Topic 6: Organisms respond to changes in their internal and external environments Flashcards

Question

# ***3.6.1.2 Receptors*** What stimulus does a pacinian corpuscle respond to? How?

Answer 1

* Stimuli = pressure * Pressure **deforms** membrane, causing **stretched mediated Na+ ion channels** to open. * If influx of Na+ ions raises membrane to threshold potential, **generator potetial** is produced. * Action potential moves along the sensory neurone.

Answer 2

* Cone cells * Rod cells

Answer 3

**CONE** mainly in the central fovea where it can receive high light intensity. **ROD** evenly distrubted around the periphery **NOT** in fovea. **BLIND SPOT** No photoreceptors located here (no cone or rod cells). No light is detected here.

Answer 4

***CONE*** **pigment:** Iodopsin = red, green, blue **visual acuity / reason:** High = each cone cell synapses with 1 bipolar neurone = no retinal convergence. **colour sensitivity:** Tricolour = red, green, blue wavelengths are absorbed by different types of iodopsin. **density in fovea:** High **density out of fovea:** Low **light intensity:** High **light sensitivity:** less sensitive = not involved in night vision. ***ROD*** **pigment:** Rhodopson = black, white **visual acuity / reason:** low = many rod cells synapse with 1 bipolar neurone. **colour sensitivity:** Monochromatic = black, white, all wavelengths of light detected. **density in fovea:** Low **density out of fovea:** High **light intensity:** Low **light sensitivity:** Very sensitive = spatial summuation of subthreshold impulses.

Answer 5

* Contraction of heart is initiated **within the muscle itself** rather than by nerve impulses.

Answer 6

* Photoreceptor -> bipolar neurone -> ganglion cell of optic nerve -> brain.

Answer 7

1. Sinoatrial node (SAN): **within** the wall of the right atrium 2. Atriventricular node (AVN): near **lower end** of right atrium in the wall that seperates the 2 atria.

Answer 8

* acts as a pacemaker by transmitting waves of electrical activity along the walls of the atria at regular intervals.

Answer 9

* **SAN initates** waves of depolarisation (WOD). * **WOD** spreads across atria and atrial systole. * Layer of fibrous, non-conducting tissue **delays impulses** while ventricles fill and valves close. Creates a delay to ensure the **atria are empty** before the ventricles begin to contract. * AVN carries WOD down septum via Bundle of His, which branches into purkinje fibres along ventricles. * **Causes ventricles to contract** from apex upwards.

Answer 10

* a collection of **conducting tissue that transmits the electrical activity** to the apex (bottom) of the heart and around the ventricle walls **along fibres called the Purkyne fibres.**

Answer 11

* Waves of electrical activity cannot pass from the atria to the ventricles due to a collection of non-conducting tissue. * Delay is created to ensure atria is empty before ventricles contract. * **Electrical activity pass through the AVN to the bundle of His.**

Answer 12

**ROLE** * sensitive in changes in CO2 concentration. * If CO2 is high, heart rate increases. **LOCATION** * found in aortic body = wall of aorta * found in carotid body = wall of the carotid artery in the neck.

Answer 13

**ROLE** * sensitive to changes in blood pressure. * If blood pressure increases, heart rate decreases. **LOCATION** * found in walls of various arteries but mainly in carotid sinus (in wall of carotid artery.)

Answer 14

* System that controls involuntary actions of muscles and glands * Consists of: sympathetic and parasympathetic

Answer 15

**SYMPATHETIC:** * involved in flight or fight response = stimulates effectors to speed up activity. **PARASYMPATHETIC:** * involved in normal resting conditions = inhibits effectors to slow down activity.

Answer 16

**CHEMORECEPTORS** * detect changes in pH e.g. increase concentration in CO2 * Carotid and aortic body. **BARORECEPTORS** * detect changes in blood pressure. * Carotid body.

