Homeostasis is maintaining a constant internal environment in response to external change. Homeodynamics is the idea that our bodies are constantly changing but we are able to maintain a dynamic equilibrium
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What is allostasis?
Achieving stability through change
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What is the set point?
The desired value for regulated values (e.g. temperature or pH)
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What is the homeostatic feedback loop?
Receptors detect deviation from set point, send AP down afferent NP to processing centre (usually CNS), CNS sends AP down efferent NP to effectors, glands or muscles
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What is negative FB? Name an example
FB system to get the changed variable BACK to the set point. Thermoregulation and increase in CO2 (lungs increase Resp.Rate)
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What is positive FB? Name an example
FB system to amplify a change in the variable (e.g. oxytocin increases uterine contractions which causes more to be released)
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What are the main variables controlled within the body?
Temperature, pH (or concentration) and pressure (osmotic and hydrostatic)
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What 2 systems are needed for communication in homeostasis?
Endocrine and nervous system
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What are exampled of external interfaces?
The gut, respiratory tract and urogenital tract
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What is the difference between core and shell temperature?
The core temperature is the temperature of the internal body. The shell temperature is the temperature of the outside of your body (skin, subcutaneous tissues and limbs), it fluctuates with the environment
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Why is it more accurate to measure the core temperature?
The shell temperature varies hugely based on environmental factors, such as the ambient temperature and direct sunlight
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How might anesthesia cause a fall in temperature?
Causes muscle relaxation (less metabolism so less heat prod), it also causes vasodilation
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How does the body produce heat and conserve it?
Prod: shivering, hormonal changes. Conserve: Piloerection, vasoconstriction (BVs less close to skin)
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What is non-shivering thermogenesis?
Increase in metabolic rate, not related to muscle contraction. Baby's use it because their NS isn't fully formed and they don't have much body hair
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What are the 4 ways heat is lost through the skin?
Conduction (transfer of heat from one atom to another), convection (transfer of heat into the air), radiation (via electromagnetic waves) and evaporation
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How does the body increase heat loss?
Sweating and vasodilation
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What is the function of thermoreceptors and where are the found?
They detect changed in body temperature. Found in the hypothalamus, dermis, liver and skeletal muscles.
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What is hypothermia and hyperthermia?
Hypo: temp below normal range (35) Hyper: above normal range (37.8)
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What is pyrexia and fever? What is apyrexia?
Pyrexia is relating to fever, an abnormally high temp. Apyrexia is not relating to fever.
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Why does hypothermia make you drowsy?
Vasoconstriction makes you drowsy. It also makes you paler
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What internal and external factors can predispose you to hypothermia?
Internal: age, pathogenesis, inactivity, slower cellular metabolism. External: homelessness, no heating, no adequate clothing
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