Internal and External Stimuli Detected and Response Flashcards

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1
Q

what are plant growth factors and where are they produced

A
  • chemicals that regulate plant growth response to directional stimuli
  • produced in plant growing regions (apical meristems)
  • diffuse from cell to cell/phloem mass transport
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2
Q

explain why shoots show positive phototropism

A
  1. Indoleacetic acid (IAA) diffuses to shaded side of shoot tip
  2. As IAA diffuses down shaded side, it causes active transport of H+ ions into cell wall
  3. Disruption to H-bonds between cellulose molecules and action of expansins make cell more permeable to water (acid growth hypothesis)
  4. cells on shaded side elongate faster due to higher turgor pressure
  5. shoot bends towards light
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3
Q

explain why roots show positive gravitropism

A
  1. gravity causes IAA to accumulate on lower side of the root
  2. IAA inhibits elongation of root cells
  3. cells on the upper side of the root elongate faster, so the root tip bends downwards
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4
Q

contrast mammalian hormones and plant growth factors on concentration

A

mammalian: response not always dependent on concentration
plant growth factor: response proportional to concentration

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5
Q

contrast mammalian hormones and plant growth factors on action

A

mammalian: bind to complementary proteins in/on target cells
plant growth factor: can affect all cells

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6
Q

contrast mammalian hormones and plant growth factors on synthesis

A

mammalian: specialised glands
plant growth factor: various tissues in growing regions

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7
Q

contrast mammalian hormones and plant growth factors on transport

A

mammalian: circulatory system
plant growth factor: diffusion or phloem translocation

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8
Q

contrast mammalian hormones and plant growth factors on speed

A

mammalian: faster-acting (homeostasis)
plant growth hormones: slower-acting (plant growth)

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9
Q

define taxis

A

directional movement in response to external stimuli

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10
Q

define kinesis

A

non-directional response to presence and intensity of external stimuli

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11
Q

advantage of taxis and kinesis

A

maintain mobile organism in optimum environment e.g. to prevent dessication

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12
Q

many organisms respond to temperature and humidity via kinesis rather than taxis. why?

A

less directional stimuli; often no clear gradient from one extreme to the other

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13
Q

how could a student recognise kinesis in an organisms movement

A
  1. organism crosses sharp division between favourable and unfavourable environment: turning increases (return to the original favourable environment)
  2. if organism moves considerable distance into unfavourable environment: turning slowly decreases; begins to move in long, straight lines; sharper turns (lead organisms to new environment)
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14
Q

outline what happens in a simple reflex arc

A

receptor detects stimulus
sensory neuron
relay neuron in CNS coordinates response
motor neuron
response by effector

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15
Q

give advantages of a simple reflex

A
  1. rapid response to potentially dangerous stimuli since only 3 neurons involved
  2. instinctive
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16
Q

suggest a suitable statistical test to determine whether a factor has a significant effect on the movement of an animal in a choice chamber

A

chi squared

17
Q

what features are common to all sensory receptors

A
  • act as energy transducers which establish a generator potential
  • respond to specific stimuli
18
Q

describe the basic structure of a Pacinian corpuscle

A
  • single nerve fibre surrounded by layers of connective tissue which are separated by viscous gel and contained by a capsule
  • stretch-mediated Na+ channels on plasma membrane
  • capillary runs along base layer of tissue
19
Q

what stimulus does a Pacinian corpuscle respond to? how?

A
  1. pressure deforms membrane, causing stretch-mediated Na+ ion channels to open
  2. if influx of Na+ raises membrane to threshold potential, a generator potential is produced
  3. action potential moves along sensory neuron
20
Q

name the 2 types of photoreceptor cell located in the retina

A
  1. cone cells
  2. rod cells
21
Q

where are rod cells located in the retina

A

evenly distributed around periphery but NOT central fovea

22
Q

where are cone cells located in retina

A

mainly central fovea no photoreceptors at blind spot

23
Q

compare and contrast rod and cone cells: pigment

A

rod: rhodopsin
cone: 3 types of iodopsin

24
Q

compare and contrast rod and cone cells: visual acuity

A

rod: low res - many rod cells synapse with 1 bipolar neuron
cone: high res - 1 cone cell synapse with 1 bipolar neuron = no retinal convergence

25
Q

compare and contrast rod and cone cells: colour sensitivity

A

rod: monochromatic - all wavelengths of light detected
cone: tricolour - red/blue/green wavelengths absorbed by different types of iodopsin

26
Q

compare and contrast rod and cone cells: light sensitivity

A

rod: V sensitive - spatial summation of subthreshold impulses
cone: less sensitive - not involved in night vision

27
Q

outline the pathway of light from a photoreceptor to the brain

A

photoreceptor
bipolar neuron
ganglion cell of optic nerve brain

28
Q

define myogenic

A

contraction of heart is initiated within the muscle itself rather than by nerve impulses

29
Q

state the name and location of the 2 nodes involved in heart contraction

A
  • Sinoatrial node (SAN) - within the wall of the right atrium
  • Atrioventricular node (AVN) - near lower end of right atrium in the wall that separates the 2 atria
30
Q

describe how heartbeats are initiated and coordinated

A
  1. SAN initiated wave of depolarisation (WOD)
  2. WOD spreads across both atria = atrial systole
  3. layer of fibrous, non-conducting tissue delays impulse while ventricles fill and valves close
  4. AVN conveys WOD down septum via Bundle of His, which branches into Purkinje fibres along ventricles
  5. causes ventricles to contract from apex upwards
31
Q

state the formula for cardiac output

A

cardiac output (CO) = stroke volume (V) x heart rate (R)

32
Q

state the formula for cardiac output

A

cardiac output (CO) = stroke volume (V) x heart rate (R)

33
Q

what is the autonomic nervous system

A
  • system that controls involuntary actions of glands and muscles
  • 2 subdivisions: sympathetic and parasympathetic
34
Q

what is the difference between the sympathetic and parasympathetic nervous system

A

sympathetic involved in ‘fight or flight’ response: stimulates effectors to speed up activity
parasympathetic involved in normal resting conditions: inhibits effectors to slow down activity

35
Q

name the receptors involved in changing heart rate and state their location

A
  • baroreceptors (detect changes in blood pressure): carotid body
  • chemoreceptors (detect changes in pH e.g. due to increase in CO2 concentration): carotid body and aortic body
36
Q

how does the body respond to an increase in blood pressure

A
  1. baroreceptors send more impulse to cardioinhibitory centre in the medulla oblongata
  2. more impulses to SAN down vagus nerve via parasympathetic nervous system
  3. stimulates release of acetylcholine, which decreases heart rate and strength of contraction
37
Q

how does the body respond to an increase in CO2 concentration

A
  1. chemoreceptors detect pH decrease and send more impulses to cardioacceleratory centre of medulla oblongata
  2. more impulses to SAN via sympathetic nervous system
  3. heart rate increases, so rate of blood flow to lungs increases = rate of gas exchange and ventilation rate increases