Nervous system

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What makes up the central nervous system?
Brain & spinal cord
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What makes up the peripheral nervous system?
Nerves & neurones
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What are the stages in responding to a stimulus?
Stimulus, receptor, coordinator, effector, response
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Give examples of some receptors
Thermoreceptor & osmoreceptor
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Give examples of coordinators
Brain & spinal cord
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What are effectors?
Muscles and glands
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How are impulses transmitted?
Electrochemically
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Where do sensory neurones carry impulses to?
relay of the brain
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What do relay neurones do?
Interpret impulses
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Where do motor neurones carry impulses to?
muscles
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Where do previous neurones attach?
dendrites
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What is the name given to the potential difference between the inside & outside of a membrane when a nerve impulse isnt being conducted
resting potential
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Is the inside of the membrane positive or negative?
negative
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Sodium and potassium ions are transported across membrane against a concentration gradient, what is the transport process?
active transport
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The sodium-potassium exchange pumps are what types of proteins?
Trans-membrane proteins
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What do the sodium-potassium exchange pumps do?
Maintain concentration & an uneven distribution of sodium & potassium ions across the membrane
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Roughly how many sodium ions are pumped OUT of axon?
Three
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How many potassium ions are pumped INTO axon?
Two
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Why do sodium ions pass out faster than the potassium ions are brought in?
As the channels that allow potassium ions to diffuse out are open, while channels that allow sodium ions to move through are closed
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What is the axon membrane more permeable to, potassium or sodium ions?
Potassium ions
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What is the net result for the outside of membrane
Positive
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Why is the outside of the membrane positive?
Unequal distribution of charged ions creating a negative electrical charge inside
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Are there less or more sodium channels that potassium channels?
less
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When is an action potential triggered?
When threshold is reached
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How many gates does the sodium channel have?
two
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How many gates does the potassium channel have?
one
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Which has a quicker response, sodium channel or potassium channel?
Sodium
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Once threshold is reached, the sodium voltage gated channel opens, how does sodium enter the cell?
facilitated diffusion
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When sodium enters the cell it becomes more positive, what is the name given to this?
depolarisation
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As the sodium voltage gated channels close, the potassium voltage gated channels open, what does this mean for the potassium ions?
They leave the cell
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How do potassium ions leave the cell?
Facilitated diffusion
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What is the name given to when the cell becomes less positive?
repolarisation
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As the potassium voltage gated channels are slow to respond, potassium continues to leave the cell, what does this mean?
hyperpolarisation (undershoot threshold)
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Once the potassium voltage gated channels close what happens?
neurone can be restimulated, resting potential re-established
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What is the absolute refractory period?
When the action potential can't be regenerated
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What is the relative refractory period?
When stimulus is much greater than threshold
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In the reflex arc what does the receptor do?
detect change caused by a stimulus & initiates action potential
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In the reflex arc what is the swelling in the dorsal root of the spinal nerve called?
Dorsal root ganglion
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Where is there a collection of cell bodies of sensory neurones (reflex arc)?
Dorsal root ganglion
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Where do sensory neurones enter the grey matter (reflex arc)
Dorsal horn
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Where are there bundles of sensory & motor neurones? (reflex arc)
White matter
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Why is the white matter white? (reflex arc)
Very myelinated
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What is in the grey matter (reflex arc)
cell bodies of motor neurones & Glial cells
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Why is the grey matter grey (reflex arc)
lack of myelin
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What do Glial cells provide? (reflex arc)
nourishment for neurones
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What does the central canal contain? (reflex arc)
cerebrospinal fluid
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What does the cerebrospinal fluid contain?
electrolytes to nourish spinal cord
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What is a reflex arc?
Rapid involuntary response to stimulus
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Why do we have reflex arcs?
Protection
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Give examples of reflex actions?
coughing, blinking, knee jerk, breathing
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Where does a synapse between the sensory & relay neurones occur?
Grey matter of the spinal cord
