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Year 2 OCR A-Level Biology > Homostasis > Flashcards

Homostasis Flashcards

(74 cards)

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1
Q

What is homeostasis

A

Homeostasis is the maintenance of a constant internal environment, dispite fluctuations in the external environment .

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2
Q

How is homeostasis achieved

A

Sensory receptors

Hormones or nervous system pass the message

Effectors, muscles and glands, provide the response

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3
Q

What is an ectotherm

A

An organisms which regulates its body temperature with help from an external source( snakes lay in the sun )

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4
Q

What’s an endotherm

A

An organism which can maintain its own body temperature

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5
Q

What’s a response when your body is to cold or to hot

A

Cold :

Shivering
Hairs on skin rise to reduce heat loss

Hot:

Sweat glands
Arterioles , rise to surface near skin to lose temperature

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6
Q

What does homeostasis keep at constant levels

A

Body temperature
pH
CO2 concentration
Blood glucose concentration
Blood pressure
Blood salt concentration

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7
Q

What is negative feedback

A

The reversal of a change , return to optimum

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8
Q

What is positive feedback

A

An increase in the change / further deviation

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9
Q

An example of an Endotherm

A

Birds, mammals

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10
Q

What’s the optimum body temperature of mammals and birds

A

37 degrees C

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11
Q

What is excretion

A

The removal of waste products of metabolism from the body

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12
Q

What are some of the main mammal waste products and where they are from

A

CO2 - lungs

Bile pigments - liver (colour faeces)

Nitrogenous waste products ( breakdown of amino acids ) - kidney, urine

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13
Q

What’s the ornithine cycle

A

Excess amino acids can’t be stored and may damage tissues, so the liver converts them into urea in the ornithine cycle

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14
Q

What does the haptic artery do

A

Delivers oxygenated blood to the liver

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15
Q

What does the hepatic vein do

A

Takes deoxygenated blood away from the liver

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16
Q

What does the hepatic portal vein do

A

Connects the liver to the intestines. This allows harmful substances to be removed from liver to be Brocken down

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17
Q

What does the bile duct do

A

Takes bile from the liver to the gall bladder, where it is stored

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18
Q

What does the liver do

A

Controls glucose , amino acids and lipid levels in blood

Stores iron and glycogen

Detoxifies blood of alcohol and drugs

Breaks down sex hormones

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19
Q

What do kidneys do

A

Filter nitrogenous waste products out of blood and urea

Maintain water balance

Maintaining pH of blood

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20
Q

What does the kidney contain millions of and what do they do

A

Nephrons

Filtering units

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21
Q

How does urine exit the body

A

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

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22
Q

Order of organs / pathways from urine to be made to leave

A

Kidneys
Ureter
Bladder
Urethra

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23
Q

What’s the renal vein do

A

Carries deoxygenated blood away from the kidney

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24
Q

What’s the renal artery do

A

Carrie’s oxygenated blood to the kidney

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25
What does the capsule do
Tough fibrous coat around the kidney
26
Medulla
Contains, nephrons tubules which form the pyramids of the kidney and the collecting ducts
27
What does the Cortex do
Where blood is filtered, dense capillary network
28
What does the renal pelvis do
Collects urine before it passes down the ureter
29
What is ultrafiltration
When glucose , urea, water and salts are pushed out of the bloodstream
30
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
31
What is selective reabsorption
Useful substances are reabsorbed passing out of the nephron and back into the capillaries
32
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
33
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
34
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.
35
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.
36
How is water gained in the body
Drinking Eating Respiration
37
How is water lost from the body
Sweating Urine Exhaling Faeces
38
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
39
Causes of kidney failure
Diabetes Heart disease Hypertension (high arteriole blood pressure) Infection
40
Treatments to kidney failure
Dialysis Haemodialysis Peritoneal dialysis Kidney transplantation
41
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
42
Haemodialysis
Blood is passed into a machine Needed 3 times a week for several hours At clinics and sometimes at home
43
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
44
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
45
Urine PH = Colour = Clear or cloudy= Amount of 24h =
PH 6 Light to dark yellow Clear 750-2,000ml
46
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
47
Order of communication in the normal system
Stimulus Receptor Hormone Effector Responce
48
Adrenal glands
Located above kidneys The medulla and cortex are well supplied with capillaries into which hormones are directly secreted
49
What 3 effects does adrenaline cause
Increase in heart rate, blood glucose, mental awareness
50
What 3 effects does noradrenaline create
Increase in heart rate, widening of pupils, air passages
51
Where is the pancreas found
Upper abdomen , behind stomach
52
What does the pancreas do
Help Control blood glucose concentration and in digestion
53
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
54
What are the digestive enzymes produced in the pancreas
Amylase Protease Lipases
55
What does the endocrine gland do
Found in small regions within the exocrine tissue (this is called the islets of langerhans)
56
What do the islets of langerhands do
Produce glucagon and insulin and secreting these hormones into the bloodstream
57
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
58
What is the normal blood glucose level
90mg per 100cm3
59
Why is it important to regulate the blood glucose
Otherwise respiration can not take place , to high glucose damages neves and blood vessels.
60
What increases blood Glucose concentration
Diet Glycogenolysis Gluconeogenesis
61
What decreases blood glucose concentration
Respiration Glycogenesis Starvation
62
What is the role of insulin
If blood glucose is to high B cells detect this and secrete insulin directly into the bloodstream
63
What cells have insulin receptors on their cell surface membrane
All body cells except red blood cells
64
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
65
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
66
What does lysis mean
Splitting
67
What does neo mean
New
68
What does genesis mean
Birth/ origin
69
Role of glucagon
If blood glucose is to low then glucagon is secreted into the bloodstream
70
What cells respond to glucagon
Liver and fat cells
71
How does glucagon raise blood glucose
Glycogenolysis Increasing gluconeogenesis Reducing the amount of glucose absorbed by the liver cells
72
What is Glycogenesis
Glycogen making
73
What is Glycogenolysis
Glycogen breakdown
74
What is Gluconeogenesis
Making new glucose

Year 2 OCR A-Level Biology (4 decks)

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