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44 Cards in this Set
- Front
- Back
- 3rd side (hint)
What is a stimulus? |
A detectable change in the internal or external environment of an organism that produces a response in the organism |
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What is taxis? |
A simple response by an organism, whose direction is determined by the direction of the stimulus. A directional response |
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What is a positive taxis |
Movement towards the stimulus |
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What is kineses |
An response where the organism does not move away from or towards the stimulus. Instead the more unpleasant the stimulus, the faster it moves and the more rapidly it changes direction |
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What is a tropism? |
A response to directional stimuli that can maintain the roots and shoots of flowering plants |
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What are the steps in a reflex arc? |
Stimulus, receptor, sensory neurone intermediate neurone, motor neurone, effector,response |
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How is the nervous system divided? |
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What is a reflex? |
A rapid response to a stimulus which is automatic/not under conscious control |
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What are the two divisions of the autonomic nervous system and what do they do? |
Sympathetic -stimulates effectors and so speeds up activity Parasympathetic - inhibits effectors and so slows down activity |
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Which part of the brain controls heart rate |
Medulla Oblongata |
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How is heart rate controlled by chemoreceptors? |
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How does a Pacinian corpuscle respond to pressure? |
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What are the two different types of light detecting cells in the eye? |
Rod cells Cone cells |
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Why can rod cells only produce black and white images? |
Cannot distinguish between different wavelengths of light |
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Why can rod cells respond respond to a low intensity of light? |
share a single sensory neurone so a certain threshold has to be exceeded before a generator potential is created in bipolar cells to which they are attached. Because more than one rod cell is attached to a single bipolar cell, there is a much greater chance that the threshold will be exceeded |
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How is a generator potential created |
Rhodopsin must be broken down |
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Why do rod cells have a low visual acuity |
Many rod cells linked to a single bipolar cell, they will only generate a single impulse regardless of how many neurones are stimulated. This means they cannot distinguish between separate sources of light that stimulated them |
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Differences between rod and cone cells |
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Why can cone cells not respond to low light intensity |
Linked to separate bipolar cells so stimulation of a large number of cone cells cannot be combined to help exceed the threshold and create a generator potential |
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What is the pigment in cone cells |
Idopsin |
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Why do cone cells have a high visual acuity |
Own connection to bipolar cell which means that if two cone cells are stimulated the brain received two separate impulses |
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Main features of hormonal and nervous system |
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Which cells do chemical mediators have an effect on |
Only cells in their immediate vicinity |
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Two examples of chemical mediators and what they do |
Histamine - released in response to an allergen. Causes dilation of small arteries and arterioles Prostaglandins - found incell membranes and also cause dilation of small arteries and arterioles |
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Three types of plant tropism |
Photo Geo Hydro |
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How does IAA work |
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What are the 6 things that make up a neurone and what are there functions |
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Bow is a resting potential established |
Na ions actively transported out of the axon K ions actively transported into the axon. However the transport of Na is greater than K Na ions diffuse back into the axon whilst K diffuse back out of the axon However, most of the K ion gates are open, but the Na gates are shut. Therefore the outside of the axon is positive relative to the inside |
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Describe be passage of an action potential |
Depolarisation Stimulus causes Na voltage-gated channels to open, so Na ions diffuse into the axon As more Na ions diffuse in, more Na channels open Hyperpolarisation . K ions diffuse out of the axon Once the action potential has been established, Na voltage-gated channels close and K voltage-gated open. K ions diffuse out of the axonThis causes a temporary overshootRepolarizationK voltage-gated channels shut and resting potential is reestablished This causes a temporary overshoot Repolarization K voltage-gated channels shut and resting potential is reestablished |
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How does an action potential pass along a myelinated axon |
Myelinated sheath acts as an electrical insulator, preventing action potentials from forming. At nodes of Ranvier, action potentials can occur, so the action potential jumps from node to node(saltatory conduction), increasing the speed of the nerve impulse |
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What factors affect the speed of the nerve impulse |
The myelin sheath Diameter of axon- the greater the diameter, the faster the impulse Temperature - this affects rate of diffusion of ions, therefore higher temperature means faster speed |
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What are the purposes of the refractory period? |
Ensures the action potential travels in one direction only Produces impulses that are separated from each other so can easily be distinguished Limits the number of action potentials |
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What is the all-or-nothing principle |
There is a certain level of stimulus, the threshold value, the needs to be exceeded for to trigger an action potential. |
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How do organisms perceive the size of a stimulus |
The number of impulses in a given time Different neurone with different threshold values. |
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What is spatial summation |
A number of different presynaptic neurones together release enough neurotransmitter to exceed the threshold and genererate an action potential |
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What is temporal summation |
A single presynaptic neurone releases neurotransmitter many times over a short period |
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Describe transmittion across a synapse |
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What is the function of slow twitch muscle fibres and how are they adapted to it? |
Contract more slowly over a longer period. Useful for endurance work Large supply of myoglobin (stores oxyen) Supply of glycogen Rich supply of blood vessels Numerous mitochondria |
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What is the function of fast twitch muscle fibres and how are they adapted to it? |
Contract more rapidly over a short period. Adapted to intense exercise. Thicker and more numerous myosin High concentration of enzymes involved in anaerobic respiration |
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Describe transmission across a neuromuscular junction |
Synaptic vesicles fuse with the presynaptic membrane and release acetycholine. This diffuses across the to the postsynaptic membrane where it binds to receptors on Na ion channels which cause them to open so Na diffuses into, depolarising the membrane |
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What happens to the I and A bands, the Z lines and the H zones when a muscle contracts |
I band become narrower Z bands move closer together H-zones become narrower A band remains the same width |
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