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Biology Y13 > Section 6:Response to stimuli > Flashcards

Section 6:Response to stimuli Flashcards

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1
Q

Define stimulus

A

A detectable change in the environment that leads to a response

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2
Q

What is the response pathway?

A

Stimulus~Receptor~Coordinator~Effector~
Response

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3
Q

How can a response lead to evolution and natural selection?

A

Response leads to evolution due to organisms that survive pass on their allels to the next generation
Therefore, there is always a selection pressure that favours organisms with more appropriate responses

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4
Q

What are animal and plants responses?

A
  • Animals=taxis and kinesis
  • Plants=Tropism
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5
Q

What are taxis and what is the difference between positive and negative?

A

Directional response to a stimulus
* Positive=movement towards a stimulus
* Negatuve=movement away from a stimulus

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6
Q

What is a kinesis and how does it work in different environments?

A

A non-directional response to a stimulus,organisms will either increase or decrease speed of movement and the rate in which it changes the direction
* Favourable environment=slower movement
* Unfavourable environment=faster movement,straight lines and turning sharply

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7
Q

What are tropisms?

A

A growth movement of a plant in response to a directional stimulus

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8
Q

What are comercial uses of auxins?

A

selective weed killer, flower initation and development

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9
Q

What is the main auxin in plants?

A

Indoleacetic acid (IAA)

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10
Q

Give examples of each animal and plant response

A
  • Taxes=moving away from the light
  • Kinesis=woodlice moving to stay in a favourable environment
  • Tropism=shoots grow towards light
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11
Q

What are the plants growth factors and what are their tropisms?

A
  • light~phototropism
  • gravity~geotropism
  • water~hydrotropism
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12
Q

Five points (concentration)

How does phototropism work in flowering plants with IAA?

A
  • IAA is initally transported evenly throughout all regions as it begins to move down the shoot
  • Light causes movement of IAA from the light side to the shaded side of the shoot
  • Greater concentration of IAA builds up on the shaded side of the shoot then the light side
  • IAA causes elongation of shoot cells, since there is a grater concentration on the shaded side, the cells elongate more
  • Shaded side elongates faster than the lgiht side, causing the shoot tip to bend towards the light
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13
Q

Where is IAA produced?

A

Shoot tips or Root tips

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14
Q

How does gravitropism work in flowering plants, involving IAA?

A
  • Cells in the tips produces IAA, which is then transported along the root
  • IAA is initially transported evenly throughout the plant
  • Gravity causes IAA to move from the upper side to the lower side
  • Greatr conc of IAA build up on lower side
  • IAA inhibits elongation of root cells of lower side
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15
Q

What are the types nervous system?

A

peripheral~sensory + motor~voluntary + autonomic
central~brain + spinal cord

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16
Q

What are nerves?

A

Collections of neurons that are joined together by connective tissues. They are responsible for transfering impulses from receptors to CNA and back to effectors

17
Q

What are the three types of neuron and where are they located?

A
  • Sensory neuron=located near receptor organs
  • Motor=located near effectors
  • Intermediate=most often in the brain and spinal cord
18
Q

What are the different types of neuron stimulated by and where do they transmit impulses to?

A
  • Sensory~receptor detecting a stimulus=coordinator-intermediate neuron(brain/spinal cord)
  • Intermediate~sensory neuron or another intermidiate neuron=motor neurone or another intermediate neuron
  • Motor~intermediate neuron=effector organ
19
Q

What is the detailed response pathway?

A

stimulus-receptor-sensory neuron-coordinator-intermediate neuron-motor neurone-effector-response

20
Q

What is reflex?

A

An automatic, rapid response to an adverse stimulus that protects the body tissues from injury

21
Q

What is the reflex arc important?

A
  • Prevents injury to the body
  • Make survival more likely :allows animal to find food or mates
  • Effective from birth
  • Fast (synapes aren’t included and they are the slowest link)
22
Q

Three points

What are the features of a receptor?

A
  • They are tansducers
  • They are specific
  • They respond to stimuli
23
Q

What are the two types of receptors?

