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Biology Paper 2 > Stimuli and Responses > Flashcards

Stimuli and Responses Flashcards

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1
Q

What is a stimulus?

A
  • A change in the internal or external environment
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2
Q

What are receptors?

A
  • A cell or proteins on cell membranes that detect a stimulus
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3
Q

What are effectors?

A
  • Muscles or glands that bring about a response to a stimulus
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4
Q

What are sensory neurones?

A
  • They transmit electrical impulses from receptors to the CNS (brain/ spinal cord)
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5
Q

What are relay neurones?

A
  • They transmit electrical impulses between sensory and motor neurones
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6
Q

What are motor neurones?

A
  • They transmit electrical impulses from the CNS to the effector
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7
Q

What 2 systems make up the nervous system?

A
  • CNS

- Peripheral nervous system

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8
Q

What is the peripheral nervous system?

A
  • Neurones that connect to the CNS and the rest of the body
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9
Q

What 2 systems make up the peripheral nervous system?

A
  • Somatic nervous system

- Autonomic nervous system

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10
Q

What is the somatic nervous system?

A
  • It controls the conscious activities
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11
Q

What is the autonomic nervous system?

A
  • Controls the unconscious activities
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12
Q

What 2 systems make up the autonomic nervous system?

A
  • Sympathetic nervous system

- Parasympathetic nervous system

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13
Q

What is the sympathetic nervous system?

A
  • It prepares the body for action

- Flight or Fight system

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14
Q

What is the parasympathetic nervous system?

A
  • Calms the body down

- Rest and digest system

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15
Q

What is a reflex?

A
  • When the body responds to a stimulus without making a conscious decision
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16
Q

What happens in a reflex action?

A
  • Information travels really fast from the receptors to the effectors
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17
Q

How are nervous responses localised, short lived and rapid?

A
  • Neurotransmitters are secreted directly onto target cells
  • Neurotransmitters are quickly removed once their job is done
  • Electrical impulses are really fast, to react quickly to stimuli
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18
Q

How do plants respond to stimuli?

A
  • Respond to light and grow towards it to maximise photosynthesis
  • Respond to gravity and grow their shoots and roots in the right direction
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19
Q

What is tropism?

A
  • Response of a plant to a directional stimulus
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20
Q

What is positive tropism?

A
  • Growth towards the stimulus
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21
Q

What is negative tropism?

A
  • Growth away form the stimulus
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22
Q

How do shoots respond to light and gravity?

A
  • Shoots are positively phototropic and negatively gravitropic
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23
Q

How do roots respond to light and gravity?

A
  • Roots are negatively phototropic and positively gravitropic
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24
Q

How does IAA work in phototropism?

A
  • IAA moves to the most shaded side of the shoot which elongates the cells so the shoot bends towards the light
  • IAA moves to the shaded side of the root so growth is inhibited, bending the root away from the light
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25
Q

How does IAA work in gravitropism?

A
  • IAA moves to the underside of the shoot which elongates the cells making the shoot grow upwards
  • IAA moves to the underside of roots where growth is inhibited so the root grows downwards
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26
Q

What does IAA stand for?

A
  • Indoleacetic acid
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27
Q

What is taxes?

A
  • When organisms move towards or away from a directional stimulus
28
Q

What is kineses?

A
  • When an organisms movement is affected by a non-directional stimulus
29
Q

How do receptor cells communicate information via the nervous system?

A
  • When the receptor is at resting rate, there is a difference in charge between the inside + outside. So there is voltage across the membrane
  • When a stimulus is detected, the cell membrane is excited + becomes more permeable. The change in PD is due to a generator potential
  • If the generator potential is big enough it will trigger an action potential, but only if it reaches the threshold
30
Q

What are pacinian corpuscles?

A
  • Pressure receptors
31
Q

What happens when a pacinian corpuscle is stimulated?

A
  • The lamallae become deformed and press on the sensory nerve ending
  • This causes the sensory neurone’s cell membrane to stretch which deforms the sodium ion channels. They open and sodium ions diffuse into the cell creating a generator potential
  • If the generator potential reaches the threshold, it triggers an action potential
32
Q

What is a mechanoreceptor?

A
  • A receptor that responds to changes in pressure
33
Q

Where are photoreceptors found?

A
  • They are found in the fovea of the retina
34
Q

How do photoreceptors convert light to electrical impulses?

A
  • Light enters the eye and hits the photoreceptors which is absorbed by the light-sensitive pigments
  • Light causes a chemical change and alters the membrane permeability to sodium ions
  • ## A generator potential is created and when the threshold is reached, a nerve impulse is sent along a bipolar neurone to the optic nerve
35
Q

Where are rods mainly found?

A
  • In the peripheral parts of the retina
36
Q

Where are cones found?

A
  • Packed in the fovea
37
Q

Why are rods sensitive to light?

A
  • There are many rods joined to one neurone , so many weak generator potentials combine to reach the threshold and trigger an action potential
38
Q

Why are cones less sensitive?

A
  • As one cone joins to one neurone, so more light is needed to reach the threshold and trigger an action potential
39
Q

Why do rods have a low visual acuity?

A
  • Due to the fact they have many rods joined to the same neurone, so 2 points close together can not be told apart
40
Q

Why do cones have high visual acuity?

