week 1 teaching: homeostasis and diabetes Flashcards
autoregulation
process that occurs when a cell, tissue, organ or organ system adjusts in response to some environmental change
extrinsic regualtion
process that results from the actitivites of the nervous system or endocrine system
these organ systems detect environmental change and send electrical signal (nervous system) or chemical messenger (endocrine system) to control/ adjust activites of other systems simultaneosuly
three parts a homeostatic regulatory mechanism consists of
receptor
control centre
effector
small change in the radius of a blood vessel
large effect on the flow of blood through capillaries and therefore large effect on blood pressure
if blood supply to tissue is inadequate
tissue becomes hypoxic- lack of oxygen
tissue becomes hypoxic,
Capillary Blood Flow: Local Autoregulation
potassium and acid e.g lactic leaks out of blood vessel
causes smooth muscle cells that surround the walls of arterioles to relax
increases the radius of arteriole
increasing blood flow to tissue
increasing O2 levels
positive feedback loop: blood clotting
damaged cells in blood vessel wall release chemicals that begin clotting process
chemicals start chain reactions in which cells, cell fragments and soluble proteins in the blood begin to form a clot
as clotting continues, each step releases chemicals that furhtur accelerates the process
formation of blood clot
dynamic equilibrium state
each physiological system functions to maintain a state of equilibrea, that keeps vital conditions within a normal range of values
metabolic rate
amount of energy used by a person per unit of time
basal metabolic rate
amount of energy per unit time that a person needs to keep a body functioning at rest
anabolism
set of metabolic pathways that construct molecules from smaller units
Catecholamines
any class of aromatic amines which include a number of neurotransmitters e.g adrenaline and dopamine
glycogenolysis
breakdown of glycogen
gluconeogenesis
generation of glucose from certain non-carbohydrate carbon substrates e.g glycerol and lactate
anabolic state
absorptive sate
energy stored in macromolecules
catabolic state
postabsorptive state
energy stores mobilised
metabolic reactions of anabolic state
insulin increases glycolysis and glycogenesis while inhibitng gluconeogenisis and gylcogenolysis
when blood glucose levels high, it is taken up by the liver and ised to provide acetyl co-A for fatty acid sysnthesis or stored as glycogen
metabolic reactions of catabolic state
fasting state, dominated by secretion of glucagon, insulin release in minimal
metabolism focused on maintaining blood gluc conc by increased hepatic breakdown of glycogen and gluconeogenesis
metabolic changes between anabolism and catobolism triggered by
endocrine signals involving pancreatic hormones insulin and glucagon
levels of insulin in blood trigger transition
pancreas
mixed endocrine and exocrine glands located behind the stomach
innervated by the sympathetic and parasympathetic nervous system
types of cells in the pancreas
acini
islets of langerhans
acini
exocrine part which releases digestive juices
lslets of langerhans
secrete 3 endocrine hormones
alpha cells: glucagon
beta cells: insulin
delta cells: somatostatin
insulin
51 aa protein hormone
derived from precursor proinsulin
synthesised in RER
converted to insulin in GA, cleaved by proteolytic enzyme
insulin storage and secreted
insulin stored in beta cells until secreted into bloodstream by exocytosis
insulin circulating in blood is bound to
beta globulin (mostly)
half life of insulin in blood
5 mins
what allows the amount of plasma glucose circulating in blood to be regulated
levels of insulin in blood triggering transition between anabolic and catabolic states
what does insulin promote
synthesis of energy storage molecules and other processes of the anabolic state
storage of FA and triglycerides in adipose tissue and liver
glycogen synthesis in liver and muscle
glucose uptake by the brain
main buffer system to regulate blood sugar levels
liver
what must be present in blood for growth hormone to have effect
insulin
what is glucagon where is it secreted
29 aa single chain polypeptide hormone
synthesised in alpha cells of islets of Langerhans in pancreas
released by exocytosis
6 min half life
what does glucagon promote
process of catabolism
what stimualtes glucagon secretion
hypoglycemia
sympathetic nervous system and adrenaline
why does adrenaline stimualte glucagon secretion
maintain high circulating plasma glucose for fuel for cells ‘fight or flight’
standard fasting blood glucose levels
70-110mg/dL
hyperglycemia blood glucose levels
> 140mg/dL
hypoglycaemia blood glucose
<60mg/dL
adrenal corticosteriods
promotes glycogen production and maintains glycogen reserves
growth hormone
anti- insulin glucose-sparing agent
important for bouts of starvation or fasting
depresses glucose uptake making more glucose available for the brain
catecholamines
when glucose level fall below 4mmol l-1, mobilise glucose for use by the brain
thyroid hormones
enhance glucose metabolism ensuring glucose reserves are mobilised
