Module 5: Section 1 - Communication and Homeostasis

Question 1

How can communication occur between adjacent and distant cells?

Answer 1

1) to produce a response, receptors need to communicate with effectors and effectors may need to commincate with other cells
2) this happens via cell signalling
3) cell signalling can occur betwen adjacent cells or between distant cells. e.g. cells in the nervous system communicate by secreting chemicals called neurotransmitters, which send signals to adjacent cells, such as other nerve cells or muscle cells. The hormonal system works by cells releasing chemicals called hormones, which travel in the blood and act as signals to distant cells
4) cell surface receptors allow cells to recognise the chemicals involved in cell signalling

Question 2

What is homeostatis?

Answer 2

homeostatis involves control systems that keep your internal environment roughly constant (within certain limits) despite external factors (e.g. the external environment)

keeping your internal environment constant is vital for cells to function normally and to stop them from being damaged

Question 3

It’s particularly important to maintain the right core body temperature. Why?

Answer 3

Because temperatute affects enzyme activity, and enzymes control the rate of metabolic reactions:
-if body temp is too high (e.g.40 degrees C) enzymes may become denatured. The enzyme’s molecules vibrate too much, which breaks the hydrogen bonds that hold them in their 3D shape. The shape of the enzyme’s active site is changed and it no longer works as a catalyst. This means metabolic reactions are less efficient.

-if body temperature is too low enzyme activity is reduced, slowing the rate of metabolic reactions

Question 4

Homeostatic systems involve receptors, a communication system and effectors.

Recepotrs detect when a level is too high or too low, and the information’s communicated via the nervous system or the hormonal system to effectors

The effectors respond to counteract the change. The mechanism that restores the level to normal is called a negative feedback mechanism - but how does it work?

Answer 4

1) negative feedback keeps things around the normal level, e.g. body temp is usually kept within 0.5 degrees C above or below 37 degrees C
2) negative feedback only works within certain limits though - if the change is too big then the effectors may not be able to counteract it

Question 5

What is a positive feedback mechanism?

Answer 5

1) some changes trigger a positive feedback mechanism, which amplifies the change
2) the effectors respond to further increase the level away from the normal level

Question 6

Positive feedback is useful to rapidly activate something - please explain the example of a blood clot after an injury

Answer 6

• platelets become activated and release a chemical - this triggers more platelets to be activated, and so on
• platelets very quickly form a blood clot at the injury site
• the process ends with negative feedback, when the body detects the blood clot has been formed

Question 7

Why isn’t positive feedback involved in homeostasis?

Answer 7

positive feedback isn’t involved in homeostasis because it doesn’t keep your internal environment constant

Question 8

Describe the three main types of neurone

Answer 8

1) sensory neurones transmit nerve impulses from receptors to the central nervous system - the brain and spinal cord
2) motor neurones transmit nerve impulses from the CNS to effectors
3) relay neurones transmit nerve impulses between sensory neurones and motor neurones

Question 9

What is the pathway between a stimulus to a response?

Answer 9

stimulus (e.g. you see a friend waving) –> receptors (photoreceptors in your eyes detect the wave) –> CNS (CNS processes information and decides what to do about it) –> effectors (muscle cells are stimulated by the motor neurones) –> response (muscles contract to make your arm move)

Question 10

Different stimuli have different forms of energy, e.g. light energy or chemical energy, but your nervous system only sends information in the form of nerve impulses (electrical impulses). How do sensory receptors enable this to happen?

Answer 10

1) sensory receptors convert the energy of a stimulus into electrical energy
2) so, sensory receptors act as transducers - something that converts one form of energy into another

Question 11

How do receptor cells that communicate information via the nervous system work?

