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Biology A-level > Response to stimuli > Flashcards

Response to stimuli Flashcards

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1
Q

What are the major divisions of the nervous system

A

The central nervous system and the peripheral nervous system

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2
Q

The central nervous system

A

made up of the brain and spinal cord

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3
Q

The peripheral nervous system

A

made up of the nerves that originate from either the brain or the spinal cord

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4
Q

What is the peripheral nervous system divided into

A

Sensory neurones and motor neurones

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5
Q

What are sensory neurones

A

carry nerve impulses from receptors from receptors towards the central nervous system

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6
Q

what are motor neurones

A

carry nerve impulses away from the central nervous system to effectors

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7
Q

what is the motor nervous system divided into

A

The voluntary nervous system and autonomic nervous system

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8
Q

Voluntary nervous system

A

carries nerve impulses to body muscles and is under voluntary control

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9
Q

Autonomic nervous system

A

carries nerve impulses to glands, smooth muscles and cardic muscles and is not under voluntary control

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10
Q

Spinal cord

A

A column of nervous tissue that runs along the back and lies inside the vertebral column for protection

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11
Q

reflec arc

A

A response that is rapid, short-lived, localised and totally involuntary

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12
Q

What are the stages of a reflex arc

A
  1. stimulus
    2.receptor
    3.sensory neurone
    4.coordinator
  2. Motor neurone
    6.effecor
    7.response
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13
Q

Explain the reflex arc involved in the withdrawal of the hand from a heat stimulus

A
  1. stimulus- heat from candle flame
  2. receptor- nerve ending in skin sensitive to heat
  3. sensory neurone-passes nerve impulse to spinal cord
    4.intermediate neurone
    - passes nerve impulse across the spinal cord
  4. motor neurone passes impulses to the muscle
    6.effector contracts (muscle)
    7.response- hand is moved quickly away from flame
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14
Q

What is the importance of a relfex arc

A

-they are involuntary and therefore do not require the decision
-protect the body from harm
-Fast because the neurone pathway is short
-Absence of any decision making means the action is rapid

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15
Q

Receptor

A

respond to specific types of stimuli

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16
Q

What does the pacinian corpuscle respond to

A

Mechanical pressure

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17
Q

What is the structure of a pacinian corpuscle

A

-found at the end of sensory neurone axons
-They are made up of membrane layers separated by a gel
-The gel between the layers contains positively charged sodium ions
-Contains stretch-mediated sodium ion channels

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18
Q

When do the stretch mediated sodium channels open in a pacinian corpuscle

A

When pressure is applied the layers become deformed so the membrane is stretched allowing sodium ions to diffuse through the channels

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19
Q

How does a pacinian corpuscle function

A

-In its resting state the stretch mediated sodium channels are closed and there is a excess of sodium surrounding the axon (resting potential)
-When pressure is applied it’s deformed and the membrane is stretched allowing sodium ions to diffuse through the stretch mediated sodium channels
-Influx of sodium ions causes depolarisation and produces a generator potential
-This triggers an action potential that passes along the axon to other neurones

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20
Q

What are the two types of light receptors found in the eye

A

-rod cells
-cone cells

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21
Q

Where are light receptors found in the eye

A

The retina

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22
Q

Describe the structure of the human retina

A

The retina contains millions of light receptor cells, these are called rods and cones.
Rods are more numerous than cones.
Rods located at the periphery of the retina, cones more concentrated at the fovea (area of the retina where light is focused)
Bipolar neurones connect the rods/cone to sensory neurone

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23
Q

Explain how rods and cones work

A

Pigment in the rod (rhodopsin)/cone (iodopsin) is broken down and this creates a generator potential causing an action potential in the bipolar neurone

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24
Q

transducer cells

A

Cells that convert a non-electrical signal (light or sound) into an electrical signal

