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biology paper 2 > topic 6- homeostasis and response > Flashcards

topic 6- homeostasis and response Flashcards

1
Q

what is a stimulus

A

a detectible change in the environment

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2
Q

what is a tropism

A

plants response in growth to a stimuli

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3
Q

describe phototropism in shoots

A

1) shoot tip cells produce IAA causing cell elongation
2) if there is unilateral light IAA diffuses to shady side of plant
3) cells elongate on shady side allowing plant to bend towards light source

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4
Q

describe phototropism in roots

A

1) IAA diffuses to shaded side of root
2) this inhibits cell elongation on shady side so the root cells elongate more on the lighter side allowing the roots to bend away from light

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5
Q

why is negative phototropism beneficial for plant roots

A

-anchors plant into ground
-as roots grow deeper into soil they can access more water sources

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6
Q

describe gravitropism in shoots

A

1) IAA will diffuse from the upper side to the lower side of a shoot
2) if plant is vertical, cells elongate so plant grows upwards
3) if plant is horizontal, it will cause the shoot to bend upwards - negative

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7
Q

describe gravitropism in roots

A

1) IAA diffuses to lower side of roots
2) upper side elongates so plant roots anchor downwards

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8
Q

what is a reflex

A

a rapid, automatic response to protect you from danger

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9
Q

steps of reflex arc

A

stimulus - receptor - sensory neurone - intermediate neurone - motor neurone - effector - response

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10
Q

what is a taxes

A

organism will move it’s entire body towards a favourable stimulus / away from unfavourable stimulus (directional)

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11
Q

what is a kinesis

A

organism changes the speed of movement and the rate it changes direction (non-directional)

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12
Q

what are receptors

A

cells (often proteins) that detect a stimuli

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13
Q

what is Pacinian corpuscle receptors

A

detect a change in pressure on skin

surrounded by capsule, sensory neurone wrapped in many layers of plasma membrane with viscous gel inbetween which contain special channel proteins

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14
Q

steps of how Pacinian corpuscle works

A

1) pressure detected deforms the plasma membrane so the stretch mediated sodium channels widen
2) Na+ diffuses into sensory neurone
3) establishes generator potential

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15
Q

what do Rod cells do

A

process images in black and white
1) rhodopsin pigment must be broken down by light energy
2) can detect light at low intensities as many rod cells connect to one sensory neurone so high visual sensitivity as just enough neurotransmitters to overcome threshold
3) brain cannot distinguish between the seperate sources of light that stimulated it - low visual acuity

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16
Q

what do Cone cells do

A

produce images in colour, 3 different types for red green and blue that absorb different wavelengths of light
1) iodopsin pigment broken down by light energy but only at high intensities
2) only one cone cell connects to a sensory neurone - why you can’t see colour in the dark
3) brain can distinguish between different sources of light as cone cells send seperate impulses to brain - high visual acuity

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17
Q

where are rod and cone cells found

A

cone cells located near fovea as this is where light is focused
rod cells further away

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18
Q

what does myogenic mean

A

the cardiac muscle contracts of its own accord, but the rate of contraction is controlled by a wave of electrical activity

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19
Q

where is the SAN

A

right atrium wall (pacemaker)

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20
Q

where is the AVN

A

near the border of right and left ventricles

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21
Q

where is the Bundle of His

A

runs through the septum

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22
Q

where are the Purkyne fibres

A

walls of ventricles

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23
Q

steps for control of the heart

A

1) SAN releases a wave of depolarisation across the atria, causing it to contract, reaches AVN
2) AVN releases another wave of depolarisation when the first reaches it, a non conductive layer prevents wave of depolarisation travelling down to ventricles
3) Bundle of His conducts wave of depolarisation down the septum and Purkyne fibres
4) apex and walls of ventricles contract, causing a delay - advantage as gives time for atria to contract and release max blood to ventricles

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24
Q

what are the 2 types of nervous system involved in controlling the heart

A

medulla oblongata
sympathetic - increases heart rate
parasympathetic - decreases heart rate

