Where do neurotransmitters bind?
Neurotransmitters bind to receptors on post-synaptic cells and can either trigger (excitatory) or prevent (inhibitory) a response
Key Terms
Where do neurotransmitters bind?
Neurotransmitters bind to receptors on post-synaptic cells and can either trigger (excitatory) or prevent (inhibitory) a response
What 3 cells can neurotransmitters trigger?
neuron
glandular cell
muscle fibre
What is the response of a neuron when triggered by neurotransmitters?
stimulation or inhibition of an electrical signal (nerve impulse)
What is the response of a glandular cell when triggered by neurotransmitters?
stimulation or inhibition of secretion (exocrine or endocrine)
What is the response of muscle fibre when triggered by neurotransmitters?
stimulation or inhibition of muscular contraction/relaxation
What is an example of a neurotransmitter?
One example of a neurotransmitter used by both the central nervous system and peripheral nervous system is acetylcholine
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| Term | Definition |
|---|---|
Where do neurotransmitters bind? | Neurotransmitters bind to receptors on post-synaptic cells and can either trigger (excitatory) or prevent (inhibitory) a response |
What 3 cells can neurotransmitters trigger? | neuron glandular cell muscle fibre |
What is the response of a neuron when triggered by neurotransmitters? | stimulation or inhibition of an electrical signal (nerve impulse) |
What is the response of a glandular cell when triggered by neurotransmitters? | stimulation or inhibition of secretion (exocrine or endocrine) |
What is the response of muscle fibre when triggered by neurotransmitters? | stimulation or inhibition of muscular contraction/relaxation |
What is an example of a neurotransmitter? | One example of a neurotransmitter used by both the central nervous system and peripheral nervous system is acetylcholine |
Where can acetylcholine be released? | neuromuscular junctions autonomic nervous system |
What is the role of acetylcholine in neuromuscular junctions? | It is commonly released at neuromuscular junctions and binds to receptors on muscle fibres to trigger muscle contraction |
What is the role of acetylcholine in the autonomic nervous system? | It is also commonly released within the autonomic nervous system to promote parasympathetic responses (‘rest and digest’) |
Where is acetylcholine created and how? | Acetylcholine is created in the axon terminal by combining choline with an acetyl group (derived from mitochondrial Acetyl CoA) |
Where is acetylcholine stored and when is it released? | Acetylcholine is stored in vesicles within the axon terminal until released via exocytosis in response to a nerve impulse |
What does acetylcholine activate? | Acetylcholine activates a post-synaptic cell by binding to one of two classes of specific receptor (nicotinic or muscarinic) |
What must be done to acetylcholine in the synapse, continuously? | Acetylcholine must be continually removed from the synapse, as overstimulation can lead to fatal convulsions and paralysis |
What breaks down acetylcholine? | Acetylcholine is broken down into its two component parts by the synaptic enzyme acetylcholinesterase (AChE) |
Where can acetylcholinesterase be found? | AChE is either released into the synapse from the presynaptic neuron or embedded on the membrane of the post-synaptic cell |
What is done with the degraded components of acetylcholine? | The liberated choline is returned to the presynaptic neuron where it is coupled with another acetate to reform acetylcholine |
What are neonicotinoid pesticides? | Neonicotinoid pesticides are able to irreversibly bind to nicotinic acetylcholine receptors and trigger a sustained response |
Why do neonicotinoid pesticides persist? | Neonicotinoid pesticides cannot be broken down by acetylcholinesterase, resulting in permanent overstimulation of target cells |
What does overstimulation of acetylcholine receptors produce? | While low activation of acetylcholine receptors promotes nerve signalling, overstimulation results in fatal convulsions and paralysis |
Why are neonicotinoids more persistent in insects? | Insects have a different composition of acetylcholine receptors which bind to neonicotinoids much more strongly Hence, neonicotinoids are significantly more toxic to insects than mammals, making them a highly effective pesticide |
What are 3 disadvantages of neonicotinoids? | Neonicotinoid use has been linked to a reduction in honey bee populations (bees are important pollinators within ecosystems) Neonicotinoid use has also been linked to a reduction in bird populations (due to the loss of insects as a food source) Consequently, certain countries (including the European Union) have restricted the use of neonicotinoid pesticides |
What is the role of neurotransmitters? | Neurotransmitters bind to neuroreceptors on the post-synaptic membrane of target cells and open ligand-gated ion channels |
What is a graded potential? | The opening of these channels cause small changes in membrane potential known as graded potentials |
When is a nerve impulse initiated? | A nerve impulse is only initiated if a threshold potential is reached, so as to open the voltage-gated ion channels within the axon |
What do excitatory neurotransmitters cause? | Excitatory neurotransmitters (e.g. noradrenaline) cause depolarisation by opening ligand-gated sodium or calcium channels |
What do inhibitory neurotransmitters cause? | Inhibitory neurotransmitters (e.g. GABA) cause hyperpolarisation by opening ligand-gated potassium or chlorine channels |
What determines whether a threshold potential is reached? | The combined action of all neurotransmitters acting on a target neuron determines whether a threshold potential is reached |
Considering depolarisation and hyperpolarisation, when will threshold potential be reached? | If overall there is more depolarisation than hyperpolarisation and a threshold potential is reached, the neuron will fire |
Considering depolarisation and hyperpolarisation, when will threshold potential NOT be reached? | If overall there is more hyperpolarisation than depolarisation and a threshold potential is not reached, the neuron will not fire |
What is the typical threshold potential? | For a typical neuron, the threshold potential (required to open voltage-gated ion channels) is approximately –55 mV |