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AQA A Level biology > organism response > Flashcards

organism response Flashcards

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1
Q

survival and response is when…

A

organisms incr. their chance of survival by responding to changes in their environment

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2
Q

survival and response in flowering plants…

A

specific growth factors more from growing regions to other tissues, where they regulate growth in response to directional stimuli

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3
Q

tropism is…

A

directional growth response in plants

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4
Q

phototropism is…

A

shoots and roots grow in response to light, due to plant hormone called IAA
1. IAA diffuses to the shaded side of the shoot, promoting growth and cell elongation
2. cell elongation of the shaded side causes the shoot to bend towards the light source - positive phototropism
different for roots= IAA diffuses towards shaded side of the root inhibits growth and cell elongation, roots bend away from light- negative phototropism

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5
Q

geotropism is…

A

shoots and roots grow in response to gravity
1. IAA diffuses towards the bottom due to gravity, incr. in IAA conc. promotes growth and cell elongation so shoot bends and grows against gravity
2. negative geotropism- IAA inhibits growth, root bends + grows towards gravity for positive geotropism

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6
Q

mobile organisms have 3 types of responses…

A
  1. taxes
  2. kineses
  3. reflexes
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7
Q

taxes are…

A

directional response in movement due to stimuli, positive taxis= towards stimuli, negative taxis= away from stimuli, chemotaxis= chemical, phototaxis= light, geotaxis=gravity, rheotaxis= movement

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8
Q

kineses are…

A

non-directional response in movement, doesn’t move towards or away from stimulus

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9
Q

reflexes are…

A

extremely rapid responses that doesn’t require thought, creates a protective effect, process referred to as reflex arc

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10
Q

reflex arc is…

A

stimulus-receptor-coordinator-effector-response

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11
Q

receptors are…

A

chemical structures, mostly proteins, that respond to specific stimuli
stimulation of a receptor leads to the establishment of a generator potential which can cause a response

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12
Q

pacinian corpuscle is…

A

has layers of connective tissue with viscous gel, surrounded by capsule
occur deep in the skin in fingers and feet

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13
Q

process of current going through pacinian corpuscle…

A

stretch-mediated sodium ion channels
at resting state, channels are too narrow for sodium ions to diffuse, so resting potential maintained
potassium ion goes to sensory neuron and channel pumps out 3 Na+ to maintain potential
resting potential= difference in electrical charge inside and outside the neuron is at rest/not conducting and impulse
pressure from stimulus causes sodium channels to stretch, sodium ions being transported can now go through to the sensory neuron
establishes a generator potential

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14
Q

the human retina contains…

A

2 types of photoreceptors- rods and cones ( function as transduces- convert external energy of light to stimuli to code of nervous impulse)

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15
Q

rods can’t…

A

distinguish between different wavelengths of light, so images are processed in black and white
can detect very low light intensities as many rod cells are connected to a single sensory neuron
action potential threshold is low as many rod cells are connected to a singular bipolar cell (summation)
rhodopsin is the main pigment used
have low visual acuity= can’t distinguish between 2 separate sources of light

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16
Q

cones have…

A

3 types that have different types of iodopsin pigment (red, blue, green)
absorb different wavelengths of light
can only respond to high light intensity as only one come cell connects to a bipolar cell (no spatial summation)
can distinguish between separate sources of detected light- high visual acuity

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17
Q

control of heart rate: the heart is…

A

myogenic
rate as which heart muscles contract is controlled by waves of electrical activity

18
Q

the sinoatrial node is…

A

located ink the right atrium
releases “wave of depolarisation’ across the atria, so atria contracts
wave of depolarisation then reaches the atrioventricular node (AVN)

19
Q

the atrioventricular node releases…

A

another wave of depolarisation when the first from SAN reaches it
non-conductive layer between atria and ventricles prevents wave of depolarisation travelling down to the ventricles
bundle of HIS transmits wave down the septum to the Purkyne fibres on the ventricle walls
before ventricular contraction, there is delay whilst the AVN transmits second wave to allow time for the atria to pump blood into the ventricles
the apex then ventricle walls contract
cardiac muscles relax as cells are repolarised

20
Q

heart rate changes due to…

A

exercise, pressure, pH etc
medulla oblongata in the brain controls heart rate via the autonomic nervous system

21
Q

2 main centres in medulla oblongata that…

A
  1. incr. heart rate via sympathetic nervous system that is linked the SAN
  2. decr. heart rate via the parasympathetic nervous system
22
Q

Heat rate: increased pressure…

A

detected by pressure receptors in wall of aorta and carotid artery
impulses sent to medulla oblongata then back to SAN via parasympathetic nervous system
decrease in frequency of electrical signals, so heart rate decreases

23
Q

Heart rate: decreased pressure…

A

decreased by pressure receptors in wall of aorta and carotid artery
impulses sent to medulla oblongata and back to SAN via sympathetic nervous system
increase in frequency of electrical signals in the heart, so heart rate increases

24
Q

heart rate: decreased pH levels…

A

happens due to exercise, as a high respiration rate increases production of CO2 and lactic acid
detected by chemoreceptors in aorta and carotid artery
impulses sent to medulla oblongata and back to SAN via sympathetic nervous system
increased frequency of electrical signals in the heart, so heart rate increases
higher volume of blood is delivered to lunges to remove CO2.

