Homeostasis Flashcards
Define homeostasis
The maintenance of a constant internal environment within restricted limits in an organism.
Ensures that all the cells of the body are in an environment that meets their requirements and allows them to functions normal despite external changes.
What is the importance of homeostasis for enzymes?
- They are sensitive to pH and temperature changes. Big changes could cause denaturing of enzymes and stop reactions occurring.
What is the importance of homeostasis for Independence?
- Stops organisms being reliant on the external environment.
- Gives them the ability to thrive almost anywhere.
What is the importance of homeostasis for Blood Glucose?
- Essential to maintain this to maintain water potential and also provides cells a constant supply of glucose for respiration.
What is the importance of homeostasis for Water potential?
- Changing this in blood/tissue fluid could make cells shrink or even burst, preventing them from operating normally.
Name the 4 main reasons homeostasis is important for?
- Enzymes
- Independence
- Blood Glucose
- Water potential
What are the stages of homeostatic control?
- The set point
- Receptor
- Controller
- Effector
- Feedback loop/mechanism
Describe negative feedback
- Occurs when the stimulus causes the corrective measures to be turned off, tending to return the system to its optimum level and preventing overshoot.
Describe the differences between positive feedback mechanisms (PF) and negative feedback mechanisms (NF)
- PF: a feedback mechanism resulting in the amplification or growth of the output system
- NF: a feedback mechanism resulting in the inhibition or the slowing down of a process
- PF: breakdown the homeostasis of the system
- NF: maintain the conditions of homeostasis
- PF: less common but occurs in specific situations
- NF: occurs more often in the body, helping maintain various body conditions.
Describe the features of hormones.
- Produced in glands which secrete the hormone directly into the blood.
- Carried in the blood plasma to the target cells, which have specific receptors on their cell-surface membrane that’s complementary to specific hormones.
- Are effective in very low concentrations but often have wide-spread and long-lasting effects.
- ## Produced in glands which secrete the hormone directly into the blood.
Describe the second messenger model involving adrenaline.
- Adrenaline binds to the receptor site in a transmembrane protein in the cell-surface membrane of a liver cell.
- This activates (changes the shape of) the enzyme adenyl cyclase inside the liver cell that is attached to the protein.
- This enzyme converts ATP to cAMP in the liver cell, which acts as the second messenger.
- cAMP then activates the protein kinase enzyme shape, which converts glycogen to glucose.
What is the role of the pancreas in regulating blood glucose concentration?
- Produces hormones insulin and glucagon.
- Made of enzyme producing cells called the islets of langerhans - alpha cells which produce glucagon and beta cells which produce insulin.
What is the role of the liver in regulating blood glucose concentration?
- It is the site of hormone effectors.
- Gluconeogenesis, Glycogenesis, Glycogenolysis
Define Gluconeogenesis
> Gluconeogenesis - production of glucose from sources other than carbohydrates (e.g: amino acids, glycerol)
Define Glycogenesis
> Glycogenesis - conversion of glucose to glycogen
Define Glycogenolysis
> Glycogenolysis - break down glycogen into glucose.
Where can blood glucose come from?
- Directly from the diet - glucose absorbed as hydrolysis of other carbohydrates.
- Hydrolysis of glycogen in small intestine - Glycogenolysis
- Production of glucose from other sources than carbohydrates - Gluconeogenesis
Define Hyperglycemia…