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25
what stimuli change the heart rate
pH - detected by chemoreceptors in carotid artery blood pressure- detected by pressure receptors in carotid artery
26
response to change in blood pH by heart
pH of blood decreases when you respire due to carbonic acid - must be removed so enzymes don't denature increase heart rate, more impulses via sympathetic neurone to SAN so carbon dioxide can diffuse into the alveoli more rapidly
27
response to differs in blood pressure by heart
too high- cause damage to artery walls - more impulses via parasympathetic neurone to decrease heart rate too low - insufficient supply of oxygenated blood to cells
28
a woman takes moderate exercise. explain the steps that cause her heart rate to increase while she exercises
1) increased CO2 conc detected by chemoreceptors due to the change in pH 2) chemoreceptors send impulses to medulla oblongata via sensory neurone 3) medulla oblongata increases frequency of impulses along the sympathetic motor neurone to the sinoatrial node 4) sinoatrial node increases heart rate so there is increased blood flow around body to provide more O2 to respiring tissues
29
where are neurotransmitters made
cell body of neurone
30
what do dendrites do
carry action potentials to surrounding cells
31
what is the axon
conductive long fibre that carries nervous impulse across neurone
32
what are Shcwann cells
wrap around the axon to form the myelin sheath which is a lipid and therefore does not allow charged ions to pass through it, gaps in myelin sheath are nodes of Ranvier
33
what is resting potential of an axon
-70mv difference in electrical charge between the outside and inside of the neuron when an impulse isn't being conducted
34
how is resting potential established
sodium potassium pump- pumps 2K+ in and 3Na+ out in active transport using ATP this creates an electrochemical gradient causing K+ to diffuse out and Na+ to diffuse in membrane has more K+ leak channels so more permeable to K+ so more K+ diffuses out than Na+ in, making negative resting potential
35
what is an action potential
when the neurone's voltage increases beyond a set point from the resting potential, generating a nervous impulse
36
describe action potential
1) stimulus activates the voltage gated sodium ion channels to open 2) Na+ diffuse in depolarising membrane to +40 if threshold of -50mv is exceeded (all or nothing principle) 3) voltage gated Na+ channels close and K+ channels open 4) K+ diffuse out of membrane hyperpolarising it past its resting potential eg -75mv 5) sodium potassium pump restores RP
37
why do some stimuli not generate an action potential
all or Nothing principle - did not reach threshold of depolarisation as not enough Na+ diffused in if stimuli reaches threshold it will always peak at the same maximum voltage (+40mv) - bigger stimuli have increased frequency of action potentials
38
which action potential can move faster, myelinated or unmyelinated neurones
myelinated as action potential jumps from nodes of Ranvier
39
what is the importance of the All or Nothing principle
to make sure animals only respond to large enough stimuli in the environment and not every change
40
what is the refractory period
after an action potential is generated, there is a period of time where axon cannot be depolarised, because Na+ channels are recovering and cannot be opened
41
importance of refractory period
- ensures discrete impulses are produced (seperate) -ensures action potentials travel in one direction -limits number of action potentials
42
factors affecting speed of conductance of action potential
1) myelination and saltatory conduction - increases rate 2) axon diameter - wider = faster 3) temperature - until optimum, enzymes denature
43
what is saltatory conduction
action potential jumps from node to node, making it travel along the axon faster
44
how does diameter increase conductance of action potential
wider diameter increases speed of conductance as there is less leakage of ions
45
how does temp increase conductance of action potential
high temp increases as 1) ions diffuse faster 2) enzymes involved in respiration work faster, there is more ATP for active transport
46
what is a synapse
gaps between the end of an axon of one neurone and the dendrites of another neurone
47
steps of function of an excitatory (cholinergic) synapse
1) action potential arrives at pre synaptic knob, depolarising it 2) voltage gated Ca2+ channels open and they diffuse into pre synaptic knob, acting as an internal signal 3) synaptic vesicles migrate to presynaptic membrane and fuse with it 4) acetylcholine released by exocytosis and diffuse across synaptic cleft 5) protein (cholinergic) receptors on post synaptic membrane bind with acetylcholine, allowing Na+ channels to open and Na+ to diffuse into post synaptic knob 6) if depolarisation reaches threshold, action potential propagates
48
how can acetyl choline be reabsorbed in cholinergic synapse
enzyme (acetylcholine esterase) breaks down acetylcholine in synaptic cleft into choline and acetate which can be reabsorbed by pre synaptic neurone
49
what is summation
rapid build-up of neurotransmitters in the synapse to help generate an action potential
50
what is spatial summation
many different neurones collectively trigger a new action potential by combining the neurotransmitter they release to exceed threshold value
51
what is temporal summation
one neurone releases neurotransmitter repeatedly over a short period of time to add up to enough to exceed the threshold value
52
what happens in inhibitory synapse as opposed to excitatory
when neurotransmitters bind Cl- channels open and they diffuse into post synaptic knob and K+ ions move out, hyperpolarising membrane
53
similarity of synapses and neuromuscular junction
both are unidirectional
54
differences of synapse and neuromuscular junction
neuromuscular- excitatory synapse- both don't connect to another neurone - connect to muscle at the end point of action potential neurotransmitter binds to muscle fibres
55
how do 2 muscles work together
in antagonistic pairs in an incompressible skeleton, when one contracts the other relaxes