A

Pacinian corpuscles and light recepotrs

24
Q

Six points

What happens when pressure is applied to pacinian corpuscles?

A
  1. Applying pressure open the sodium channels
  2. More sodium on the outside of the axon
  3. When channels are open Na enters by FD
  4. Influx of sodium by FD causes depolorisation
  5. This creates generator potential which creates an action potential causes depolorisation
  6. This nerve impulse is passed along to the CNS
25
Q

What is the function of the retina, fovea and blind spot?

A
  • Retina=contains light-sensitive (photo) receptors (rod and cone cells)
  • Fovea=part of the retina that is directly opposite the pupil and contains only one cells/is responsible for good visual acuity
  • Blind spot=where the optic nerve leaves the eye/ contains no light-sensitive receptors
26
Q

Give three differences between rod cells and cone cells

A
  • Rods= outer-segment rod shaped, poor visual acuity and are not sensitive to different wavelengths of light=does not distinguish colour
  • Cones=outer-segment cone shaped, good visual acuity and are sensitive to different wavelengths of light=does distinguish colour
27
Q

Define visual acuity and how is high visual acuity attained

A

Visual acuity is the amount of detail that can be seen
To get high visual acuity, we constantly move our eyes so the image focuses on the fovea

28
Q

Six points

How does a pacinian corpsucle work?

A
  1. Pressure on the skin changes the shape
  2. Deformes the membrane~strech mediated Na+ channels open
  3. Sodium ions diffuse in via FD
  4. This causes depolorisation of the membrane
  5. Generator potential occurs
  6. Action potential created (nerve impulse) which is passed along the neurone to the CNS
29
Q

What is the autonamic NS responsible for and what parts are included in it?

A

Autonamic NS controls involuntary activities of internal muscles and glands
* sympathetic NS and parasympathetic NS

30
Q

What does the sympathetic NS and parasympathetic NS?

A
  • Sympathetic=stimulates effectors and speeds up any activity~copes with stressful situations by hightening awarness
  • Parasympathetic=inhibits effectors and slows down activity~conserves energy and replenishes the body’s reserves/controls normal resting conditions
31
Q

What does the sinoatrial node (SAN) do?

A

Generates a wave of electrical activity which spreads around the heart, inital stimulus for contraction originates

32
Q

What is cardiac conduction?

A

The rate at which the heart conducts electrical impulses

33
Q

Six points

Describe the cardiac cycle sequence

SAN and AVN

A
  • SAN generates a wave of electrical activity~spreads out over the heart
  • Wave spreads from SAN to atria causing them to contract
  • This wave reaches AVN but is delayed~allow atria to contract and empty its contents into the ventricles
  • Wave sent down bundle of Hs directing the wave throught the interventricular septum of the heart
  • At the base bundle of Hs divides further into purkyne fibres
  • When the wave reaches these fibres the heart contracts from the bottom upwards
34
Q

How is heart rate changed through the SAN by the NS?

A
  • Centre in medulla oblongata speeds up heart rate=sympathetic nerves~increases frequency of nerve impulses to SAN via sympathetic nerves
    SAN initiates heart beat at an increased rate leading to increased heart rate
35
Q

Desrcibe the role and location of chemoreceptors

A

Located in the walls of the aorta carotid artery
Sensitive to changes in pH~may be a result of increased CO2 conc due to exercise

36
Q

How does exercise effect cardiac output?

A
  1. Increased musuclar activity=increased CO2 conc
  2. Blood pH is lowered
  3. Chemoreceptors send an impulse to the centre of the medulla oblongata that speeds up heart rate
  4. Centre sends impulses via sympathetic to the SAN
  5. Increase in frequency of electrical activity to SAN
  6. Increase in heart rate=increases blood flow=removes CO2 quicker
  7. Blood CO2 conc lowered=blood pH is normal
37
Q

What happens to the SAN when blood pressure is higher than normal?

A
  • Centre that slows down heart rate
  • Via parasympathetic nerve system
  • Descreases frequency SAN initiates heart rate
  • Decreases heart rate
  • Decreases blood pressure

Biology Y13 (6 decks)

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