Unit 5 AQA Biology

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  • Created by: Yarnie
  • Created on: 19-04-14 22:20
What is a stimulus?
A detectable change in the internal or external environment that produces a response in the organism.
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What do receptors do?
They detect stimuli and transform the energy of the stimulus into a form of energy that can be processed by an organism - leading to a response
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Summarise the sequence of events once a stimulus has been detected
Stimulus ---> receptor ---> coordinator ---> effector ---> response
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What is taxis?
Taxis: A simple directional response to a stimulus
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What is kinesis?
Kinesis: an undirected movement in response to an external stimulus.
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What is tropism?
Tropism: A growth moevement of part of a plant in response to a directional stimulus. Eg plant shoots grow towards light (positive phototropism)
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What are the two major divisions of the nervous system?
The central nervous system (CNS) and the peripheral nervous system (PNS - made up of pairs of nerves from the brain/spinal cord)
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What is the central nervous system made up of?
Brain and spinal cord
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What is the peripheral nervous system divided into?
Sensory neurones (carry impulses from receptors to CNS) and motor neurones (carry impulses from CNS to effectors). Pairs of nerves that connect the CNS to the rest of the body
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The motor nervous system can be subdivided into:
The voluntary (under conscious control) and autonomic nervous (subconscious-involuntary) system
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How many neurones are involved in a reflex arc, name them
Three: Sensory neurone, intermediate/relay neurone, motor neurone
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Name the main stages of a reflex arc
Stimulus detected by receptor ---> Sensory neuorne to CNS ---> relay neurone ---> motor neurone to effector ---> response
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Why is the reflex arc important?
It's involuntary (doesn't require the brain's decision making) so doesn't overload the brain with situations where the response is always the same. They protect the body from harmful stimuli and are fast which is important for withdrawl.
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What does the sympathetic nervous system do in general?
Stimulates effectors - speeding up activity (helps us cope in stressful situations - fight or flight)
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What does the parasympathetic nervous system do in general?
Inhibits effectors - slows an activity (controls activities under normal resting conditions, aims to conserve energy)
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Name the region of the brain that controls heart rate
Medulla oblongata
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What do chemoreceptors detect and where are they found?
Detect changes in pH (as a result of CO2 conc) found in the walls of the carotid arteries.
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What is the function of the autonomic nervous system?
controls involuntary activities of the internal muscles and glands
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What are the four types of tropism in plants?
Positive phototropism, negative phototropism, positive geotropism, negative geotropism.
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What are auxins and what do they do?
What are Auxins and what do they do? Auxins are growth factors that stimulate the growth of shoots by cell elongation.
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what is cell elongation?
Where the cell walls 'stretch' so the cell gets longer.
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How does infoleacetic acid (IAA) cause cell elongation?
It increases the H+ conc. in the cell walls, which weakens the bonds between the cellulose fibres. The cell then expands due to water moving into the cell by osmosis and causes elongation. The cell walls then reform.
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What are chemical mediators?
Substances that are released from certain mammalian cells (mostly injured or infected) that cause small arteries & arterioles to dilate which leads to a rise in temp. and swelling in infected area.
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Give two examples of chemical mediators
Histamine (for swelling, redness & itching) and Prostaglandins (affects blood pressure and neurotransmitters).
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What is potential difference?
The difference in voltage across the membrane of a cell.
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What is generator potential?
When a nervous system receptor is in its resting state (not being stimulated) and the outside of the membrane is more positively charged compared to the inside.
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What is an action potential?
The change in potential difference sue to a stimulus.
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What is an action potential and when is it triggered?
An action potential is an electrical impulse along a neurone where the inside of the membrane is more positive than the outside (the membrane is said to be depolarised) which is triggered when the generator potential is big enough.
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What are pacinian corpucles?
Pressure receptors in the skin which detect mechanical stimuli.
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What happens when pacinian corpuscles are stimulated?
Pressure changes the shape of the membrane - widening the sodium channels, there is an influx of sodium ions - depolarising the membrane producing a generator potential which in turn produces an action potential which passes to CNS via neurones.
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What is the refractory period?
Period during which the membrane of the axon of a neurone cannot be depolarised and no new action potential can be initiated.
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What are the three main purposes of the refractory period?
1. Ensures action potential is propegated in one direction. 2,Produces discrete impulses (action potentials are separated) 3. Limits the number of action potentials generated.
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What is the all or nothing principal?
There is a threshold level which must be reached by a stimulus to produce an action potential, below this no action potential is generated.
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What are the two types of refractory period?
The absolute refractory period and the relative refractory period.
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What is a synapse?
A junction between neurones in which they do not touch but have a narrow gap - the synaptic cleft, across which a neurotransmitter can pass.
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What is spatial summation?
Where a number of pre-synaptic neurones together release enough neurotransmitter to exceed the threshold value of the postsynaptic neurone to trigger an action potential.
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What are the three main features of synapses?
1. Unidirectionality 2. Summation 3.Inhibition
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Other cards in this set

Card 2

Front

They detect stimuli and transform the energy of the stimulus into a form of energy that can be processed by an organism - leading to a response

Back

What do receptors do?

Card 3

Front

Stimulus ---> receptor ---> coordinator ---> effector ---> response

Back

Preview of the back of card 3

Card 4

Front

Taxis: A simple directional response to a stimulus

Back

Preview of the back of card 4

Card 5

Front

Kinesis: an undirected movement in response to an external stimulus.

Back

Preview of the back of card 5
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Comments

Rosie

I think you did the clues and the answers the wrong way around? Otherwise, great :)

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