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Biology-Corinna > 14.Response To Stimuli > Flashcards

14.Response To Stimuli Flashcards

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1
Q

What is phototropism

A

Directional movement to unilateral light, shoot tip bends towards light due to IAA moving moving to the shaded side of the shoot top, cells on shaded side elongate faster than those on light side, so top bends towards light

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2
Q

What is gravitrophism

A

Directional to gravity, root tip bends downwards due to IAA moving to lower side, IAA inhibits the cells elongation so those on top side elongate faster and so tip bends downwards

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3
Q

What is IAA

A

Auxin - hormone produced by frowning shoot and root tips

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4
Q

What were Darwin’s experiments

A

Normal plant shoot
Shoot tip removed
Lightproof cover on tip

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5
Q

What was boysens-jensons experiments

A

Thin impermeable mica inserted in sunny side of tip - tip bends same away and hormone can pass down to shaded side

Mica inserted on shaded side-tip doesn’t bend as movement of IAA prevented down shaded side

Tip removed and gelatin block placed between-gelatin allowed movement of chemicals to pass through it, bending must be due to chemical passing from tip

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6
Q

What was Paals experiment

A

Removed tip and placed to one side of shoot-shoots bend towards the side where no tip is present

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7
Q

What was Briggs experiment

A

Put shoot in darkness

Thin glass plate between two sides of shoot-amount or IAA is same on either side of plate as chemical can’t move across

Glass plate half way up shoot, not through tip-shoot bends towards light as chemical can move to shaded side

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8
Q

What is a stimulus

A

Detectable change in the internal or external environment of an organism that leads to a response in the organism

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9
Q

What are receptors

A

Specific to one type of stimulus

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10
Q

What’s an effector

A

What produced the response

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11
Q

What’s the sequence of nervous system

A 
Stimulus 
Receptor
Sensory
Coordinator
Motor
Effector
Response
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12
Q

What’s a taxis

A

Simple response whose direction is determined by the direction of stimulus as result motile organism response directly to environs changes by moving whole body either towards favourable stimulus or away from unfavourable one.

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13
Q

What’s a kineses

A

Form of response in which organism doesn’t move towards or away from stimulus, changes speed at which it moves and rate at which it changes direction
If organism crosses from favourable to unfavourable area it’s turning rate increases

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14
Q

What’s a tropism

A

Growth part of a plant in response to directional stimulus.
Shoot tips positive phototropism
Root tips positive gravitropism

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15
Q

What are the external stimulus plants respond to

A

Light - need for photosynthesis

Gravity - need to be firmly anchored

Water - to absorb for support, metabolic processes and photosynthesis

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16
Q

What’s an example of a plant growth factor

A

IAA - indolescetic acid

Type of auxin

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17
Q

What does IAA do to shoot tips

A

IAA moves to shaded side of shoot

Greater conc of IAA builds up on shaded side than light side

IAA causes elongation of shoot cells and as there’s greater concern on shaded side, shaded side cells elongate more

Shaded side of shoot elongates faster than light side causing it to bend towards light

18
Q

What does IAA do to root tips

A

Gravity influences IAA to build up on lower side of tip

Greater conc on lower side

IAA inhibits elongation of root cells

Greater conc on lower side, cells elongate less than those on top side of root

Causing root to bend downwards towards force of gravity

19
Q

What are the major divisions of the nervous system

A

Central nervous system - brain spinal chord

Peripheral nervous system - pairs of nerves originate from brain or spinal chord

20
Q

What is the peripheral nervous system split into

A

Sensory neurones-impulse from receptor to cns

Motor neurones-impulse away from cns to effectors

21
Q

What’s the further split of the motor neurone nervous systems

A

Voluntary- nerve impulse to body muscles and under conscious control

Autonomic-nerve impulses to glands,smooth muscle and cardiac muscle under unconscious control

22
Q

What’s the spinal chord made of

A

Column of nervous tissue run alongside back and lies inside vertebral column for protection

Emerging at intervals along spinal chord are pairs of nerves

23
Q

What’s the steps of a reflex arc

A 
Stimulus 
Receptor
Sensory neurone 
Coordinate/intermediate 
Motor 
Effector
Response
24
Q

