Biology OCR, B6

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What is a stimulus?
a change in the environment of an organism
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What do simple reflexes produce?
rapid involuntary responses to stimuli
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What do the simplest animals rely on for the majority of their behaviour?
reflex actions
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What do reflex actions for simple animals ensure?
ensures that the simplest animals respond to a stimulus in a way that is most likely to result in their survival, including finding food and sheltering from predators
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What are examples of simple reflexes in humans?
newborn reflexes (stepping, grasping, sucking) , pupil reflex, knee jerk and dropping a hot object
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What does nervous co-ordination require?
receptors to detect stimuli, processing centres to receive information and coordinate responses, effectors to produce the response
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What are examples of effectors and receptors in complex organs?
light receptor cells in the retina of the eye, hormone secreting cells in a gland, muscle cells in a muscle
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What do nervous systems use for fast, short-lived responses?
electrical impulses
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What are hormones?
chemicals produced in glands that travel in the blood and bring about slower, longer-lasting responses E.G: insulin and oestrogen
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What does the development of nervous and hormonal communications systems depend on?
the evolution of multicellular organisms
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What are nervous systems made up of?
neurons (nerve cells) linking receptor cells (eg in eyes, ears and skin) to effector cells (in muscles/glands)
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What do neurons transmit when stimulated?
electrical impulses
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What is an axon?
a long extension of the cytoplasm in a neuron and is surrounded by cell membrane
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What are some axons surrounded by?
by a fatty sheath, which insulates the neuron from neighbouring cells and increases the speed of transmissions or a nerve impulse
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What is the central nervous system (CNS) made up of in humans?
the spinal cord and brain
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In mammalian nervous systems, how is the CNS connected to the body?
via the peripheral nervous system (sensory and motor neurons)
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How does the CNS coordinate an animal's response?
sensory neurons carry impulses from receptors to the CNS and motor neurons carry impulses from the CNS to effectors
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In the CNS how are impulses passed from sensory neurons to motor neurons?
through relay neurons
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What is the pathway for a reflex action?
a receptor is stimulated, causes impulses to pass along a sensory neuron into the spinal cord, sensory neuron synapses with a relay neuron, relay neuron synapses with a motor neuron sending impulses to effectors, the effectors respond
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What allows responses to be automatic and very rapid?
the arrangement of neurons in a fixed pathway allows reflex responses to be automatic and rapid, since no processing of information is required
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What is the synapses?
the gap between adjacent neurons, which impulses are transmitted across
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What happens in the synapse?
an impulse triggers the release of chemicals (transmitter substances) from the first neuron into the synapse, which diffuses across and binds to receptor molecules on the membrane of the next neuron. Only specific chemicals bind to receptor molecule
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What can affect the transmissions of impulses across synapses?
some toxins and drugs, for example: Ecstasy, beta blockers and Prozac
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What does Ecstasy do to the brain's synapses?
Ecstasy blocks the sites in the brain's synapses where the transmitter substance, serotonin, is removed. This increases the serotonin levels in the synapse and affects the nervous system
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What is the cerebral cortex?
the part of our brain most concerned with intelligence, memory, language and consciousness
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How can scientists map the regions of the brain to particular functions?
by studying patients with brain damage, carrying out studies in which parts of the brain are stimulated electrically and brain scans, such as MRI, showing brain structure and activity
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What is conditioning?
when a reflex response to a new stimulus can be learned by introducing the secondary (new) stimulus in association with the primary stimulus. In a conditional reflex response, the final response has no direct connection to the secondary stimulus
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What are two examples of conditioning?
Pavlov's dogs and the feeling of hunger you get just by looking at the time on the clock
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What are conditioned reflexes an example of and what can they do?
they are a form of simple learning that can increase an animal's chance of survival
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How can the brain modify a reflex response and what is an example?
the brain can modify a reflex response via a neuron to the motor neuron of the reflex arc. For example, keeping hold of a hot object
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During evolution, what gave early humans a better chance of survival?
the evolution of a larger brain
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What allows mammals to learn?
mammals have a complex brain of billions of neurons that allows learning by experience, including social behaviour
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What does the interaction between mammals and the environment result in?
results in neuron pathways in the brain forming
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Why are some skills learnt through repetition?
certain pathways in the brain become more likely to transmit impulses than others and new neuron pathways form and other neuron pathways are lost
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What makes it possible for the animal to adapt to new situations?
the variety of potential pathways in the brain
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What is memory?
the storage and retrieval of information
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What can memory be divided into?
short-term memory and long-term memory
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What makes humans more likely to remember information?
if they can see a pattern in it or impose a pattern on it, if there is repetition of the information - especially over an extended period of time and if there is a strong stimulus associated
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Why do we forget?
physical- neurons decaying e.g:Alzheimers and lack of retrieval - if we don't use information for a long time, the pathway is lost
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What is an example of a model scientists have produced to explain how the brain stores information?
the multi-store model
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What do simple reflexes produce?

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rapid involuntary responses to stimuli

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What do the simplest animals rely on for the majority of their behaviour?

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Card 4

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What do reflex actions for simple animals ensure?

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Card 5

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What are examples of simple reflexes in humans?

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