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biology paper 2 > Section 6- Response To Environment > Flashcards

Section 6- Response To Environment Flashcards

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1
Q

What is a stimulus?

A

A detectable change in the environment

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2
Q

What are stimuli detected by?

A

Receptors

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3
Q

What is taxis?

A

Simple directional response
Organisms move their body towards favourable environment

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4
Q

What is kinesis?

A

A non directional response to stimuli
If it is in an unfavourable environment, the rate at which it changes increases

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5
Q

What is a tropism?

A

Growth of part of a plant in response to directional stimuli
Plant shoots grow towards light and away from gravity

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6
Q

What is photo tropism?

A

Response of the shoots to unilateral light

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7
Q

What is photo tropism?

A

Response of the shoots to unilateral light

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8
Q

What are the controls of tropisms by IAA?

A
  • the shoot produces IAA which is then transported down the shoot
  • IAA is transported evenly throughout the shoot
  • light causes IAA to move from the light side to the shaded side
  • greater conc of IAA to shaded side
  • IAA causes elongation on shaded side, causes root to grow towards the light
  • inhibits in roots
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9
Q

What is gravitropism?

A

Response of a horizontally growing root to gravity

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10
Q

What are the controls of gravitropism by IAA?

A
  • cells in the root produce IAA which is transported along the root
  • IAA is transported to all sides of the root
  • gravity influences the movement of IAA from the upper to lower side of the root
  • greater conc of IAA on lower side
  • IAA inhibits elongation of root, cells on the upper side have a greater elongation
  • root bends towards gravity
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11
Q

Role of IAA in growth:

A
  • transport of IAA is away from the tip of the shoots and roots
  • IAA increases ability to stretch in the cell walls
  • this is by the acid growth hypothesis, e.g the active transport of hydrogen from the cytoplasm into spaces of the cell wall causing it to elongate
  • a stimuli (light) causes uneven distribution leading to the response
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12
Q

What are the two divisions of the nervous system?

A

Central nervous system
Peripheral nervous system

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13
Q

What is apart of the central nervous system?

A

Brain and spinal cord

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14
Q

What is apart of the peripheral nervous system?

A

Pairs of nerves originating from brain or spinal cord

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15
Q

What is the peripheral nervous system divided into?

A

Sensory nervous system- carries nerve impulses from receptors towards CNS
Motor nervous system- carries nerve impulses away from CNS to effectors

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16
Q

What is the motor nervous system subdivided into?

A

Voluntary nervous system
Autonomic nervous system

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17
Q

What is the voluntary nervous system?

A

Carries nerve impulses to body muscles under voluntary control

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18
Q

What is autonomic nervous system?

A

Carries nerve impulses to glands, smooth muscle and cardiac muscle

19
Q

What is the spinal cord?

A

Column of nervous tissue that runs along the back, lies at the back for protection, emerging at intervals and pairs of nerves

20
Q

What is a reflex arc?

A

Where the response is rapid, short lived and involuntary

21
Q

What is the pathway of neurones?

A

Stimulus -> receptor -> sensory neurone-> coordinator -> intermediate neurone -> motor neurone -> effector -> response

22
Q

What is a pacinian corpuscle?

A

A sensory receptor which responds to changes in mechanical pressure

23
Q

What does a pacinian corpuscle produce?

A
  • a generator potential
24
Q

Where can a pacinian corpuscle be found?

A
  • on the fingers, feet, joints, tendons and ligaments
25
Q

What is the structure of a pacinian corpuscle?

A
  • the sensory neurone at the end of the pacinian corpuscle contains sodium ion channels, they are stretch mediated
26
Q

What is the function of a pacinian corpuscle?

A
  • at normal resting rate the Na+ channels are too narrow to allow Na+ to pass through
  • when pressure is applied it deforms and the membrane around the neurone becomes stretched
  • this widens the channel allowing Na+ to diffuse through
  • the Na+ depolarises the membrane which produces a generator potential
  • this creates an action potential that passes along the neurone
27
Q

What are the receptors in the eye?

A
  • light receptors
28
Q

Where are light receptors found?

A

The retina

29
Q

What are the two main types of light receptors?

A
  • rod cells
  • cone cells
30
Q

What are both their functions?

A

To act as transducers converting light energy into electrical energy of a nerve impulse

31
Q

What does the autonomic nervous system do?

A

Controls involuntary activities of internal muscles and glands

32
Q

What is the autonomic nervous system made of?

A

Sympathetic nervous system
Parasympathetic nervous system

33
Q

What is the sympathetic nervous system?

A

Stimulates effectors to speed up activity used in ‘fight or flight’
Helps to respond to stressful situations by heightening awareness

34
Q

What is the parasympathetic nervous system?

A

Inhibits effectors, slows down activity, conserves energy and controls under normal resting conditions

35
Q

How do you control heart rate?

A
  • muscle of the heart = cardiac muscle
  • contraction is initiated within itself, within the right atrium (SAN) wheee the stimulus for the contraction originates
36
Q

What is the control for the basic heart rate?

A

1) waves of electrical excitation spreads out from senatorial node across both atria causing them to contract
2) the atrioventricular septum prevents the wave crossing over to the ventricles, it enters the AVN
3) after a short delay, AVN conveys the waves over purkinje fibres which makes the bundle of His
4) the bundle of His conducts the wave through the atrioventricular septum to the base of the ventricles
5) the wave of electrical excitation is released from purkinje fibres causing the ventricles to contract

37
Q

How do you modify the heart rate?

A
  • changes in the heart rate are controlled in the brain by medulla oblongata
  • has a centre that increases heart rate via SAN
  • centres are stimulated by chemical or pressure changes
38
Q

What are chemoreceptors?

A

Found in the wall of the caretol arteries and aorta

39
Q

What do they do?

A
  • sensitive to changes in the pH that result from changes in CO2 conc
  • they detect lower pH and increase the frequency of nerve impulses to the acceleratory centre in the medulla oblongate (to increase the heart rate)
  • the centre increases the frequency of impulses via the sympathetic nerve to SAN, that increases the rate of production of electrical waves from SAN, increasing heart rate
  • increasing blood flow causes more CO2 to be removed by lungs
  • blood pH returns to normal, chemoreceptors reduce their frequency to the medulla which reduces the frequency to SAN
40
Q

What are pressure receptors?

A
  • found in walls of carotid arteries and aorta
41
Q

What do they do?

A
  • when blood pressure is higher than normal, pressure receptors transmit more nerve impulses to the centre in the medulla oblongata that decreases heart rate, this sends impulses in the parasympathetic nervous system to the SAN which decreases heart rate
  • when the blood pressure is lower than normal, pressure receptors transmit more nerve impulses to the medulla, this sends more SAN and increases heart rate
42
Q

What are the three types of neurone?

A

Sensory
Motor
Intermediate

43
Q

Where does the sensory neurone relay the message to?

A

Brain or spinal cord

biology paper 2 (4 decks)

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