definition of homoestasis
maintenance of a constant internal environment
features of negative feedback process
- normal/set point -> needs to be maintained
- stimulus -> change from normal condition in internal environment
- receptors -> detect stimulus
- corrective mechanism -> brings about reverse effect of stimulus, carried out by effectors
definition of a hormone
a chemical messenger produced in minute quantities by an endocrine gland transported carried by blood which alters activity of one or more specific target organs
effects of hormones
-> influence growth, development and activity of an organism
-> control and coordinate body activities
definition of endocrine glands
ductless glands that transport their secretions through bloodstream
definition of exocrine glands
ducts present to transport secretions to target organs
beta cells of Islets of Langerhans in pancreas
-> secretes more insulin into bloodstream
-> increase glucose uptake by cells
-> makes cell membranes more permeable to glucose
-> stimulates liver and muscle cells to convert excess glucose into glycogen for storage
-> increases use of glucose for tissue respiration
alpha cells of Islets of Langerhans in pancreas
-> secretes more glucagon into the bloodstream
-> converts glycogen to glucose
-> converts fats and amino acids to glucose
importance of maintaining a constant blood glucose level - lack of insulin secretion
-> results in abnormally high blood glucose concentration
-> tissue cells cannot utilise or store glucose
-> muscle cells unable to store glucose
symptoms: weak body, continual weight loss, and glucose present in urine
*may lead to diabetes mellitus
importance of maintaining a constant blood glucose level - over-secretion of insulin
-> results in abnormally low blood glucose concentration
-> results in a condition called shock
*in severe cases person may develop fits and seizures, lapse into a coma or even die
effectors - increase in body temperature
- arterioles near the skin’s surface dilate
-> allows more blood to flow through blood capillaries in the skin
-> more heat lost through skin - sweat glands become more active and produce more sweat
-> more water in the sweat evaporates from surface of skin
-> more heat is lost from body to surroundings - metabolic rate decreases
-> reduces amount of heat heat released within the body
effectors - decrease in body temperature
- vasoconstriction of arterioles near skin’s surface
-> allows less blood to flow through blood capillaries in the skin
-> less heat is lost through skin - sweat glands become less active and produce less sweat
-> less water in the sweat evaporates from skin surface
-> less heat is lost from body to surroundings - metabolic rate increases
-> increases amount of heat released within body - when the above responses are not sufficient in preventing a drop in body temperature, shivering occurs
-> rapid contraction and relaxation of skeletal muscles
-> generates heat and increases amount of heat released
definitions of diabetes mellitus
= condition where blood glucose concentration cannot be regulated because blood glucose concentration exceeds the ability of kidneys to reabsorb all glucose and glucose is excreted in urine
= persistently higher than normal blood glucose concentration due to body’s resistance to insulin or insufficient production of insulin
what are the symptoms of diabetes mellitus?
- persistently higher than normal blood glucose level
- presence of glucose in urine
- healing of wounds is slow and difficult
- frequent urination
- weight loss
- thirst
risk factors of type 2 diabetes mellitus
obesity: liver and muscle cells do not respond well to insulin (resistance to insulin)
age: liver and muscle cells do not respond well to insulin (resistance to insulin)
family history: inherited risk
blood lipid levels: high levels of “bad” cholesterol, low-density lipoproteins, and low levels of “good” cholesterol, high-density lipoproteins in blood
sedentary lifestyle: physical activities control weight and use up excess glucose, allowing liver and muscle cells to maintain sensitivity to insulin
cause and management of type 1 diabetes mellitus
cause: inherited, Islets of Langerhans in pancreas unable to produce or secrete sufficient insulin
management:
- regular testing of blood glucose concentrations and urine
-> watch diet carefully
-> regular injections of insulin
cause and management of type 2 diabetes mellitus
cause: target organs, such as muscle organs, do not respond well to insulin
management:
- regular testing of blood glucose concentrations and urine
-> watch diet carefully and change lifestyle
-> oral medication
