6-7. Electrophysiology and Neuronal signalling Flashcards
Example of cells which convey electrical signals
muscle cells blood cells endocrine cells sensory cells glial cells immune cells nerve cells
What did Luigi Galvani do in the 1790s?
Frog leg nerve stimulation
Advantages of cell-attached patch clamp recording (2)
Can record single channels
Do not change the channel properties
Disadvantages of cell-attached patch clamp recording (3)
Poor pharmacology
Cannot change external medium in vicinity of the channel
Do not know the resting potential
Advantages of cell-excised patch clamp recording (3)
Record single channels
Good pharmacology
Change inside/outside solutions
Disadvantages of cell-excised patch clam recording (2)
May change the channel properties
Disrupted connection to cytoskeleton and intracellular effector proteins
Advantages of whole-cell patch clamp recording (5)
Control of membrane potential and current
Multiple channel recording but properties of single channel can be evaluated
Good pharmacology
Change inside/outside solutions
Various modifications
Disadvantages of whole-cell patch clamp recording (2)
Higher noise and leakage current
Some intracellular proteins can be washed out
How many activation gates and inactivation gates in Na conductance determined by?
3 activation
1 inactivation
The 3 voltage sensitive K+ Channels
K IR - inward rectifier
K V2.1 - delayed rectifier
K V4.1 - A type/transient
3 K channels that require factors to open/close
BK - Ca++ dependent
SK - Ca++ dependent
K-ATP - ATP dependent
5 Types of Na+ Channels
I II IIA III VI
Which type of Ca++ HVA channel is involved in muscle contraction?
L type
Which toxin blocks N type Ca++ channels
Conus snail toxin
Which toxin blocks P/Q type Ca++ channels
Funnel web spider toxin
What forms the ion selectivity filter in ion channels?
S5 and S6
What forms an inactivation gate in ion channels?
peptide chain between S6 of subunit III and segment S1 of subunit IV
How is the inner ring of Na+ channel highly selective for monovalent Na+?
Contains D- E- K+ A - net charge of -1
How is the inner ring of Ca++ channel highly selective for monovalent Ca++?
E-E-E-E- net charge of minus 4 so selective for divalent ions
How does K+-channel pore filter the smaller Na+ ions out?
K+ ions can interact with O atoms on amino acids at the filter region to strip hydration shell.
Na+ ions are too small to interact with all 4 O atoms
4 Characteristics of principal neurones
usually excitatory
usually have pyramidal shape and spines,
integrate numerous long-range inputs from other circuits
and local inputs from interneurons;
send their axons (innervate) other networks
4 Characteristics of interneurones
usually inhibitory
do not have spines
get most inputs from local principal neurons,
send their outputs locally
