Communication between excitable cells

Question 1

How do cardiac cell communicate with each other

Answer 1

There are gap junctions which allows for the flow of charge between the cells- inherit nerve conduction

NO SYNAPSES- quick response

Question 2

Where are synapses found

Answer 2

Between nerves there are synapses

These are specialised junctions between cells- contributing to the processing of nerve conduction

Question 3

Types of synapses

Answer 3

Axo dendritic
Axo Somatic

axo-axonic- capability to prevent AP- important in controlling movement. Infliuential as it decides whether to fire an action potential

Question 4

Sequence of AP

Answer 4

1) Resting AP
2) Depolarisation of synaptic terminal
3) Openning of voltage gated Ca channels
4) Synaptic vesicles fuse with the membrane
5) Transmitter is released
6) ACH receptor is activated, cation channels open
7) Causes local depolarisation which causes a circuit and leads to the opening of Na and K

Question 5

Propagation of Action Potential

Answer 5

Na + flows in and K+ flows out- leading to a small action potential

This leads to the depolarisation of the membrane which leads to the flow of current and opening of voltage gated channels

Question 6

Drugs and transmission

Answer 6

KEY- many drugs act on synapses

Question 7

Describe the Bernard Katz experiment

Answer 7

Low calcium, High Mg, Curare—> leads to decreased vesicle release

This shows that not enough Ca can move into the presynaptic membrane
No extra NTs move into the post synaptic membrane
Small End plate potentials
Sub Threshold
No AP triggered

Question 8

Describe the propagation of the signal

Answer 8

The further away one goes from the end plate the smaller the potenial gets - electronic conduction

Question 9

The knee jerk reflex

Answer 9

Causes the quadriceps to elongate by fraction of mm
The muscle spindles lengthen which causes depolarisation

The impulse bifocates- towards the muscle contraction and other muscle relaxation

Excitatory Post synaptic potentials- glutamate released to the motor neurone in the spinal cord - depolarisation - nT release at the Neuromuscular junction

Inhibitory- gultamate released to the interneurone- interneurone releases inhibitory NT to the motor neruone causing the hyper depolarisation of motor neurone.

Question 10

EPSPs and IPSPs

Answer 10

Sub threshold events which determine if the neurone will reach the threshold or not- and hence if a AP is fired or not

EPSPs add to generate depolarisation and IPSPs add to generate hyper polarisation. they cancel each other out