Answer 11

• when a nervous system receptor is in its resting state there’s a difference in charge between the inside and outside of the cell - this is generated by ion pumps and ion channels. This means there’s a voltage across the membrane. Voltage is also known as potential difference.
• the potential difference when a cell is at rest is called its resting potential. When a stimulus is detected, the cell membrane is excited and becomes more permeable, allowing more ions to move in and out of the cell - altering the potential difference. The change in potential difference due to a stimulus is caled the generator potential
• a bigger stimulus excites the membrane more, causing a bigger movement of ions and a bigger change in potential difference - so a bigger generator potential is produced
• if the generator potential is big enough it’ll trigger an action potential (nerve impulse) along a neurone. An action potential is only triggered if the generator potential reaches a certain level called the threshold level
• if the stimulus is too weak the generator potential won’t reach the threshold, so there’s no action potential

Question 12

Explain what Pacinian corpiscles are and how they work please

Answer 12

Pacinian corpiscles are mechanoreceptors - they detect mechanical stimuli, e.g. pressure or vibrations. They’re found in your skin. They contain the end of a sensory neurone, called a sensory nerve ending. The sensory nerve ending is wrapped in lots of layers of connective tissue called lamellae.

When a Pacinian corpuscle is stimulated, e.g. by a tap on the arm, the lamellae are deformed and press on the sensory nerve ending. This causes deformation of stretch-mediated sodium channels in the sensory neurone’s cell membrane. The sodium ion channels open and sodium ions diffuse into the cell, creating a generator potential. If the generator potential reaches the threshold, it triggers an action potential

Question 13

Describe (and draw if you fancy it) the structure of a sensory neurone please

Answer 13

sensory neurones have short dendrites and one long dendron to carry nerve impulses from receptor cells to the cell body, and one short axon that carries impulses from the cell body to the CNS.

see pg. 129 for a diagram

Question 14

Describe (and draw if you fancy it) the structure of a motor neurone please

Answer 14

motor neurones have many short dendrites that carry nerve impulses from the CNS to the cell body, and one long axon that carries nerve impulses from the cell body to effector cells

see pg. 129 for a diagram

Question 15

Describe (and draw if you fancy it) the structure of a relay neurone please

Answer 15

relay neurones have many short dendrites that carry nerve impulses from sensory neurones to the cell body, and many short axons that carry nerve impulses from the cell body to motor neurones

Question 16

Neurone cell membranes are polarised at rest. Explain how please! Go on… think of having to go through clearing..

Answer 16

1) in a neurone’s resting state the outside of the membrane is positively charged compared to the inside. This is because there are more positive ions outside the cell than inside
2) so the membrane is polarised - there’s a difference in charge. The voltage across the membrane when it’s at rest is called the resting potential - it’s about -70mV
3) the resting potential is created and maintained by sodium-potassium pumps and potassium ion channels in a neurone’s membrane
4) the sodium-potassium pumps move sodium ions out of the neurone, but the membrane isn’t permeable to sodium ions, so they can’t diffuse back in. This creates a sodium ion electrochemical gradient (a concentration gradient of ions) because there are more positive sodium ions outside the cell than inside
5) the sodium-potassium pumps also move potassium ions in to the neurone, but the membrane is permeable to potassium ions so they diffuse back out through potassium ion channels
6) this makes the outside of the cell positibely charged compared to the inside

see pg 129 for a pretty useful diagram

Question 17

Neurone cell membranes become depolarised when they’re stimulated. A stimulus triggers sodium ion chenncles in the cell membrane to open. If the stimulus is big enough, it’ll trigger a rapid change in potential difference. The sequence of events that happen are known as an action potential. Please explain each event (it may help you out to draw and label the graph, you can see the graph on page 130)

