulation
Vasodilation = effector arterioles near the skin dilate, increasing blood flow to the skin and heat radiation from the skin surface
How does thermoregulation increase body temperature when it’s too low?
Shivering = effector skeletal muscles contract to generate heat through increased cellular respiration (exothermicaly)
Minimising sweating = effector sweat glands produce less sweat helping to conserve body heat
Erecting hair = effector pili muscles contract raising hairs trapping a layer of warm air increasing insulation
Vasoconstriction = effector arterioles near the skin constrict reducing blood flow to the skin and heat radiation from the skin surface
Releasing adrenaline = effector glands release speed up cellular metabolism producing more heat
How does the hypothalamus control body temperature?
1) collects info about body temperature from temp receptors in hypothalamus and about surface temp from peripheral receptors in the skin
2) this information is processed in the hypothalamus to detect deviations from normal levels in temp
3) hypothalamus sends signals to effectors like muscles and sweat glands
4) these effectors implement mechanisms to restore the ideal temp
What 2 centres in the hypothalamus are involved in thermoregulation?
heat loss and heat gain centre
How does the hypothalamus coordinate a response when temperature increases?
- impulses sent to the heat loss centre in the hypothalamus
- this sends impulses to the effector organs to increase heat loss
- the body temp returns to optimum