What is a reflex arc

A

Rapid short lived response that’s localised and involuntary

25
Q

Whata the importance of reflex arcs

A
  • involuntary, don’t require decision making powers of brain-leaving it free to carry out more complex responses-brain not overloaded-some go to brain to be overridden if needed
  • protect body from harm- not learnt
  • fast- neurone pathway short and don’t have lots of synapses which slow transmission
  • absence of decisions means action rapid
26
Q

What does a pacinian corpuscle detect

A

Changes in mechanical pressure

27
Q

What does a pacinian corpuscle do

A

Response to mechanical pressure and produces a generator potential by acting’s as a transducer

28
Q

What is a generator potential

A

Receptors convert energy of stimulus into nervous impulse

29
Q

What’s the structure of pacinian corpuscle

A

Sensory Neurone that ends in layers of connective tissue that has viscous gel between

Sensory neurone ending has special type of sodium channels in its plasma membrane-stretch mediated sodium channels.

30
Q

How does the Pacinian corpuscle function

A
  • in resting state stretch mediated challenge too narrow to allow sodium ions to diffuse through, has resting potential
  • when pressure applied to pacinian corpuscle, it’s deformed and membrane and neurone becomes stretched
  • widens sodium channels and na+ diffuse into neurone
  • influx of sodium ions changes membrane potential and it becomes depolarised producing generator potential
  • generator potential creates action potential and that propagates along neurone
31
Q

What are the two types of receptors in a mammalian eye

A

Rod and cones

32
Q

Difference between cone cells and rod cells

A

Rod shaped / cone shaped
More / less
More at periphery / concentrated at fovea
Poor visual acuity / give visual acuity
Sensitive to low intensity / not sensitive to low intensity
One type / three types for different wavelength

33
Q

How does a rod cell act as a transducer

A

Conserve light energy into the electrical energy of a nerve impulse

Pigments in rod cell must be broken by light in order for this to happe

34
Q

What’s a cone cells job in the eye

A
  • Contain different pigment which requires higher intensity light to break it down and create generator potential
  • each cone cell specific range of wavelengths
  • each has own connection to bipolar cells so if two adjacent cone cells stimulated brain receives two impulses, two dots can be resolved
35
Q

What’s the distribution of rod n cone cells

A

Uneven

  • Light focused by lens on part part of retina opposite pupil-fovea
  • fovea receives highest internist, cone cells found at fovea
  • conc of cone cells diminish further away from fovea
  • at peripheries of retina only rod cells found
36
Q

What’s the importance of having different light receptors

A

Both respond to different stimuli

Mammals benefit form good all round vision day n night

37
Q

Why are the types of autonomic nervous systems

A

Sympathetic-stimulates effectors, speed up activity (heightens awareness - fight or flight)

Parasympathetic-inhibits effectors and slow down activity, controls under normal resting conditions, conserve energy

38
Q

How in heart rate controlled

A
  • wave of electrical excitation spread out from sinoatrial node across both atria-contract
  • layer of non/conductive tissue prevents wave crossing to ventricles
  • wave of excitation enters atrioventricular node
  • atrioventricular node after short delay conveys wave of excitation along bundle of his to purkyne tissue fibres
  • bundle of his conducts wave through atrioventricular septum to base of ventricles
  • wave of electrical excitation released and moved up from base, ventricles contract from bottom upwards simultaneously
39
Q

How is heart rate modified

A
  • Medulla oblongata
  • sympathetic nervous system which increases HR which is linked to sinoatrial node
  • parasympathetic nervous system which decreased heart rate which linked to sinoatrial node
40
Q

How do chemoreceptors control heart rate

A
  • found in wall or carotid arteries
  • when blood has higher conc of carbon dioxide, pH lowers
  • chemoreceptors detect this and increase frequency of impulse to medulla oblongata
  • increases frequency of impulses via sympathetic system to sinoatrial node, increasing procession of electrical waves and therefore increase HR
  • increases blood flow leads to more carbon dioxide being removed by lungs
  • pH roses to normal and chemoreceptors reduce their frequency of nerve impulses to medulla oblongata
  • therefore medulla oblongata reduces frequency of impulses to sinoatrial node and leads to recursion in HR
41
Q

How is heart rate controlled by pressure receptors

A

-when blood pressure higher, pressure receptions transmit more nervous impulses to centre in medulla oblongata that decreased HR, centre sends impulses via parasympathetic system to sinoatrial node which leads to decrease in rate of heart beat

42
Q

Why is the pigment in cone cells

A

iodopsin

Biology-Corinna (22 decks)

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