paper 2: Homeostasis Flashcards
define the term homeostasis
maintaining a constant internal environment within restricted limits
why does homeostasis take place
to prevent damage to cells
explain what happens to enxymes when core body temperature is too high
- hydrogen bonds break within enzymes
- changing thier tertiary structure and the shape of the active site
- less enzyme-substrate complexes form
explain what happens to enzymes when core body temperature is too low
- eznymes have too low kinetic energy
- less enzyme-substrate complexes form
- metabolic rate is reduced
explain what happens to enzymes when blood pH is too high
- hydrogen bonds break within proteins
- chaning the tertiary structure
explain what happens to enzymes when blood pH is too low
- hydrogen bonds break within enzymes
- changeing their tertiary structure
what happens to water potential when blood glucose concentration is too high
- blood has lower water potential than cells
- water leaves cells into blood by osmosis
- cells lack water for metabolic reactions such as hydrolysis and as a solvent
what happens when blood glucose concentration is too low
- glucose is not provided to cells fast enouugh for anhigh enough rate of respiration
what happens when blood water potential is too high
- water enters cells by osmosis
- too much can cause cell lysis
- lots of water in blood causes high blood pressure
what happens when blood water potential is too low
- water leaves cells by osmosis
- cells lack ater for metabolic recations such as hydrolysis and as a solvent
define negative feedback
reverses the direction of change back to its original level
how is regulation of the body temperature an example of negative feedback
- when body is too high, the body responds to decrease it back to original
- when body temperature is too low, the body responds to increase it back to its original
what is the advantage of having separate mechanisms to increase or decrease the factor
- separate mechanisms are used to increase or decrease the factor, as this gives a greater degree of control
define positive feedback
where a change in one direction is amplified
(an increase leads to a further increase)
give an example of positive feedback
sigmoid curve for oxygen dissociation
what type of messenger is a hormone
chemical messenger
where are hormones secreted from
glands
how are hormones transported around the body
in the blood stream
where do specific hormones act and why
target cells as they have complimentary hormone receptors
describe the effect of hormones. how is this different to the nervours sytem
- effect of hormones is widespread and longlasting
WHEREAS - effect of nervous system is local and short term
what will make blood glucose rise
- eating foods high in glucose and starch as g;uvose is absorbed into the bloodstream
what will cause blood glucose to fall
- increase in cell respiration
when is insulin released
when blood glucose is high
when is glucagon released
when blood glucose is too low
which cells produce insulin
beta cells in islets of Langerhans in the pancreas
which cells produce glucagon
alpha cells in islets of Langerhans in the pancreas
what effect does insulin have on blood glucose
decrease blood glucose levels
what effect does glucagon have on blood glucose
increase blood glucose levels
what are the target cells for insulin
liver and muscle cells
what are the target cells for glucagon
liver cells
how does insulin decrease blood glucose levels
- inserting more glucose channel proteins into the cell membrane, glucose enters the cell by facilitated diffusion
- activating enzymes to convert glucose into glycogen for storage (glycogenesis)
how does glucagon increase blood glucose levels
- activates enzymes to hydrolyse glycogen into glucose (glycogenolysis)
- activates enzymes to convert glycerol/ amino acds into glucose (gluconeogenesis)
what is the role of adrenalin in the body
increase blood glucose
how does adrenaline increase blood glucose
- adrenalin release from adrenal glands
- binds receptors on liver cells
- enzymes are activated which hydrolyse glycogen to glucose (glycogenolysis)
dra wand label a diagram showing the secondary messenger pathway of glucagon and adrenaline
describe type 1 diabetes
- cant produce insulin due to the death of beta cells in the islets of Lagerhans
describe type 2 diabetes
insulin is produced by the beta cells but the insulin receptors do not respond to the insulin
- blood glucose decreases more slowly
- can be causes by obesity
what 2 ways can a type 1 diabetic control their blood glucose levels
- inject insulin
- eat complex carbs over sugars
how does injecting insulin help control the blood glucose of a type 1 diabetic
- as insulin cannot be produced due to beta cells being destoryed
- insulin (protein) cannot be taken orally as it will be digested or denatured by stomach acid
how does eating complex carbs instead of sugars help control blood glucose of a type 1 diabetic
- prevents a rapid spike in blood glucose
- absorbed more slowly than monosaccharides because gycosidic bonds need to be hydrolysed first before absorption