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What does the relay neurone then synapse with?
Ascending nerve fibres
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Where do the ascending nerve fibres take impulses to?
Brain
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Where do you find nerve nets?
Hydra
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What do nerve nets coordinate?
movement
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What do nerve cells in the body wall connect with?
Sense organs with muscle fibrils
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What may a strong stimulus cause?
The entire animal to contract
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Why is the transmission speed of impulses slow in nerve nets
short extensions with many branches
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What are sensory receptors of pressure & vibration?
Mechanoreceptors
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Where are mechanoreceptors found?
Skin, tendons, joints & muscles
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What do the ends of a pacinian corpuscle consist of?
concentric rings of connective tissue
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What do the concentric rings of connective tissue do?
Reduce sensitivity of nerve
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What is the membrane before the synaptic cleft called?
pre-synapatic membrane
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What is the membrane called before the synaptic cleft?
post-synaptic membrane
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What is the gap between the two membranes called?
Synaptic cleft
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How are the vesicles containing neurotransmitters released?
exocytosis
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What are chemical impulses converted to?
neurotransmitters
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How does the neurotransmitter cross the synaptic cleft?
Diffusion
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What is an advantage of neurotransmitters?
Nerve impulse can be given some more specificity
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How can neurotransmitters control the operation of the nervous system?
Inhibition or excitation
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What channels open at the end of the pre-synaptic membrane when action potential reaches?
Calcium ion channels
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Once calcium has stimulated neurotransmitter containing vesicles, what happens?
The vesicles move & fuse with pre-synaptic membrane
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What does the neurotransmitter bind to on the post-synaptic membrane?
neuroreceptors
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What does the binding of neurotransmitters to neuroreceptors cause?
Sodium ion channels open
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When sodium enters the post-synaptic membrane, what happens?
Depolarisation
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How is the neurotransmitter broken down
specific enzyme in synaptic cleft
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Once products are broken down, what are they absorbed by?
Pre-synaptic membrane by endocytosis
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What are the absorbed products used for?
Resynthesising more neurotransmitters
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Where does the energy for resynthesising more neurotransmitters come from?
mitochondria
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What is the name given to the influence of light & darkness on the activities of plants
Photoperiodism
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What is phototropism?
response to light
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What is a tropism?
Growth movement of part of a plant in response to a directional stimulus
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If the direction of response is positive...?
movement is towards the stimulus
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If the direction of response is negative..?
movement is away from the stimulus
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What type of plant has flowering that doesnt seem to be affected by day-length?
Day neutral plants e.g. tomato, cucumber
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What type of plant has flowering that is induced by exposure to dark periods that are shorter than a critical length?
Long-day plants
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What type of plant has flowering that's induced by exposure to dark periods longer than a critical period?
short-day plants
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What is phytochrome?
Photoreceptor that absorbs light
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What colour pigment is phytochrome?
blue-green
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What does phytochrome red (Pr) absorb?
red light with an absorption peak at 600nm
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What does phytochrome far red (Pfr) absorb?
far-red light with an absorption peak at 730nm
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What happens when phytochrome absorbs red light?
It's converted to far red light
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What type of light is there more of in natural sunlight?
red-light
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When does far-red light accumulate?
During the day (due to conversions from red-light)
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What happens to far-red light at night?
It's converted back to red-light
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In short day plants when is flowering inhibited?
Exposure to red light
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What type of light brings about flowering in short day plants?
far-red light
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What type of light triggers flowering in long day plants?
far-red light
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In long day plants even if the light period is interrupted with a short period of darkness what happens?
flowering still happens
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Other cards in this set

Card 2

Front

What makes up the peripheral nervous system?

Back

Nerves & neurones

Card 3

Front

What are the stages in responding to a stimulus?

Back

Preview of the front of card 3

Card 4

Front

Give examples of some receptors

Back

Preview of the front of card 4

Card 5

Front

Give examples of coordinators

Back

Preview of the front of card 5
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