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25
What are rod cells used for
used to detect light at very low intensity
26
What are cone cells used for
Allows us to perceive images in full colour
27
How are cone cells linked to bipolar neurones
Only one cone cell is linked to a bipolar neurone so it takes more light to reach the threshold and trigger an action potential
28
How are rod cells linked to bipolar neurones
many rod cells are linked to a single bipolar neurone so there is a much greater chance that the threshold value will be exceeded than with a single rod cell
29
Light sensitivity of rod and cone cells
Light sensitivity: Rod cells detect low levels of light because rhodopsin can be broken down in low intensity light. Many rod cells are conected to a single bipolar cell. Summation means that there is greater chance that threshold will be reached and a generator potential will occur in the bipolar cell. Cone cells are connected individually to bipolar cells so summation cannot occur and a generator potential is unlikey to occur in low levels of light. Additionally iodopsin requires greater light intensities for it's breakdown.
30
colour sensitivity of rod and cone cells
Colour sensitivity: Only cone cells can detect colour. There are three different types of cone cell each containing a different pigment that responds to a different wavelength of light. Rod cells cannot distinguish between wavelengths of light and so images are in black and white.
31
visual acuity of rod and cone cells
Visual acuity: Cones cells have good visual acuity. There is one cone cell connected to each bipolar cell so if two adjacent cone cells are stimulated the brain receives two separate impulses, this means two dots of light close to each other can be resolved giving accurate vision. Rod cells have low visual acuity as there a several connected to each biopolar cell
32
Stimulus
detectable change in the internal or external environment or an organism that leads to a response
33
How does being able to respond to a stimulus aid survival
-to be able to detect and move away from harmful stimuli such as predators -to be able to detect and move towards a source of food
34
Taxes
is a simple response where motile organisms respond directly to a stimulus (they move towards a beneficial stimulus and away from harmful stimuli)
35
What is a an example of positive taxis
Daphnia (water fleas) move towards the light (positive phototaxis)
36
What is a an example of negative taxis
earthworms move from the light (negative phototaxis)
37
Kineses
A change in speed and rate of change in direction
38
What is an example of kinesis
Woodlice move quickly and in random directions, stopping frequently for a short period of time in dry areas In wet areas woodlice move slowly and change direction less frequently, stopping for longer
39
Tropism
Plants response to a directional stimulus
40
What is an example of tropism (Plant shoots)
grow towards light (positive phototropism) away from gravity (negative gravitropism)
41
What is an example of tropism (Plant roots)
away from light (negative phototropism) towards gravity (positive gravitropism)
42
What do plants respond to
-light-shoots grow towards light/roots away -gravity - roots towards/ shoots away -water -plant roots grow toward water (positive hydrotropism)
43
What is indoleacetic acid (IAA)
a type of auxin that controls plant cell elongation
44
How IAA affects phototropism in flowering plants
-IAA is produced in the shoot -IAA moves through the shoot -IAA moves to the shaded side -higher concentration of IAA on shaded side than light side so cell elongation of shoot is more on the shaded side than on the light side -Shaded side elongates faster causing the shoot to bend towards the light
45
How IAA affects gravitropism in flowering plants
-IAA is produced in root tips -IAA moves down the root tip -IAA moves to lower side of the root -inhibits cell elongation -roots bend towards gravity
46
Why does IAA affect cell elongation
-acid growth hypothesis -increases plasticity of cell walls by hydrogen ions moving into spaces within the cell wall via active transport which changes the bonding within cellulose layers
47
function of autonomic nervous system
controls involuntary activities of internal muscles and glands
48
what does the sympathetic nervous system do
-stimulates effectors by speeding up activity -controls effectors when we exercise strenuously / experience powerful emotion -help cope with stressful situations by heightening awareness and preparing us for activity ( fight or flight)
49
what does parasympathetic nervous system do
-inhibits effectors to slow down any activity -controls activities under normal resting condition -concerned with conserving energy + replenishing the body's reserves
50
what are SNS and PNS
antagonistic ( as they oppose each other)
51
What does myogenic means?
a muscle that can contract/relax without receiving electrical impulses from nerves
52
sequence of events that controls the basic heart rate
1) sinoatrial node (SAN) acts as a pacemaker > regular waves of electrical excitation across both atria causing simultaneous contraction 2) layer of non-conducting tissue (atrioventricular septum) prevents waves crossing to ventricles > so preventing immediate contraction of ventricles 3) waves of electrical activity reach atrioventricular node (AVN) which delays impulse > allowing atria to fully contract and empty before ventricles contract 4) AVN sends waves of electrical activity down bundles of His, conducting wave between ventricles to apex where branches into purkyne tissue > causing ventricles to contract quickly and simultaneously from bottom of heart upwards
53
What is the SAN?
(sinoatrial node) is a group of cells/tissues found in the right atrium that can release a wave of electricity/depolarisation which causes contraction
54
What is the AVN? Where is it located?
Atrio-ventricular node, located in the atria, near the border of the right and left ventricles
55
What is the bundle of His?
conductive tissue located in the septum and ventricular walls
56
What are the Purkyne fibres?
conductive tissues that go all the way through the walls of the ventricles
57
What is the role of the SAN?
to release a wave of depolarisation, causing both atria to contract
58
What does the AVN do?
release another wave of depolarisation (when the 1st reaches it)
59
Why cant the electricity from the AVN move straight to the ventricles?
insulating fibres between atria and ventricles
60
What is the role of the bundle of His?
to carry the wave of depolarisation from the atria through to the purkyne fibres in the walls of the ventricles
61
What part of the heart contracts first?
apex/tip
62
Why is non-conductive tissue an advantage?
results in a delay, which allows enough time for the atria to fully contract, filling the ventricles allowing the maximum volume of blood to be pumped
63
What are changes to the heart rate controlled by
medulla oblongata
64
what does medulla oblongata have
-centre that increases heart rate which is linked to sinoatrial node by sympathetic nervous system -centre that decreases heart rate which is linked to sinoatrial node of parasympathetic nervous system
65
why is it essential for heart rate to be modified
rate can be altered to meet varying demands for oxygen
66
what does the centres being stimulated depend on
depends upon the nerve impulse they receive from 2 types of receptors which respond to stimulus of either chemical / pressure changes in the blood
67
What receptors detect changes in the pH of the blood? changes in pressure?
chemoreceptors, pressure receptors/baroreceptors

Biology A-level (31 decks)

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