Homoeostasis of body temperature and body fluids Flashcards
what is core body temperature?
36.8 degrees
why does body temperature need to be kept around an optimum range?
for cellular respiration
what is thermoregulation?
the balance between heat production and heat loss
what are the risks of increased body temperature?
nerve malfunction, enzyme denaturing, changing structures of proteins, death
what is energy used for?
muscle contractions, active transport, building compex molecules, heat production
what is metabolic rate?
the rate at which energy is released by the breakdown of food
what are peripheral thermoreceptors and where are they located?
skin and mucous membranes; procide hypothalamus with info about external environment
where are central thermoreceptors located?
in the hypothalamus
what are the four ways heat is lost in the body?
conduction, convection, radiation, evaporation
how does sweating cool the body?
evaporation has a cooling effect
which nervous system stimulates sweating?
sympathetic
what types of substances are dissolved in sweat?
urea, lactic acid, salt, potassium ions
what is vasoconstriction?
constriction of blood vessles if the body is exposed to cold temperatures; reduces heat loss, increases heat production
what is secreted as a result of vasoconstriction?
adrenaline and noradrenaline (adrenal medulla)
what controls shivering?
the hypothalamus –> sends stimuli to increase skeletal muscle tone
cerebral cortex –> conscious imput
why would an increased amount of thyroxine increase heat?
increases metabolic rate (by-product = heat)
what is an example of a behavioural response to cold temperatures?
put on a jumper, put the heater on, curl up into a ball
what is vasodilation?
dilation of blood vessels to increase heat loss
why is sweating important and when is it effective?
above 28 degrees, in dry environments (to allow sweat to evaporate)
due to high specific heat capacity of water
why would a decreased metabolic rate decrease heat production?
less heat produced as a by-product of respiration
what are some examples of behavioural responses to cool down>
turn on aircon, remove clothing, reduce physical activity
what is heat stroke?
rise in body temp = cease of regulatory mechanisms
how is heat stroke treated?
cooling body as quickly as possible
what is heat exhaustion?
occurs as a result of extreme sweating and vasodilation; loss of water in plasma + vasodilation = reduces resistance to blood flow = reduced output of blood from heart = collapse
what is hypothermia?
low metabolic rate, body unable to replace heat lost causing body temp to continue to fall
what is considered the max and min temperatures before death?
33 degrees or below and 42 degrees or above
what is metabolic water?
water obtained as a by-product of chemical processes
what are some examples of where fluid can be lost from?
kidneys, surface of lungs, alimentary canal, sweating
what is excretion and why can’t faeces be considered excretory products?
excretion: removal of metabolic wastes.
faeces is not metabolic wastes (it is undigested food matter)
what do the lungs excrete?
CO2
what do the sweat glands exrete?
water containing by-products of metabolism
what does the alimentary canal excrete?
bile pigments
what do they kidneys excrete?
urea
what is the basic process for filtration in the kidneys?
- Blood enters glomerulus; high pressure
- Filtration: high pressure forces small dissolved molecules from blood (large molecules remain)
- Filtrate collected in glomerular capsule
- Reabsorption: filtrate passes through proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct (water and other useful substances absorbed)
- Secretion: wastes are secreted into kidneys
- Urine: carried by collecting ducts to the ureters then bladder
what is the role of ADH in fluid balance?
increased ADH = high permeability to water (increased water absorption)
what is the role of aldosterone in fluid balance?
increases amount of sodium reabsorbed + increases amount of potassium excreted in urine
what are osmoreceptors responsible for?
stimulating the thirst centre of they hypothalamus
what is dehydration?
loss of more than 2% of water (sweating, vomiting, diarrhea)
what are symptoms of dehydration?
severse thirst, low blood pressure, dizziness, headache
why do elederly people get dehydrated?
their thirst reflex is less effective
what is water intoxication?
body fluids become diluted and cells take on extra water by osmosis
when does water intoxication occur?
when the person has lost a lot of water and salts through sweating then replaces this with plain water
what are symptoms of water intoxication?
light-headedness, collapse, vomiting
what are the four responses to a decreased core body temperature?
- vasoconstriction of skin blood vessels
- shivering
- increased BMR
- behavioural reponses
what are the four responses to an increaesd core body temperature?
- vasodilation
- sweating
- decreased BMR
- behavioural responses
