Organisms Response To The Environment - Homeostasis Flashcards
What is the definition of homeostasis?
The maintenance of a constant internal environmemt via physiological control systems to survive a greater range of habitats
Why is temperature controlled by homeostais?
Too high: enzymes will denature as their tertiary structure will become distored due to the breaking of r group interactions
Too low: kinetic energy of the substrates decreases and so less emzyme substrate complexes are formed
Why is blood glucose concentration controlled by homeostasis?
Too high: water potential of blood plasma decreases so water leaves cells by osmosis
Too low: glucose is a respiratory substrate so the ATP cycle decreases which if stops could cause cell death
Why is water potential controlled by homeostasis?
Too high: the cell swells which could cause it to burst
Too low: the solute concentration increases distrorting r group interactions in proteins such as transport proteins and enzymes altering their tertiary structure so much less escs are formed
How do organisms know when to trigger a response to a change in their internal environment?
- greater deviation from set point
- stronger error signal from the hypothalamus
- effectors have to work more to counteract the deviation
- deviation from set point decreases
- error signal decreases
- effectors reduce their response
What is positive feedback? Give an example
When a deviation from the optimum causes changes that result in even greater deviation from the normal e.g. in the neurones where a stimulus causes a small influx of sodium ions which increases the permeablity of the neurone membrane to sodium ions so more enter
Give the negative feedback loop for the increase in temperature (include all the effectors)
- Stimulus = the increase in temperature as the input stimulus
- Receptors = thermoreceptors in the hypothalamus
- Output signal triggers autonomic nervous system or hormones
- Effectors:
- vasodilation in the arterioles so blood runs closer to the skim surface for faster heat loos
- erector muscles relax so body hair is lowered
- sweat glands release water by evaporation - Response = cooling effects reducing the input signal so the output signal is reduced as negative feedback
What is negative feedback?
When the change produced by the control system leads to a change in the stimulus detected by the receptor and turns the system off
What hormone is released at hyperglycaemia?
Blood glucose concentration too high from set point so insulin released
What hormones are released at hypoglycaemia?
Blood glucose comcentration is too low from set point so glucagon and adrenaline are released
What chemical processes occur during hyperglycemia?
- glycogenisis = the conversion of glucose to glycogen
- conversion of glucose to lipid
- increased metabolism so increased respiration to reduce blood glcuose levels
What chemical processes occur during hypoglycaemia
- glycogenolysis = breakdown of glycogen to glucose
- gluconeogenisis = production of glucose from non carbohydrate sources e.g amino acides to glucose
How is the increase in blood glucose regulated?
- Stimulus of the increased blood glucose concentration is detected as the input signal by the receptors being beta cells in the pancreas
- The output signal triggers insulin release which is a polypeptide hormone so a chemical messenger
- Effectors = liver/ muscle tissue
- Insulin binds to the protein receptor in the cell surface membrane of liver / muscle cells.
- Tertiary protein structure changes shape and the cells insert carrier proteins through which the glucose can enter the cell via facilitated diffusion
- Glucose is polymerised into glycogen
- Response is triggered of blood glucose concentration being lowered
- Negative feedback
How is a decrease in blood glucose concentration regulated?
- Stimulus of the decreased blood glucose concentration is detected as the input signal by the receptors being alpha cells in the pancreas
- The output signal triggers glucagon release which is a polypeptide hormone so a chemical messenger
- Effectors = liver
- Glucagon binds to the protein receptor in the cell surface membrane of liver cells.
- Tertiary protein structure changes shape and the cells insert carrier proteins
- Glycogen glycosidic bonds are hyrolysed to release alpha glucose which moves out if tge carrier proteins by facilitated diffusion
- Response is triggered of blood glucose concentration being increased
- Negative feedback
What three factors influence blood glucose concentration?
- glucose from hydrolysis of consumed carbohydrates such as starch
- glycogenolysis
- gluconeogenisis