Homeostasis blood sugar + temp - Chapter 5 Flashcards
Homeostasis
process whereby body’s internal environment is maintained in a steady state.
Properties of tissue fluid maintained by homeostasis:
- core body temperature (normal range 37ºC)
- pH and concentration of dissolved substances in body fluids
- fluid concentrations
- concentration of nutrients, metabolic waste and gases
Tolerance limits
conditions which body can function - if conditions change beyond tolerance limits the body systems don’t function properly.
- blood pressure 120/180mm Hg
- blood glucose 3.5-8mmol/L
Feedback systems
a circular situation in which body responds to change or stimulus
negative - response decreases original stimulus
positive - response increases original stimulus
Feedback loop
involves a stimulus, receptor, modulator, effector, response and feedback
Role of the liver
- largest gland in the body, and involved in blood glucose regulation
- converts glucose to glycogen for storage (glycogenesis)
- converts glycogen to glucose for release (glycogenolysis)
- most of livers blood supply comes from the hepatic portal vein which carries blood from the stomach, spleen, pancreas and intestines
Glycogenesis
glucose –> glycogen
Glycogenolysis
glycogen –> glucose
(breakdown of glycogen)
Gluconeogenesis
fats/proteins –> glucose
Role of the pancreas
- is an endocrine and exocrine gland
- contains clusters of hormone secreting cells called islets of langerhans
Alpha cells
secrete glucagon
Beta cells
secrete insulin
Role of the adrenal glands
- situated above the kidneys
- composed of an adrenal medulla and an adrenal cortex
(outer) cortex - cortisol [sstimulates conversion of glycogen to glucose, stimulate movement of amino acids from cells to liver, and some may be converted to glucose]
(inner) medulla - noradrenaline/adrenaline [breakdown of glycogen to glucose, stimulates production of lactic acid from glycogen which is then used to form glucose]
Glands involved in glucose regulation
- liver
- pancreas
- adrenal glands
Optimum core body temperature
36.8ºC
- this temp is achieved when heat lost = heat gained (thermoregulation maintains this)
Metabolic rate
the rate at which energy is released by the breakdown of food.
When does metabolic rate increase
- during exercise, stress or rising body temperature
- during exercise, metabolic rate increases for muscle contractions producing more energy
- stress stimulates sympathetic nerves releasing noradrenaline raising metabolic rate of the cells
- 1ºC increase in body temp increases metabolic rate by 10%
Peripheral thermoreceptors
detect changes in external temperature.
- found in skin and some mucous membranes
- send info to hypothalamus
Central thermoreceptors
detect changes in internal temperature.
- found in hypothalamus
Two types of thermoreceptors
cold receptor - stimulated by lower temperatures
heat receptors - stimulated by higher temperatures
Role of the skin
skin has a large surface area and separates the internal and external environments.
initiates heat loss through conduction, convection, radiation and evaporation.
Conduction
transfer of heat via direct contact of particles.
Convection
transfer of heat by movement of liquid or gas
Radiation
transfer of heat through emission of electromagnetic radiation
Evaporation
process of liquid absorbing heat and transforming into a gas
Role of blood vessels
blood vessels located in dermis of skin carry heat to skin from core
autonomic nerves control the diameter of blood vessels.
Vasodilation
increased diameter allows higher blood flow to capillaries in the skin and greater heat loss.
Vasoconstriction
decreased diameter allows less blood to be transported to the capillaries of the skin and decreases heat loss.
Role of sweat glands
sweating: alive secretion of fluid by sweat glands
-sweat is transported to the skins surface where it absorbs heat and evaporates
- only occurs once blood vessels are already at max dilation
Evaporation of sweat as a cooling effect:
- sweat absorbs latent heat from skin as it evaporates
- this leaves the skin cooler which results in the cooling of blood passing through
Role of the muscles
shivering: rhythmic tremors (small contractions) occurring at a rate of 10-20 per second
- no work occurs, so the heat produced is released as heat
Heat exhaustion
the collapse of a person after heat exposure during which their body’s heat regulating mechanism continue to function normally.
Heat stroke
failure of temperature regulation mechanisms when exposed to excessive heat.
Hypothermia
abnormally low body temperature (below 35ºC)
- causes speech failure, mental processes become irrational, lack of insulation, heart and organs fail if body temp drops too low.
- treated through passive rewarming (using own body heat + dry warm clothes), active external warming (hot bottles, warm bath), active internal core warming (warm, moist air and drinks).