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AQA A-LEVEL BIOLOGY > 6. Response to Changes in the Environment > Flashcards

6. Response to Changes in the Environment Flashcards

1
Q

Taxis

A

directional response by simple mobile organisms, move towards favourable stimuli (positive taxis) or away from unfavourable stimuli (negative taxis)

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2
Q

Kinesis

A

non-directional response by simple mobile organisms, increased speed of movement and rate of turns in region of unfavourable stimuli to return to favourable stimuli

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3
Q

Stimulus

A

detectable change in the environment, detected by receptors

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4
Q

Tropism

A

response of plants to stimuli via growth, can be positive (growing towards stimulus) or negative (growing away from stimulus), controlled by specific growth factors (IAA)

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5
Q

IAA

A

type of auxin (plant hormone), controls cell elongation in shoots, inhibits growth of cells in roots, made in tips of shoots/roots, can diffuse to other cells

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6
Q

Phototropism in shoots

A

shoot tip produces IAA, diffuses to shaded side of shoot, IAA stimulates cell elongation so shoot moves towards light (positive phototropism)

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7
Q

Phototropism in roots

A

root tip produces IAA, diffuses to shaded side of root, IAA inhibits cell elongation so root moves away from light (negative phototropism)

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8
Q

Gravitropism in shoots

A

shoot tip produces IAA, diffuses to lower side of shoot, IAA stimulates cell elongation so plant grows upwards (negative gravitropism)

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9
Q

Gravitropism in roots

A

root tip produces IAA, diffuses to lower side of root, IAA inhibits cell elongation so root grows downwards, anchoring plant (positive gravitropism)

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10
Q

Receptors

A

respond to specific stimuli, stimulation of receptor leads to generator potential causing a response

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11
Q

Pacinian corpuscle

A

receptor that responds to pressure changes in the skin, sensory neurone wrapped with layers of tissue (lamellae)

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12
Q

Pacinian corpuscle activation

A

pressure causes lamellae to stretch and deform, stretch-mediated sodium ion channels open causing Na+ to diffuse into the neurone so generator potential established

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13
Q

Rod cells

A

concentrated at periphery of retina, contain rhodopsin pigment, allow monochromatic vision, more sensitive to light, lower visual acuity as several rods connected to one bipolar neurone (retinal convergence) so spatial summation to overcome threshold

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14
Q

Cone cells

A

concentrated on the fovea, contain idopsin pigments, allow trichromatic vision, less sensitive to light, higher visual acuity as one cone connects to one bipolar neurone so brain receives separate impulses

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15
Q

Myogenic

A

cardiac muscle can contract and relax without receiving signals from nerves

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16
Q

SAN

A

known as the pacemaker, located in right atrium, releases wave of depolarisation across the atria, causing muscles to contract

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17
Q

Non-conductive tissue

A

located between atria and ventricles, prevents wave of depolarisation travelling down to ventricles, causes slight delay so ventricles can fill before contracting

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18
Q

AVN

A

located near border of right atria with ventricle, detects first wave from SAN and releases second wave of depolarisation after short delay so ventricles can fill before contracting

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19
Q

Bundle of His

A

runs through septum, can conduct and pass wave of depolarisation down septum and perkyne fibres

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20
Q

Perkyne fibres

A

in walls of ventricles, spread wave of depolarisation from AVN across ventricles so musclular walls of ventricles contract bottom up

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21
Q

High blood pressure

A

baroreceptors (located in carotid artery and aorta) detect high blood pressure, impulse sent to medulla, more impulses sent to SAN via parasympathetic neurones releasing acetylcholine, slowing heart rate

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22
Q

Low blood pressure

A

baroreceptors detect low blood pressure, impulse sent to medulla, more impulses sent to SAN via sympathetic neurones releasing noradrenaline, increasing heart rate

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23
Q

High blood pH

A

chemoreceptors detect low CO2 concentration, impulse sent to medulla, more impulses sent to SAN via parasympathetic neurones releasing acetylcholine, slowing heart rate