Answer 17

**BARORECEPTORS** * baroreceptors send **more impulses** from the **medulla oblongata** to the SAN via **parasympathetic nervous system** * **acetylcholine** is released (neurotransmitter) * heart rate slows down = blood pressure decreases.

Answer 18

**BARORECEPTORS** * baroreceptors send **more impulses** from **medulla oblongata** to SAN via **sympathetic nervous system** * **noradrenaline** is released (neurotransmitter) * Heart rate increases = blood pressure increases.

Answer 19

**CHEMORECEPTORS** * Chemoreceptors detect **pH decrease** and send **more impulses** from the **medulla oblongata** to the SAN via **sympathetic nervous system** * **Noradrenaline** is released * Heart rate rises and O2, rate of blood flow to lungs increases = CO2 level decrease.

Answer 20

**CHEMORECEPTORS** * chemoreceptor sends **more impulses** from the **medulla oblongata** to the SAN via a **parasympathetic nervous system** * **Acetylcholine** is released (neurotransmitter) * Heart rate slows down and O2 levels decrease = CO2 levels increase.

Answer 21

* when stimulated baro and chemoreceptors send a signal to a part of the brain called medulla oblongata. * Part of the medulla oblongata that modifies heart rate is **cardiovascular centre** **CARDIOVASCULAR CENTRE** has two regions: 1. Cardio-inhibitory centre 2. Cardio-acceleratory centre * Nerve impulses sent from theses centres via the autonomic nervous system to SAN.

Answer 22

* Cardiac output = stroke volume x heart rate CO = V x R

Answer 23

* term used to describe the volume of blood that is pumped by the heart (the left and right ventricle) per unit of time

Answer 24

* volume of blood pumped out of the left ventricle during one cardiac cycle. * cm3

Answer 25

* number of times a heart beats per minute This can also be described as the number of cardiac cycles per minute

Answer 26

**Step 1: Find the heart rate** 1 cardiac cycle (atrial systole, ventricular systole and diastole) takes 1 second To find the number of cardiac cycles completed in a minute, multiply by 60 60 x 1 = 60 bpm **Step 2: Insert relevant figures into the equation** Cardiac output = heart rate x stroke volume Cardiac output = 60 x 73 = 4,380 cm3 CO = 4.38 dm3 | 1dm3 = 1000cm3

Answer 27

1. **CELL BODY:** contains usual cell organelles (nucleus, mitrochondria) and large amounts of R.E.R Produces proteins and neurotransmitters. 2. **DENDRONS:** extension of cell body which divides into **dendrites**. Carry nerve impulses **towards** cell body. 3. **AXON:** single fibre carrying nerve impulses **away** from cell body. Can be myelinated. 4. **SCHWANN CELLS:** surround axon for **electrical** insulation & protection. Wrap around axon many times so layers of their membrane build up around it. 5. **MYELIN SHEATH:** made from myelin-rich membranes of schwann cells. 6. **NODES OF RANVIER:** short gaps between schwann cells that are next to each other when there is no myelin sheath.

Answer 28

1. electrical insulation. 2. phagocytosis. 3. nerve regeneration.

Answer 29

1. Sodium-potassium pumps move **Na+ ions out**of the axon = **electrochemical gradient is created** = more Na+ ions outside and the membrane is not permeable to Na+ ions. 2. Sodium-potassium pumps actively transports **K+ ions in** the axon. 3.**BUT** K+ ions **move out of the axon** via FD due to potassium ion channels being opened and Na+ ion channels are closed. 4. Outside of membrane is **positively charged** due to the **imbalance** of positive charged ions. 5. 3Na+ ions = pumped **out** of axon. 2K+ ions = pumped **in** axon. **PROCESS REQUIRES ATP - active transport.**

Answer 30

* Potential difference (voltage) across neurone membrane when not stimulated (usually -70mV) * Outside membrane = + charged. * Inside membrane = - charged.

Answer 31

* Any stimulus that causes the membrane to reach the **threshold potential (-55mV)** will generate an action potential. * **NO THRESHOLD (-55mV) REACHED = NO AP** * Small stimulus = less frequent AP * Bigger stimulus = more frequent AP.

