Homostasis Flashcards
What is homeostasis
Homeostasis is the maintenance of a constant internal environment, dispite fluctuations in the external environment .
How is homeostasis achieved
Sensory receptors
Hormones or nervous system pass the message
Effectors, muscles and glands, provide the response
What is an ectotherm
An organisms which regulates its body temperature with help from an external source( snakes lay in the sun )
What’s an endotherm
An organism which can maintain its own body temperature
What’s a response when your body is to cold or to hot
Cold :
Shivering
Hairs on skin rise to reduce heat loss
Hot:
Sweat glands
Arterioles , rise to surface near skin to lose temperature
What does homeostasis keep at constant levels
Body temperature
pH
CO2 concentration
Blood glucose concentration
Blood pressure
Blood salt concentration
What is negative feedback
The reversal of a change , return to optimum
What is positive feedback
An increase in the change / further deviation
An example of an Endotherm
Birds, mammals
What’s the optimum body temperature of mammals and birds
37 degrees C
What is excretion
The removal of waste products of metabolism from the body
What are some of the main mammal waste products and where they are from
CO2 - lungs
Bile pigments - liver (colour faeces)
Nitrogenous waste products ( breakdown of amino acids ) - kidney, urine
What’s the ornithine cycle
Excess amino acids can’t be stored and may damage tissues, so the liver converts them into urea in the ornithine cycle
What does the haptic artery do
Delivers oxygenated blood to the liver
What does the hepatic vein do
Takes deoxygenated blood away from the liver
What does the hepatic portal vein do
Connects the liver to the intestines. This allows harmful substances to be removed from liver to be Brocken down
What does the bile duct do
Takes bile from the liver to the gall bladder, where it is stored
What does the liver do
Controls glucose , amino acids and lipid levels in blood
Stores iron and glycogen
Detoxifies blood of alcohol and drugs
Breaks down sex hormones
What do kidneys do
Filter nitrogenous waste products out of blood and urea
Maintain water balance
Maintaining pH of blood
What does the kidney contain millions of and what do they do
Nephrons
Filtering units
How does urine exit the body
Urine created in kidney
Passes out of kidney via tubes called ureters
Urine collected in bladder , a muscular sac
What bladder is full it uses the spinster to leave
Urine then passes out of the body down the urethra
Order of organs / pathways from urine to be made to leave
Kidneys
Ureter
Bladder
Urethra
What’s the renal vein do
Carries deoxygenated blood away from the kidney
What’s the renal artery do
Carrie’s oxygenated blood to the kidney
What does the capsule do
Tough fibrous coat around the kidney
Medulla
Contains, nephrons tubules which form the pyramids of the kidney and the collecting ducts
What does the Cortex do
Where blood is filtered, dense capillary network
What does the renal pelvis do
Collects urine before it passes down the ureter
What is ultrafiltration
When glucose , urea, water and salts are pushed out of the bloodstream
How does ultrafiltration work
Bowman’s capsule, surrounds a ball of capillaries called the glomerulus
Blood inside the glomerulus is under high pressure
Small molecules (glucose, urea, water, salts) are pushed out of the bloodstream into bowman’s capsule
Larger molecules (blood cells, proteins) stay inside capillaries which form a substance called glomerular filtrate which moves through the nephron
What is selective reabsorption
Useful substances are reabsorbed passing out of the nephron and back into the capillaries
Is selective reabsorption what happpens to water , glucose and remaining filtrate
Glucose - reabsorbed by PCT , by active transport + facilitated diffusion
Water - reabsorbed by the loop of henle , DCT and collecting duct ; by osmosis
The remaining filtrate is urine which passes to the bladder
What is water reabsorption and how does ADH effect this
Water reabsorbed along most of the nephron
Regulated water potential takes place in DCT, loop of Henle and collecting duct
Water is removed from nephron , DCT and collecting duct by osmosis and sodium ions (Na) are actively pumped into the medulla which lowers the water potential
How does ADH control water content in urine
By increasing the reabsorption of water from the collecting duct
This works as when permeability of the collecting duct increases it becomes more porous , which allows more water to pass from the kidney into the bloodstream.
What is osmoregulation and basic idea of how it works
The process of maintaining the water balance in the blood no matter what water and solutes you take in or lose.
The water concentration of the urine is the main way water is retained in the body or released.
ADH is released to increase the permeability of the collecting duct to water to retain more water in the body.
