Section 6 - 16 Homeostasis Flashcards
Define - Homeostasis
- Maintainance of a constant internal environment within a living organism.
Give 4 examples of homeostasis within a mammal
- Blood pH - optimum enzyme activity, maintaining shape of antibodies
- Core temp - optimum enzyme activity
- Blood glucose conc. - effective energy transfer and maintaining water potential of the blood
- Water potential of blood - maintain correct cellular water potential and structure.
How can homeostasis be controlled?
- Nervous system
- Endocrine system
- A combination of both
What is a feedback loop?
- Stimulus - change
- Receptor - detected change
- Coordinator - thinking
- Effector - doing
What are the two types of feedback?
- Negative - change in conditions, reversed and returned to set point to maintain optimum conditions
- Positive - change detected is increased further away from the optimum condition does not lead to homeostasis. - only good application in pregnancy as oxytocin hormone released to endorse labour.
What is an endotherm?
- Maintaining body temp at set point
- generate heat energy through respiration
- change cellular and physiological processes
- warm blooded animals
What is an ectotherm?
- Rely on external heat energy
- warm/cool body by changing behaviour in response to changing conditions
- cold blooded
How do ectotherms control temperature?
- basking in sun
- taking shelter
- gaining warmth from ground or rocks
How do endotherms get warmer?
- vasoconstiction
- shivering
- hair raising
- increased metabolic rate
- decreased sweating
- behaviour - finding heat
How do endotherms lose heat?
- vasodilation
- increased sweating
- lowering hair
- behaviour - finding cooler
What are the two types of gland in the endocrine system?
- Exocrine (chemicals outside body)
- Endocrine (chemicals within body)
What are some examples of endocrine glands?
- Pituitary
- Thyroid
- Parathyroid
- Adrenals
- Pancreas
- Ovaries/uterus
- Prostate/testes
What effect do hormones have?
- Effect permeability of cell membrane
- cause release of the second messenger inside a cell
- diffuse into cell and promote/inhibit transcription
Why do blood glucose levels need to be controlled?
- Hypoglycamia (too little) and hyperglycaemia (too much) can kill cells due to the effect on water potential of blood and tissue fluid.
- Required in respiration
- Required for the manufacture of many other cellular products
Explain how blood glucose is detected
- Monitored by pancreas
- In islets of Langerhans (tissue wall of pancreas) - which acts as receptor and cendocrine cell
- Two types of cell:
- Alpha cells - larger, detect low glucose conc. and secrete glucogen
- Beta cells - smaller, detect high glocose conc. and secrete insulin
- Capillaries run throughout so blood is constantly monitored.
What are the two types of cell within the islets of Langerhans?
- Alpha cells - larger, detect low glucose conc. and secrete glucogen
- Beta cells - smaller, detect high glucose conc. and secrete insulin
What are some factors that affect blood glucose conc.?
- Diet
- Glycogen converted into glucose in the liver
- from gluconeogenesis
Where is glycogen stored?
Liver
What three processes occur in the liver?
- Glycogenesis - synthesis of glycogen from glucose
- Glycogenolysis - break down of glycogen into glucose
- Gluconeogenesis - synthesis of glucose from lipids, amino acids or nucleic acids
What is Glycogenesis?
- Synthesis of glycogen from glucose
- In liver
What is Glycogenolysis?
- In liver
- break down of glycogen into glucose
What is Gluconeogenesis?
- in liver
- synthesis of glucose from lipids, amino acids or nucleic acids
What is the process of regulating if blood glucose is too high?
- Beta cells in islets of Langerhans detect change
- Immediately secrete insulin into the bloodstream
- Insulin binds to receptors on the surface of muscle and liver cells
- In Liver cells - activates enzymes that convert glucose to glycogen (Glycogenesis)
- In muscle cells - control uptake of glucose into cells regulating the activity to channel proteins on cell surface membrane
- Excess glucose can also undergo conversion to far.
How is blood glucose regulated if too low?
- Alpha cells in islets of langerhans detect low glucose levels
- Glucagon secreted into the bloodstream
- glucagon binds to receptors on the surface of muscle and liver cells
- Liver cells - enzyme to convert glycogen to glucose (glycogenolysis)
- Both cells - enzymes to convert glycerol and amino acids into glucose (Gluconeogenesis)
What does adrenaline do?
- Increase blood glucose levels
- Attaching to protein receptors on the cell-surface membrane of target cells
- Activate enzyme that causes the breakdown of glycogen to glucose in liver cells
- Causing glycogenolysis for rapid response.
What is the second messenger model?
- Adrenaline (1st messenger) bind to transmembrane protein receptor site
- Bind cause receptor site to change in shape and adenyl cyclase is activated
- Activated adenyl cyclase converts ATP to cAMP
- cAMP binds to protein kinase enzyme (inactive) changing shape and activating it.
- Enzyme converts glycogen to glucose - glycogenolysis
- Glucose uses facilitated diffusion out of the liver cell into the bloodstream
- blood glucose levels increase.