Communication and Homeostasis

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Give an example of a stimulus and a response
Arctic fox, changing from winter to summer coat/ light meaning that the Iris of the eye should limit the amount entering the eye
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What is Excretion?
The removal of waste products from the blood in order to prevent accumulation of toxic substances.
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What 5 factors should a good communication system contain?
Cover the whole body, Enable cells to communicate with each other, enable specific communication, enable rapid communication and have both long term and short term responses.
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What are the two major systems of communication that work by cell signalling?
The Neuronal system and the Hormonal system
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What are the three main features of negative feedback?
Any change must be detected, the change must be signaled to other cells, there must be a response to change the conditions back to optimum
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What structures are required in order for cell signalling to take place?
Sensory receptors, such as temp and glucose receptors, a system such as the nervous or hormonal system and also effector cells
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What is positive feedback?
Instead of trying to reverse the change caused by the stimulus, positive feedback amplifies it.
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What is one example of positive feedback that is not harmful?
Within pregnancy the dilation of the cervix is an example of the process of positive feedback, as the contractions occur, Oxytocin is release by the pituitary gland and makes the cervix dilate further.
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What is the difference between Ectotherms and Endotherms?
Ecotherms have an internal temperature that is dependent on the external environment, meaning that it can fluctuate depending on this. Endotherms are able to control their own internal temperature and therefore are not reliant on the external factors
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What are some advantages of being an Ectotherms?
They use less of their food in respiration, they need to find less food therefore they can live for longer lengths of time, they can put the majority of there energy into growth.
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What are disadvantages of Ectotherms?
They are less active in cooler conditions and may need to warm up in the morning, this means that they may be less active and are therefore at more risk of predation as they are unable to get away fast enough.
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What are some behavioral changes that an Ectotherm may display in order to change its body temperature?
Warm up - Bask in the sun, orientate body towards sun alter body shape to expose more surface area to sun Cool down- Go into shade/ Orientate away from the sun, Alter body shape to reduce surface area to the sun, Increase breathing-water evaporation
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What are some advantages of endothermy?
Able to maintain a constant internal temperature, activity is possible even when he environment is cold, ability to inhabit colder parts of the plant
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What are some disadvantages of edothermy?
A significant part of energy intake is used to maintain the body temperature, More food is required, Less energy from food is used fro growth
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Where in the body is temperature monitored
Hypothalamus
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What is the name of a receptor that can convert on type of energy to another?
Energy Transducer
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Neurons contain ion channels for two different types of ions, what are they?
Potassium and sodium
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Within the carrier proteins how many Sodium ions are transported out Compared to Potassium in?
3 Sodium out and 2 potassium in.
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When the inside of the cell is negatively charged compared to the outside the cell is said to be what?
Polarised
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When the inside of the cell becomes less negative compared to the outside it is said to be what?
Depolarised
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How does the cell become depolarised?
The sodium ion channels open, causing an influx of sodium ions down their concentration gradient.
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What is a generator potential?
A small change in potential caused by a few ion channels opening, the larger the stimulus the more likely the generator potential will be large enough to cause an action potential
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What are the three different types of neurons?
Sensory neurons- carry impulse from sensory receptors to CNS , Motor neurons carry the impulse from the CNS to the effector cell and Relay neurons that connect the sensory and motor neurons.
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What are some features of Neurone ?
Long- meaning they can transmit impulses over a long distance, the cell membrane has gated ion channels in order for the impulse to be transmitted, they are surrounded by shwann cells, these create a myelin sheath,this insulates the action potenital
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What feature does a Sensory Neurone contain that a Motor Neurone doesn't
Long dendron, Cell body outside the CNS and a short axon
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What features does a Motor Neurone contain that a sensory Neurone doesn't
Cell body inside the CNS, Long Axon, carries impulse to effector
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When the cell membrane is Polarised what is its voltage?
-60mv
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When the membrane is polarised it can also said to be at...
Resting Potential
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What do voltage gated channels respond to?
Depolarisations within the membrane
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What voltage is the Threshold potential?
-50mv
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When the threshold potential is exceeded it causes a large influx of sodium ions it achieves an action potential, what is the voltage for this?
+40mv
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What occurs during Repolaristaion?
The potassium ions diffuse out of the of the cell bringing the the potential difference back down to negative
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Why does the refractory period occur?
It allows the cell to recover after an action potential, it also ensures that action potentials are only transmitted in one direction
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what does a local current consist of?
It is when on sodium channel causes the others further along the neuron to open meaning that the impulse is transmitted.
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When the impulse jumps from one node to the next what is this called?
Saltatory conduction
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What is the purpose of the nodes of Ranvier
they speed up the conduction of the impulse by only allowing sodium ions to flow into the neurone at specific points.
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What is the neurotransmitter within the nerve junction?
Acetylcholine
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How are the synaptic knobs specialised?
They contain many mitochondria, many smooth endoplasmic reticulum, vesicles containing acetylcholine and also voltage gated calcium channels
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What sort of channels on the post synaptic knob have receptors for acetylcholine
sodium
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The removal of waste products from the blood in order to prevent accumulation of toxic substances.

Card 3

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Card 4

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What are the two major systems of communication that work by cell signalling?

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Card 5

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What are the three main features of negative feedback?

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