L13

Question 1

Diff pathologies in excitable cells

Answer 1

Heart:
Sino-atrial node - pacemaker activity HCN
Cardiac myocyte - ventricular AP (hERG)
Pancreas:
insulin-secreting ß cells - sensing glucose (Kir6.2)

Question 2

3 phase cycle

Answer 2

Electrical activity in the heart and the current/ion channels that contribute to pacemaker activity
0 - upstroke. Ca2+ current, slow depolarisation
3 - repolarisation. K+ current repolarisation
4 - pacemaker. If pacemaker current, It subthreshold Ca2+ current

Question 3

If pacemaker current

Answer 3

supports AP
inward current, but activated by hyperpolarisation at -50 to -40. opposite to conventional voltage channels, hence FUNNY

Question 4

HCN

Answer 4

Hyperpolarisation activated Cyclic Nucleotide-gated channels

Question 5

CNBD

Answer 5

Cyclic Nucleotide (cGMP/cAMP) Binding Domain shifts voltage - dependence of activation to a more +ve level

Question 6

Automatic modulation

Answer 6

Heart controlled by parasympathetic input (VAGUS), Ach release slows pacemaker firing
Spinal nerve increases HR through sympathetic input, noradrenaline speeds up pacemaker firing rate

Question 7

HCN drugs

Answer 7

Ivabradine is a HCN blocker, slows HR
also for chronic stable angina

Question 8

K+channels with unusual features

Answer 8

partial inactivation at >0mV
if QT isnt spot on, complications. Na+ doesn’t deactivate.
prolonged AP is bad
Long QTs –> arrhythmias, loss of consciousness, death

Question 9

what are long QTs?

Answer 9

Abnormally long interval between onset of excitement and contraction of ventricles and their subsequent relaxation.
12+ LQT genes, hard to test drugs

Question 10

islets of longerhans

Answer 10

dotted around the pancreas
ß cells stimulate glucose uptake, metabolism and storage following ingestion of carbs and reduces extracellular levels.
K.ir6.2

Question 11

What are islets of lonerghans made up of

Answer 11

four inward rectifiers K.ir6.2 (closed), and four SUR1s (open)