Answer 17

1) STIMULUS - this excites the neurone cell membrane, causing sodium ion channels to open. The membrane becomes more permable to sodium, so sodium ions diffuse into the neurone down the sodium ion electrochemical gradient. This makes the inside of the neurone less negative
2) DEPOLARISATION - if the potential difference reaches the threshold (around -55mV), voltage-gated sodium ion channels open. More sodium ions diffuse into the neurone. This is positive feedback.
3) REPOLARISATION - at a potential difference of around +30 mV the sodium ion channels close and voltage-gated potassium ion channels open. The membrane is more permeable to potassium so potassium ions diffuse out of the neurone down the potassium ion concentration gradient. This starts to get the membrane back to its resting portential. This is negative feedback.
4) HYPERPOLARISATION - potassium ion channels are slow to close so there’s a slight ‘overshoot’ where too many potassium ions diffuse out of the neurone. The potential difference becomes more negative than the resting potential (i.e. less than -70mV)
5) RESTING POTENTIAL - the ion channels are reset. The sodium-potassium pump returns the membrane to its resting potential and maintains it until the membrane’s excited by another stiumulus

Question 18

After an action potential, the neurone cell membrane can’t be excited again straight away. Why is this?

Answer 18

This is because the ion channels are recovering and they can’t be made to open - sodium ion channels are closed during repolarisation and potassium ion channels are closed during hyperpolarisation. This period of recovery is called the refractory period.

Question 19

The action potential moves along the neurone as a wave of depolarisation. When an action potential happens, some of the sodium ions that enter the neurone diffuse sideways. What does this cause?

Answer 19

1) this causes sodium ion channels in the enxt region of the neurone to open and sodium ions diffuse into that part
2) this causes a wave of depolarisation to travel along the neurone
3) the wave moves away from the parts of the membrane in the refractory period because these parts can’t fire an action potential

Question 20

A bigger stimulus causes more frequent impulses. Why is this? To fully answer you need to include what happens when the threshold is reached and isn’t reached

Answer 20

1) once the threshold is reached, an action potential will always fire with the same change in voltage, no matter how big the stimulus is
2) if the threshold isn’t reached, an action potential won’t fire. This is the all-or-nothing nature of action potentials
3) a bigger stimulus won’t cause a bigger action potential, but it will cause them to fire more frequently (so if the brain recieves a high frequency of action potentials, it interprets this as a big stimulus and responds accordingly)

Question 21

Some neurones are myelinated - they have a myelin sheath. The myelin sheath is an electrical insulator. In the peripheral nervous sytem the myelin sheath is made of a type of cell called a Schwann cell. What are between the Schwann cells and what do these parts between the Schwann cells enable? Look at page 131 for a diagram if youre confused

P.S. in your answer please include information on saltatory conduction

Answer 21

1) between the Schwann cells are tiny patches of bare membrane called the nodes of Ranvier. Sodium ion channels are concentrated at the nodes
2) in a myelinated neurone, depolarisation only happens at the nodes of Ranvier (where sodium ions can get through the membrane)
3) the neurone’s cytoplasm conducts enough electrical charge to depolarise the next node, so the impulse ‘jumps’ from node to node
4) this is called saltatory conduction and it’s really fast
5) in a non-myelinated neurone, the impulse travels as a wave along the whole length of the axon membrane
6) this is slower than saltatory conduction

Question 22

What is a synapse?

Answer 22

A synapse is the junction between a neurone and another neurone, or between a neurone and an effector cell

Question 23

What is a synaptic cleft?

Answer 23

The tiny gap between the cells at a synapse is called the synaptic cleft

Question 24

What is presynaptic neurone and what does it do?

Answer 24

The presynaptic neurone (the one before the synapse) has a swelling called a synaptic knob. This contains synaptic vesicles filled with chemicals called neurotransmitters

Question 25

What happens when an action potential reaches the end of a neurone?

Answer 25

When an action potential reaches the end of a neurone it causes neurotransmitters to be released into the synaptic cleft. They diffuse across to the postsynaptic membrane (the one after the synapse) and bind to specific receptors

Question 26

What happens when neurotransmitters bind to receptors and why are neurotransmitters removed from the cleft?

Answer 26

1) when neurotransmitters bind to receptors they might trigger an action potential (in a neurone), cause muscle contraction (in a muscle cell), or cause a hormone to be secreted (from a gland cell)
2) neurotransmitters are removed from the cleft so the response doesn’t keep happening, e.g. they’re taken back into the presynaptic neurone or they’re broken down by enzymes (and the products are taken into the neurone)

Question 27

There are many different neurotransmitters, e.g. acetylcholine (ACh) and noradrenaline. What’re are synapses that use acetylcholine called?

