L5 Physiology Of Neurons

Question 1

What are 2 ways an electrical synapse differs from chemical synapse?

Answer 1

No chemical release in electrical synapse and no amplification because signal is degraded due to electrical resistance

Question 2

What is spatial summation?

Answer 2

The sum of signals from several pre-synaptic neurone dictates a neurone’s response.
- Can be excitatory or inhibitory.

Example of convergent neuronal signalling.

Question 3

What is temporal summation?

Answer 3

Input neuron is firing fast enough so that the receiving neuron can ‘add together’ many signals to reach threshold.
The pre-synaptic neurone fires several signals fast enough for the post-synaptic neurone to not recover and receive another signal.

Question 4

Coding of intensity by neurons

Answer 4

Increased firing frequency = increased intensity of activity

Increased excitatory synaptic activity= increased firing frequency.

Higher threshold voltage= decreased firing frequency, thus intensity of activity is lower.

Question 5

What is accommodation?

Answer 5

changes in the face of continued stimulation

Lengthy small synaptic currents increase threshold potential for AP generation.
- Na+ channels are inactivated

Question 6

What is excitability?

Answer 6

How easy it is to fire an AP.

Increased threshold potential = lower excitability.

Question 7

What is the difference between an inactivated channel and a closed channel

Answer 7

Both non-conducting
inactivated channel- membrane is positive

closed channel- when membrane is negative

Question 8

Lidocaine = Lignocaine

Answer 8

Local anasthetic applied topically
MOA: blocks Na+ channels
raises threshold, lowers excitability, which stops AP

Question 9

Carbamezapine

Answer 9

Anticonvulsant
Neuropathic pain and seizure disorders.
inactivates Na+
raises threshold, lowers excitability

Question 10

What is an equilibrium potential?

Answer 10

When the Electrical force and the chemical force of an ion is equal
- Voltage flowing in is equivalent to voltage out.

Question 11

Graded potentials

Answer 11

*Decrease as they move along*
Electrically localised  
Last a long time
much Flatter in shape
Are conducted almost instantly
Can trigger AP if large enough

Question 12

Clinical Uses of Conduction Velocity

Answer 12

allows you to investigate source of motor weakness in arms and legs
can detect conduction block and slowing

Question 13

Ek

Answer 13

-90 mV

Question 14

ENa

Answer 14

+55mV

Question 15

ECa

Answer 15

+123mV

Question 16

ECl

Answer 16

-65mV