Section 6

Question 1

What is taxis and give an example

Answer 1

Directional movement in response to a stimulus
The direction of the stimulus affects the response
Example -
Woodlice move away from a light source to favourable damp conditions

Question 2

What is kinesis and give an example?

Answer 2

Non- directional (random) movement in response to a stimulus
The intensity of the stimulus affects the response
Example -
In high humidity woodlice move slowly and turn less often so they stay where they are and in dry enviroments they more quicker and turn more often so they move into a new area

Question 3

What is a choice chamber?

Answer 3

Container with different compartments to create different envirmental conditions (maggot practical)

Question 4

What is a receptor and what do they do?

Answer 4

They detect stimuli and can be cells or proteins on membranes
Receptors are specific to one type of stimuli

Question 5

What is an effector and what do they do?

Answer 5

Cells that bring around a response to a stimuli to produce an effect
Can be muscles or glands

Question 6

What is the nervous system made up of?

Answer 6

Sensory neurones - transmit electrical impulses from receptors to the central nervous system (the brain and spinal cord)
Motor neurone - transmits electrical impulses from the CNS to the effectors
Relay neurone - trabsmit electrical impulses between these neurones

Question 7

Describe the term simple reflex

Answer 7

A rapid involentary response to a stimuli
The pathway goes through the spinal cord and not the conscious part of the brain

Question 8

What is a reflex arch?

Answer 8

The pathway of neurones linking receptors to effectors
Stimulus - receptor - sensory neurone - CNS (relay neurone in spinal cord) - motor neurone - effector - response

Question 9

What is tropism?

Answer 9

The response of a plant to a directional stimulus from a particular direction by regulating its growth

Question 10

What are auxins/ IAA?

Answer 10

Chemicals in the tip of plants which diffuse into plant cells and cause them to elongate - the cell wall becomes loose and stretchy so the cell can get longer
They stimulate growth in shoots but inhibit growth in roots

Question 11

What is the resting potential? (general)

Answer 11

When a receptor is in its resting state there is a difference in charge between the inside and outside of the cell - the inside is negatively charged relative to the outside - the membrane is polarised an is -70mv
This resting potential is created by ions pumps and channels

Question 12

What is the generator potential?

Answer 12

When a stimulus is detected the cell membrane is excited and becomes more permable allowing more ions to move in and out of the cell changing the potential difference.
This change is called the generator potential

Question 13

What is the action potential? (general)

Answer 13

If the generator potential is big enough it will trigger an action potential - an electrical impulse along a neurone
An action potential is only triggered if the generator potential reaches the threshold level
Action potentials are all one size so the strength of the stimulus is measured by the frequency of action potentials triggered in a time period

Question 14

What are pacinian corpuscles and how are they activated?

Answer 14

Mechanoreceptors - detect mechanical stimuli
Found in the skin
Contains the end of a sensory neurone wrapped in loads of layers of connective tissue called lamellae
When the pacinian corpuscle is stimulated (pressure) the lamallae and deformed and press on the sensory nerve ending
This causes the sensory neurone cell membrane to stretch deforming the stretch mediated sodium ion channels
These channels open and sodim ions diffuse into the cell creating a generator potential

Question 15

Describe the structure of the eye

Answer 15

Iris muscles - controlls how much light goes in
Lense - focuses the light
Retina - lines the inside of the eye and contains photoreceptor cells
Fovea - area of the retina where there are lots of receptors
Optic nerve - carries impulses from receptor to brain
Blind spot - where the optic never leaves the eye - no receptors

Question 16

How to photoreceptors work?

Answer 16

Light enters the eye, hits the photoreceptor and is absorbed by light snesitive optical pigments.
Light bleaches the pigments casuing a chemical change and altering the permability to sodium ions
A generator potential is created and if the threshold is reached a nerve impulse is sent along the bipolar neurone (connects photoreceptors to the optic nerve)

Question 17

What are the differences between rods and cones?

Answer 17

Rods
Found around the outside
Black and white
Very sensitive to light becuase many rods join to one bipolar neurone so many generator potentials combine to reach the threshold
Low visual acuity becuase many rods join to the same bipolar neurone so they brain doesn’t know which one the signal is coming from

Cones
Gathered in the middle
Colour
3 types (RBG)
Less sensitive becuase one cone connects to one bipolar neurone
High visual acuity becuase one cone is joined to one bipolar neurone so they brain knows exactly where the signal is coming from

Question 18

What is visual acuity?