Answer 27

There are many different neurotransmitters, e.g. acetylcholine (ACh) and noradrenaline. Synapses that use acetylcholine are called cholinergic synapses. Their structure is exactly the same as a typical synapse. They bind to receptors called cholinergic receptors, and they’re broken down by an enzyme called acetylcholinesterase (AChE)

Question 28

How do neurotransmiters transmit nerve impulses between neurones?

Answer 28

1) An action potential triggers calcium influx
- an action potential arrives at the synaptic knob of the presynaptic neurone
- the action potential stimulates voltage-gated calcium ion channels in the presynaptic neurone to open
- calcium ions diffuse into the synaptic knob (they’re pumped out afterwards by active transport)

2) Calcium influx causes neurotransmitter release
- the influx of calcium ions into the synaptic knob causes the synaptic vesicles to move to the presynaptic membrane. They then fuse with the presynaptic membrane
- the vesicles release the neurotransmitter into the synaptic cleft by exocytosis

3) The neurotransmitter triggers an action potential in the postsynaptic neurone
- the neurotransmitter diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic membrane
- this causes the sodium ion channels in the postsynaptic neurone to open. The influx of sodium ions into the postsynaptic membrane causes depolarisation. An action potential on the postsynaptic membrane is generated if the threshold is reached
- the neurotransmitter is removed from the synaptic cleft so the response doesn’t keep happening

Question 29

Synapses allow information to be dispersed or amplified. Please explain what synaptic divergence and what synaptic convergence is

Answer 29

1) when one neurone connects to many neurones information can be dispersed to different parts of the body. This is called synaptic divergence
2) when many neurones connect to one neurone information can be amplified. This is called synaptic convergence

Question 30

If a stimulus is weak, only a small amount of neurotransmitter will be released from a neurone into the synaptic cleft. This might not be enough to excite the postsynaptic membrane to the threshold level and stimulate an action potential. Summation is where the effect of neurotransmitters can be combined. What is spatial summation?

Answer 30

SPATIAL SUMMATION

1) when neurones converge, the small amount of neurotransmitter released from each neurone can be enough altogether to reach the threshold in the postsynaptic neurone and trigger an action potential
2) stimuli might arrive from different sources. Spatial summation allows signals from multiple stimuli to be coordinated into a single response

Question 31

If a stimulus is weak, only a small amount of neurotransmitter will be released from a neurone into the synaptic cleft. This might not be enough to excite the postsynaptic membrane to the threshold level and stimulate an action potential. Summation is where the effect of neurotransmitters can be combined. What is temporal summation?

Answer 31

TEMPORAL SUMMATION

1) temporal summation is where two or more nerve impulses arrive in quick succession from the same presynaptic neurone. This makes an action potential more likely because more neurotransmitter is released into the synaptic cleft

Question 32

What does spatial summation and temporal summation do?

Answer 32

both types of summation mean synapses accurately process information, finely tuning the response

Question 33

How do synapses ensure that impulses are only transmitted one way?

Answer 33

receptors for neurotransmitters are only on the postsynaptic membranes, so synapses make sure impulses can only travel in one direction

Question 34

What is the hormonal system made of and what do hormones do?

Answer 34

the hormonal system is made up of glands (called endocrine glands) and hormones:

• endocrine glands are groups of cells that are specialised to secrete hormones
• hormones are ‘chemical messengers.’ Many hormones are proteins or peptides, e.g. insulin. some hormones are steroids, e.g. progesterone

Question 35

Hormones are secreted when an endocrine gland is stimulated. How are glands stimulated?