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24
Q

Low blood pH

A

chemoreceptors detect high CO2 concentration, impulse sent to medulla, more impulses sent to SAN via sympathetic neurones releasing noradrenaline, increasing heart rate

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25
Q

Resting potential

A

difference between electrical charge inside (more -) and outside (more +) the axon when a neurone is not conducting an impulse

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26
Q

Resting potential maintenance

A

sodium potassium pump actively transports 3Na+ out and 2K+ into the axon, K+ channels open (membrane more permeable to K+) so K+ diffuses out down concentration gradient by facilitated diffusion, Na+ channels closed (membrane less permeable to Na+) so electrochemical gradient established

27
Q

Generator potential

A

stimulus causes Na+ channels open (membrane more permeable to Na+) so Na+ diffuse into neurone down electrochemical gradient, depolarising membrane

28
Q

Depolarisation

A

when threshold is reached an action potential is generated (all or nothing principle), voltage-gated Na+ channels open so Na+ diffuse into neurone down electrochemical gradient, potential difference becomes more positive

29
Q

Repolarisation

A

Na+ channels close (membrane less permeable to Na+), K+ channels open (membrane more permeable to K+) so K+ diffuse out neurone down concentration gradient, voltage decreases

30
Q

Hyperpolarisation

A

K+ channels slow to close so too many K+ diffuse out neurone, causing overshoot in voltage, action potential can’t be generated (refractory period), sodium-potassium pump returns neurone to resting potential

31
Q

Myelination

A

acts as electrical insulator preventing depolarisation, impulse jumps from Nodes of Ranvier (saltatory conduction) so depolarisation across whole length of axon not required, increasing speed of conductance

32
Q

Effect of axon diameter

A

larger axon diameter means less resistance and leakage of ions, increasing speed of conductance

33
Q

Effect of temperature

A

increasing temperature increases kinetic energy so increases rate of ion movement, increasing rate of conductance

34
Q

Synaptic transmission

A

action potential arrives at presynaptic knob, voltage-gated Ca2+ channels open so Ca2+ diffuses in, vesicles full of neurotransmitter (ACh) fuse with pre-synaptic membrane, releasing ACh which diffuses across synaptic cleft and binds to receptors on postsynaptic membrane, causing Na+ enter and depolarisation of postsynaptic membrane

35
Q

Acetylcholinesterase

A

breaks down ACh, products reabsorbed into presynaptic knob and recycled

36
Q

Spatial summation

A

neurotransmitters from multiple neurones combine to trigger action potential in postsynaptic neurone

37
Q

Temporal summation

A

neurotransmitters released from one neurone over a short period of time combine to trigger an action potential in postsynaptic membrane

38
Q

Neuromuscular junction

A

synapse between a motor neurone and muscle fibre, more receptors (nicotinic cholinergic receptors) on muscle fibre so always excitatory

39
Q

Antagonistic pairs

A

the contracting muscle is the agonist and relaxing muscle the antagonist

40
Q

Skeletal muscle

A

act in antagonistic pairs against an incompressible skeleton, responsible for voluntary movement, made of muscle fibres (large bundles of long cylindrical cells)

41
Q

Muscle fibre structure

A

sarcolemma membrane folding into the sarcoplasm helping spread electrical impulses, contain networks of scarcoplasmic reticulum, many mitochondria, many nuclei and myofibrils

42
Q

Myofibril ultrastructure

A

made of many short units called sarcomeres, contain bundles of actin (thin myofilaments) and myosin (thick myofilaments), I bands (light) contain actin only, A band (dark) contains myosin and some overlapping actin, H zone contains only myosin, M line marks middle of sarcomere, Z lines marks end of sarcomere

43
Q

Sliding filament theory

A

action potential arrives at muscle fibre, depolarising the sarcolemma, causing Ca2+ to diffuse from the sarcoplasmic reticulum into myofibrils, Ca2+ cause tropomyosin move out the actin-myosin binding site, exposing the binding sites on actin, myosin heads bind to the binding sites on actin, forming an actin-myosin cross bridge, hydrolysis of ATP causes myosin heads to bend, pulling the actin filament along and myosin head to detach, Ca2+ actively transported back into sarcoplasmic reticulum

