9700 · 15.1
Control and coordination in mammals flashcards
Revision flashcards for Cambridge 9700 Control and coordination in mammals (syllabus 15.1). Flip, recall, then mark a real past-paper question.
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What is the resting potential of a neurone and how is it maintained?
The resting potential is the charge difference across the membrane when a neurone is not firing, typically -70mV. It is maintained by the Na+/K+ pump (3 Na+ out, 2 K+ in) and the higher permeability of the membrane to K+ ions through leak channels.
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Define 'action potential'.
An action potential is a rapid, temporary reversal of the membrane potential from negative to positive, caused by the influx of Na+ ions. It functions as the nerve impulse.
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What is saltatory conduction?
It is the 'jumping' of action potentials from one node of Ranvier to the next along a myelinated axon. This process is much faster than continuous conduction in unmyelinated axons.
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Describe the role of Ca²⁺ ions in synaptic transmission.
When an action potential reaches the presynaptic terminal, it causes voltage-gated Ca²⁺ channels to open. The influx of Ca²⁺ ions triggers the fusion of synaptic vesicles with the presynaptic membrane, leading to the release of neurotransmitters into the synaptic cleft.
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What is the function of acetylcholinesterase?
Acetylcholinesterase is an enzyme located in the synaptic cleft of cholinergic synapses. It breaks down the neurotransmitter acetylcholine into choline and ethanoic acid, terminating the signal and allowing the postsynaptic membrane to repolarise.
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State two key differences between the nervous and endocrine systems.
1. **Speed:** The nervous system is very fast (milliseconds), while the endocrine system is slower (seconds to days). 2. **Signal Type:** The nervous system uses electrical impulses, while the endocrine system uses chemical hormones in the blood.
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What is negative feedback?
A homeostatic control mechanism where the response produced counteracts the initial stimulus, bringing the internal environment back to its set point. For example, insulin lowers high blood glucose, which in turn reduces the stimulus for insulin secretion.
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Name the two hormones that regulate blood glucose and the gland that secretes them.
Insulin (lowers blood glucose) and glucagon (raises blood glucose). Both are secreted by the islets of Langerhans in the pancreas.