Define action potential
AKA nerve impulses
Communication electrochemical signals occurring over long distances.
They are triggers by graded potentials (short distances) either as muscle or nerve action potentials along neuronal axons.
Every action potential is dependent on resting membrane potential and present ion channels to provide path for ions to flow across plasma membrane.
What effect do ion channels have on action potentials?
Flow down electrochemical gradients from high to low conc. Areas due to electrical energy
What are the two types of synapses?
Electrical and chemical
What are electrical synapses?
Less common than chemical
Consisting of gap junctions. Channel proteins connect cytoplasm of adjacent neurons and allow ions and small molecules to flow directly from one neuron to the next.
These neurones are electrically coupled and transmission across these synapses are rapid.
-This can be unidirectional or bidirectional
Provide simple means of synchronising the activity of all interconnected neurones.
WHat are chemical synapses?
Most common type of synapse.
Release and reception of chemical messengers known as neurotransmitters.
What’s the structure of chemical synapses?
- Consists of Axon Terminal of presynaptic neuron containing synaptic vesicles containing neurotransmitters.
- And receptor region on postsynaptic neurons membrane located on dendrite or cell body.
These membranes separated by synaptic cleft
Explain the process of synaptic communication at neuromuscular junction
- Action potential arrives at axon terminal
- Voltage gated calcium channels open and calcium enters then axon terminal
- Calcium entry causes synaptic vesicles to release neurotransmitter by exocytosis.
- Neurotransmitter diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic membrane.
- Binding of neurotransmitter opens ion channels, creating graded potentials
- Neurotransmitter effects are terminated.
WHats the refractory period/ synaptic delay?
Time before next chemical signal can be sent.