Answer 32

1. Stimulus 2. Depolarisation 3. Repolarisation 4. Hyperpolarisation 5. Resting potential. | **S**illy **D**onkeys **R** **H**yper **R**arely

Answer 33

1. **STIMULUS:** * **neurone membrane is exicted** causing the **Na+ ion channels to open**. * The membrane is **more permeable to Na+**. * Na+ ions diffuse into neurone **down the electrochemical gradient**. * The membrane **inside** the neurone is **less negative**. 2. **DEPOLARISATION:** * Potential difference reaches **threshold (-55mV)** more Na+ ion channels will open allowing a rapid influx of Na+ ions in the neurone. * Significant influx of Na+ ions **reverses** P.D to **+40mV.** 3. **REPOLARISATION:** * P.D of +40mV causes **Na+ voltage gated channels to be closed** * **K+ voltage gated channels to be opened**. * membrane **more permeable** to K+ ions. * K+ ions diffuse **out** of neurone **down K+ ion concentration gradient.** * Membrane begin back to resting potential. 4. **HYPERPOLARISATION:** * K+ ion channels **too slow to close.** * **"overshoot"** - too many K+ ions diffuse out of neurone. * PD become **more negative** than the RP (-70mV) 5. **RESTING POTENTIAL:** * Ions channels **reset** * Na+-K+ pump **returns** membrane to RP. * membrane is maintained until **stimulation excites the membrane again.**

Answer 34

* No AP can be generated in hyperpolarisation section in the membrane. * ion channels are **recovering** -> can't be opened. * Ensures unidirectional impulses. * Ensures discrete impulses. * Limits frequency of impulses transmission.

Answer 35

1. **RESTING POTENTIAL** * concentration of **Na+ ions** is **higher outside** than inside the membrane. * concentration of **K+ ions is higher inside** that outside the membrane. * Axon membrane is **polarised** = overall conc. of + ions is **greater outside** making it positive. 2. **STIMULUS:** * causes sudden influx of Na+ ions hence a **reversal of charge** on axon membrane = **AP** = now **depolarised** 3. **LOCALISED ELECTRICAL CURRENT:** * established by influx of Na+ ions = Na+ voltage gated channels open along axon = influx of Na+ ions = depolarisation. * **Na+** voltage gated channels **close**, **K+** voltage gated channels **open**. * K+ ions leave axon along **ECG** 4. **DEPOLARISATION MOVES ALONG MEMBRANE:** * outward movement of K+ ions continue = membrane behind AP returns back to its **orginal charged state** = repolaristion. 5. **REPOLARISATION:** * allows Na+ ions to be actively transported out , returns to the axon to resting potential waiting for a stimuli.

Answer 36

* Fatty sheath of myelin around axon acts an **electrical insulator** = prevents AP from forming, * AP can only occur at the **node of ranvier** * Localised circuits arrise between adjacent nodes of ranvier = AP jump from node to node via saltortary conduction. * AP pass along **myelinated neurone faster** than along an unmyelinated neurone.

Answer 37

1. Myelination. 2. Saltatory conduction. 3. Axon diameter. 4. Temperature

Answer 38

**MYELINATED:** * myelin sheath = electrical insulator. * Depolarisation occurs at the nodes of ranvier **only** * impulses jump between the gaps in the myelin sheath (node to node) = **saltatory conduction.** } **more faster** than generation of AP at each point of axon.

Answer 39

* Saltatory conduction.

Answer 40

**BIG DIAMETER:** * AP are conducted quicker along axons. * Less resistance to flow of ions. * Depolarisation reaches other parts of neurone quicker.

Answer 41

**INCREASE IN TEMPERATURE:** * Increases the speed of conductance. * Ions diffuse faster only up to 40^c - denature above 40^c/ * affect rate of respiration.

