16 homeostasis Flashcards
3.6.4.1
what is homeostasis
- the maintenance of an internal environment within restricted limits in an organism.
- involves trying to maintain the chemical make up and volume of blood and tissue fluid
- the ability to return to the optimum point and maintain an organism in a balanced equilibrium
the importance of homeostasis
- fluctuations in temperature and pH can impair the ability of enzymes to carry out their role effectively
- changes to water potential of the blood may cause cells to shrink or expand as a result of water leaving or entering
- organisms that maintain a constant internal environment are more independent of changes in the external environment and so have a greater chance of finding food and shelter
what is the optimum point
the point at which they system operates best and is monitored by a receptor
what is the receptor
detects deviations from the optimum point and informs the coordinator
what is the coordinator
coordinates information from the receptors and sends information to the appropriate effector
what is the effector
a muscle or gland which brings about the changes needed to return the system to the optimum point
what is the feedback mechanism
A receptor responds to a stimulus created by the change to the system brought about by the effector
what is negative feedback
the changes produced by the control system leads to a change in the stimulus detected by the receptor
what is positive feedback
a deviation from an optimum causes changes that result in an even greater deviation from the normal
what is a hormone
- produced in the glands which secrete the hormone directly into the blood
- carried in the blood plasma target cells which have specific receptors in their cell surface membrane that are complementary to a specific hormone
- are effective in very low concentration but have widespread and long lasting effects
what is the second messenger model
- used by 2 hormones involved in the regulation if blood glucose concentration namely adrenaline and glucagon
mechanism involving adrenaline and glycogen
- adrenaline binds to a trans membrane protein receptor within the cell surface membrane of a liver cell
- the binding of adrenaline causes the protein to change shape on the inside of the membrane
- this change of protein shape leads to the activation of adenyl cyclase. The activated adenyl cyclas converts ATP to cyclic AMP (cAMP)
- the cAMP acts as the second messenger that binds to protein kineses enzyme changing its shape and activating it
- the active protein kinase enzyme catalyses the conversion of glycogen to glucose which moves out of the liver cell by facilitated diffusion and into the blood , through channel proteins
what is the pancreas
- large gland in the upper abdomen
- produces enzymes protease, amylase and lipase for digestion
- produces hormones insulin and glucagon for regulating blood glucose concentration
what is the islets of Langerhans
- hormone producing cells
- includes alpha cells which are larger and produced glucagon
- beta cells which are smaller and produce insulin
what is the liver
- located underneath the diaphragm
made up of hepatocytes cells - regulates blood glucose concentrations
what are the 3 process associated with regulating blood sugar levels
- glycogenesis
- glycogenolysis
- gluconeogenesis
what is glycogenesis
- the conversion of glucose into glycogen
- when blood glucose concentration is higher than normal the liver removes glucose from the blood and converts it into glycogen
- can store 100g of glycogen which is sufficient to a humans blood glucose concentration for 12 hours at rest
what is glycogenolysis
- the breakdown of glycogen to glucose
- when blood glucose concentration is lower than normal the liver can covert stored glycogen back into glucose which diffuses into the blood to restore the normal blood glucose concentration
what is gluconegenesis
- the production of glucose from sources other than carbohydrates
- the supply of glycogen is exhausted the liver can produce glucose from non carbohydrate sources such as glycerol and amino acids
what is diabetes
a metabolic disorder caused by the inability to control blood glucose concentration due to the lack of insulin or a loss of responsiveness to it
characteristics of type 1 diabetes
- insulin dependent
- bodys inability to produce insulin
- begins in childhood
- response of an autoimmune response where the body immune system attacks the beta cells of the islet of Langerhans
- develops quickly and its signs and symptoms are obvious
charctersitics of type 2 diabetes
- insulin independent
- glycoprotein receptors lose their receptiveness to insulin or inadequate supply of insulin from the pancreas
- develops in people over 40 years
- obesity and a poor diet can lead to diabetes in adolescents
- develops slowly and its signs and symptoms are less severe
- 90% of people with obesity have type 2
how is type 1 controlled
- injections of insulin which cannot be taken by mouth as it is a protein which would be digested in the alimentary canal
- dosage of insulin must be matched to glucose intake
- if a person takes too much insulin it can lead to low blood glucose concentration that can result in unconsciousness
- blood glucose concentration is monitored using biosensors
how is type 2 diabetes controlled
- regulating the intake of carbohydrates on diet and matching this to exercise taken
- may be supplemented by insulin injections or by drugs that stimulate insulin production
- other drugs can slow down the rate at which the body absorbs glucose from the intestine
what is osmoregulation
the homeostatic control of the water potential of blood
where are kidneys located
2 kidney at the back of the abdominal cavity one on each side of the spinal cord
fibrous capsule
an outer membrane that protects the kidney
cortex
a lighter coloured outer region made up of renal (bowsmans) capsule, convulated tubules and blood vessels
medulla
a darker coloured inner region made op of loops of henle collecting duct and blood vessels
renal pelvis
a funnel- shaped cavity that collects urine into the ureter
ureter
a tube that carries urine to the bladder
renal artery
supplies the kidney with blood form the heart via the aorta
renal vein
returns blood to the heart via the vena cava
what is the nephron
- functional u it of the kidney
- narrow tube up to 14 mm long
- closed at one end
- has two twisited regions separated by a long hairpin loop
what is the renal (Bowman) capsule in the nephron
- closed end at the Start of the nephron
- cup shaped
- surrounds a mass of blood capillaries (glomerulus)
- inner capsule made up of podocytes
what is the proximal convulated tublue in the nephron
- a series of loops surrounded by blood
- walls are made of epithelial cells which have micro villi
what is the loop of henle in the nephrom
- long hairpin loop that extends form the cortex into the medulla of the kidney and back again
- surrounded by blood capillaries
what is the distal convulated tubule
a series of loops surrounded by blood capillaries
- walls made up of epithelial cells
- surrounded by less capillaries than the proximal tubule
what is the collecting duct in the nephron
- a tube with a number of distal convulated tubules form a number of nephron empty
- lined by epithelial cells
- becomes increasingly wide as it empties into the pelvic of the kidney
what is the afferent arteriole in the kidney
- a tiny vessel that arises from the renal artery and supplies the nephron with blood
- enters the renal capsule of the nephron where it forms the glomerulus
what is the glomerulus in t he kidney
- many branched knots of capillaries from which fluid is forced out of the blood
what is the efferent arteriole in the kidney
- a tiny vessel that leaves the renal capsule
- has a smaller diameter than the afferent arteriole and so causes an increase in the blood pressure when the glomerulus
- carries blood away form the renal capsule and later branches to form the blood capillaries
blood capillaries in the kidney
- concentrated network of capillaries that surround the proximal convoluted tubules, the loop of henle and the distal convulated tubules form which they reabsorb mineral slats glucose and water
