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AQA Biology A-level > Responding to change > Flashcards

Responding to change Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

stimulus

A

detectable change in internal or external environment of an organism that produces a response in the organism.

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2
Q

sense organs

A

made up of groups of receptor cells.

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3
Q

receptor

A

detects a specific stimulus

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4
Q

effectors

A

Carry out the response.

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5
Q

endocrine system

A

chemicals (hormones) carried in blood stream, slower, less specific communications, responses long-lasting and widespread.

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6
Q

nervous

A

involves neurones that link the receptor and effector to central coordinator of some type. Rapid communication, responses short lived and restricted to a localised region.

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7
Q

sequence of events from stimulus to response

A

stimulus -> receptor -> coordinator -> effector -> response

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8
Q

how does the ability to respond to stimuli increase an organisms chance of survival?

A
  • detect and move away from harmful stimuli, e.g. predators
  • detect and move towards stimuli e.g. food
  • organisms that survive have greater chance of reproducing, raising offspring and passing alleles onto next generation.
  • selection pressure favours organisms with more appropriate responses.
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9
Q

simple response

A

direction is determined by the direction of the stimulus.

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10
Q

a motile organism reponds directly to environmental changes by…

A

moving its body towards a favourable stimulus (positive taxis) or away from an unfavourable stimulus (negative).

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11
Q

phototaxis

A

light e.g. algae move towards light (positive phototaxis), earthworms move away from light (negative phototaxis)

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12
Q

chemotaxis

A

chemical - e.g. bacteria moving towards a region where glucose is highly concentrated.

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13
Q

kineses

A

a form of response in which the organism doesn’t move towards or away from a stimulus. Instead, it changes the speed at which it moves and the rate at which it changes direction.

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14
Q

tropism

A

growth movement of part of a plant in response to a directional stimulus.

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15
Q

phototropism (light)

A

plant shoots grow towards light, plant roots grow away from light

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16
Q

geotropism (gravity)

A

plants grow towards gravity (positive)

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17
Q

hydrotropism (water)

A

plant roots grow towards water (positive)

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18
Q

plants respond to:

A
  • light - shoots grow towards light, as light is needed for photosynthesis
  • gravity - plants need to be firmly anchored in the soil. Roots are sensitive to gravity and grow in direction of its pull.
  • water - most plants roots grow towards water in order to absorb it for use in photosynthesis and other metabolic processes.
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19
Q

reflex

A

involuntary response to stimulus

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20
Q

reflex arc

A

the pathway of neurones involved in a reflex.

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21
Q

the nervous system has 2 major divisions

A
  1. CNS made up of brain and spinal cord
  2. PNS made up of pairs of nerves that originate either from brain or spinal cord.
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22
Q

sensory neurones

A

carry nerve impulses from receptors towards CNS

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23
Q

motor neurones

A

carry nerve impulses away from CNS to effectors.

24
Q

the importance of reflex arcs

A
  • make survival more likely
  • involuntary - don’t require decision making powers of brain, leaving it free to carry out more complex responses.
  • protect body from harmful stimuli. effective from birth
  • fast - short neurone pathway with one or two synapses.
25
Q

Sensory reception

A

function of sense organs

26
Q

sensory perception

A

function of brain

27
Q

Pacinian corpuscle respond to changes in mechanical pressure. They are:

A
  • specific to a single type of stimulus
  • produces a generator potential by acting as a transducer - converts info provided by stimulus into nerve impulses. Receptors convert one form of energy into another. All receptors convert the energy of the stimulus into a nerve impulse known as the generator potential.
28
Q

structure and function of a pacinian corpuscle

A
  • respond to mechanical stimuli such as pressure
  • occur deep in skin, abundant on fingers, soles of feet, joints, ligaments and tendons - enable the organism to know which joints are changing direction.
29
Q

synoptic link

A

plasma membranes and protein channels; some carry a specific ion e.g. sodium channels only carry sodium ions.

30
Q

the pacinian corpuscle functions:

A
  1. in resting state the strath-mediated sodium channels are too narrow to allow sodium ions to pass along them. The neurone of the Pacinian corpuscle has a resting potential
  2. when pressure is applied the pacinian corpuscle changes shape, and the membrane of the neurone is stretched.
  3. the stretching widens the sodium channels and sodium ions diffuse into the neurone.
  4. the influx of sodium ions depolarises the membrane producing a generator potential.
  5. the generator potential turns into an action potential that passes along the neurone, and then via other neurones to the CNS.
31
Q

Rod cells

A
  • can’t distinguish different wavelengths of light = black and white
  • many rods are connected to single sensory neurone in optic nerve
  • used to detect light of low intensity.
  • retinal convergence - greater chance that threshold value will be exceeds than if only a single rod cell were connected to each bipolar cell - summation.
32
Q

cone cells

A
  • 3 different types, each responding to different wavelengths.
  • full colour
  • 6 million cone cells, with own bipolar cells connected to sensory neurone in optic nerve.
  • own connection to single bipolar cell - if 2 adjacent cone cells are stimulated, the brain receives 2 separate impulses - distinguish between 2 separate sources of light that stimulated the 2 cone cells.
33
Q

sympathetic nervous system

A

stimulates effectors and controls them. Helps with fight or flight

34
Q

parasympathetic nervous system

A

inhibits effectors and controls activities under normal conditions. Conserves and replenished body reserves.

