T1L11: Neuronal signalling

Question 1

Voltage

Answer 1

+20 mV = muscle cells contract, -90mV = cells relax

Question 2

Voltage

Answer 2

Difference in electric potential energy per unit charged between 2 points

Question 3

Current

Answer 3

Flow of electric charge through medium

Question 4

Resistance

Answer 4

opposition to the passage of an electric current - inverse quantity is electrical conductance, measure how easily electricity flows along a certain path

Question 5

Transmembrane potential

Answer 5

○ Measurement of overall electrical potential energy across membrane
○ Vm depends on relative electrical currents and conductance of different ions
Fully permeable = 0 Vm

Question 6

Gating = making channel conduct or not

Answer 6

• Na+ channels open when inside more positive than outside
• Conformational change of the channel molecule
Inactivation = process when membrane is positive, -> channel closure

Question 7

mV for different ions

Answer 7

ENa = +60 mV
EK = -90 mV
ECa = +123 mV
ECl = -40 mV

Question 8

Initial depolarisation

Answer 8

• Na+ conductance shoots up, Na+ goes in and membrane potential depolarises
• Time delay = Na+ conduction diminishes, K+ conductance increases so K+ leaves the cell and voltage returns to resting potential
Not a failed initiation

Question 9

Repolarisation

Answer 9

• Voltage becomes less positive inside cell
• Passage od time = 2 delayed action events (Na+ channel inactivate & delayed rectifier K+ open)
Membrane become more negative as more K+ out and less Na+ in

Question 10

After hyperpolarisation

Answer 10

• Voltage temporarily slightly more negative than at rest
• K+ permeability increases and Na+ decreases -> closer to Ek
Refractory period

Question 11

Neurotransmitter example

Answer 11

Acetylcholine

Noradrenaline

Question 12

Not neurotransmitter

Answer 12

• Drugs eg fluoxetine

Hormones eg growth hormone

Question 13

Small molecules - neurotransmitter

Answer 13

Amino acids - glutamate
Monoamines - dopamine
Acetylcholine

Question 14

Proteins, peptides & larger molecules

Answer 14

Neuropeptides - substance P

Question 15

Catecholamines

Answer 15

Dopamine - parkinson’s
Noradrenaline - reticular activating system - locus coeruleus
Adrenaline - fight/flight

Question 16

Activation of receptor will typically open an ion channel

Answer 16

○ Some receptors cause the postsynaptic cell to depolarise, which may lead to an action potential *E
○ But some receptors do the opposite and tend to prevent the postsynaptic cell (which will have inputs from many cells) from having an action potential,
○ Thus, some inputs to the postsynaptic cell are excitatory and some are inhibitory
Each NT has a different way of being removed from the synapse
○ There are drugs that inhibit the enzymes that breakdown neurotransmitters, e.g. acetylcholine esterase inhibitors
There are drugs that inhibit the transporter proteins that transport the NTs back into the cell, e.g. selective serotonin reuptake inhibitors