Synaptic transmission Flashcards
What is a synapse?
A junction between two synapses or between a synapse and an effector.
Draw the structure of a synapse.
How do the structures involved in synaptic transmission make sure the electrical impulse is unidirectional?
The receptors are only present in the postsynaptic neurone meaning that is the only place an action potential can be triggered.
Describe how an action potential travels across a synapse.
- When an action potential arrives at the end of the presynaptic neurone the membrane becomes excited.
- The membrane becomes more permeable to calcium ions.
- The calcium ions diffuse into the neurone.
- The sudden influx of calcium ions causes the vesicles to fuse with the presynaptic membrane and release neurotransmitters into the synaptic cleft.
- The neurotransmitters bind to receptors on the postsynaptic membrane.
- This causes the sodium ion channels to open and the sodium ions diffuse into the neurone.
- This changes the resting potential and if the potential goes above the threshold level an action potential is triggered.
What are excitatory enzymes?
They depolarise the postsynaptic membrane and trigger the release of an action potential.
What are inhibitory enzymes?
They repolarise the postsynaptic membrane and stop the release of an action potential.
What is summation?
When the effect of many neurotransmitters released from many neurones is combined.
What is spatial summation?
Many presynaptic membranes fire their neurotransmitters at one postsynaptic membrane. These then generate a generator potential large enough to reach the threshold level and trigger an action potential.
What is temporal summation?
Many action potentials arrive at the presynaptic membrane in quick succession. This releases many neurotransmitters into the synaptic cleft. These are then large enough to generate a generator potential large enough to reach the threshold level and trigger an action potential
How is acetylcholine broken down?
Acetylcholinesterase
What is a neuromuscular junction?
A synapse between a motor neuron and a muscle cell.
What are the differences between a neuromuscular junction and a cholinergic synapse?
- A neuromuscular junction has clefts which store acetylcholinesterase.
- A junction has more receptors on the postsynaptic membrane.
- ACh is always excitatory.
What effect do drugs have if they are the same shape as the neurotransmitters?
They can bind to the receptors instead of the neurotransmitters and mimic their actions at receptors.
What effect do drugs have if they block receptors?
The neurotransmitters can no longer bind to the receptors and the receptors can’t be activated.
What effect do drugs have if they inhibit the drug that breaks down the neurotransmitters?
This means the neurotransmitters will continue to bind to the receptors and activate them.