Answer 35

Hormones are secreted when an endocrine gland is stimulated:

• glands can be stimulated by a change in concentration of a specific substance (sometimes another hormone)
• they can also be stimulated by electrical impulses

Question 36

Hormones trigger a response in the target cells (the effectors) Talk me through how the hormones trigger a response from stimulus to response

Answer 36

1) stimulus - e.g. low blood glucose concentration
2) receptors - receptors on pancreas cells detect the low blood glucose concentration
3) hormone - the pancreases releases the hormone glucagon into the blood
4) effectors - target cells in the liver detect glucagon and convert glycogen into glucose
5) response - glucose is released into the blood, so glucose concentration increases

Question 37

Why is a hormone called a first messenger?

Answer 37

a hormone is called a first messenger because it carries the chemical message the first part of the way, from the endocrine gland to the receptor on the target cells

Question 38

What happens when a hormone binds to its receptor?

Answer 38

1) when a hormone binds to its receptor it activates an enzyme in the cell membrane
2) the enzyme catalyses the production of a molecule inside the cell called a signalling molecule - this molecule signals to other parts of the cell to change how the cell works
3) the signalling molecule is called a second messenger because it carries the chemical message to the second part of the way, from the receptor to other parts of the cell
4) second messengers activate a cascade inside the cell

Question 39

Hormones bind to receptors and trigger second messengers. Explain how this works using the example of the hormone adrenaline

Answer 39

1) the hormone adrenaline is a first messenger
2) it binds to specific receptors on the cell membranes of many cells e.g. liver cells
3) when adrenaline binds it activates an enzyme in the membrane called adenylyl cyclase
4) activated adenylyl cyclase catalyses the production of a second messenger called cyclic AMP (cAMP) from ATP
5) cAMP activates a cascade, e.g. a cascade of enzyme reactions make more glucose available to the cell by catalysing the breakdown of glycogen into glucose

Question 40

The adrenal glands secrete hormones. Where are the adrenal glands found and what do they do?

Answer 40

1) the adrenal glands are endocrine glands that are found just above your kidneys
2) each adrenal gland has an outer part called the cortex and an inner part called the medulla
3) the cortex and the medulla have different functions and produce different responses

Question 41

The cortex (in the kidney) secretes steroid hormones, e.g. it secretes cortisol and aldosterone when you’re stressed. These hormones have a role in both the short-term and the long-term responses to stress. What’re their effects?

Answer 41

• stimulating the breakdown of proteins and fats into glucose. This increases the amount of energy available so the brain and muscles can respond to the situation
• increasing blood volume and pressure by increasing the uptake of sodium ions and water by the kidneys
• suppressing the immune system

Question 42

The medulla (in the kidney) secretes catecholamine hormones (modified amino acids), e.g. it secretes adrenaline and noradrenaline when you’re stressed. These act to make more energy available in the short-term -how?

Answer 42

• increasing heart and breathing rate
• causing cells to break down glycogen into glucose
• constricting some blood vessels so that blood is diverted to the brain and muscles

Question 43

The pancreas is a gland that’s found below the stomach. You need to know about its endocrine function. What are the islets of Langerhans, where are they found, what do they do and what are they made up of

Answer 43

1) the areas of the pancreas that contain endocrine tissue are called the islets of Langerhans
2) they’re found in clusters around blood capillaries
3) the islets of Langerhans secrete hormones directly into the blood

4) they’re made up of two types of cell:
- alpha cells secrete a hormone called glucagon
- beta cells secrete a hormone called insulin

5) glucagon and insulin help to control blood glucose concentration

Question 44

How is temperature controlled by ectotherms (e.g. reptiles and fish)

Answer 44

• ectotherms can’t control their body temperature internally - they control their temperature by changing their behaviour
• their internal temperature depends on the external temperature
• their activity level depends on the external temperature - they’re more active at higher temperatures and less active at lower temperatures
• they have a variable metabolic rate and they generate very little heat themselves

Question 45

How is temperature controlled by endotherms?

