The Chemical Synapse: Signal Transmission

Question 1

What are the structures in the chemical synapse?

Answer 1

-presynaptic neuron (by axon terminal)
-has vesicles and CA+ and ion channels
-synaptic cleft
-postsynaptic neuron (various ion channels)

Question 2

What happens at the presynaptic neuron in the process at the chemical synapse

Answer 2

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

Question 3

What happens in the synaptic cleft in the process at the chemical synapse?

Answer 3

NT diffuse across

Question 4

What happens at the postsynaptic neuron in the process at the chemical synapse?

Answer 4

-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

Question 5

Why do ion channels open?

Answer 5

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.

Question 6

What are the two types of ion channels?

Answer 6

• 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.

Question 7

What triggers voltage gated ion channels to open?

Answer 7

A change in membrane potential

For example, Ca++ channels in the axon terminal open in response to positive charge inside.

Question 8

What are ionotropic receptors?

Answer 8

Receptors that open channels directly

Ionotropic receptors allow ions to flow immediately upon neurotransmitter binding.

Question 9

What are metabotropic receptors?

Answer 9

Receptors that open channels indirectly

Metabotropic receptors typically involve a second messenger system to affect ion channel activity.

Question 10

Are all ion channels in the postsynaptic membrane transmitter-gated?

Answer 10

Yes

All postsynaptic ion channels respond to neurotransmitter binding.

Question 11

How do different neurotransmitters affect ion channels?

Answer 11

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.

Question 12

Fill in the blank: Voltage gated ion channels respond to _______ in membrane potential.

Answer 12

a change

This change is critical for initiating action potentials in neurons.

Question 13

True or False: All ion channels in the postsynaptic membrane are voltage gated.

Answer 13

False

All postsynaptic channels are transmitter-gated, responding to neurotransmitters.

Question 14

What is the effect of excitatory neurotransmitters on a neuron?

Answer 14

Depolarisation, making an action potential more likely

This occurs due to positive ions entering the neuron.

Question 15

What is the effect of inhibitory neurotransmitters on a neuron?

Answer 15

Hyperpolarisation, making an action potential less likely

This occurs due to negative ions entering the neuron.

Question 16

What determines whether a post-synaptic neuron will become active?

Answer 16

The combined input of pre-synaptic neurons

This input depends on the neurotransmitter released and the ion channels and receptors present.

Question 17

What is post-synaptic summation?

Answer 17

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.

Question 18

How does the generator potential (GP) differ from an action potential (AP)?

Answer 18

GP is slow and graded, while AP is rapid and all-or-nothing

GP integrates changes caused by multiple action potentials.

Question 19

What are the two types of summation in post-synaptic neurons?

Answer 19

• Temporal summation
• Spatial summation

Temporal summation combines post-synaptic potentials (PSPs) in rapid succession, while spatial summation combines PSPs from different synapses.

Question 20

Fill in the blank: The combined input of pre-synaptic neurons determines whether the post-synaptic neuron will become _______.

Answer 20

active

This is influenced by the type of neurotransmitter and the receptors present.

Question 21

What is the function of GP?

Answer 21

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.

Question 22

What happens to neurotransmitters (NT) when they bind to a receptor?

Answer 22

They do not change and must be removed to stop their influence.

This process is crucial for neurotransmitter signaling.

Question 23

What are the two types of neurotransmitter removal?

Answer 23

• Degradation
• Re-uptake

These methods ensure that neurotransmitters are cleared from the synaptic cleft.

Question 24

What is the process of degradation in neurotransmitter removal?

Answer 24

Enzymes in the synaptic cleft break down neurotransmitters, which are partly recycled.

This process involves enzymatic activity that helps in neurotransmitter turnover.

Question 25

What occurs during re-uptake in neurotransmitter removal?

Answer 25

Receptor molecules at the presynaptic terminal take up neurotransmitters, returning them to the presynaptic cell.

This process helps recycle neurotransmitters for future use.