35
Q

the heart is myogenic;

A

its contraction is initiated from within the muscle itself, rather than by nervous impulses from outside.

36
Q

Sinoatrial node (SAN) located in wall of right atrium -

A

where the initial stimulus for contraction originates. It has a basic rhythm of stimulation that determines the beat of the heart (pacemaker).

37
Q

sequence of events that controls the basic heart rate:

A
  1. wave of electrical excitation spreads out from the SAN across both atria, causing them to contract
  2. non-conductive tissue prevents the wave crossing to the ventricles
  3. wave of excitation enters a second group of cells called the atrioventricular node (AVN), which lied between the atria
  4. AVN conveys a wave of electrical excitation between ventricles along series of specialised muscle fibres which collectively make up bundle of His.
  5. bundle of His conducts wave through AV septum to base of ventricles, where bundle branches into smaller fibres called Purkyne tissue.
  6. wave of excitation is released fro Purkyne tissue, causing the ventricles to contract quickly at the same time, from the bottom of the heart upwards.
38
Q

changes to the hear rate are controlled by the

A

medulla oblongata

39
Q

medulla oblongata has 2 centres concerned with heart rate:

A
  • centre that increases heart rate, which is linked to sinoatrial node by sympathetic nervous system
  • centre that decreases heart rate, linked to sinoatrial node by parasympathetic nervous system.
40
Q

chemoreceptors are sensitive to

A

changes in the pH of the blood that result from changes in CO2 concentration.
CO2 forms an acids and therefore lowers pH.

41
Q

Process of chemoreceptors

A
  • when blood has higher than normal concentration of CO2, pH is lowered.
  • chemoreceptors in carotid arteries and aorta detect this and increase frequency of nervous impulses to centre in medulla oblongata that increases heart rate.
  • centre increases frequency of impulses via the sympathetic nervous system to SAN. This increases rate of production of waves by SAN and increases heart rate.
  • increased blood flow leads to more CO2 being removed by lungs and so CO2 concentration of blood returns to normal.
  • pH of blood rises to normal and chemoreceptors in wall of carotid parties and aorta reduce frequency of nerve impulses to medulla oblongata
  • medulla oblongata reduces frequency of impulses to SAN, which leads to reduction in heart rate.
42
Q

When blood pressure is higher than normal,

A

pressure receptors transmit more nervous impulses to the centre in the medulla oblongata that decreases heart rate. This centre sends impulses via parasympathetic nervous system to SAN of heart, which leads to decrease in rate at which heart beats.

43
Q

when blood pressure is lower than normal

A

pressure receptors transmit more nervous impulses to centre in medulla oblongata that increases heart rate. This centre sends impulses via sympathetic nervous system to SAN, which increases the rate at which the heart beats.

44
Q

the nervous system;

A
  • uses nerve cells to pass electrical impulse on
  • stimulate target cells by secreting neurotransmitters directly onto them
  • rapid communication between specific parts on an organism
  • responses are short-lived and restricted to localised region of body
45
Q

the endocrine system;

A
  • produces hormones that are transported in blood plasma to target cells
  • target cells have specific receptors on cell-surface membranes and change in conc of hormones stimulates them
  • slower, less specific form of communication
  • long-lasting and widespread
46
Q

nerve impulse

A

self-propagating wave of electrical activity that travels along the axon membrane.

47
Q

factors affecting speed at which an action potential travels:

A
  • myelin sheath -> electrical insulator, jump from node to node, increasing speed of conductance
  • diameter of axon -> greater diameter, faster speed
  • temperature -> affects rate of diffusion.
48
Q

refractory period

A

after an action potential has been created in any region of an axon, there is a period afterwards when inward movement of sodium ions is prevented because the sodium voltage-gated channels are closed.
During this time it is impossible for a further action potential to be generated.

49
Q

the refractory period serves 3 purposes:

A
  1. ensures that action potentials are propagated in one direction
  2. produces discrete impulses
  3. limits number of action potentials
50
Q

features of synapses

A
  • unidirectionality
  • summation
51
Q

unidirectionality

A

synapses can only pass information in 1 direction - from the presynaptic neurone to post synaptic neurone. Synapses act like valves.

52
Q

Summation

A

spatial - a number of different presynaptic neurones together release enough neurotransmitter to exceed the threshold value of the postsynaptic neurone. Together they trigger a new action potential
- Temporal - single presynaptic neurone releases the neurotransmitter many times over a short period. If the conc of neurotransmitter exceeds the threshold value of the postsynaptic neurone, then a new action potential is triggered.

53
Q

there are 3 types of muscle in the body:

A
  • cardiac muscle
  • smooth muscle
  • skeletal muscle
54
Q

myofibrils are made up of mainly 2 types of protein filament:

A
  • actin - thinner and consists of 2 strands twisted around each other
  • myosin - thicker and consists of long rod-shaped tails with bulbous heads that project to the side.
55
Q

tropomyosin

A

AQA Biology A-level (8 decks)

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