Answer 45

• endotherms control their body temperature internally by homeostasis. They can also control their temperature by behaviour
• their internal temperature is less affected by the external temperature (within certain limits)
• their activity level is largely independent of the external temperature - they can be active at any temperature (within certain limits)
• they have a constantly high metabolic rate and they generate a lot of heat from metabolic reactions

Question 46

How does sweating reduce body temperature?

Answer 46

more sweat is secreted from sweat glands when the body’s too hot. The water in sweat evaporates from the surface of the skin and takes heart from the body. The skin is cooled

Question 47

How does hairs lying flat reduce body temperature?

Answer 47

mammals have a layer of hair that provides insulation by trapping air. When it’s hot, erector pili muscles relax so the hairs lie flat. Less air is trapped, so the skin is less insulated and heat can be lost more easily

Question 48

How does vasodilation reduce body temperature?

Answer 48

when it’s hot, arterioles near the surface of the skin dilate. More blood flows through the capillaries in the surface layers of the dermis. This means more heat is lost from the skin by radiation and the temperature is lowered

Question 49

How does shivering increase body temperature?

Answer 49

when it’s cold, muscles contract in spasms. This makes the body shiver and more heat is produced from increased respiration

Question 50

How does sweating less increase body temperature?

Answer 50

less sweat is secreted from the sweat glands when it’s cold, reducing the amount of heat loss

Question 51

How does hairs standing up increase body temperature?

Answer 51

erector pili muscles contract when it’s cold, which makes the hairs stand up. This traps more air and so prevents heat loss

Question 52

How does vasoconstriction increase body temperature?

Answer 52

when it’s cold, arterioles near the surface of the skin constrict so less blood flows through the capillaries in the surface layers of the dermis. This reduces heat loss

Question 53

How do hormones increase body temperature?

Answer 53

the body releases adrenaline and thyroxine. These increase metabolism and so more heat is produced

Question 54

Body temperature in mammals is maintained at a constant level by the hypothalamus. What do thermoreceptors in the hypothalamus and skin detect?

Answer 54

• thermoreceptors in the hypothalamus detect internal temperature
• thermoreceptors in the skin (called peripheral temperature receptors) detect external temperature (the temp of the skin)

Question 55

What pathway does a thermoreceptor follow?

Answer 55

thermoreceptors send impulses along sensory neurones to the hypothalamus, which sends impulses along motor neurones to effectors

Question 56

What is typically the concentration of glucose in the blood and what is it monitored by?

Answer 56

the concentration of glucose in the blood is normally around 90 mg per 100 cm cubed of blood. It’s monitored by cells in the pancreas

Question 57

When does blood glucose concentration rise or fall?

Answer 57

• blood glucose concentration rises after eating food containing carbohydrate
• blood glucose concentration falls after exercise, as more glucose is used in respiration to release energy

Question 58

The hormonal system controls blood glucose concentration using two hormones called INSULIN and GLUCAGON. They’re both secreted by clusters of cells in the pancreas called…. ?

Answer 58

they’re both secreted by clusters of cells in the pancreas called the islets of Langerhans:

Beta cells secrete insulin into the blood
Alpha cells secrete glucagon into the blood

Insulin and glucagon act on effectors, which respond to restore the blood glucose concentration to the normal level

Question 59

Please explain how insulin lowers blood glucose concentration when it is too high

Answer 59

1) insulin binds to specific receptors on the cell membranes of liver cells and muscle cells
2) it increases the permeability of cell membranes to glucose, so the cells take up more glucose
3) insulin also activates enzymes that convert glucose into glycogen
4) cells are able to store glycogen in their cytoplasm, as an energy source
5) the process of forming glycogen form glucose is called glycogenesis
6) insulin also increases the rate of respiration of glucose, especially in muscle cells

Question 60

Please explain how glucagon raises blood glucose concentration when it’s too low

Answer 60

1) glucagon binds to specific receptors on the cell membranes of liver cells
2) glucagon activates enzymes that break down glycogen into glucose
3) the process of breaking down glycogen is called glycogenolysis
4) glucagon also promotes the formation of glucose from fatty acids and amino acids
5) the process of forming glucose from non-carbohydrates is called gluconeogenesis

Question 61

beta cells contain insulin stored in vesicles. B cells secrete insulin when they detect high blood glucose concentration. How does this happen?

