Homeostatic Control Flashcards
what are the main 5 homeostatic control systems
- Temperature control
- Glucose-
- Oxygen homeostasis
- Coagulation -
- Osmolality ( ADH pathway)
what is the definition of homeostasis
this is the physiological process by which the internal systems of the body are maintained at equilibrium despite variations in the external conditions.
This is not an unchanging state but a dynamic state of equilibrium.
list the parts of the control mechanism
- Sensory(receptor) this monitors variable
- Control centre – determines set points, analyses input, determines course of action
- Effector – means of changing the level of a variable
describe negative feedback of temperature for hot and cold
- Stimulus – increase body temperature, sensed by peripheral nervous sensors
- vasodilation and sweat happens
- body temperature decreases
- Body temperature decreases and hypothalamus shuts off
- (if too cold, vasco constriction, blood cappilaries draw into deeper tissue and skeletal muscles constrict causing shivering warms the body up)
describe the negative feedback for glucose
- Stimulus – raising blood glucose level
- Pancreas effector causes beta cells to produce insulin
- Insulin increases stimulates glycogen formation and glucose turns to glycogen in the liver and muscles
- Stimulates glucose uptake by cells
- Decreases blood glucose falls to normal range of 90mg/100ml
- Stops glucose converted to glycogen
- (increasing glucose level – pancreas produces glucagon in alpha cells, this converts glycogen to glucose in the liver and muscle cells increasing the amounts of glucose that there is to normal level of 90mg/100ml
describe type 1 diabetes
caused by an virus or genetic reason this means that the pancreas does not produce any insulin or only small amounts of insulin
describe type 2 diabetes
caused by pancreas not making enough glucagon and insulin therefore the glucose does not get converted into glycogen, can also be caused by resistance, this is due to being obese, lack of exercise, high sugary diet, or hereditary conditions
what is hypoxia
this is when the oxygen saturation is low
what Is the homeostatic mechanism to come out of hypoxia
- Detection of low oxygen levels, carotid bodies (bifurcation of carotid artery- bifurcation is the point at which division into two branches occur for example in the treachea)/renal cortex
- Erythropoietin production is stimulated– EPO kidney
- Which stimulates bone marrow to produce more RBCs – more haemoglobin has higher oxygen supply
- More oxygen carrying capacity
- Correct hypoxia and increases oxygen saturation
- Turn off EPO
what systems does oxygen homeostasis depend on
- Haematology – red blood cell and bone marrow
- Respiratory medicine – gaseous exchange
- Cardiology – circulatory competence
- Renal medicine – hypoxia detection and EPO
- Gastroenterology – iron absorption – need iron to make haemoglobin, acts as a haem group allows it to pick up oxygen as oxygen binds to Fe2+
describe osmolality homeostatic control
- Sensory in hypothalamus – supraoptic nucleus ( a nucleus of neurosecretory cells in the hypothalamus)
- Rise in concentration of extracellular fluid (ECF)
- Secretion of ADH from posterior pituitary
- Effect water absorption from renal tubules
- Correct concentration of ECF detected by SON (supraoptic nucleus)
- ADH turned off
- Renal abosption of water is reduced
(Posterior pituitary gland produces ADH, binds to the collecting duct as complimentary, causes vesicles to move towards the collecting duct this creates aqauporins causes more water to leave collecting duct )
describe positive feedback of blood clotting
- Break in tear in blood vessel and wall
- Clotting occurs as platelets adhere to site and release clotting factors clotting factor and tissue factor mix in the blood
- Released clotting factors causes inactive thrombiknase to covert to active thrombokinase this combines with calcium and causes prothrombin to covert to thrombin this causes soluble fibrous to convert to fibrin forming a mesh this catches more platelets and forms a platelet plug
- Clotting proceeds and newly formed clot grows
- Feedback cycle ends after clot seal breaks
what is positive feedforward
Positive feedforward is the anticipatory effect that one intermediate in a metabolic or endocrine control system exerts on another intermediate further along the pathway this may be positive or negative
what cause loss of homeostatic control
- Extreme physiological conditions such as extreme environment, altitude
- Pathology – diabetes mellitus and insipidus, coagulation defect
- Both – trauma
what is positive feedback
the mechanism that increases a change taking the system further away from the optimum