44
Q

Generating ATP

A

aerobic respiration, anaerobic respiration or phosphocreatine

45
Q

Phosphocreatine

A

chemical stored in muscles, can rapidly regenerate ATP by providing a Pi group

46
Q

Slow twitch muscle fibres

A

contract slowly with low force, resistant to fatigue as respire aerobically, specialised for long periods of low intensity exercise, contain many mitochondria, capillaries and myoglobin

47
Q

Fast twitch muscle fibres

A

contract quickly with high force, fatigue quickly as respire anaerobically, specialised for short periods of high intensity exercise, contain few mitochondria, capillaries and myoglobin

48
Q

Homeostasis

A

maintenance of a stable internal environment via physiological control systems

49
Q

Negative feedback

A

restores systems to their original levels

50
Q

Positive feedback

A

increases levels to amplify the change

51
Q

High blood glucose concentration

A

receptors in the pancreas detect high blood glucose concentration, causing beta cells in the islets of Langerhans to secrete insulin, insulin binds to receptors on liver and muscle cells causing vesicles containing channel proteins to fuse with the membrane increasing it’s permeability to glucose so more glucose is absorbed by facilitated diffusion, activating glycogenesis and increasing rate of respiration

52
Q

Low blood glucose concentration

A

receptors in the pancreas detect low blood glucose concentration, causing alpha cells in the islets of Langerhans to secrete glucagon, glucagon binds to receptors on liver cells, activating glycogenolysis and gluconeogenesis and decreasing rate of respiration

53
Q

Adrenaline

A

secreted from the adrenal glands when blood glucose concentration is low, binds to receptors on liver cells, activating secretion of glucagon, glycogenolysis and gluconeogenesis

54
Q

Second messenger model

A

glucagon/adrenaline bind to specific receptors on liver cells, activating adenylate cyclase which converts ATP into cAMP (a second messenger), cAMP activates protein kinase, activating glycogenolysis

55
Q

Type I diabetes

A

immune system attacks beta cells in the islets of Langerhans so they can’t produce insulin, results in hyperglycaemia after eating carbohydrates, treat with insulin injections and control sugar intake

56
Q

Type II diabetes

A

receptors on liver and muscle cells no longer respond to insulin, results in hyperglycaemia after eating carbohydrates, treat with regular exercise and control sugar intake

57
Q

Investigating glucose concentration

A

make five serial dilutions of known glucose concentrations, heat with quantitative Benedict’s reagent, use a colorimeter to measure absorbance, plot calibration curve, measure absorbance if urine sample and read across the calibration curve

58
Q

Kidney structure

A

renal cortex and medulla containing millions of nephrons, connected to ureter, bladder and urethra

59
Q

Ultrafiltration

A

blood flows along the renal artery, afferent arteriole into the glomerulus, there is high hydrostatic pressure in the glomerulus (as the afferent arteriole is wider than the efferent) so water and small molecules are forced out into the Bowman’s capsule, large proteins stay in the blood as they can’t pass through pores in the capillary endothelium, basement membrane and podocytes

60
Q

Reabsorption of glucose

A

glomerular filtrate passes along the proximal convoluted tubule which is lined with microvilli providing a large surface area for facilitated diffusion and active transport of glucose

61
Q

Reabsorption of water

A

Na+ are actively transported out the ascending limb into the medulla, lowering water potential of medulla, water moves out the distal convoluted tubule and collecting duct by osmosis

62
Q

Osmoregulation

A

control of the water potential of blood

63
Q

Low blood water potential

A

osmoreceptors in the hypothalamus loose water by osmosis, stimulating the pituitary gland to secrete more ADH into the blood, more ADH binds to specific receptors on the collecting duct and DCT, making walls more permeable so more water is reabsorbed into the blood by osmosis, volume of urine decreases, concentration of urine increases

AQA A-LEVEL BIOLOGY (8 decks)

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