5.2: Homeostasis Flashcards
1
Q
What is excretion?
A
The removal of metabolic waste from the body
2
Q
What are the main excretory products?
A
- CO2 from respiration
- Nitrogen-containing compounds such as urea
- Bile pigments
3
Q
What are the excretory organs?
A
- Lungs
- Liver
- Kidneys
- Skin
4
Q
What is excreted out of the lungs and how?
A
- Carbon dioxide from respiring tissues —> bloodstream as hydrogencarbonate ions —> llungs
- CO2 diffuses into the alveoli to be excreted as you breathe out
5
Q
What is excreted out of the liver and how?
A
- Some substances produced from metabolic roles will be passed into bile for excretion
- Involved in converting excess amino acids into urea (broken down by deammination)
- Nitrogen containing part of molecule is combined in CO2 to make urea
6
Q
What is excreted out of the kidneys and how?
A
- Urea passed into the bloodstream to the kidney
- Transported in solutions: dissolved in plasma
- Removed from blood to be part of urine
7
Q
What is excreted out of the skin and why?
A
- Sweat contains salts, urea, water, uric acid & ammonia
- Losing this maintains body temperature and water potential of the blood
8
Q
Why is excretion important?
A
Some products are toxic and may interfere with cell processes, altering the pH
This means normal metabolism is prevented
Other products may act as inhibitors
9
Q
What is deammination and why does it occur?
A
Amino acid + oxygen —> keto acid + ammonia
- The body cannot store excess amino acids
10
Q
What is the formation of urea and why does it occur?
A
Ammonia + carbon dioxide —> urea + water
- Urea is less toxic than ammonia
11
Q
What does the liver do?
A
Responsible for ensuring that everything in the blood is at the correct concentration (products of digestion, toxins and vitamins)
12
Q
What is the hepatic artery?
A
- Oxygenated blood from the heart travels towards the liver
- Supplies the oxygen that is essential for aerobic respiration
13
Q
What is the hepatic portal vein?
A
Deoxygenated blood enters the liver from the digestive system
14
Q
What is the hepatic vein?
A
Carries blood to the vena carva
At the end of a lobule
15
Q
What is the deoxygenated blood like in the hepatic portal vein?
A
- Blood is rich in the products of digestion
- Concentration are uncontrolled
- Important that substances do not continue to circulate around the body before their concentrations are adjusted
- Blood is rich in glucose and amino acids from the small intestine
- Blood is rich with insulin and glucagon from the pancreas
16
Q
What is the structure of the liver?
A
- Liver is divided into lobes
- Lobes are further divided into lobules
- Cells, blood vessels and chambers are arranged to ensure the greatest possible contact between the blood and the liver cell
17
Q
What are interlobular vessels?
A
Smaller vessels that are split from hepatic artery and hepatic portal vein when they enter the liver
- They run parallel to the lobules
18
Q
What are sinusoids?
A
Special chamber lined with liver cells where the mixed blood from the two vessels are passed through
- Blood concentrations is modified and regulated when it reaches the end of the sinusoid
- Connect the hepatic artery to the hepatic vein allowing hepatocytes to remove harmful substances from the blood
19
Q
What are liver cells?
A
- Relatively unspecialised
- Simple cubiodal shape with many microvilli on their surface
20
Q
What are features of hepatocytes?
A
- Cuboidal shape
- Organelles for protien, cholesterol and bile salt synthesising transformation and storage of carbohydrates
21
Q
What are kupffer cells?
A
Specialised macrophages
Destroy worn out red and white blood cells, bacteria and foreign matter arriving form digestive tract
Breakdown haemoglobin to make billrubin - excrted in bile and faeces
22
Q
What is the bile duct?
A
Runs alongside the sinuisoids
- Carries bile form the centre of the lobule to the outside where it enters a branch of the bile duct
- Transports bile to the gall bladder where it is stored until needed to aid the digestion of fate in the small intestine
23
Q
What are the metabolic functions of liver cells?
A
- Protein synthesis
- Transformation
- Storage of carbohydrates
- Synthesis of cholesterol
24
Q
What are the three functions of the liver?
A
- Formation of urea from amino acids
- Storage of glycogen
- Detoxicification
25
What happens in detoxification of alcohol?
Ethanol is converted to ethanal by ethanol dehydrogenase, reducing NAD
Ethanal is converted to ethanoate (acetate) by ethanal dehydrogenase, oxidising NAD
* Ethanoate enters the kreb cycle
26
What happens if someone has too much alcohol?
NAD is used to oxidise fatty acids in the liver
* If NAD is reduced it cannot oxidise the fatty acids
* It accumulates and is converted into fat
* Fat is deposited in the liver
27
What is the role of the kidney?