Answer 42

1. Transmits information not impulses from one neurone to another by neurotransmitters. 2. Neurones sepearated by a gap called **synaptic cleft.** 3. Neurone that releases neurotransmitters (acetylcholine) = **presynaptic neurone** 4. Axon the neurone is swollen = **synaptic knob** = contains many mitrochondria and large amount of endoplasmic reticulum = required for the making of neurotransmitter (acetylcholine) . 5. **Synaptic vesicle:** where neurotransmitters (acetylcholine) are stored. 6. Once NT (acetylcholine) is released from vesicles diffuses across to the **postsynaptic neurone** = specific receptor proteins on its membrane to recieve it.

Answer 43

* contains many mitrochondria and large amounts of endoplasmic reticulum.

Answer 44

* contains specific receptor proteins / molecules on its membrane for the neurotransmitter.

Answer 45

only one end can produce neurotransmitter and so this end alone can create a new action potential in the neurone on the opposite side of the synapse. At the other end there is no neurotransmitter than can be released to pass across the synapse and so no new action potential can be set up.

Answer 46

1. AP arrives at the end of the neurone, **voltage-gated calcium ion channels open.** 2. Ca2+ ions diffuse into the synaptic knob causing vesicles to fuse with the **presynaptic membrane** 3. Vesicles release neurotransmitter called **acetylcholine** into synaptic cleft. 4. Binds to cholingeric receptors on **postsynaptic membrane** 5. Na+ ion channels open in postsynaptic neurone results in Na+ ion entering, may generate an AP. 6. **Acetylchloinesterase** (AChE) break down acetylcholine in synaptic cleft and products absorbed by **presynaptic neurone** to make more ACh.

Answer 47

* Synapses can only pass information in **one direction** from pre to post synaptic neurone. * Only presynaptic neurones contain vesicles of NT * Only postsynaptic neurones contain specific receptors (proteins) on its membrane.

Answer 48

* low frequency action potentials lead to the release of insufficient conc of NT to trigger a new action potential in the **postsynaptic neurone** * Temporal summation * Spatial summation.

Answer 49

* A number of **different presynaptic neurones** release enough NT to **exceed the threshold value** of the **postsynaptic** neurone together. * Together they trigger a new AP.

Answer 50

* A **single presynaptic neurone** releases NT many times over a short period of time. * If conc of NT **exceeds threshold value** of the **postsynaptic neurone**, AP is generated.

Answer 51

* prevents **overstimulation** of skeletal muscle cells. * Enables acetyl and choline to be **recycled**

Answer 52

* A synpase that makes it less likely that a new AP is generated on the **postsynaptic neurone**

Answer 53

1. **PRESYNAPTIC NEURONE:** releases NT that binds to chloride ion protein channels on the **postsynaptic neurone** 2. NT causes chloride ion protein channels to be **open** 3. Chloride ions move into the **postsynaptic neurone** via FD. 4. Binding of NT causes K+ protein channels to be opened. 5. K+ ions move out of the **postsynaptic neurone** into the **synapse** 6. Outside of postsynaptic neurone = more positive Inside of postsynaptic neurone = more negative. K+ ions moving out **at the same time** Cl- ions move in. 7. Membrane potential **increases** to -80mV from -65mV at resting potential. } **HYPERPOLARISATION** = makes it less likely new AP will be generated as a large influx of **Na+ ions** needed to **produce one**

Answer 54

* Synaptic cleft between the **presynaptic neurone** and the **skeletal muscle cell.**

Answer 55

1. AP arrives at the end of neurone, **voltage-gated Ca2+ ion channels** open. 2. Ca2+ ions diffuse into the synaptic knob = synaptic vesicles to fuse with presynaptic membrane. 3. Vesicles release NT (acetylcholine) into synaptic cleft which binds to **nicotinic cholinergic receptors** on postsynaptic membrane. 4. **ACh** = excitatory **always** triggers respone in muscle cells. 5. Large n.o of **Na+ ions** diffuse into effector whilst small amount of **K+** move into synaptic cleft. 6. **Acetylcholineestrase** stored in clefts, **breaks down** ACh, products absorbed by presynaptic neurone to make **more ACh**.

