Neurotransmission

Question 1

What is membrane potential a result of?

Answer 1

an ion gradient

Question 2

Why do cell gradients form?

Answer 2

• cell membrane is very impermeable to ions
• allows electrical signalling and excitability

Question 3

Where is the action potential generated from + where it travels down?

Answer 3

Action potential generated in axonal
hillock and travels down axon

Question 4

What does an excitable membrane need?

Answer 4

• A negative membrane potential
• Ion concentration gradients
• Ion channels
• Voltage gated
• Ligand gated
• Sodium (Na+)
• Potassium (K+)
• Calcium (Ca2+)

Question 5

What are the levels of different ions inside the membrane during a rest state?

Answer 5

K⁺ = 155mM
Na+ = 12mM
Ca²+ = 0.0001mM
Cl⁻ = 4mM

Question 6

What are the levels of different ions outside the membrane during a rest state?

Answer 6

K⁺ = 4mM
Na+ = 145mM
Ca²+ = 1-2mM
Cl⁻ = 120mM

Question 7

What is the resting membrane potential of a neurone?

Answer 7

-70mV

Question 7

What are some key facts about nerueones?

Answer 7

• Neurones are highly specialised cells
• Transmit information as electrical signals (nerve impulses or action potentials)
• Action potentials only travel one way
• Propagated by axon (begins at axonal hillock)

Question 8

How does the action potential change the value from -70mV?

Answer 8

changes it to +30mV

Question 9

What is an action potential?

Answer 9

Electrical impulses formed by ions moving into the neurone

Question 10

How does the action potential of a membrane work?

Answer 10

The action potential is propagated
down the axon by voltage sensitive channels
* When as action potential occurs, Na+ voltage
sensitive channels open due to the local change in
membrane potential
* This causes more Na+ channels to open
* Na+ channels behind the action potential become
inactive
* Therefore the action potential can only move in ONE
direction

Question 11

What are the phases of action potential?

Answer 11

• depolarisation
• repolarisation
• refractory period

Question 12

What happens when an action potential reaches the end of a neurone?

Answer 12

• At the end of the axon is the synapse
• Presynaptic neuron, synaptic cleft, post synaptic neurone
• Presynaptic terminal contains synaptic vesicles
• Post synaptic terminal has receptors that neurotransmitter binds to

Question 13

What are the two types of neurotransmitter receptors?

Answer 13

• Ionotropic/ligand gated
• Metabotropic (G-protein coupled /
  GPCR

Question 14

What are the differences between the 2 receptors?

Answer 14

• Ionotropic responses are faster
• Metabotropic responses can have
  more diverse effects

Question 15

What is a excitatory neurotransmitter?

Answer 15

*ligand gated
* allow positive ions into the post synapic cell like Na+

Question 16

What is an inhibatory neurostransmitter?

Answer 16

*ligand gated
*allows negative ions into the post synaptic cell like Cl-