56
description of myofibrils
made up of fused cells that share nuclei and cytoplasm, known as sarcoplasm (muscle fibres), and there is a high number of mitochondria
57
what is a sarcomere
myofibrils formed from 2 different proteins, myosin and actin
58
describe bands in a sarcomere
A band - myosin and actin H zone - myosin I band - actin Z line - end of sacromere
59
how do the bands change when a muscle contracts
A band - stays same H zone - shorter I band - shorter Z lines - closer together
60
describe steps to the sliding filament theory
1) when AP reaches muscle it depolarises sarcolemma via T tubules 2) calcium ions released from sarcoplasmic reticulum to sarcoplasm 3) Ca2+ bind pulling the tropomyosin aside and exposing myosin binding sites on actin 4) while ATP is attached to the myosin head, it binds to myosin binding sites forming a cross bridge 5) creating tension, actin filament is pulled and slides over myosin in power stroke powered by the energy released from ATPase converting ATP -> ADP + Pi 6) ATP binds to myosin head and myosin head cocks back to original position
61
what does phosphocreatine do and the importance of it
providing phosphate to regenerate ATP from ADP, important because muscles require high conc of ATP to contract and aerobic respiration may not provide enough ATP to reach this demand
62
properties of slow twitch muscles (endurance activities e.g marathon)
dark red colour high myoglobin conc (o2 storage) high capillary density low force of contraction, shorter duration many mitochondria aerobic respiration make ATP from oxygen low reliance on PC low ease of fatigue
63
properties of fast twitch muscles (intense exercise e.g sprinting)
pale in colour low myoglobin conc low capillary density higher force of contraction, long duration not many mitochondria anaerobic respiration glucose used to make ATP high reliance on PC high ease of fatigue
64
what is homeostasis
process of regulating an organisms internal conditions in response to internal/external changes maintains body temp and blood pH
65
what is negative feedback
when any deviations from normal values are restored to their original level
66
insulin function
released when blood glucose levels are too high to decrease them
67
glucagon function
released when blood glucose levels are too low to increase them
68
adrenaline function
released by adrenal glands when your body anticipates danger resulting in more glucose being released to blood
69
how does insulin decrease blood glucose
-Beta cells in liver detect blood glucose is too high -insulin attaches to receptors on target cells -vesicles containing glucose channel proteins fuse with membrane, increasing its permeability to glucose so more absorbed into cell by facilitated diffusion -activates enzymes that catalyse glycogenesis
70
how does glucagon increase blood glucose
-attaches to receptors on Liver cells -activates adenylate cyclase which converts ATP into cyclic AMP , cAMP acts as second messenger and activates enzyme protein kinase -hydrolyses glycogen to glucose (glycogenolysis) -activates enzymes that convert glycerol and amino acids into glucose (gluconeogenesis)
71
what is glycogenesis
converts excess glucose to glycogen, occurs in liver
72
what is glycogenolysis
hydrolyses glycogen to glucose, occurs in liver
73
what is gluconeogenesis
creation of glucose from non carbohydrate stores in the liver eg amino acids/glycerol
74
what is type 1 diabetes
body unable to produce insulin starts in childhood could be a result of autoimmune disease where antibodies attack beta cells in liver treatment= insulin injections
75
what is type 2 diabetes
receptors on target cells lose their responsiveness to insulin develops in adults due to obesity/poor diet treatment= increasing exercise, regulating uptake of carbohydrates
76
what could give you hypertonic blood
too much sweating not drinking enough water lots of ions in diet eg salt
77
steps of ultrafiltration in kidneys
1) blood enters glomerulus from afferent arteriole 2) has high HP due to afferent arteriole being wider than efferent 3) pressure outweighs HP and OP in renal Bowmans capsule so small solutes and water are filtered out down a pressure gradient 4) pass through fenestra, basement membrane and podocytes 5) plasma proteins too large to pass through 6) glomerular filtrate goes through to proximal convoluted tubule
78
steps of selective reabsorption in kidneys
Na+ actively transported from epithelial cells into blood, setting up an Na+ conc gradient Na+ diffuses from PCT lumen into epithelial cells, carrying glucose with it in a cotransport protein sets up glucose conc gradient so glucose can be selectively reabsorbed into the blood by facilitated diffusion
79
how does the Loop of Henle concentrate urine
1) Na+ and Cl- actively transported out of AL which is impermeable to water 2) raises conc of Na+ and Cl- in tissue fluid (low WP) 3) water diffuses by osmosis out of the DL and then enters blood capillaries down WP gradient by osmosis 4) loss of water concentrates Na+ and Cl- in DL 5) Na+ and Cl- diffuse out of conc solution in DL, sets up an increasing salt conc deeper into the medulla 6) water moves out of the DCT and collecting duct by osmosis 7) collecting duct runs parallel to Loop of Henle so ion conc increases as you move down into medulla
80
why is their glucose in the urine of someone with untreated diabetes
high blood glucose not all glucose can be reabsorbed from proximal convoluted tubule as carrier proteins are saturated for facilitated diffusion
81
where is ADH released into blood
posterior pituitary gland
82
what happens if the blood water potential is too low to restore it
-detected by osmoreceptors in the hypothalamus -water leaves osmoreceptors by osmosis and they shrivel, causing hypothalamus to produce more ADH -ADH travels to posterior pituitary gland where it is released into blood -binds to receptors on collecting duct and activates phosphorylase enzyme -vesicles containing aquaporins fuse with membrane -increases water permeability/ urea permeability
83
where is ADH produced
hypothalamus

biology paper 2 (4 decks)

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