Homeostasis Flashcards
(45 cards)
Define homeostasis
Homeo- sameness
Stasis- standing still
Maintenance of a constant internal environment
Dynamic equilibrium
Mechanism of regulation in homeostasis with examples
Positive and negative feedback loops
Neg= blood glucose Positive= coagulation cascade
Name parameters in homeostasis
Carbon dioxide/ oxygen Salt and electrolytes Waste products PH and temp Vol/pressure
What four things are needed in a system
Disruptor- change parameter
Detector- detect change
Control system- control response
Effector- return parameter to normal level
What is core body temperature?
Head, neck and torso
37 +/- 0.5 degrees
Elderly lower
Fluctuates throughout day- circadian rhythm
Increase at certain stages of menstrual cycle- LUTEAL
What acts as ‘thermostat’ in thermoregulation? What is the set point? Areas of hypothalamus that respond?
Hypothalamus input from peripheral and central thermoreceptors
Approximately 37 degrees can be altered in response to things such as pyrogens
Preoptic area of H increase discharge rate in response o increase core temp
Other areas increase firing when temperature drops
What glands produce sweat?
Eccrine
How does the body respond to decrease in core temp?
Increase sympathetic nerve activity
Vasoconstriction AV anastomoses closed Shivering (increase metabolic waste) Piloerection Behavioural e.g. Curl up to reduce SA from which heat can be lost
Name three things that trigger vasodilation?
Decrease sympathetic nerve activity
Bradykinin in sweat
Local increase in metabolites
How does the body respond to an increase in core temp?
Vasodilation
Sweating
Pilorelaxation
Behavioural- stretch out to increase SA from which heat can be lost
Define pyrexia?
Core body temp above 38.5
What causes pyrexia?
Most often infection Produce IL-1/6 and TNF alpha Increase prostaglandin E2 PGE2 acts on preoptic area Induce febrile response
Why pyrexia in the elderly a problem?
Elderly reduced thermoregulatory ability therefore temperature could reach dangerous level
Why pyrexia a good thing?
Optimal temperature for immune system to function and fight infection
What could be given to treat pyrexia?
Paracetamol
Aspirin
NSAIDs
Other antipyretic drugs
Define hyper pyrexia
Temperature above 41.5
Define pH
Power of H
Give pH range of the body. What are the names given to the condition when the pH is above/ below this range?
7.35-7.45
Above= alkalosis
Below = acidosis
What are the pH limits of human tissue survival?
6.8-7.8
What are the two organs mainly responsible for the maintenance of pH?
Kidney
Lungs
Change in h+ concentration by factor of 2 correlats to a pH change of
0.3
What are the systems called that help regulate pH? Name two
Buffer systems
Carbonic acid- bicarbonate system
Sodium phosphate buffer system
What is gastric pH? Why is it different?
1.5-3.5
Enzymes in digestive system work better at these pH’s
Name an antacid used of indigestion. What property makes it effective?
Aluminium hydroxide
Mildly alkaline but insoluble
