4 regulation of systems Flashcards
Describe how plants can maintain their water balance in the short-term & long-term
Short-term: plants adjust the size of their stomata (tiny pores on the surface of leaves that allow for gas exchange)
Long-term: plants adjust the no. and size of their roots to help absorb more water from the soil. Some adaptations help them survive in dry environments
Explain how stomatal guard cells minimise water loss when a plant is under water stress
The stomatal guard cells become swollen to close the stomata to decrease the rate of transpiration (water loss)
Define homeostasis
condition of a relatively stable internal environment maintained within narrow limits
Provide 3 examples of factors under homeostatic control
- Hypothalamus regulates temperature and osmotic pressure
- Kidneys maintain water balance
- Pancreas regulates blood sugar
Define these parts of the stimulus-response model: stimulus, receptor, control centre, effector, response
Stimulus: a change (increase/decrease) in the level of an internal variable
Receptor: detects change and sends signals to the control centre
Control centre: evaluates the change for that variable and sends signals to the effector about the correction needed
Effector: adjusts its output to make the required correction
Response: corrective action taken
Complete a stimulus-response diagram for water balance and blood glucose regulation
Compare negative and positive feedback
Negative feedback: response counteracts the change in the variable — homeostatic mechanism
- may increase a variable to bring it back to normal
Positive feedback: change in a variable produces a response that amplifies the stimulus and increases its effect
Explain the importance of blood glucose level regulation
Blood glucose level regulation helps prevent or delay long-term, serious health problems
State where ‘glucose’ is stored in the body
Glycogen is a stored form of glucose – primarily stores glycogen in your liver and muscles. Glucagon is a hormone that triggers liver glycogen to convert back into glucose
State the role of insulin
Insulin: the glucose-storing hormone
- Stimulates movement of glucose from blood to skeletal muscle and adipose tissues (body fat)
- Activates enzymes that build glucose into glycogen in liver and skeletal muscle cells
- Breaks down fats in adipose tissue
State the role of glucagon
Glucagon: the glucose-releasing hormone
- Depending on blood glucose levels, glycogen in liver cells can store or release glucose
- This allows regulation of blood glucose and enables us to endure periods of fasting
Explain how these hormones act to regulate blood glucose levels
Insulin: its secretion is triggered by a rise in blood glucose above the normal level. It allows blood glucose levels to decrease
Glucagon: its secretion is triggered by a fall in blood glucose below the normal level. It allows blood glucose levels to increase
State how changes to water levels in the body are detected
Osmoreceptors work to detect changes in water balance
State how the body responds to bring water levels back to required levels
Water levels decrease:
- message is sent to the hypothalamus
- activation of thirst centres in the brain
- increase in ADH leads to greater reabsorption of water in the kidneys
Water levels increase:
- message is sent to the hypothalamus
- suppression of thirst centres in the brain
- decrease in ADH leads to less reabsorption of water in the kidneys
- increase in water excreted in urine.
Explain type 1 diabetes - cause, effect and treatment
Cause: blood glucose levels are above the normal range due to the individual’s inability to produce insulin
Effect:
- increased thirst and frequent urination
- low energy levels, fatigue
- extreme hunger and possible weight loss
- blurred vision
- diabetic ketoacidosis (DKA); inadequate amount of insulin to allow blood sugar into the cells to produce energy
Treatment: administration of insulin to reduce blood glucose levels (injection or insulin pump)