A
  • Cones are close together and one cone joins to one neurone.
  • 2 action potentials are triggered and go to the brain so you are able to distinguish between 2 points
41
Q

Distribution of rod cells

A
  • Numerous

- Distributed evenly on the retina but not found on the fovea

42
Q

Distribution of cone cells

A
  • Less numerous than rod cells

- Distributed mainly at the fovea

43
Q

How is heart rate controlled?

A
  • Starts w/ SAN, found in right atrium. SAN sets the rhythm by sending out regular waves of electrical activity to atrial walls
  • Causes right & left atria to contract at the same time, however collagen tissue prevents waves of electrical from being passed directly from atria to ventricles, so passed onto the AVN
  • AVN responsible for passing waves of electrical activity to bundle of His, but there’s a delay before AVN reacts so that the atria empties before the ventricles contract
  • Bundle of His is responsible for conducting waves of electrical activity between ventricles to apex of the heart + is split into the Purkyne tissue
  • Purkyne tissue carries waves of electrical activity into muscular walls of right & left ventricles, causing them to contract simultaneously
44
Q

What controls the rate of the SAN?

A
  • Medulla oblongata of the brain
45
Q

What are baroreceptors stimulated by?

A
  • High and low blood pressure in the aorta and carotid arteries
46
Q

Where are baroreceptors found?

A
  • In the walls of various arteries especially carotid arteries
47
Q

What are chemoreceptors stimulated by?

A
  • By a change in oxygen level in the blood, carbon dioxide and pH in the aorta, carotid arteries and in the medulla
48
Q

Where are chemoreceptors found?

A
  • In the wall of the aorta

- In the wall of the carotid artery

49
Q

How does the heart respond to high blood pressure?

A
  • Baroreceptors detect high blood pressure, which send impulses to the medulla along the parasympathetic neurones.
  • These secrete ACh which bind to receptors on the SAN
  • This results in the heart rate slowing down
50
Q

How does the heart respond to low blood pressure?

A
  • Baroreceptors detect low blood pressure and send impulses to the medulla along the sympathetic neurones
  • These secrete noradenaline which binds to receptors on the SAN
  • This results in the heart rate speeding up
51
Q

How does the heart respond high blood oxygen, low carbon dioxide or high pH level?

A
  • Chemoreceptors detect the chemical change in the blood which sends impulses along the parasympathetic neurones
  • These secretes ACh which binds to receptors on the SAN
  • This results in heart rate decreasing
52
Q

How does the heart respond low blood oxygen, high carbon dioxide or low pH level?

A
  • Chemoreceptors detect the chemical change in the blood which sends impulses along the sympathetic neurones
  • These secrete noradrenaline which binds to receptors on the SAN
  • This results in the heart rate increasing
53
Q

What is a reflex?

A
  • A quick, automatic response to a stiumuli
54
Q

What do thermoreceptors detect?

A
  • Temperature
55
Q

What does rhodopsin detect and where is it found?

A
  • Light and dark

- Rod cells

56
Q

What does lodopsin detect and where is it found?

A
  • Colour

- Cone cells

57
Q

How is a generator potential created by a photoreceptor cell?

A
  • Light is absorbed by the pigments in rod and cone cells
  • This changes the permeability of the membrane so Na⁺ flood in and a generator potential is generated
  • If it reaches the threshold, a nerve impulses flows along the bipolar neurone
58
Q

What is SAN and where is found?

A
  • Sinoatrial node

- Wall of the right atrium

59
Q

What is the role of SAN?

A
  • Acts as a pacemaker by transmitting waves of electrical activity along the walls of the atria at regular intervals
60
Q

What is AVN?

A
  • Atrioventricular node
61
Q

What is the bundle of His?

A
  • A collection of tissue that transmits electrical to the apex of the heart around ventricle walls along the Purkyne fibres
62
Q

What is the medulla oblongata?

A
  • A region in the brain that modifies heart rate in the cardiovascular centre
63
Q

What 2 regions are found in the cardiovascular centre?

A
  • Cardio-inhibitory centre

- Cardio-acceleratory centre

64
Q

What happens when blood pressure is too high?

A
  • It is detected by baroreceptors
  • The nerve impulse travels from the medulla along the parasympathetic neurones to the SAN
  • This releases ACh
  • Heart rate slows down, blood pressure decreases
65
Q

What happens when blood pressure is too low?

A
  • It is detected by baroreceptors
  • Nerve impulse travels from the medulla down the sympathetic neurone to the SAN
  • This releases noradrenaline
  • Heart rate slows rises, blood pressure increases
66
Q

What happens if there is low CO₂/ high O₂

A
  • It is detected by chemoreceptors
  • Nerve impulse travels from the medulla along parasympathetic neurones to the SAN
  • ACh is released
  • Heart rate slows down, CO₂ increases/ O₂ decreases
67
Q

What happens if CO₂ is high/ O₂ low?

A
  • Detected by chemoreceptors
  • Nerve impulse travels from the medulla along the sympathetic neurone to the SAN
  • Noradrenaline is released
  • Heart rate rises, CO₂ decreases/O₂ increases

Biology Paper 2 (10 decks)

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