GS - Neurotransmitters of the brain

Question 1

What is the resting membrane potential of a cell defined as

Answer 1

Goldmann equation - conc ions inside and outside cell and membrane permeability for each ion

Question 2

How does a neuron achieve its resting potential

Answer 2

Membrane proteins act as ion pumps and achieve resting potential (main one is Na K ATPase)

Question 3

What is an action potential and how is it generated

Answer 3

AP’s are electrical impulses or changes in membrane potential that travels along the surface of a neuron.

Initially increased permeability to Na which is caused by Na channels opening and sodium influxes into cell and rapidly depolarises the cell membrane. Na channels shut, membrane becomes more permeable to K, even more than at rest so we get undershoot.

Question 4

What is saltatory conduction

Answer 4

Saltatory Conduction - In myelinated axons, Na channels are grouped together at the gaps in the myelin sheath (nodes of Ranvier). A passive currently is shuttled along a long segment of the myelinated axon then at the node of Raniver the change in membrane potential causes Na channels to open and the action potential is regenerated. It appears to jump from node to node.

Question 5

What is synaptic transmission

Answer 5

Occurs at either electrical or chemical synapse.
Electrical - 2 neurons are coupled together electrically via gap junctions (e.g connexons)
Chemical - pre-synaptic terminal. Synaptic cleft and post synaptic terminal and communication delivered via neurotransmitters

Question 6

What is an ion channel, and what is the difference between a voltage sensitive ion channel and a ligand gated ion channel

Answer 6

Ion channels are membrane proteins that allows ions to pass through them causing a current flow.
Voltage - regulated by membrane potential, a change opens pore
Ligand-gated - regulated by specific molecule that binds to it which opens the pore, e.g Phosphate that comes from ATP

Question 7

What is an IPSP and which ions are usually involved in generating it

Answer 7

IPSP - Inhibitory post synaptic potential - influx of cl- causes membrane potential to move away from threshold

Question 8

What is the difference in signalling process between an ionotropic signal and a metabotropic signal

Answer 8

Ionotropic - Neurotransmitter is coupled with an ion channel, when NT binds it causes a conformational change to open ion channel and allow ions to flow

Metabotropic - Neurotransmitter receptor is coupled with intracellular signalling cascades often through G protein coupled mechanisms (often enzymes involved). These will have a direct effect on ion movements through the modulation of either postsynaptic channels or selective opening or closing of channels

Question 9

What is a neurotransmitter

Answer 9

Neurotransmitters are molecules released by presynaptic neurons and are the means of communication at a chemical synapsee. They bind to neurotransmitter receptors in the post synaptic cleft which can be coupled with an ion channel or intracellular signalling process. Cause either excitory or inhibitory post synaptic potential

Question 10

Name two amino acid neurotransmitters (one inhibitory & one excitatory)

Answer 10

Acetylcholine (Ach - excitory)

Glycine (Inhibitory)

Question 11

Name two biogenic amine neurotransmitters (one inhibitory & one excitatory)

Answer 11

Dopamine Via D1 receptors (excitory)

Dopamine Via D2 receptors (Inhibitory)

Question 12

Name two neuropeptide neurotransmitters (one inhibitory & one excitatory)

Answer 12

Substance P (excitory),

Opioids (Inhibitory)