Answer 18

The ability to tell apart points that are close together

Question 19

What is the difference between the central nervous system (CNS) and the peripheral nervous system (PNS)?

Answer 19

CNS - brain and spinal cord
PNS - the neurones that connect the CNS to the rest of the body

Question 20

What is the PNS made up of?

Answer 20

The somatic (controls conscious activities) and autonomic system (controls unconsicous activities)
The autonomic nervous system is split into sympathetic (fight or flight system) and parasympathetic (rest and digest system)

Question 21

What does myogenic mean?

Answer 21

the muscle can contract and relax with out signals from nerves

Question 22

Describe control of heat beat

Answer 22

Starts in the sinoatrial node (SAN) which is a small mass of tissue in the wall of the right atrium - it is like a pacemaker - it sets the rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls
This causes the right and left atria to contract at the same time. A band of non- conducting collagen tissue prevents the electrical activity from being passed directly from the atria to the ventricles. The waves are transfered from the SAN to the atrioventricular node (AVN)
The AVN passes the waves to the bundle of His. There is a slight delay before the AVN reacts to make sure the atria have emptied before the ventricles contract
The bundle of His is a group of muscle fibers which conduct waves between ventricles to the apex (bottom) of the heart
The bundle splits into finer muscle fibers in the right and left ventricle walls called the Purkyne tissue - this carries the aves into the muscular walls of the right and left ventricles causing them to contract at the same time from the bottom up

Silly Ants Have Pants
SAN AVN bundle of His Purkyne fibers

Question 23

Describe commonication between the heart and the brain

Answer 23

The SAN generates electrical impulses the cause cardic muscles to contract. The rate at which the SAN fires (heart rate) is controlled by the medulla.
There are pressure receptors called baroreceptors in the aorta and carotid atreries - stimulated by high and low blood pressure
There are chemical receptors called chemoreceptors in the aorta, carotid arteries and the medulla. They monitor oxygen levels in the blood and CO2 and pH
Electrical impulses sent from receptors are sent to the medulla along the sensory neurones and the medulla sends impulses to the SAN along sympathetic or parasympathetic neurones.

Question 24

How is high blood pressure controlled?

Answer 24

Baroreceptors detect high blood pressure and send impulses along sensory neurones to the medulla which sends impulses along parasympathetic neurones. These secrete acetylcholine which binds to receptors on the SAN causing heart rate to slow

Question 25

How is low blood pressure contolled?

Answer 25

Baroreceptors detect low blood pressure and send impulese along sensory neurones to the medulla which sends impulses along sympathetic neurones. These secret noradernaline which bind to receptors on the SAN increasing blood pressure

Question 26

How is high blood O2/ low CO2/ high pH controlled?

Answer 26

Chemoreceptors detect chemical changes in the blood and send impulses along sensory neurones to the medulla which sends impulses along parasympathetic neurones. These secrete acetylcholine which binds to receptors on the SAN causing heart rate to decrease to return oxygen, CO2 and pH back to normal

Question 27

How is low blood O2/ high CO2/ low pH controlled?

Answer 27

Chemoreceptors detect chemical changes in the blood and send impulses along the sensory neuonres to the medulla which sends impulses along sympathetic neurones these secrete noradrenaline which binds to receptors in the SAN causing heat rate to increase to return oxygen, CO2 and pH back to normal

Question 28

How is the resting potential made in terms of ions moving?

Answer 28

Sodium potassium pumps are use active transport to more 3 sodium ions out of the neurone and 2 potassium ions in - ATP needed Potassium ions channels allow facilitated diffusion of potassium ions out of the neruone down their conc gradient

Question 29

What happens in an action potential in terms of ions moving?