Answer 56

**POSTSYNTAPTIC CELL** **C** = another neurone **NMJ** = skeletal muscle cell **AChE location** **C** = synaptic cleft. **NMJ** = Postsynaptic membrane **ACTION POTENTIAL** **C** = new AP produced. **NMJ** = end of neural pathway. **RESPONSE** **C** = excitatory or inhibitory. **NMJ** = always excitatory. **NEURONS INVOLVED** **C** = motor, sensory, and relay **NMJ** = only motor.

Answer 57

* They depolarise the postsynaptic membrane, making it fire an AP if threshold is reached. * i.e. ACh = excitatory NT at cholinergic synapses in the CNS and at NMJ

Answer 58

* They hyperpolarise the postsynaptic membrane (makes the PD more negative), prevents it from firing an AP. * I.e. ACh = inhibitatory NT at cholinergic synpases in the heart.

Answer 59

1. Same shape. 2. Block receptors. 3. Inhibit enzyme. 4. Stimulation of NT. 5. Inhibit release of NT.

Answer 60

* Mimic their action at receptors = drugs are called **agonists** * more receptors are activated. * i.e. nicotine mimics ACh so binds to nicotinic cholinergic receptors in brain.

Answer 61

* Receptors can't be activated by the NT. * **Fewer receptors** are activated. * These drugs are called **antagonists** * i.e Curare blocks the effects of ACh by blocking nicotinic cholernigic receptors at NMJ, so muscle cells cannot be stimulated. = muscle paralysed.

Answer 62

* more NT left in the synaptic cleft left to bind to receptors hence are there for longer. * i.e. nerve gases stop ACh from being broken down in synaptic cleft = loss of muscle control.

Answer 63

* more receptors are activated. * i.e. amphetamines

Answer 64

* fewer receptors are activated. * i.e. alcohol.

Answer 65

1. **cardiac:** found **only** in the heart. Under involuntary (subconscious) control. * Contract rhymatically **without** fatigue. 2. **smooth muscle:** found in the walls of the **blood vessels and gut.** Under involuntary (subconscious) control. * slow contraction **without** fatigue. 3. **skeletal muscle:** attached to incomprehensible skeleton by tendons. * Under voluntary (conscious) control. * The quicker they contract the **faster they fatigue**

Answer 66

* pairs of muscles that act together to move bones around a joint. * pair pull in opposite directions : agonist contract muscle, antagonist relax muscle

Answer 67

* muscle cells fused together to form **bundles of parallel muslce fibres** (myofibrils) = share nuceli and cytoplasm (sacroplasm) * Within sacroplasm large concentration of mitrochondira and ER. * Arrangement ensures no point of weakness between cells. * Each bundle surrounded by **endomycium:** loose connective tissue with many capillaries.

Answer 68

* Each muscle fibre made up of myofibrils. * Myofibrils (site of contraction) made up of 2 proteins: * **Actin:** thinner and consists of two strands twisted around one another. * **Myosin:** thicker and consists of long rod-shaped tail with bulbous heads that project to side. * Myosin + Actin = **Sarcomere.** * **Sacroplasm:** shared nuclei and cytoplasm with lots of mitrochondria and ER. * **Sacrolemma:** fold inwards towards sacroplasm to form **T tubules.** Many myofibrils = muscle fibres = surrounded by a membrane called sacrolemma.

Answer 69

* **Z line**= boundary between sarcomeres. Z-Z line is one sacromere. * **I band** = contains **only actin.** Decreases during muscle contraction. The band is **light**. There is no overlap of actin and myosin. * **A band** = contains **actin and myosin** except in H-zone. Thick filament = myosin Thin filament = actin. * **H band** = **only contains myosin** (**no** overlap of actin and myosin) Decreases during contraction of muscle. * **M-line** = marks the middle of the myosin filaments.

