C15 - Homeostasis Flashcards
What is homeostasis
Maintaining a constant internal environment despite internal/external changes
Name 4 things we have to control in homeostasis
Body temp
ion levels
water levels
glucose levels
What is negative feedback
When a response to a change returns the system to the ideal levels
what is positive feedback
response to a change that increases the degree of change
What are endotherms
Generate heat yourself eg. mammals
What are ectotherms
dependant on external heat sources eg. lizards
Describe how an ectotherm maintains its body temperature
Behaviours
- exposing themselves to sun
- taking shelter
- gaining warmth from ground
- colour variations
- shaking and moving
Describe how an endotherm maintains its body temperature
Detection in thermoregulation centre in the hypothalamus and skin temp receptors
Heat gain centre- activated by a fall in blood temp
- causes heat gain
Heat loss centre - activated by a rise in temp
- causes heat loss
What is the role of the liver?
converts lactic acid to glucose produces bile metabolism of alcohol and toxins deamination disposal of RBCs
What are essential amino acids
amino acids we can not synthesise, they are essential to get from our diet
How can non-essential amino acids be synthesised
essential amino acids –> (transamination)–> converted to non-essential amino acids
What is the name of the series of reactions that form urea in the liver
Ornithine cycle
Name the 3 main blood vessles in the liver
Hepatic artery
Hepatic vein
Hepatic portal vein
What is the role of the hepatic artery
carries oxygenated blood to the liver
What is the role of the hepatic vein
carries deoxygenated blood away from the liver
What is the role of the hepatic portal vein
carries blood from the digestive system to liver
blood is deoxygenated and nutrient-rich
Describe the structure of a sinusoid
hepatic portal vein and hepatic artery at top of sinusoid
a single layer of cells forming the wall of sinusoid surrounded by hepatocytes
Blood drains through the lumen to hepatic vein
What are Kupffer cells
Adapted macrophages
Ingest foreign particles and protect against disease
What are the 3 main vessels in the kidney
renal artery
renal vein
ureter
Where does urine from the ureter go?
ureter –> bladder –> urethra
Describe the basic structure of the kidney
pelvis in centre
cortex (bark) on outside
medulla on inside
made of nephrons
What are the medulla and cortex made of
Cortex - Bowmans capsule, convoluted tubules etc.
Medulla - loop of henle, collecting duct
What is a group of nephrons called
Pyramind
Describe the structure of a nephron
(glomerulus feeding into) Bowmans capsule proximal convoluted tubule descending limb of loop of henle ascending limb of loop of henle distal convoluted tubult collecting duct
Describe the movement of blood through the Bowmans capsule into proximal convoluted tubule
Enters glomerulus through the afferent artery and glows through the glomerulus
leaves through the efferent artery
afferent artery wide, efferent artery narrow causes high pressure forces plasma out of glomerulus through basement membrane and podocytes into bowmans capsule and to proximal convoluted tubule
What is the role of the basement membrane and podocytes
prevents blood cells from leaving
double filter system
What happens to filtrate in the proximal convoluted tubule
reabsorption of amino acids , glucose, vitamins, hormones
reabsorption of most NaCl and H2O
What is osmolarity
a measure how how much (moles) of a xolute is dissolved (0 is pure water, higher is more concentrated)
Describe how the loop of henle filters water out of the filtrate
initially filtrate is isotonic with surroundings
Na and Cl ions actively transported out of ascending limb, osmolarity of interstitial fluid increases
Water moves out descending limb due to osmotic gradient, creating more concentrated filtrate
This replaces the more diluted filtrate in ascending limb
cycle repeats
Filtrate in interstitial space can diffuse into blood vessles
How are the nephrons of desert animals adapted?
Longer loop of henle - allows more water absorption
What happens to filtrate in distal convoluted tubule?
Fine tuning of water balance
What happens in the collecting duct
Takes urine to pelvis and then ureter
What sections of nephrons are affected by ADH
distal convoluted tubule and collecting duct
What is osmoregulation?
Maintaining the water balance in your blood within the narrow boundary
What is water balance affected by (why many we need osmoregulation)?
Water uptake
Solute conc
what would happen if the water balance was too high
cells would lyse (burst)
what would happen if the water balance was too low
no transport medium
water is essential for chemical reactions
what is ADH
Anti Diuretic Hormone
When is ADH produced?
When you’re All Dried up - when water balance is too low in the blood
Where is ADH detected and produced?
detected in hypotalamus
produced in pituitary gland
What does ADH do
Increase the absorption of water into the blood, negative feedback
How does ADH effect its target cells?
ADH binds to ADH receptor
Secondary messenger cAMP produced
Causes vesicles to fuse to cell surface membrane
Vesicles contain aquaporin
creates pores for water to diffuse through (from urine to interstitial fluid)
Names the components of urine
water urea NaCl Hormones Metabolites of drugs
What are the medical uses of urine
Pregnancy testing
DIabetes testing
Detection of drugs/drug metabolites
How does haemodialysis work?
Blood from veins run through dialysis fluid (that is kept at constant temp)
Dialysis fluid isotonic for hormones, amino acids etc. but contains no urea
Urea diffuses out