Answer 61

1) when blood glucose concentration is high, more glucose enters the B cells by facilitated diffusion
2) more glucose in a B cell causes the rate of respiration to increase, making more ATP
3) the rise in ATP triggers the potassium ion channels in the B cell plasma membrane to close
4) this means potassium ions can’t get through the membrane - so they build up inside the cell
5) this makes the inside of the B cell less negative because there are most positively-charged potassium ions inside the cell - so the plasma membrane of the B cell is depolarised
6) depolarisation triggers calcium ion channels in the membrane to open, so calcium ions diffuse into the B cell
7) this causes the vesicles to fuse with the B cell plasma membrane, releasing insulin (by exocytosis)

Question 62

What is diabetes mellitus?

Answer 62

diabetes mellitus is a condition where blood glucose concentration can’t be controlled properly

Question 63

Please explain what type one diabetes is and what affect this has on the body

Answer 63

1) type 1 diabetes is an auto-immune disease, in which the body attacks and destroys the beta cells in the islets of Langerhans
2) this means people with Type 1 diabetes don’t produce any insulin
3) after eating, the blood glucose concentration rises and stays high, which can result in death if left untreated
4) the kidneys can’t reabsorb all this glucose, so some of it’s excreted in the urine
5) type 1 diabetes usually develops in children or young adults. Risk of developing the disease is increased if there’s a close family history of the disease

Question 64

How is type 1 diabetes treated with insulin therapy?

Answer 64

• most people with type 1 need regular insulin injections throughout the day
• some people use an insulin pump - this is a machine that continuously delivers insulin into the body via a tube inserted beneath the skin

Question 65

How is some peoples diabetes treated with islet cell transplantation?

Answer 65

some people have been successfully treated by having islet cell transplantation - they receive healthy islet cells from a donor so their pancreas can produce some insulin (although they usually still need some additional insulin therapy)

Question 66

When does type 2 diabetes occur and what factors can cause it

Answer 66

1) type 2 occurs when the beta cells don’t produce enough insulin or when the body’s cells don’t respond properly to insulin
2) cells don’t respond properly because the insulin receptors on their membranes don’t work properly, so the cells don’t take up enough glucose
3) this means the blood glucose concentration is higher than normal
4) type 2 is usually acquired later in life than type 1, and it’s often linked with obesity

Question 67

Give three medications and explain the effect they have on treating type 2 DIABEEETUS

Answer 67

1) metformin mofos - this is usually the first med to be prescribed. Metformin acts on liver cells to reduce the amount of glucose that they release into the blood. It also acts to increase the sensitivity of cells to insulin so more glucose can be taken up with the same amount of insulin
2) sulfonylureas - these stimulate the pancreas to produce more insulin
3) thiazolidinediones - these also make the body cells more sensitive to insulin

Question 68

Give four reasons why using GM bacteria to produce insulin is better than extracting it from animal pancreases

Answer 68

1) producing insulin using GM bacteria is cheaper
2) larger quantities of insulin can be harvested from GM bacteria
3) GM bacteria make human insulin which is more effective than using pig/cattle insulin and less likely to trigger the immune system or an allergic response
4) some people prefer insulin from bacteria for religious or ethical reasons

Question 69

Stem cells are unspecialised cells - they have the ability to develop into any type of cell

How could stem cells potentially be used to cure diabetes?

Answer 69

• stem cells could be grown into beta cells
• the beta cells would then be implanted into the pancreas of a person with type 1
• this means the person would be able to make insulin as normal
• this treatment is still being developed, but if it’s effective it’ll cure type 1

Question 70

fun fact there are 69 cards in this deck

Answer 70

jesus christ take a fucking break this one has been long