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homeostasis
the maintenance of a relatively stable internal environment despite fluctuations in the external environment
aspects of internal environment that need to be regulated
core body temp; ph; concentration of glucose, oxygen and carbon dioxide in blood; blood pressure; concentration of metabolic wastes
homeostatic mechanisms
work to maintain homeostasis; main sensory and controlling body systems: nervous system (fast) and hormonal system (slow); operate through feedback loops
negative feedback loop
a circular situation in which the body responds to a stimulus, with the response altering the original stimulus
negative feedback
when the body’s response has the effect of reducing or eliminating the stimulus that caused it
positive feedback
when the body’s response has the effect of reinforcing or intensifying the stimulus that caused it
components of the feedback system
stimulus: a change in the environment
receptors: sensory cells that detect changes
modulator: control centre that processes the messages received by the receptor
effector: muscles or glands that make the necessary adjustments
response: the reaction from the effector
feedback: response changes original stimulus
how heat is generated in the body
body processes; heat gained by environment; illness; stress/emotions; medications; increase in adrenaline
how heat is lost from the body
evaporation from water in body and lungs; warm air breathed out; voiding of warm urine and feces; radiation of body heat; conduction and convection
normal body temperature of humans
37.6 degrees celsius: cells function optimally
location of thermoreceptors
central (hypothalamus) and peripheral (skin)
detect temperature of blood
radiation
transfer of heat emitted as infrared radiation by objects.
conduction
transfer of heat by direct contact between particles.
convection
transfer of heat by convection currents
only occurs in liquids and gases
evaporation
change of state from liquid to gas
physiological response to fall in body temp
Constriction of blood vessels in the skin
Less sweat produced
Shivering
Increase in secretion of adrenaline and thyroxine
behavioural response to fall in body temp
Put on more/warmer clothes
take a warm shower
sit in front of a heater
Decrease surface area
Increase voluntary activity
physiological response to rise in body temp
Dilation of blood vessels in the skin
Sweat is produced
Decrease the secretion of thyroxine.
Change blood flow to skin
behavioural response to rise in body temp
Wear less/lighter clothes
take a cool shower
sit in the shade/fan yourself
Increase surface area
Reduce voluntary activity
vasodilation
the widening of blood vessels, which increases blood flow and lowers blood pressure
vasoconstriction
the narrowing (constriction) of blood vessels by small muscles in their walls
glucose
simple carb, source of energy for cellular respiration, sugar in the blood
glycogen
complex carb, made up of long chains of glucose molecules, glucose is stored as glycogen
liver - regulation of blood sugar
converts glucose into glycogen for storage, converts glycogen into glucose for release into the blood
glucagon
raises blood glucose levels through glycogenolysis and gluconeogenesis
insulin
lowers blood glucose level through glycogenesis and lipogenesis
glycogenesis
to make glycogen (glucose --> glycogen)
Gluconeogenesis
to make glucose from non- carbohydrate sources (amino acids or fats--> glucose)
Glycogenolysis
to breakdown glycogen (glycogen --> glucose)
cortisol
glucocorticoid, increase blood glucose levels, stimulates glycogenolysis, and increases the rate of gluconeogenesis
adrenaline
increases blood glucose level, stimulates glycogenolysis, lactic acid is converted to glucose, insulin receptors become more sensitive
hyperglycemia
abnormally high blood glucose level
hyperglycemia symptoms
thirst, urination, feeling hungry and tired, blurred vision
hyperglycemia causes
taking too little insulin, too many carbs/sugars, not exercising enough
thirst reflex in maintaining water balance
Water concentration of blood plasma decreases; osmotic pressure of the blood is increased; mouth becomes dry
Osmoreceptors in the thirst center of the hypothalamus are stimulated
Person feels thirsty
Person responds to the feeling of thirst by drinking
Water drunk is absorbed into the blood from the alimentary canal
Water leaves the blood and the extracellular and intercellular fluids return to their normal concentration
dehydration
When 2% or more of body fluid lost, in elderly, thirst reflex less effective, Can lead to thirst, head aches, low blood pressure, and dizziness
water intoxication
body fluids become diluted and cells take in extra water due to osmosis, can happen if you lose lots of water through sweating and replace with plain water. Lightheadedness , vomiting and collapse.
intracellular fluid
Fluid contained within the cells of an organism 2/3 of total body water
extracellular fluid
Fluid that is outside the cells of an organism 1/3 of total body water
plasma
1/4 of extracellular fluid, the fluid part of the blood
intercellular fluid
3/4 of the extracellular fluid, found in lymph, cerebrospinal fluid, synovial fluid in joints, fluids of eyes and ears, chest and abdominal cavities and around the heart, alimentary canal and kidney filtrate
role of intercellular fluid
surrounds body cells and acts as a medium for exchanging substances between capillaries (vascular fluids) and the cytoplasm of cells
nutrient movement
Oxygen and nutrients diffuse from capillaries into tissue fluid and then into cells following a concentration gradient, glucose and amino acids may also be transported by facilitated diffusion or active transport.
waste removal
Metabolic wastes like carbon dioxide (CO₂) and urea move from cells into tissue fluid and then diffuse into capillaries, where they are transported for excretion, CO₂ diffuses into the blood, where it dissolves in plasma or binds to haemoglobin before being transported to the lungs
water movement
Water moves by osmosis from areas of low concentration to areas of high concentration (inside cells or blood plasma). The lymphatic system helps return excess tissue fluid to the bloodstream, preventing swelling
excretion
the removal from the body of the waste products of metabolism, maintain constant concentration of materials in body fluid
filtration
substances are separated from a fluid by passing it through a membrane or filter, occurs in renal capsule
selective reabsorption
substances are reabsorbed back into the bloodstream from the filtrate in the kidneys
tubular secretion
substances are actively transported from the blood into the tubular fluid