How is water gained in the body
Drinking
Eating
Respiration
How is water lost from the body
Sweating
Urine
Exhaling
Faeces
Detailed analysis of how ADH works
Osmoreceptor cells shrink at low water potential and this is detected by neusecretory cells (in the hypothalamus)
ADH is then realised into vesicles stored against blood supply in the posterior lobe of pituitary gland
ADH then travels in the blood to the collecting duct
ADH is the detected by the cell surface receptors
There’s is then an enzyme controlled reaction
water permeable channels (aquaporins) fuse to membrane
Water is then absorbed into the cells and back into the bloodstream
Causes of kidney failure
Diabetes
Heart disease
Hypertension (high arteriole blood pressure)
Infection
Treatments to kidney failure
Dialysis
Haemodialysis
Peritoneal dialysis
Kidney transplantation
What is dialysis
blood passed over partially permeable membrane which allows exchange of substances
The dialysis fluid contains correct amounts of salts , urea , water so that the blood is corrected
Patients must carefully regulate diet
Haemodialysis
Blood is passed into a machine
Needed 3 times a week for several hours
At clinics and sometimes at home
Peritoneal dialysis
Dialysis fluid is inserted into the peritoneal cavity using catheter
Waste products + excess water is passed through the peritoneal membrane into the peritoneal cavity
After several hours fluid is drained out and discarded
Patients can carry out normal activities
Kidney transplantation
Must have closely matched tissue type and blood group to prevent rejection
Must take immunosuppressant drugs for rest of life so kidney isn’t rejected
Kidney must be transplanted within 48h of removal
Urine
PH =
Colour =
Clear or cloudy=
Amount of 24h =
PH 6
Light to dark yellow
Clear
750-2,000ml
How does a pregnancy test work
Urine poured onto test stick
HCG binds to mobile antibodies attached to a blue bead
Mobile antibodies move down test stick
If HCG is present , it binds to FIXED antibodies holding bead in place - a blue line forms
Mobile antibodies bind to another fixed site to show test is working
Order of communication in the normal system
Stimulus
Receptor
Hormone
Effector
Responce
Adrenal glands
Located above kidneys
The medulla and cortex are well supplied with capillaries into which hormones are directly secreted
What 3 effects does adrenaline cause
Increase in heart rate, blood glucose, mental awareness
What 3 effects does noradrenaline create
Increase in heart rate, widening of pupils, air passages
Where is the pancreas found
Upper abdomen , behind stomach
What does the pancreas do
Help Control blood glucose concentration and in digestion
What does the exocrine gland do
Produces digestive enzymes and and alkaline fluid (pancreatic juice) and then releases them via a duct into the duodenum (part of the small intestine)
Most of the pancreas is made up of exocrine glandular tissue
What are the digestive enzymes produced in the pancreas
Amylase
Protease
Lipases
What does the endocrine gland do
Found in small regions within the exocrine tissue (this is called the islets of langerhans)
What do the islets of langerhands do
Produce glucagon and insulin and secreting these hormones into the bloodstream
What is the difference in what the a and b cells in the islets of langerhans produce
A = produce and secrete glucagon
B = produce and secrete insulin
What is the normal blood glucose level
90mg per 100cm3
Why is it important to regulate the blood glucose
Otherwise respiration can not take place , to high glucose damages neves and blood vessels.
What increases blood
Glucose concentration
Diet
Glycogenolysis
Gluconeogenesis
What decreases blood glucose concentration
Respiration
Glycogenesis
Starvation
What is the role of insulin
If blood glucose is to high B cells detect this and secrete insulin directly into the bloodstream
What cells have insulin receptors on their cell surface membrane
All body cells except red blood cells
How does insulin work , and what breaks it down
When insulin binds to its glycoprotein receptor it changes the tertiary structure to of the glucose transport protein channels
This causes the channels to open allowing more glucose to enter the cell
Insulin also activates enzymes in some cells which convert glucose to glycogen and fat
Insulin is then Brocken down by enzymes in liver cells
Insulin lowers blood glucose concentrations by
+
Absorption of glucose by cells
Respiration in cells
Glycogenesis
Glucose to fat conversion
Inhibiting the trapeze of glucogen from a cells
What does lysis mean
Splitting
What does neo mean
New
What does genesis mean
Birth/ origin
Role of glucagon
If blood glucose is to low then glucagon is secreted into the bloodstream
What cells respond to glucagon
Liver and fat cells
How does glucagon raise blood glucose
Glycogenolysis
Increasing gluconeogenesis
Reducing the amount of glucose absorbed by the liver cells
What is Glycogenesis
Glycogen making
What is Glycogenolysis
Glycogen breakdown
What is Gluconeogenesis
Making new glucose
