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B > unit 6 > Flashcards

unit 6 Flashcards

1
Q

how are changes in the environment detected (stimuli)

A

detected by receptors
initiation of nerve impulses
then leads to a response
by effectors

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2
Q

what could effectors be

A

muscles
endocrine glands - secretes hormones

brings response to stimulus

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3
Q

endocrine system

A

involves release of hormones
secreted by endocrine glands
hormones travel to target cells
affecting their activity
the responses are slow + long lasting

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4
Q

what is the nervous system divided into

A
  • CNS (central)
  • PNS (peripheral)
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5
Q

what can PNS be further divided into

A
  • autonomic nervous system
    -voluntary nervous system

*know divisions of nervous system

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6
Q

3 main types of nerve cells

A
  1. sensory neurones
  2. motor neurones
  3. relay neurones
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7
Q

function of sensory neurones

A

have receptors which are stimulated by specific stimulus
impulse transmitted along this neurone to CNS

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8
Q

function of motor neurones

A

transmits impulses to appropriate effector (muscle/gland)

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9
Q

function of relay neurones

A

transmit impulses between sensory + motor neurones
found in CNS

also known as intermediate/ coordinator neurones

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10
Q

need to know structure of myelinated motor neurone

A

see on phone folder

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11
Q

function of cell body in motor neurone

A

contains nucleus + most cell organelles

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12
Q

function of axon

A

conducts nerve impulses
may be myelinated or unmyelinated

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13
Q

function of myelin sheath

A

consists of mainly lipid
surrounds axon
formed from schwann cells
provides electrical insulation

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14
Q

what are nodes of ranvier

A

gaps in myelin sheath along the axon
where impulse can occur

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15
Q

synaptic knobs

A

allow communication with other neurons/ effectors

transmits impulse to effector

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16
Q

what do dendrites do

A

connect w other neurones

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17
Q

what do schwann cells do

A

secrete myelin (phospholipid)
to form myelin sheath

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18
Q

what is a reflex

A

rapid, automatic response to a stimulus

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19
Q

what is a reflex arc

A

pathway taken by impulses during a reflex action

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20
Q

how are the neurones involved in simple reflex

A
  1. receptor detect the stimulus + transmit impulse along the sensory neurone to brain or spinal chord (CNS)
  2. sensory neurone synapses with a relay neurone , passing impulse to motor neurone
  3. impulses transmitted along motor neurone to effector e.g muscle (effector) removes hand from hot object (stimulus)
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21
Q

advantages / importance of reflex actions

A
  • automatic. rapid response which prevents damage to tissues ( doesn’t need to be learnt)
  • helps escape from predators
  • plays a role in homeostasis
22
Q

how do organisms increase their chances of survival

A

by responding to changes in ther environment

23
Q

what is a stimulus

A

detectable change in the external/ internal environment that produces a response in an organism

24
Q

2 responses that maintain mobile organisms in a favourable environment

A
  1. taxes
  2. kinesis
25
Q

describe what taxes is

A
  • directional response
  • direction of movement of organism is the same as the direction of the stimulus
  • organism moves towards environment (__) they’re used to/ cultured in
  • move in direction that would increase rate of survival
26
Q

what is positive taxes

A

organism moves towards directional stimulus

27
Q

what is negative taxes

A

organism moves away from direction stimulus

28
Q

positive phototaxis

A

movement of photosynthesising organisms
towards light
increase chance of survival as need light to produce organic compounds in photosynthesis

29
Q

negative phototaxis

A

move away from light
move away from light so not exposed to predators
also less likely to become dehydrated

30
Q

advantages of positive taxis

A

increase survival by:
- avoid competition
- positive phototaxis allows production of organic compounds with light
- more access to food

31
Q

advantages of negative taxis

A

increase survival by:
- not exposed to predators
- less likely to become dehydrated

32
Q

chemotaxis

A

movement towards/ away from high conc of particular substance

e.g enables bacteria to move towards a food source or away from toxic compounds

33
Q

describe what kinesis is

A

non directional movement
organism doesnt move towards/ away from stimulus

response related to intensity of the stimulus
and involves change in rate of movement + turning of organism

34
Q

example of kinesis

A

woodlice in dry environment :
move more rapidly but turn less
increasing chance of moving into more favourable environment

woodlice in humid environment:
rate of movement decreases but turning increases
this is so the animal can remain in this area

prefer humid environment to protect from predators + dehydration

35
Q

how can an organism in kinesis response remain in their favoured environment

A

rate of movement decreases
but turning increases
so animal remains in favoured environment

36
Q

how can an organism in kinesis response move towards its favoured environment / away from non favoured

A

move more rapidly
turning less often
to move to favoured environment

37
Q

what is a tropism

A

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

can maintain the shoots + roots of flowering plants in a favourable environment

38
Q

phototropism

A

growth of a plant in response to light

39
Q

positive phototropism

A

plant shoot grows towards light so their leaves can absorb light for photosynthesis

40
Q

plant roots tropisms

A
  • negative phototropism ( grow away from light)
  • positive gravitropism ( grow towards gravity) - increasing chance roots will grow into soil to absorb water + mineral ions
  • positive hydrotropism ( root grows towards water )
  • some roots grow towards or away from chemicals ( positive/ negative chemotropism)
41
Q

IAA

A

indoleacetic acid
is an auxin
plant growth factor
stimulates plant growth

42
Q

where is IAA produced

A

in growing regions of a plant (root and shoot tips)
then diffuses from these regions to other tissues

43
Q

how does IAA growth factor move to other parts of the plant

A

diffusion from growing region to other parts of plant

44
Q

even distribution of growth in shoot due to IAA

A

cells in shoot tip produce IAA that diffuses down shoot
IAA is evenly distributed
stimulating upward growth of the shoot
equal cell elongation on both sides

45
Q

effect of IAA on shoots if exposed to a unidirectional (one direction) light stimulus in terms

A

greater conc of IAA on shaded side of shoot (rather than illuminated side)
stimulating greater elongation of the cells on the shaded side
shaded side grows faster
causing shoot to bend towards light
due to unequal growth

46
Q

effect of IAA (growth factor) on roots

A

increased IAA conc inhibits cell growth
inhibiting cell elongation
grows slower
root bends away from light

47
Q

if the shoot tip is removed/covered when a light stimulus is present what will happen

A

shoot tip detects light stimulus so
shoot will not respond to directional light stimulus

48
Q

features of auxins

A
  • high conc of auxins inhibit growth in roots
  • stimulate growth of shoots by cell elongation
  • they move by diffusion or active transport
49
Q

what happens to growth of plant if opaque cap covers the shoot tip

A

growth response occurs in region behind the shoot tip

50
Q

what happens to growth if shoots are covered by fine black sand

A

region covered by sand is not involved in detecting the light stimulus

51
Q
A

B (7 decks)

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