Answer 29

When a neurone is stimulated voltage gated sodium ion channels open and if the stimulus is big enough it will trigger a change in the potential difference causing the membrane to become depolarised (no longer polarised)

Question 30

Describe what a stimulus does to the neruone

Answer 30

excited the neurone cell membrane causing soidum ion channels to open The membrane becomes more permable to soidum so it diffuses into the neurone down its conc gradient making the inside of the neurone less negative

Question 31

Describe what depolarisation does to the neruone

Answer 31

if the potential difference reaches the threshold more sodium ion channels open so more diffuse into the neurone

Question 32

Describe what repolarisation does to the neruone

Answer 32

at a potential difference around +30 the sodium ion channels close and potassium ion channels open The membrane is more permable to potassium ions so they diffuse out of the neurone down their conc gradient Returning back to the resting potential

Question 33

Describe what a hyperpolarisation does to the neruone

Answer 33

potassium ion channels are too slow to close so there is a slight overshoot where too many potassium ions diffuse out of the neurone and the potential difference becomes more negative than the resting potential

Question 34

Describe what the resting potential does to the neruone

Answer 34

the ions channels are reset the sodium potassium pump returns the membrane to its resting potential

Question 35

What is the refractory period?

Answer 35

After an action potential the neurone cell membrane can't be excited again straigth away The ion channels are recovering and can't open This makes sure that the action potentials don't overlap

Question 36

What is the all or nothing principle?

Answer 36

When an action potential threshold is reached is will fire with the same change in volatge no matter how big the stimulus is If the threshold is not reached there won't be an action potential A bigger stimulus won't cause a bigger action potential but it will cause them to fire more frequently

Question 37

What affects the speed of conduction in a neurone?

Answer 37

Myelination, axon diameter and temp

Question 38

What is myelination?

Answer 38

The myelin sheath is a electrical insulator made of Schwann cells Between the are patched of bare membrane called the nodes of ranvier where sodium ion channels are concentrated

Question 39

How does myelination affect speed of conduction in a neuonre?

Answer 39

Saltatory conduction Depolarisation only happens at the nodes of ranvier where sodium ions can get through the membrane The neruones cytoplasm conducts enough electrical charge to depolarise the next node so the impulse jumps from node to node In a non myelinated neurone the impulse travels along the whole length of the axon membrane so the whole thing is depolarised which is slower

Question 40

What is the structure of a neurone?

Question 41

How does axon diameter affect speed of conduction in a neuonre?

Answer 41

Action potentials are conducted quicker along axons with bigger diameters becuase there is less resistance to the flow of ions than in the cytoplasm of a smaller axon With less resistance depolarisation reaches other parts of the neurone cell membrane quicker.

Question 42

How does temperature affect speed of conduction in a neuonre?

Answer 42

The speed of conduction increases as the temperature increases because ions diffuse quicker Only up to 40C as proteins begin to denature and speed deceases

Question 43

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

Answer 43

It causes neurotransmitters to be released into the synaptic cleft The diffuse arcoss to the postsynaptic membrane and bind to specific receptors and can trigger an action potential, cause a muscle contraction or cause a hormone to be secreted

Question 44

What is the neurotransmitter you need to know?

Answer 44

Acetylcholine which binds to cholinergic receptors across cholinergic synapses

Question 45

How is a nerve impulse transmitted across a cholinergic synapse?

Answer 45

An action potential arrives stimulates voltage gated calcium ions channels in the presynaptic neurone to open Calcium ions diffuse in (actively transported out afterwards) This causes vesicles to fuse with the presynaptic membrane and release a neurotransmitter called acetylcholine into the synaptic cleft by exocytosis It diffuses across the synaptic cleft and binds to specific cholinergic receptors on the post membrane causing sodium ion channels to open This causes depolarisation and an action potential is generated if the threshold is reached AC is broken down by acetylcholinesterase and the products are re absorbed by the presynaptic neurone and used to make more AC

Question 46

What is the difference between excitatory and inhibitory neurotransmitters?

Answer 46

Exitatory neurotransmitters depolarise the post synaptic membrane making it fire an action potential if the threshold is reached Inhibitory neurotransmitters hyperpolarise the post synaptic membrane preventing it from firing an action potential

Question 47

Describe spatial summation

Answer 47

Two or more presynaptic neurones release their neurotransmitters at the same time onto the same postsynaptic neurone adding together their effect

Question 48

Describe temporal summation

Answer 48

Two or more nerve impulses arrive qucikly after each other in the same presynaptic neurone making more neurotransmitter diffuse out

Question 49

What is a neuromuscular junction?

Answer 49

A specialised cholinergic synapse between a motor neurone and a muscle cell and use acetylcholine

Question 50

How is a neuromuscluar junction difference to a cholinergic synapse?

Answer 50

In a neuromuscluar junction... The postsynaptic membrane has lots of folds that form celfts which store AC The post synaptic membrane has more receptors than other synapses AC is always exitatory

Question 51

How can drugs affect synapses?

