chap9: homeostasis & hormonal control Flashcards
what is homeostasis
the maintenance of a constant internal environment
what is negative feedback
a corrective mechanism where the body detects a change away from the normal condition and causes a change back towards the normal condition
what happens when blood glucose concentration increases above normal
islets of langerhans in the pancreas is stimulated and produces more insulin to secrete into the blood. the insulin stimulates the liver to convert excess glucose into the glycogen for storage in the liver. this decreases the blood glucose concentration back to normal
what happens when blood glucose concentration decreases above normal
the islets of langerhans in the pancreas is stimulated to produce and secrete more glucagon into the blood. glucagon stimulates the liver to convert glycogen into glucose which is released into the blood. this increases the blood glucose concentration back to normal
effect of normal insulin levels
makes cell membrane more permeable to glucose, allowing more glucose to diffuse into liver and muscle cells
stimulates the liver and muscle cells to convert glucose to glucagon for storage
increases the use of glucose for respiration
effect of low insulin levels
glucose cannot be stored or utilised by tissue cells
muscles have no reserve of glycogen, the body grows weak and loses weight
effect of high levels of insulin
low blood glucose concentration
results in fits, shocks, passing out
purpose of glucagon
converts glucose into glycogen
converts fats and amino acids into glucose
what is type 1 diabetes
develops early in a person’s life
occurs when the islets of langerhans are unable to produce sufficient insulin
can be inherited
what is type 2 diabetes
occurs later in a person’s life
overweight people are more susceptible to developing
occurs when target cells like muscle cells do not respond well to insulin
what is type 2 diabetes
occurs later in a person’s life
overweight people are more susceptible to developing
insulin resistant: occurs when target cells like muscle cells do not respond well to insulin
how is type 1 diabetes treated
insulin injections
how is type 2 diabetes treated
oral medication
control of dietary intake
exercise
what are risk factors to type 2 diabetes
obesity
high lipid levels
inactive lifetstyle
ageing
family history
what is a hormone
hormones are chemical substances produced in small quantities by exocrine glands that are transports in the bloodstream to target organs where it exerts its effects
what are exocrine glands
exo = outwards
they have a duct/tube to carry away their secretions
eg. salivary gland -> salivary duct -> saliva -> mouth
sweat gland -> sweat duct -> sweat -> out of body
what are endocrine glands
endo = within
they are ductless glands and secrete hormones directly into the bloodstream which then distributes the hormone around the body
eg. pituitary gland -> ADH
what organ is considered both an exocrine and endocrine gland, why?
the pancreas is considered an exocrine gland as it produces pancreatic juice which is carried by the pancreatic duct to the duodenum
the pancreas is also considered an endocrine gland as it contains islets of Langerhans which secreates insulin and glucagon into the bloodstream
what affects body temperature
the environment, change in temperature, time of day, weather
human behaviour
how is the skin adapted for temperature regulation
how do blood vessels help to regulate body temperature
the constriction and dilation of arterioles are caused by the contraction and relaxation of muscles in the arterioles walls, this helps to regulate body temperature
vasodilation is the dilation of the arterioles which sends blood to the blood capillaries in the skin.
vasoconstriction is the constriction of the arterioles in the skin which reduces the amount of blood flowing through the the capillaries in the skin
how do sweat glands help regulate body temperature
secreted sweat flows through a sweat duct and to a sweat pore that opens up on the skins surface. secreted sweat is made out of water and excretory products like urea and dissolved salts. when swear is excreted, heat in the surrounding causes it to evaporate and hence cooling down the surface of the skin
how do thermoreceptors help to regulate body temperature
thermoreceptors help detect change in the temperature
how is heat gained in the body
heat is released when metabolic activities take place like cellular respiration
vigorous muscular exercise, consumption of hot food, being in warm environments
how is heat lost by the body
through the skin
evaporation of water ins went from surface of the skin
faeces and urine
in the air that is exhaled
what happens when body temperature rises above normal
thermoreceptors in the skin and the hypothalamus in the brain is stimulated. the arterioles in the skin becomes more dilated and more blood can flow through blood capillaries in the skin to increase heat lost through the skin. sweat glands become more active and produce a larger volume of sweat to be excreted on the surface of the skin. more sweat is being evaporated and more heat is lost. metabolic rate is decreased which reduces the amount of heat released within the body. body returns to normal temperature.
what happens when body temperature falls below normal
thermoreceptors in the skin and hypothalamus in the brain is stimulated. arterioles in the skin constricts and lesser blood can flow through the blood capillaries in the skin, this reduces heat lost from the skin to the environment. sweat glands become less active and produce less sweat to evaporate from the skin surface, hence conserving heat. metabolic rate speeds up which increases body temperature. shivering is the rapid contraction and relaxation of the skeletal muscles which increases the amount of heat released. this brings the body temperature back to normal.
