Physiology: Homeostasis Flashcards
what is the normal range for pulse?
60-100 BPM
what is the normal range for resting respiratory rate?
12-20 breaths/min
what is a normal capillary refil time?
less than two seconds
what is a normal oxygen saturation?
over 95%
what is average core body temperature?
37.8
what is core body temperature?
the temperature of structures deep within the body
what is normothermia?
normal core body temperature
why is normal core body temperature 37 degrees?
this is the optimum temperature for cellular metabolism and function
what effect does increasing body temperature have on metabolism?
speeds it up
what can overheating cause?
denaturation of proteins
nerve malfunctions
death
what effect can decreased body temperature have on metabolism?
can be fatally slowed down
what are the three possible sites for monitoring body temperature?
ear drum
rectal
oral
what does tympanic temperature mean?
temperature in the ear drum
when is rectal temperature measurement done?
at extremes of body temperature
why isnt the mouth a good place to measure body temperature?
the temperature of the mouth is affected by the consumption of food and drinks
when is body temperature at its lowest?
very early in the morning
what must be balanced for the body to have a constant core temperature?
heat gain and heat loos
what causes heat gain from the internal environment?
metabolc heat
how is metabolic heat produced?
via oxidation of metabolic fuel derived from food
what can increase metabolic heat?
increasing muscle activity
what three ways can heat be gained from the external environment?
radiation
convection
conduction
what are the four methods of heat loss to the external environment?
convection
conduction
radiation
evaporation
what is radiation?
the emission of heat energy in the form of EM waves from a surface
how can heat be gained and lost by radiation?
the body can absorb and emit radiant heat
how much heat is lost by radiation?
half
what is conduction?
transfer of heat between objects in contact
what direction does heat move in via conduction?
from the warm object to the cold object
what is convection?
the transfer of heat energy by air/water currents that carry the heat away from the body
what does convection combine with to move heat away from the body?
conduction
describe how convection and conduction work to cause heat loss?
air beside the skin is warmed by conduction, and is moved away by convection
what increases the effect of convection?
forced air movement across a surface
what decreases the effect of convection?
tight, air trapping clothes
what mechanism maintains the bodies core temperature?
a homeostatic negative feedback system
what are the sensors for maintaining core temperatture?
central and peripheral thermoceptors
where are central thermoreceptors found?
hypothalamus
organs
where are peripheral thermoreceptors found?
the skin
what is the control centre for maintaining core temperature?
the hypothalamus
what are the effectors for maintaining core temperature?
skeletal muscles
skin arterioles
sweat glands
what acts as the body’s thermostat and what does this mean?
the hypothalamus
maintains the temperature at a set point
what part of the hypothalamus is activated by cold?
posterior hypothalamic centre
what part of the hypothalamus is activated by heat?
the anterior hypothalamic centre
what do skin arterioles do in response to cold?
vasoconstrict to reduce blood flow to the skin and conserve heat
what do skeletal muscles do in response to cold?
shiver and move more to produce more heat
what do skin arterioles do in response to heat?
vasodilate to increase blood flow to the skin and increase heat loss
what do sweat glands do in response to heat?
sweat so this can evaporate and increase heat loss
what do skeletal muscles do in response to heat?
decrease tone and movement to decrease heat production
what happens to the hypothalamic temperature set point in fever?
it becomes raised
what do chemicals released from macrophages in response to inflammation act as in fever?
endogenous pyrogens
what do endogenous pyrogens do in fever?
stimulate release of prostaglandins in the hypothalamus
what do prostaglandins do in fever?
act on the hypothalamic thermoregulatory centre to reset body temperature at a higher value
when is the hypothalamic set point returned to normal in fever?
when there is no pyrogens or prostaglandins being made
what temperature is considered to be a fever?
38-40C
what is hyperthermia?
temperature over 40
what is hypothermia?
temperature under 35
what does a group of cells make?
a tissue
what is a tissue?
a group of cells with similar structure and specialised function
what do our bodies need to do to remain healthy?
maintain tightly regulated optimum physiological conditions
what is homeostasis?
the maintenance of steady states within our bodies by coordinated physiological mechanisms
what are the two types of homeostatic controls?
intrinsic controls
extrinsic controls
what are intrinsic controls?
local controls that are inherent in an organ
what are extrinsic controls?
regulatory mechanisms initiated outside an organ
what two systems play a role in extrinsic controls?
nervous and endocrine
what are the two types of control systems?
feedforward
feedback
what is a feedforward system?
one where responses are made in anticipation of a change
what is a feedback system?
one where a response is made after a change has been detected?
what are the two types of feedback systems?
positive and negative
what does a positive feedback system do?
amplifies an initial change
what does a negative feedback system do?
opposes an initial change
what is the main type of homeostatic control in the body?
negative feedback systems
what are the three components of a negative feedback system?
sensors, a control centre and effectors