Answer 70

* ATP is essential for muscle contraction.

Answer 71

* **I band** = light * **A band** = dark

Answer 72

* Sliding filament theory.

Answer 73

* **Action potential** reaches many NMJ causing voltage-gated Ca2+ channels to open. * **Ca2+** ions diffuse into **synaptic knob.** * **Ca2+** ions cause synaptic vesicles to **fuse with presynaptic membrane.** * Acetylcholine is released into the synaptic cleft. * Acetylcholine diffuses across the synaptic cleft and binds with the receptors on **Na+ protein channels** on muscle cell membrane. * Influx of Na+ = depolaristation.

Answer 74

* Action potential moves into T tubules and into the sarcoplasm. * Tubules are in contact with **ER of muscle** (sarcoplasmic reticulum) which actively transports Ca2+ ions from cytoplasm of muscle = low conc. of Ca2+ ions in muscles. * Ca2+ ion protein channels open in **sarcoplasmic reticulum** and Ca2+ ions diffuse into muscle of cytoplasm **down a conc. gradient.** * Ca2+ ions attach to protein and causes **tropomyosin** that were blocking the binding sites on actin filament to move and **uncover binding sites.** * Allows actin-myosin bridges to form.

Answer 75

1. Ca2+ ions enter & attaches with a protein. This causes the tropomyosin molecule that were blocking the binding sites on the actin filament to **uncover the binding sites.** 2. **ADP** attaches to myosin head and can bind to actin filament to form **actin-myosin bridges** 3. Myosin heads **change shape** = causes tension. Actin filament moves along and **ADP is released.** 4. **ATP** attaches to myosin head, changes shape of myosin = **detaches from actin.** 5. Ca2+ ions **activate** **ATPase** hydrolyses ATP -> ADP + Pi. This provides **energy** for myosin head to return to orignal position. 6. Myosin head reattaches to binding site further along actin filament and cycle is repeated.

Answer 76

* Active muscles require **high conc. of ATP** to fully contract. * In times when aerboic respiration cannot create enough ATP, muscles respire anaerobically i.e. sprinters need high amount of ATP rapidly and they don't need it for long, muscles respire anaerobically. * Chemical that assists anaerobic respiration is **phosphocreatine** = stored in muscles. Provides **phosphates** to **regenerate ATP** from ADP. * Phosphocreatine is "refilled" using inorganic phosphate from ATP when **muscle is relaxed.**

Answer 77

* If SFT is correct then there will be **more overlap of actin and myosin** in a **contracted muscle** * When muscle contracts: sacromere changes: 1. ***I band*** = more narrower. 2. ***H band*** = more narrower. 3. ***Z line*** = move close together / sacromere shortens. ***A band*** remains the **same width** = proves myosin filament do not shorten.

Answer 78

**SLOW-TWITCH FIBRES** **S:** 1. **large store of myoglobin** = high affinity for O2 than haemoglobin at lower partial pressures. 2. **Many mitrochondria** = aerobic respiration produces more ATP. 3. **Surrounded by many blood vessels** = high supply of O2 and glucose. 4. **Glycogen store** = many ends can be hydrolysed to release glucose for respiration. **L:** site of sustained contraction i.e. calf muscles. **GP:** 1. Contract / respire aerobically for longer durations due to rich blood supply to prevent build up of lactic acid. 2. Contract for slower durations 3. Large store of myoglobin = high affinity for O2 at lower partial pressures. 4. Adapted for endurance work like marathons.

Answer 79

**FAST-TWITCH FIBRES:** **S:** 1. Thicker and more myosin filaments. 2. Large store of **phosphocreatine** to help make ATP from ADP. 3. High concentration of enzymes involved in anaerobic respiration. 4. Extensive sarcoplasmic / endoplasmic reticulum for rapid uptake and release of Ca2+ ions. **L:** * Sites of short-term, rapid contractions = biceps. **GP:** 1. Contracts faster = provides short burst of powerful contraction. 2. High concentration of glycogen 3. Short period of time 4. Adapted to intense exercise.