Answer 51

- They are the shape of neurotransmitters so they mimic their action at receptors - The block receptors so they can't be activated by neurotransmitters - They inhibit the enzyme that breaksdown neurotransmitters so they are there for longer and keep binding - They stimulate the release of neurotransmitter from the presynaptic neuonre so more receptors are activated - They inhibit the release of neurotransmitters so fewer receptors are activated

Question 52

Describe the types of muscles

Answer 52

Smooth - contracts without conscious control, found in the walls of internal organs Cardiac - contracts without conscious control but only found in the heart Skeletal - muscles used to move (biceps and triceps)

Question 53

What are antagonistic pairs of muscles?

Answer 53

Muscles that work together to move a bone one contracts and on relaxes

Question 54

Describe the structure of a skeletal muscle

Answer 54

Made up of large bundles of long cells called muscle fibers The cell membrane of the muscle fibers is called the sarcolemma The sarcolemma have folds inwards which are called T tubules which stick into the sarcoplasm and help spread electrical impulses throughout the sacroplasm The sacroplasmic reticulum are internal membrane in the sarcoplasm - it stores and releases calcium ions needed for muscle contraction Muslce fibers have lots of mitochondria to provide ATP Contain many nuceli Have myofibrils - cylindrical organelles made up of proteins

Question 55

What is the structure of myofibrils?

Answer 55

Myosin - thick filament Actin - thin filament Dark band (A) contains myosin and actin overlap Light band (I) contains actin only A myofibril is made up of short untis called sarcomeres The end of each sarcomere is marked with a Z line and the middle of the mysoin is the M line, around the M line is the H zone, the H zone only contains myosin

Question 56

What is the sliding filament theory?

Answer 56

Myosin and actin slide over each other making the sacromeres contract Z lines get closer A band stays the same I band and H zone get shorter

Question 57

What is the structure of actin and myosin filaments?

Answer 57

Myosin Globular heads that can move back and forth Each head has a binding site for actin and one for ATP Actin Have binding sites for myosin heads Tropomyosin is found in between actin filaments helping the myosin move past each other

Question 58

Describe actin and myosin in their resting state

Answer 58

The actin myosin binding site is blocked by tropomyosin so they can't slide past each other

Question 59

What happens in a muscle contraction?

Answer 59

An action potential depolarises the sacrolemma and it spreads down the T tubules to the sacroplasmic reticulum causing it to release calcium ions into the sacroplasm Calcium ions bind to a protein attached to topomyosin causing it to change shape and move out of the binding site it is blocking allowing the myosin to bind forming an actin myosin cross bridge. Calcium ions also activate ATP hydrolase which breaks down ATP to provide energy neneded for the muscle contraction. It causes the myosin head to bend pulling the actin along. Another ATP molecule provides energy to break the bridge so myosin detaches and returns to its origional position and re attaches futher along and the cycle repeates

Question 60

How does a muscle return to its resting state?

Answer 60

When the muscle stops being stimulated calcium ions leave their binding site and are actively transported back into the sacroplasmic reticulum Causing tropomyosin to move back so they block the binding site again

Question 61

How is ATP made from phosphate creatine?

Answer 61

Phosphorylating ADP from PCr PCr is stored insdie cells but runs out after a few seconds so is used during short bursts of exersize It is anaerobic and doesn't make lactic acid Some of the Cr is broken down into creatinine which is removed by the kidneys

Question 62

Desribe the difference between fast and slow twitch muscles

Answer 62

Slow Contract slowly and can work for a long time Energy is released slowly through aerobic respiraation Lots of mitochondria and blood vessles to supply the muscles with oxygen Lots of myoglobin - stores oxygen Fast Contract quickly so get tired qucikly Energy released quiclkly through anaerobic respiration using glycogen in fast twitch muscle fibers Have stores of PCr so energy can be generated quickly Few mitochondria and blood vessles and no myoblibin so can't store much oxygen

Question 63

What is homeostasis?

Answer 63

Maintaining a stable internal enviroment

Question 64

What is negative feedback?

Answer 64

When there is a change in the internal enviroment and mechanism responsed to oppose the change and return contidions back to normal

Question 65

What is positive feedback?

