Physiology Of Neurons

Question 1

What is the gap of electrical synapses?

Answer 1

3.5nm

Question 2

What can electrical synapses not do?

Answer 2

Amplification
And no plasticity

They are coupled via gap junctions

Question 3

Where are electrical synapses used?

Answer 3

In invertebrates for defensive reflexes, Brain and retina

Question 4

Spatial summation?

Answer 4

A neuron decides to fire based on the number of tiny signals synpasing on it i.e convergent neuronal signalling

Question 5

Temporal summation?

Answer 5

When the input neuron is firing fast enough so that the receiving neuron can add together the many signals ultimately reaching threshold .

Question 6

At -70mV which channels are open?

Answer 6

Inward rectifier K+, K+ leaving cell

Question 7

What is threshold voltage?

Answer 7

-50mV

Question 8

What is overshoot?

Answer 8

When Vm is over 0

Question 9

What happens in repolarisation?

Answer 9

Na channels inactivated

Delayed rectifier channels open

Question 10

What is refractory period?

Answer 10

Period of time during which neuron ins incapable of reinitiating an AP, happens during after hyperpolarisation

Question 11

Refractory period is of 2 type?

Answer 11

Absolute- impossible to start new PA

Relative- starting a new PA is difficult

Question 12

How to code for intensity?

Answer 12

Increasing threshold lowers Firing frequency

When lengthy synaptic currents are small, they create higher threshold potential, accommodation of Na, which inactivated during the slower sub threshold depolarisation

Different neurons for different strength stimuli

Question 13

What is the difference between inactivated and a closed channel?

Answer 13

Inactivated- channel stops conducting after a delay when the membrane is positive inside

Closed- membrane is negative inside

Question 14

How does lidocaine work?

Answer 14

Local anesthetic, raises the threshold, lowers excitability, stopping action potential locally

Specifically blocks Na channel in the inactivated state

Question 15

How does carbamazepine work?

Answer 15

Inactivates sodium channels, raises AP threshold and lowers excitability

Question 16

Antiarrhythmic drugs e.g quinidine work by?

Answer 16

Lowering conduction velocity, which extends the refractory period

Na channel blocker

Fugu fish and tetrodoxin

Question 17

Another name for chemical force?

Answer 17

Diffusional

Based on difference in conc across membrane

Question 18

Mnemonic for equilibrium potentials?

Answer 18

A Cat is easy as 123
A Nag retires early at 60
A Club for fighting Ali Baba’s 40 their RS
A king will die at 90

Question 19

Features of a graded potential and examples?

Answer 19

Electrically localised
Decrease as they move along
Last a long time 
Much flatter in shape
Are conducted almost instantly 

E.g rods and cones, hair cells , some smooth cells

Question 20

Conduction velocity of alpha motor fibres?

Answer 20

100m/s, because they are myelinated and have 15 micrometer diameter

Question 21

Conduction velocity of c nociceptive fibres?

Answer 21

1m/s unmyelinated 0.2-1.5 micrometer