Biology Topic 8

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What is the difference bewteen the autonomial and somatic nervous system?
The autonomic is involuntary while the somatic is voluntary.
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What is the myelin sheath made off?
Schwann cells.
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What is the antagonistic pair of muscles in the eye?
Radial (contracts to dilate the pupil, sympathetic reflex) and circular (contracts to constrict the pupil, parasymathetic reflex)
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What is the resting potential in an axon?
-70 mv
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How is the resting potential formed?
The sodium and potassium ion pump means there is a high concentration of Na outside the cell and a high concentration of k inside the cell. K ions diffuse out of the cell (conc gradient). The potential difference created pulls the K back. Equal =-70
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What causes an action potential?
Changes in voltage across the membrane causes the sodium gate to open allowing ions to flow into the cell. This causes depolarisation which causes more gates to open.
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How does the membrane repolarise?
After 0.5ms the Na channels close. K channels open and K diffuses out of the cell. The insdie of the axon becomes hyperpolarised so the voltage dependent channels shut and K diffuses into the cell.
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Why can a dead axon no longer transmit an impulse?
No ATP present so Na/K pump no longer works so resting potential cannot be maintaned.
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What stops the impulse from traveling the wrong way down an axon?
Refractory period. It lasts until all the voltage dependent channels have closed again.
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How is an impulse conducted across a synapse?
Action potential arrives, membrane depolaruses and calcium channels open. Ca causes vesicles containing the neurotransmitter to fuse with the presynaptic membrane. Neurotransmitter is released and binds to the post synpatic membrane. Na channels open
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What are the two types of summation?
Spatial- Impulses from several neurones creates an action potential in the post synaptic neurone. Temporal- Several impulses along the same neurone creates an action potential.
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How do inhibitory synapses work?
When the neurotransmitter binds it opens chloride and potassium ion channels. This makes the axon more negatvie (hyperpolarized) so an impulse is less likely to be depolarized.
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How does auxin work?
Auxin is a hormone that activates a secondary messanger which acts as a transcription factor. This causes proton pumps to move hydrogen ions into the cell wall lowering the pH. This loosens the cell wall and casuses ions and water to move in.
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How do Rod cells work in the dark?
Sodium ions diffuse through open cation channels. They are then actively pumped out further down the cell causing a slight depolarisation. This releases a neurotransmitter which binds to the bipolar cell. It is an inhibitory synapse.
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How do rod cells work in the light?
Lights falls on the rhodopsin molecule which breaks into retinal and opsin. This results in the closing of the cation channels. Na is still actively pumoed out so hyperpolarisation occurs. No neurotransmitter is released so signal is formed in optic.
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Explain how long day platns work.
They need all the Pr to be converted into Pfr as it stimulates flowering.
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Explain how short day plants work.
They need long hours of darkness in order for all the Pfr to convert to Pr. Pfr inhibits germination.
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Describe the different lobes of the brain.
Frontal lobe- decision making, planning, includes the primary motor cortex. Parietal lobe- orrentation, movement, sensation. Occipital lobe- visula cortex, shape recognition. Temporal lobe- auditory information.
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Describe the white matter in the brain.
Thalamus- routes all the sensory information to the correct area. Hypothalamus- thermoregulation and sleep, hunger, thirst. Hippocampus- memory.
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Describe the lower regions in the brain.
Cerebellum- balance coordinates movement. Midbrain- relays information to the cerebral hemispheres. Medulla oblongata- regulates unconscious body processes.
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What is a critical period?
Periods of time where the nervous system must obtain specific experiances in order to develop properly.
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What parts of the brain are involved in memory?
Parietal lobe, temporal lobe, hippocampus.
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What are the two ways memories can be created?
Alter the pattern of connections, alter the strength of the synapses.
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How does habituation occur?
With repeated stimulation calcium channels become less responsive so less calcium enters the axon. This means less neurotransmitter is released and so less depolarisation occurs so no action potential.
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What treatments are there for parkinsons?
MAO inhibitor stops dopamine from being broken down, L-dopa is used to create more dopamine, agonists which are drugs that activate the dopamine receptor, gene therapy, depp brain stimulation is a form of surgery.
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What can excess dopamine cause?
Schizophrenia.
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How does MDMA work?
It binds to molecules in the presynaptic membrane responsible for moving the serotonin back into the cytoplasm. Seretonin stays in the synaptic cleft.
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Why is MDMA dangerous?
Disrupts the ability of the brain to regulate body temperature. Long term effects also include depression and insomnia.
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Why does MDMA have long term effects?
Because the drug has stimulated so much serotonin release the cells cannot synthesise enough to meet demand when it is gone.
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What is an SNP?
It is a DNA sequence variation where a single nucleotide is altered in at least 1% of the population.
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How do scientists test which plant cells have the genetically modified gene?
They insert a gene for antibiotic resistance (marker gene) along with the desired gene and treat the plant cells with the antibiotic. Only the ones that have been sucessfully modified surive.
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Card 2

Front

What is the myelin sheath made off?

Back

Schwann cells.

Card 3

Front

What is the antagonistic pair of muscles in the eye?

Back

Preview of the front of card 3

Card 4

Front

What is the resting potential in an axon?

Back

Preview of the front of card 4

Card 5

Front

How is the resting potential formed?

Back

Preview of the front of card 5
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