Answer 65

Effectors respond to further increase the level away from the normal level

Question 66

Where does inuslin and glucagon come from?

Answer 66

Insulin and glucagon are secretd by the iselts of langerhans which contain alpha and beta cells Beta cells secrete insulin into the blood and alpha cells secrete glucagon

Question 67

What is the effect of insulin?

Answer 67

Lowers glucose conc Binds to specific receptors on cell membranes on muscle cells and liver cells It increases permability to glucose by increasing the amount of channel proteins in the membrane Also activates enzymes that convert glucose into glycogen Cells can store glycogen in cytoplasm as an energy source Isulin increases rate of respiration

Question 68

What is glycogenesis?

Answer 68

Making glycogen from glucose

Question 69

What is the effect of glucagon?

Answer 69

Raises glucose conc Binds to specific receptors on cell membranes of the liver and activates enzymes that break down glycogen into glucose and enzymes that form glucose from a glycerol and amino acids Decreases the rate of respiration of glucose in cells

Question 70

What is glycogenolysis?

Answer 70

Breaking down glycogen into glucose

Question 71

What is gluconeogenesis?

Answer 71

Making glucose from non- carbohydrates (glycerol and amino acids)

Question 72

What does adernaline do?

Answer 72

Activates glycoenolysis Stops glycogenesis Activates glucagon secretion Increasing glucose conc

Question 73

What is the second messenger system?

Answer 73

A hormone binds to receptors on the outside of the cell membrane which activates an enzyme inside the cell which produces a chemical (the second messenger) This activates other enzymes to bring about a response

Question 74

What is the second messenger system in adrenaline and glucagon?

Answer 74

The hormone binds to their receptors and activates an enzymes called adenylate cyclase. This converts ATP into cAMP which is a second messenger cAMP activates an enzyme called protein kinase A

Question 75

What is type I diabetes?

Answer 75

The immune system attacks the beta cells in the islets of langerhans so they can't produce insulin Treated with insulin shots

Question 76

What is type II diabetes?

Answer 76

Beta cells don't produce enough insulin or the body cells don't respond properllly to insulin

Question 77

Describe ultrafiltration

Answer 77

Takes place in the bowmans capsule from the glomerulus. The high pressure in there forces liquid and small molecules out of the blood and into the bowmans capsule. Larger molecules like protiens and RBCs can't pass through so stay in the blood. The substances that enter the bowmans capsule is the glomerular filtrate which passes along the rest of the nephron and substances are re abrosbed.

Question 78

Describe the structure of the kindeys

Answer 78

Blood from the renal artery enters smaller arterioles amd they split into the glomerulus - a bundle of capillaires looped inside a bowl called the bowmans capsule. Afferent arteriole - takes blood into the glomerulus Effecert arteriole - takes blood away (narrower - causing high pressure) The then the proximal convoluted tubule, loop of henle, distal convoluted tubule, collecting duct and ureter

Question 79

What happens in the loop of henle?

Answer 79

Neat the top of the ascending limb Na+ is activley pumped out into the medulla. The acsending limb is impermable to water so the water stays inside creating a lower WP in the medulla. There is a lower WP in the medulla than the desending limb so water moves out of the DL (permable to water) into the medulla by osmosis. This makes the glomerula filtrate more concentrated. The water in the medulla is absrobed into the bloodstream. Near the bottom of the ascending limb Na+ diffuses out to the medulla further lowering the WP in the medulla Water moves out of the DCT by osmosis and is reabsrobed into blood

Question 80

How do osmoreceptors work?

Answer 80

Found in the hypothalamus When WP of blood decreases water will move out of the osmoreceptors (cells) by osmosis causing them to shrink. This sends a signal to the posterior pituatry gland which releases ADH.

Question 81

What does ADH do?

Answer 81

ADH binds to receptors on the membrane of the cells in the DCT and CD and aquaporins are inserted into the membrane allowing more water through

Question 82

What happens when blood water content is too low?

Answer 82

WP drops Detected by osmoreceptors in the hypothalamus Posterior pituatry gland releases more ADH More ADH makes DCT and CD more permable to water with aquaporins More water abrosrbed and less lost

Question 83

What happens when blood water content is too low?

Answer 83

WP rises Detected by osmoreceptors in the hypothalamus Posterior pituatry gland releases less ADH Less ADH makes DCT and CD less permable to water with aquaporins Less water abrosrbed and more lost