25
Q

structure of myelinated neuron…

A

cell body= protein and neurotransmitter production
dendrites= carry action potential to surrounding cells
axon= carries nerve impulse along neuron
myelin sheath= doesn’t allow charged ions or the impulse to pass through

26
Q

resting potential is…

A

the difference in electrical charge between the outside and inside of the neuron when an impulse isn’t being conducted
resting potential is about -70mV because there are more Na+ and K+ ions outside the neuron

27
Q

how is resting potential maintained…

A

by sodium-potassium pump, involves active transport and therefore requires ATP

28
Q

action potential is…

A

chemical disturbance that is carried along the surface membrane of the axon
when an impulse is received from receptors, sodium ion channels open so Na+ ions enter the neuron, causing depolarisation, so charge becomes more positive

29
Q

what happens if depolarisation reaches threshold potential (-50mV)…

A

voltage gated sodium ion channels are activated, leading to an even higher influx, causing an action potential (+40mV)
voltage gated Na+ channels close, whilst voltage gated K+ channels open so depolarisation occurs as K+ ions leave the neuron
causes hyperpolarisation, so the voltage gated K+ ion channels close
sodium potassium pump returns neuron back to its resting potential

30
Q

action potentials are an all or nothing response…

A

Once the threshold potential is reached, each action potential depolarises the con to the same voltage by voltage gated sodium ion channels

31
Q

refractory period is…

A

period in an action potential when the axon can’t be depolarised to imitate another action potential
important because= limits frequency of action potential, ensures action potentials only travel in one direction and are discrete
overshoot= voltage drops below -70mV, so ensures signal only goes one way, allow it to return to normal

32
Q

transmission of AP in myelinated and non-myelinated neurons…

A

non-myelinated= transmission acts like a ‘Mexican wave’ because when depolarisation occurs, voltage gated sodium channels open further down the axon, by the time depolarisation has spread, part of the neuron has already repolarised (Salvatore period)
myelinated= action potentials only occur at the Nodes of Ranvier, so action potentials ‘jump’ from node to node, which is quicker and is called saltatory conduction

33
Q

factors affecting speed of conduction…

A

myelination= increase speed
axon diameter= wider the axon, faster the impulse
temperature= higher temps increase speed of impulse

34
Q

structure of a synapse…

A

axon terminal- synaptic gap- receptor

35
Q

structure of neuromuscular junction…

A

connect to a muscle instead of a post-synaptic neuron
place where 2 neurons functionally meet

36
Q

transmission of cholinergic synapse…

A
  1. action potential arrives at the synaptic knob, depolarising it so voltage-gated calcium channels open and calcium ions diffuse into the synaptic knob
  2. vesicles containing acetylcholine fuse with the pre synaptic membrane
  3. acetylcholine is released into the synaptic cleft by exocytosis
  4. acetylcholine diffuses across the synaptic cleft to the post-synaptic membrane, and binds to cholinergic receptors
  5. Na+ channels on the post-synaptic membrane open and Na+ diffuse into the post-synaptic neuron, causing depolarisation
  6. if the threshold is reached, action potential is formed
  7. acetylcholine removed from synaptic cleft + degraded by acetylcholine esterase to prevent a continuous impulse
  8. products are transferred into presynaptic neuron and Na+ channels close, allowing post-synaptic neuron to reach resting potential
37
Q

cholinergic synapses can be inhibitory…

A

chloride ions move into the post-synaptic neuron and potassium ions move out
membrane potential reaches -80mV, causing hyperpolarisation, so an action potential would be very unlikely

38
Q

summation is…

A

rapid build up of neurotransmitters to help generate an action potential
temporal summation= 1 neuron releases neurotransmitters repeatedly over a short time period do the threshold value is exceeded
spatial summation= many neurons collectively stimulate an action potential by combining the neurotransmitters they release to exceed the threshold value

39
Q

how are the neuromuscular junctions different…

A

unidirectional as neurotransmitter receptors are only on the post-synaptic membrane
only excitatory
connects motor neurons and muscles
end point of the action potential
acetylcholine binds to receptors on muscle fibre membranes

40
Q

drugs can mimic or inhibit neurotransmitters…

A

mimic shape and action of neurotransmitter, so binds to post-synaptic receptors and causes action potentials (agonist)
bind to receptor but to block it, so preventing action potentials. (antagonist)
bind to acetylcholine esterase, so fewer t-s complexes formed with acetylcholine, causing a continuous impulse
can cause the release or blocks release of neurotransmitters

AQA A Level biology (8 decks)

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