Answer 80

* The maintainence of internal environment within restricted limits in an organisms.

Answer 81

* Cells of the body are in an environment that meets their requirements and allows them to function normally desptie **external changes**

Answer 82

1. **Enzymes that control biochemical reactions within cells and other proteins (i.e channel proteins) are sensitive to changes in pH and temperature.** Any changes to these factors reduces rate of reaction of enzymes or may denature them. 2. **Changes to water potential of blood and tissue fluids may cause cells to shrink and expand** water may leave or enter via osmosis. Both cases cells cannot operate normally. Maintentance of constant blood glucose concentration **essential** in ensuring constant water potential. Constant blood glucose concentration ensures **reliable source of glucose = respiration in cells.** 3. Organisms with ability to maintain constant internal environment are more **independent of changes in the external environment**. May have a wider geographical range = greater chance of finding food, shelter.

Answer 83

* Maintain **stable rate of enzyme-controlled reactions** and prevent damage to membranes. * **Temp. too low** = Enzymes & substrate molecules have **less kinetic energy.** * **Temp. too high** = enzymes **dentature**

Answer 84

* **Maintain stable rate of enzyme-controlled reactions** and optimum conditions for other proteins. * Acidic pH = H+ ions interact with H bonds and ionic bonds in tertiary structure of enzymes. Shape of active site changes so **no enzyme-substrate complexes are formed**

Answer 85

* Maintain constant blood water potential ; **prevents osmotic lysis** = occurs when a cell bursts due to osmotic imbalance that causes excess water to diffuse into the cell. * Maintains constant concentration of respirtatory substrates = organism maintain constant level of activity regardless of enviromental conditions.

Answer 86

* When any deviation from the normal values are restored to their original level (optimum level) and prevents any overshoot. * involves nervous system and hormones too.

Answer 87

* Occurs when a deviation from an optimum causes changes that result in even greater deviation from the normal one. * **EXAMPLE:** in the neurones a stimulus causes an influx of Na+ ions. Influx increases permeability of neurone membrane to Na+ ions, more ions will enter = further increase in permeability. **Small stimulus can bring a large and rapid response**

Answer 88

1. Blood glucose concentration increases beyond set limit due to ingestion of food and drink that **contains carbohydrates**, negative feedback will occur to bring the BGC back to the normal limit. (can be because of opposite way round)

Answer 89

* Provides more control, especially in cases of "overcorrection" = lead to deviation in opposite direction from the orignal one.

Answer 90

* Gives a greater degree of homeostatic control.

Answer 91

1. Amount of carbs digested from the diet. 2. Rate of glycogenolysis. 3. Rate of gluconeogenisis.

Answer 92

* The process of **excess glucose being converted to glycogen** when blood glucose is higher than normal. * Occurs mainly in liver.

Answer 93

* Hydrolysis of glycogen back into glucose in the liver. * Occurs when blood glucose levels are lower than normal.

Answer 94

* Process of creating glucose from **non-carbohydrate** stores in the liver. * Occurs if all glycogen has been hydrolysed into glucose and your body is still in need of glucose.

Answer 95

1. BGL have increased. 2. Detected by **beta cells** (endocrine cells) in the islets of Langerhans (in the pancreas). 3. Beta cells release **insulin** into bloodstream. 4. **Insulin decreases BGL** in following ways: * **attaches to the receptors on the surfaces on the target cells.** This changes the **tertiary structure** of channel proteins = **more glucose** being absorbed via FD. * More protein carriers incorporated into CSM so more glucose is absorbed from the blood and into cells. * Activates enzymes in **conversion of glucose to glycogen**. = **glycogenesis in the liver**