what are the 3 ways of controlling blood glucose of a type 2 diabetic
- regular exercise
- loss of weight
- glucose lowering medication
why can a type 2 diabetic not inject insulin to control blood glucose
they already produce insulin as beta cells are present but the receptors do not respond
how does regular exercise help control the blood glucose of a type 2 diabetic
more respration so more glucose used so decreases concentration of glucose in cells so more glucose enters by faciliatated diffusion
how does a loss of weight help control blood glucose of a type 2 diabetic
due to obesity being a cause of type 2 diabetes
what is the function of the kidney
- substances are filtered out of the blood, including water
- useful substances are reabsorbed back into the blood
- unwanted substances travel to the bladder where they excreted within urine
if water potential is too high what happens at the kidney
- less water reabsorbed
- greater urine volume
- lower urine concentation
if blood water potential is too low what happens at the kidney
- more water reabsorbed
- lower urine volume
- greater urine concentration
label a diagram of a nephron
decsribe how ultrafiltration occurs
- there is a high blood pressure in the glomerulus
- water and small molecules e.g. glucose and amino acids are forced out
- this forms the glomerular filtrate in the tubule
- proteins and cells are too large to pass through so they stay in the blood
what are the 3 layers molecules pass through during ultrafiltration
- pores in the capillary endothelium
- basement membrane
- the Bowman’s capsule epithelium (made of podocytes)
why does proteinurea occur
- damage made to the basement membrane
describe selective reabsoption
most of the useful molecules and water are reabsorbed at the proximal convuluted tubule into the blood
how are the epithelial cell lining the proximal convuluted tubul adapted for absorption
- many mitochondria to provide lots of ATP to be hydrolysed and release energy for active transport
- microvilli - to provide a large surface area for more diffusion of small molecules
- microvilli increases number of channel protiens/ carrier proteins for facilitated diffusion
what causes water potential of the blood to be lower after ultrafiltration
- the proteins in the blood that were not filtered
describe how glucose is reabsorbed in the proximal convuluted tubule
- Na+ ions are actively transported out of the epithelial cell of the convuluted tubule into the blood to maintain the Na+ concentration gradient
- Na+ ions and glucose are co-transported from the filtrate into the epithelial cell of the proximal convuluted tubule through carrier proteins by facilitated diffusion
- glucose is then transported from the epithelium into the blood by facilitated diffusion
describe the steps of how the loop of Henle reabsorbs water in the ascending limb
- Na+ ions are actively transported out of the ascending limb
- this creates a lower water potential in the medulla
- the walls of the ascending limb are impermeable to water so water remains in the tubule
- filtrate becomes less concentrated
describe the steps of how the loop of Henle reabsorbs water in the descending limb
- the walls of te descending limb are permeable to water
- water moves out by osmosis into the lower water potential of the medulla
- Na+ actively transported into the descending limb
- due to the loss of water and Na+ moving in, the filtrate becomes more concentrated down the descending limb
- this creates an increasing Na+ concentration deeper into the medulla
describe the steps of how the loop of Henle reabsorbs water in the collecting duct
- a water potential gradient is maintained along the whole length of the collecting duct
- water will leave along the whole length of the collecting duct into the medulla
- water is then reabsorbed into the surrounding capillaries
how does the length of the loop of Henle effect the concentration of Na+ ions in the medulla
- the longer the loop of Henle, the greater the Na+ concentration, deeper into the medulla.
- the water potential gradient is maitained for longer
- more water is reabsorbed from the collecting duct by osmosis
describe osmoregulation by ADH when you are dehydrated
- decrease in blood water potential
- water moves out of osmoreceptors in the hypothalamus in the brain into blood by osmosis
- imoulses are sent to the posterior pituitary gland and it releases more ADH into blood
- more ADH causes collecting duct membrane to become more permeable to water as there are more aquaporins
- more water is reabsorbed into the blood
- urine volume becomesless and is more concentrated
describe osmoregulation by ADH when you drink too much water
- increase in blood water potential
- water moves into osmoreceptors in the hypothalamus in the brain out of the blood by osmosis
- sends impulses to the posterior pituitary gland and releases less ADH into the blood
- less ADH causes collecting duct membrane to become less permeable to water as there are less aquaporins
- less water is reabsorbed into the blood
- urine volume becomes more and is less concentrated
