Edexcel A2 Level Biology Unit 5 Topic 8 Processes

All the processes from the edexcel a2 biology course unit 5 topic 8

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  • Created on: 20-06-10 11:11
Preview of Edexcel A2 Level Biology Unit 5 Topic 8 Processes

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Topic 8 Processes
Reflex Arcs:
1. Receptors detect a stimulus and generate a nerve impulse.
2. Sensory neurones conduct a nerve impulse to the CNS along a sensory
3. Sensory neurones enter the spinal cord through the dorsal route.
4. Sensory neurone forms a synapse with a relay neurone.
5. Relay neurone forms a synapse with a motor neurone that leaves the
spinal cord through the ventral route.
6. Motor neurone carries impulses to an effector which produces a response.
Resting Potential
1. Na+/K+ pump creates concentration gradients across the membrane.
2. K+ diffuse out of the cell down the K+ gradient, making the outside of the
membrane positive and the inside negative.
3. The electrical gradient will pull K+ back into the cell.
4. At -70mV potential difference, the two counteract each other and there is
no net movement of K+.
Action Potential
1. Resting potential.
2. Depolarisation: Voltage-dependant Na+ channels open, Na+ flows into
axon, depolarising the membrane.
3. Repolarisation: Voltage-dependant Na+ channels close,
voltage-dependant K+ channels open, K+ leave the axon repolarising the
4. Hyperpolarisation: The membrane is hyperpolarised, voltage-dependant
K+ channels close, K+ diffuse back into the axon to recreate the resting

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Propagation of an Impulse along an axon
1. At resting potential there is positive charge on the outside of the
membrane and negative charge on the inside, with higher sodium ion
concentration outside and high potassium ion concentration inside.
2. When stimulated, voltage-dependent sodium ion channels open, and
sodium ions flow into the axon, depolarising the membrane. Localised
electric currents are generated in the membrane.…read more

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Visual Transduction: In the dark
1. Na+ diffuse in through open cation channels.
2. Na+ move down the concentration gradient.
3. Na+ is actively pumped out.
4. Membrane slightly depolarised -40mV.
5. Inhibitory neurotransmitter is released and binds to bipolar cell, preventing
it depolarising.
Visual Transduction: In the light
1. Rhodopsin is broken down.
2. Na+ channels closed.
3. Na+ actively pumped out.
4. Membrane hyperpolarised.
5. No neurotransmitter is released.
6.…read more

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Frontal Lobe
decision making
consciousness of emotions
forming associations and ideas
Parietal Lobe
Occipital Lobe
processing information from the eyes:
Temporal Lobe
processing auditory information
-hearing…read more

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Cerebral Hemispheres
Blood concentration
coordinate movement
checks motor programme
Medulla oblongata
control of heartbeat
blood pressure
Thalamus…read more

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Laying down long term memory
Basal Ganglia
Selecting and initiating stored programmes for movement
Mid Brain
relays information to the cerebral hemispheres.
auditory information to temporal lobe.
visual information to occipital lobe.
1. With repeated stimulation, Ca+ channels become less responsive so less
Ca2+ crosses the presynaptic membrane.
2. Less neurotransmitter is released.
3. There is less depolarisation of the postsynaptic membrane so no action
potential is triggered in the motor neurone.…read more

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Cells multiply in fermenter.
7. Produce human insulin.
8. Insulin protein extracted and purified.
9. Bacterial cells destroyed.
Genetically Modified Plants
1. Plasmid carrying the desired gene and an antibiotic resistance gene
(marker gene) is used.
2. DNA gun or insertion of a new gene of virus DNA used to incorporate
genes into the plant DNA of some cells.
3. Incubation in growth medium with antibiotic.
4. Only cells with the new genes survive.
5.…read more


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