Answer 96

1. BGL have decreased. 2. Detected by **alpha cells** (endocrine cells) in Islets of Langerhans (in the pancreas). 3. Alpha cells secrete **glucagon** into bloodstream. 4. **Glucagon increases BGL** in the following ways: * Glucagon binds to the complementary **receptors** on the surfaces of the target cells (liver cells). * When glucagon binds it causes protein to be activated into **adenylate cyclase** and convert ATP to **Cyclic AMP** (cAMP) by removing 2 phosphate groups. * cAMP activates enzyme **protein kinase** that hydrolyses **glycogen into glucose** --> **GLYCOGENOLYSIS** * Activating enzymes involve the conversion of **glycerol and amino acids into glucose.** | Bullet points are the second messenger model.

Answer 97

* Glucagon.

Answer 98

* Cyclic AMP or cAMP.

Answer 99

* cAMP activates the enzyme = protein kinase to hydrolyse glycogen into glucose.

Answer 100

1. BGL have decreased. 2. Adrenal glands secrete **adrenaline**. 3. **Adrenaline increases the BGL** in the following ways: * Adrenaline attaches to the complementary **receptors** on the surfaces of the target cells. This causes a **protein (G protein) to be activated** and converts **ATP into cAMP**. * cAMP activates enzyme (protein kinase) that **hydrolyses** glycogen into glucose. (glycogenolysis) ## Footnote Also second messenger model as process results in the formation of cAMP, which acts as second messenger.

Answer 101

**CAUSE:** * body cannot produce insulin. * starts in childhood and could be due to autoimmune disease where **beta cells are attacked** of Islets of Langerhans. **TREATMENT:** * Insulin injections. * Insulin pump. } **HYPOGLYCAEMIA must be monitored.** * Eating regularly and controlling simple carbohydrate intake prevents sudden rise in glucose.

Answer 102

**CAUSE:** * Receptors on target cells **lose their responsiveness to insulin**. * Glucose stays inside the blood increasing the concentration. * develops later in life because of **obesity, poor diet, kidney failure, visual impairment.** **TREATMENT:** * Eating balanced diet = control intake of carbs. * Exercise regularly. * Glucose lowering medications can be taken if not under control. * Insulin injections may be taken if not enough insulin is produced.

Answer 103

* very low. * between 0.0mM - 0.8mM * anything **higher** indicates possible prescence of **diabetes**.

Answer 104

1. Take the stock of glucose solution and perform a serial dilution. 2. Carry out benedicts test on diluted solutions. (place in water bath for 5 minuites) 3. Use colorimeter to create calibration curve (absorbance reading on red-coloured light.) 4. Carry out benedicts test on all three urines. (place in water bath for 5 minuites.) 5. Use colorimeter and find an absorbance reading for each urine sample. 6. Check glucose concentration for each urine sample using the calibration curve. **REMEMBER** when placing the samples inside the cuvettes and then in the colorimeter to measure the absorbance to **place a cuvette filled with distilled water first** to reset colorimeter to 0. ## Footnote High concentration of glucose = less blue = less red light is absorbed. Low concentration of glucose = more blue = more red light is absorbed.

Answer 105

* control of blood water potential via homeostatic mechanisms.

Answer 106

**HYPERTONIC:** * Blood with too low water potential = too much water will leave cells and move into blood via osmosis. Cells will shrivel. Not enough water = cannot dissolve solutes in cells. **EXAMPLES:** * too much sweating = hot day * not drinking enough water. * Lots of ions in diets = lots of salts. **CORRECTIVE MECHANISM:** * **More water** is **reabsorbed** by osmosis into blood from tubules of the nephrons. * Urine is **more concentrated**. * Less water is lost in urine.

Answer 107

**HYPOTONIC:** * Blood with too high water potential. * Too much water will move from the blood into the cells by osmosis. Cells will burst. **EXAMPLES:** * Drinking too much water. * Not enough salt in diet. **CORRECTIVE MECHANISM:** * **Less water** is **reabsorbed** by osmosis into the blood from the tubules of the nephrons. * Urine is **more dilute** * more water is lost in urine.