The Chemical Synapse: Signal Transmission Flashcards
What are the structures in the chemical synapse?
-presynaptic neuron (by axon terminal)
-has vesicles and CA+ and ion channels
-synaptic cleft
-postsynaptic neuron (various ion channels)
What happens at the presynaptic neuron in the process at the chemical synapse
AP arrives and CA channel opens and the ions enter axon on terminal
These vesicles fuse with pre-membrane and release NT into synaptic cleft
What happens in the synaptic cleft in the process at the chemical synapse?
NT diffuse across
What happens at the postsynaptic neuron in the process at the chemical synapse?
-NT bind to ion channels at receptor site
-these open + ions enter post and generate PSP
-NT removed + channels close
-ions drift off down to to axon hillock
Why do ion channels open?
To let ions into dendrites, soma, axon hillock, axon, pre and post
Ion channels facilitate the movement of ions across the membrane, which is crucial for neuronal signaling.
What are the two types of ion channels?
- Voltage gated ion channels
- Transmitter-gated ion channels
Voltage gated channels respond to changes in membrane potential, while transmitter-gated channels respond to neurotransmitter binding.
What triggers voltage gated ion channels to open?
A change in membrane potential
For example, Ca++ channels in the axon terminal open in response to positive charge inside.
What are ionotropic receptors?
Receptors that open channels directly
Ionotropic receptors allow ions to flow immediately upon neurotransmitter binding.
What are metabotropic receptors?
Receptors that open channels indirectly
Metabotropic receptors typically involve a second messenger system to affect ion channel activity.
Are all ion channels in the postsynaptic membrane transmitter-gated?
Yes
All postsynaptic ion channels respond to neurotransmitter binding.
How do different neurotransmitters affect ion channels?
Different channels respond to different neurotransmitters based on receptor shape
The specific neurotransmitter acts like a key, determining which channel opens and the type of ion involved.
Fill in the blank: Voltage gated ion channels respond to _______ in membrane potential.
a change
This change is critical for initiating action potentials in neurons.
True or False: All ion channels in the postsynaptic membrane are voltage gated.
False
All postsynaptic channels are transmitter-gated, responding to neurotransmitters.
What is the effect of excitatory neurotransmitters on a neuron?
Depolarisation, making an action potential more likely
This occurs due to positive ions entering the neuron.
What is the effect of inhibitory neurotransmitters on a neuron?
Hyperpolarisation, making an action potential less likely
This occurs due to negative ions entering the neuron.
What determines whether a post-synaptic neuron will become active?
The combined input of pre-synaptic neurons
This input depends on the neurotransmitter released and the ion channels and receptors present.
What is post-synaptic summation?
The process where electrochemical changes in post-synaptic neurons are triggered by a single action potential
This leads to a gradual build-up of generator potentials.
How does the generator potential (GP) differ from an action potential (AP)?
GP is slow and graded, while AP is rapid and all-or-nothing
GP integrates changes caused by multiple action potentials.
What are the two types of summation in post-synaptic neurons?
- Temporal summation
- Spatial summation
Temporal summation combines post-synaptic potentials (PSPs) in rapid succession, while spatial summation combines PSPs from different synapses.
Fill in the blank: The combined input of pre-synaptic neurons determines whether the post-synaptic neuron will become _______.
active
This is influenced by the type of neurotransmitter and the receptors present.
What is the function of GP?
GP refers to the removal of neurotransmitters (NT) from the synaptic cleft to stop their influence.
GP stands for the process involved in neurotransmitter removal.
What happens to neurotransmitters (NT) when they bind to a receptor?
They do not change and must be removed to stop their influence.
This process is crucial for neurotransmitter signaling.
What are the two types of neurotransmitter removal?
- Degradation
- Re-uptake
These methods ensure that neurotransmitters are cleared from the synaptic cleft.
What is the process of degradation in neurotransmitter removal?
Enzymes in the synaptic cleft break down neurotransmitters, which are partly recycled.
This process involves enzymatic activity that helps in neurotransmitter turnover.
What occurs during re-uptake in neurotransmitter removal?
Receptor molecules at the presynaptic terminal take up neurotransmitters, returning them to the presynaptic cell.
This process helps recycle neurotransmitters for future use.