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Year 2 OCR A-Level Biology > Homostasis > Flashcards

Homostasis Flashcards

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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
Q

What does the capsule do

A

Tough fibrous coat around the kidney

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26
Q

Medulla

A

Contains, nephrons tubules which form the pyramids of the kidney and the collecting ducts

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27
Q

What does the Cortex do

A

Where blood is filtered, dense capillary network

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28
Q

What does the renal pelvis do

A

Collects urine before it passes down the ureter

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29
Q

What is ultrafiltration

A

When glucose , urea, water and salts are pushed out of the bloodstream

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30
Q

How does ultrafiltration work

A

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
Q

What is selective reabsorption

A

Useful substances are reabsorbed passing out of the nephron and back into the capillaries

32
Q

Is selective reabsorption what happpens to water , glucose and remaining filtrate

A

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
Q

What is water reabsorption and how does ADH effect this

A

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
Q

How does ADH control water content in urine

A

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
Q

What is osmoregulation and basic idea of how it works

A

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
Q

How is water gained in the body

A

Drinking

Eating

Respiration

37
Q

How is water lost from the body

A

Sweating

Urine

Exhaling

Faeces

38
Q

Detailed analysis of how ADH works

A

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
Q

Causes of kidney failure

A

Diabetes

Heart disease

Hypertension (high arteriole blood pressure)

Infection

40
Q

Treatments to kidney failure

A

Dialysis

Haemodialysis

Peritoneal dialysis

Kidney transplantation

41
Q

What is dialysis

A

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
Q

Haemodialysis

A

Blood is passed into a machine

Needed 3 times a week for several hours

At clinics and sometimes at home

43
Q

Peritoneal dialysis

A

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
Q

Kidney transplantation

A

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
Q

Urine

PH =
Colour =
Clear or cloudy=
Amount of 24h =

A

PH 6

Light to dark yellow

Clear

750-2,000ml

46
Q

How does a pregnancy test work

A

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
Q

Order of communication in the normal system

A

Stimulus
Receptor
Hormone
Effector
Responce

48
Q

Adrenal glands

A

Located above kidneys

The medulla and cortex are well supplied with capillaries into which hormones are directly secreted

49
Q

What 3 effects does adrenaline cause

A

Increase in heart rate, blood glucose, mental awareness

50
Q

What 3 effects does noradrenaline create

A

Increase in heart rate, widening of pupils, air passages

51
Q

Where is the pancreas found

A

Upper abdomen , behind stomach

52
Q

What does the pancreas do

A

Help Control blood glucose concentration and in digestion

53
Q

What does the exocrine gland do

A

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
Q

What are the digestive enzymes produced in the pancreas

A

Amylase

Protease

Lipases

55
Q

What does the endocrine gland do

A

Found in small regions within the exocrine tissue (this is called the islets of langerhans)

56
Q

What do the islets of langerhands do

A

Produce glucagon and insulin and secreting these hormones into the bloodstream

57
Q

What is the difference in what the a and b cells in the islets of langerhans produce

A

A = produce and secrete glucagon

B = produce and secrete insulin

58
Q

What is the normal blood glucose level

A

90mg per 100cm3

59
Q

Why is it important to regulate the blood glucose

A

Otherwise respiration can not take place , to high glucose damages neves and blood vessels.

60
Q

What increases blood
Glucose concentration

A

Diet

Glycogenolysis

Gluconeogenesis

61
Q

What decreases blood glucose concentration

A

Respiration

Glycogenesis

Starvation

62
Q

What is the role of insulin

A

If blood glucose is to high B cells detect this and secrete insulin directly into the bloodstream

63
Q

What cells have insulin receptors on their cell surface membrane

A

All body cells except red blood cells

64
Q

How does insulin work , and what breaks it down

A

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
Q

Insulin lowers blood glucose concentrations by

A

+
Absorption of glucose by cells
Respiration in cells
Glycogenesis
Glucose to fat conversion

Inhibiting the trapeze of glucogen from a cells

66
Q

What does lysis mean

A

Splitting

67
Q

What does neo mean

A

New

68
Q

What does genesis mean

A

Birth/ origin

69
Q

Role of glucagon

A

If blood glucose is to low then glucagon is secreted into the bloodstream

70
Q

What cells respond to glucagon

A

Liver and fat cells

71
Q

How does glucagon raise blood glucose

A

Glycogenolysis

Increasing gluconeogenesis

Reducing the amount of glucose absorbed by the liver cells

72
Q

What is Glycogenesis

A

Glycogen making

73
Q

What is Glycogenolysis

A

Glycogen breakdown

74
Q

What is Gluconeogenesis

A

Making new glucose

Year 2 OCR A-Level Biology (4 decks)

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