Helps make urine and remove urea
28
What makes up the nephron?
* Glomerulus
* Bowman's capsule
* Proximal convulated tubule
* Loop of Henle
* Distal convulated tubule
* Collecting duct
29
Where does ultrafiltration occur?
Glomerulus and bowman's capsule
30
What are the barriers in ultrafiltration?
1. Gaps between the cells of the endothelium of the capillary - also contain fenestrations
2. Basement membrane - consists of a mesh of collagen fibres and glycoproteins
3. Epithelial cells of the bowman's capsule - have podocytes which have finger like projections
31
What filtrate can pass through the bowman's capsule?
Glucose
H2O
Urea
Salt
Amino acids
Vitamins
Hormones
32
What is the mechanism of reabsorption in the proximated convulated tubule
| 5 steps
1. Sodium ions are actively pumped out of the cells lining the tubule
2. Concentration of sodium ions in cell cytoplasm decreases, creating a concentration gradient
3. Sodium ions diffuse into the cell through a cotransport protien - carrying glucose or an amino acid at the same time
4. Water moves into the cell by osmosis
5. Glucose/ amino acids diffuse into the blood
33
What happens at the distal convulated tubule?
Reabsorption selective to body needs
* Balance the H2O, salt, needs and pH of the blood
34
What happens in the ascending limb?
* Na+ and Cl- are actively transported out of the loop of henle, decreasing the water potential of the surrounding tissue in the medulla
* The movement of ions causes a decrease in water potential going down the medulla
* Impermeable to water
35
What happens in the bottom of the loop?
* High concentration of Na+ and Cl- so they diffuse out
* Causes surrounding tissue to decrease further
36
What happens in the descending limb?
* Permeable to water
* Water is removed from the descending limb by osmosis into the surrounding tissue
* As the water potential is low
37
What are osmoregulators?
Specialised cells in hypothalamus and monitor the water potential of the blood
38
What are neurosecretory cells
* Connected to anterior pituritary
* Connected to posterior pituritary
* Produce releasing and release-inhibiting hormones
* Produce ADH and oxytocin
39
What happens if there is low water potential in the body?
* Osmoreceptor loses water by osmosis and shrink
* Stimulates neurosecretory cells in the hypothalamus
* Produce and release ADH
40
What is ADH?
Anti dieretic hormone
Produced in hypothalamus and stored in the pituritary gland
* It travels in the blood to the kidney
* It signals for more aquaporins to be deposited onto wall of collecting duct
41
What is the mechanism for ADH?
| 4 steps
1. ADH binds to receptor on tubule wall
2. Triggers cAMP formation
3. cAMP signals vesicles with aquaporins to move and fuse with plasma membrane
4. Insert aquaporins on inner wall which increases permeability to H2O which increases water reabsorption
42
What happens in haemodialysis?
* Blood from the patient's vein is passed through very small tubes made from a partially permeable membrane
* On the outside of the membrane the dialysis flows in the opposite direction
* The fluid has the water potential and concentration of ions and glucose that patients blood should have
* Creates/maintains concentration gradient
* Anything needed in blood diffuses in (+vice versa)
* Air bubbles removed from blood before re-entering the body
43
What is heprin?
DNA given to patients to stop blood clotting
44
What can urine be tested for?
* Glucose - diagnosis of diabetes
* Recreational drugs
* Anabolic steroids - to detect improper use in sporting competiton
45
What do anabolic steriods do?
Increase protein synthesis within cells
This results in the build up of cell tissuse
46
What are the steps for urine drug tests for anabolic steriods?
| 4 steps
1. Carry out immunoassay, where monoclonal antibodies bind to a substance such as a drug to indicate whether a urine sample contains them
2. Vaporise the urine sample with a known solvent
3. Separate the components of the sample using gas chromatography
4. Use mass spectrometry to identify the molecular structures in the sample
47
Why does a pregnancy test work?
Humana chrorionic gonadotrophin (hCG) is produced once a human embryo is implanted in the uterine lining
* Monoclonal antibodies bind to hCG in urine so they are used
48
How does a pregancy test work?
| 5 steps
1. Urine poured onto test stick
2. hCG bind to mobile antibodies attached to a blue head
3. Mobile antibodies move down test stick
4. If hCG is present, it bind to fixed antibodies holding head in place, a blue line forms
5. Mobile antibodies with no hCG attached bind to another fixed site to show the test works
49
Why are immunosuppresants needed for kidney transplant?
* New kidney not recognised as seld
* Different antigens present on the baby
* Causes rejection by the immune system
* Therefore immunosuppresants are needed
