chapter 14 Homeostasis Flashcards
homeostasis
maintenance of constant internal environment
negative feedback
.response counteracts the original stimulus
.to maintain homeostasis
deamination
.remove the amine group and a H atom from amino
acid
.produce ammonia
urea cycle
NH3 + CO2 -> urea -> excreted via kidney
renal vein
going out
renal artery
going in
ureter
urine out from kidney to urinary bladder
urethra
urine out from urinary bladder
afferent arteriole
going in
efferent arteriole
going out
structure of glomerular wall and bowman’s capsule wall
- endothelium of the blood capillaries of the
glomerulus -> with many more gaps - basement membrane -> a mesh of collagen and
glycoprotein fibres which is the main selective barrier - epithelial cells of the bowman’s capsule -> inner
lining of the bowman’s capsule which wraps around
the capillary of glomerulus and have finger-like
projections (podocytes) which form gaps
how the structure adapts for ultrafiltration
- the endothelium and filtration slits between the foot
processes of podocytes provides a large amount of
filtrate which allows the movement of substance from
the blood plasma to the bowman’s capsule lumen - the diameter of lumen of afferent arteriole is wider
than the efferent arteriole this results in a high blood
pressure in the glomerulus than bowman’s capsule
which forces fluid out of the glomerulus into the
lumen of bowman’s capsule - basement membrane acts as a filtrate which
prevents large plasma proteins, red blood cells and
white blood cells to pass through
where does selective absorption happens?
. proximal convoluted tube
. loop of henle
. distal convoluted tube
. collecting duct
selective reabsorption @ PCT
- active transport of NA+ ions from the PCT cells into
the capillary via the Na+/K+ ion pump. Concentration
of the Na+ ions in the PCT cells decreases which
builds up a concentration - Na+ ions in PCT lumen diffuses into the cells lining
the PCT down the gradient by facilitated diffusion via
the co-transporter carrier protein. Na+ ions are co-
transported with glucose, amino acid and vitamins - Glucose and amino acid diffuses into the
bloodstream down the concentration gradient via
facilitated diffusion.
adaptations of PCT cells
- Numerous microvilli which increases the surface area
of absorption - high density of mitochondria which provides energy
in the form of ATP for processes such as active
transport - high infoldings of basal membrane
- presence of different transport proteins in the
membrane - tight junctions holding adjacent cells together which
separate proteins of front and basal membrane, so
fluid cannot pass between cells and must pass
through the cells
selective reabsorption @ loop of henle (ascending limbs)
- Na+ and Cl- moves out of the tube by active
transport into the tissue fluids in the medulla spaces - high concentrations of Na+ and Cl- ions in the
medulla space causes renal fluid o become more
dilute and enters the distal convoluted tube. The
longer the tube the more concentrated the urine and
more water reabsorbed
selective reabsorption @ loop of henle (descending limbs)
- due to the high concentrations of solutes in the
medulla space, water moves out the tube into the
medulla tissue fluid by osmosis and water is reabsorb - urea, Na+ and Cl- ions and medulla space diffuse
into descending limbs this causes the fluid in
descending limbs to become very concentratedas it
moves down the loop
selective reabsorption @ distal convoluted tube
- Na+ and Cl- ions are transported actively back into
the blood - Water is reabsorbed by osmosis back into the blood
selective reabsorption @ collecting duct
.the tissue fluid has a high concentration of solutes so water moves out of the collecting duct by osmosis back into the blood
.formation of urine occurs
.rate of water reabsorption determine by ADH (antidiuretic hormone)
glucagon
.secreted by alpha cells
.increase blood sugar
insulin
.secreted by beta cells
.decrease blood sugar
when blood glucose level increases
- beta cells secretes more insulin into the blood
- insulin binds to receptors on the cell surface
membrane of liver cells - increases permeability of membrane to glucose in
liver cells which triggers the vesicles carrying glucose
transport proteins(GLUT protein) to fuse with the
plasma membrane increasing the facilitated diffusion
of glucose into cells - increase glucose uptake, activates the enzyme
glucokinase which phosphorylates glucose and
glucose are trapped in cells - increase rate of respiration of glucose
- increase conversion of glucose to glycogen by
activating the enzymes phosphofructokinase and
glycogen synthetase which will be stores in the liver
and muscles - increase protein and lipid synthesis
- inhibit the secretion of glucagon by alpha cells and
inhibit the breakdown of glycogen to glucose - inhibit the production of glucose form proteins and
fats
when blood glucose decreases
- alpha cells secrete glucagon into blood
- glucagon binds to receptor on cell surface
membrane, the receptor changes shape activating G
protein which then activates adenyl cyclase - adenyl cyclase produces cyclic AMP (cAMP) from
ATP which acts as the second messenger activating
protein kinase which triggers an enzyme cascade and
the signal amplifies - cAMP activates the enzyme glycogen phosphorylase
which increases the breakdown of glycogen into
glucose. - use fatty acids and proteins as respiratory substance
instead of glusoce - increase the production of glucose from proteins
and fats - glucose diffuse through GLUT proteins fro liver into
blood
