ion channels n ionotropic receptors

Question 1

why is phosolipid bilyer called as parallel capacitor and resistor

Answer 1

ions are unable to penetrate the lipid bilayer of the cell membrane(resistor)

and phospholipid bilayer (insulator ) separates the intracellular space from the extracellular space

the intrinsic electivcal conducted of this structure is very poor(resistor function)

Question 2

presence of ion channel effect on resistance

Answer 2

since the ion channel act as conduits, allow fro flow of ions across the phospholipid bilayer

• decreased resistance

Question 3

what is membrant potential

Answer 3

generated by the differential distribution of ions, particularly Na+, K+ and Cl-

unequal distribution is maintained by ionic pumpus and exchanges

usually -60–75 (diff resting potential for. iff cells )
can also change while the cells are at different level of activity

Question 4

what are important ions in resting potential and where are they present at higher conc

Answer 4

na -outisde
k-inside
ca-outside
cl-outside

Question 5

what are the propertioes of ion channel

Answer 5

rate and direction of ion movemnr thru the pores is governed by electrochemical gradient of the ions in question, which is a function of its concentrations on either side of the membrane , and of the membrane potential

• selectivity( selective to specific ions)
• gating properties (type of control of the ion channel)

Question 6

ion channels protein

Answer 6

transmembrane protein
- pore domain
have voltage sensing domain
ligand binding domain
span across the membrane

Question 7

what are the different type of gatinf of the ion channels

Answer 7

passice (kk + leak channel)
voltage gated (Na, ca, k voltage gated channel)
mechnically gated(baroreceptors and hair cells)
ligand gated (nicotinic acetylcholine, GABA receptor )

Question 8

what s action potential mechanism

Answer 8

1. resting potenital (with ligand gat are closed )
2. stimulus cause some channel to open
3. when the threshold is reached, the action potential occue, more gated channel opens
4. depolarization occcuer: sodium rush into the cell
5. when the voltage is more than 30mv, voltage channel NA+ closes
6. k+ channel opens
7. repolarisation occur where k rush out of the cell
8. voltage will decrease below -70
9. k + channel clsoes
10. an + and k+ pump restore the resting potential of the cell

Question 9

how does signalling happen in one direction only?

Answer 9

when is it depolarsing the behind is repolarising, allowing for signal to only move in one direction

Question 10

two different type of refracotry period an what they do

Answer 10

absoulte and relative
absolute means that another action potential cannot be triggered during this time
Na+ channel are briefly inactviated
and membrane need to be hyper polarised before depolarisation can happen

for relative refractory period,
a stong stimular can cause Ap
- Since membrane is below the resting potential, strong EPSP can trigger the threshold

Question 11

what improves the AP propogation

Answer 11

myeline shealths which are rich in lipids, they are made of oligodendrocytes in CNS and svuann cell in PNS

Question 12

what happens when AP reaches the end

Answer 12

depolarisaion trigger voltage gaterd channel
ca2+ channel open
ca2+ enetr
exocytosis of vesicles
neurotransmitters released into synaptic cleft
neurotransmitters bind to receptor on post synaptic neurons
EPSP/IPSP
Trigger another AP

Question 13

what happens when sodium channel is clocked

Answer 13

increase in threshold for excitation
slow impulse conduction
decreased rate of rise of AP
decreased amplitude of AP
when blocked at critical length, propagation across the blcojed area is impossibl

Question 14

what are drugs used as sodium blocker

Answer 14

local anaestheitc agents , cocaine, lidocaine

Question 15

what are channels that regulate the calcium in and out

Answer 15

ligand gated ca channle
voltage gated ca channel
ryanodine receptor
store operated calcium channels
NA ca exchange

Question 16

state the calcuim effect on cardiac/skeletal msucle

Answer 16

AP travel down the sacolemma

causes openong of the ryanodine and voltage gated ca channel

ca rush into the cell

ca diffuse with cytoplasm towards active filaments(g actin monomers)

ca bind to troponin

confirmation change in troponin

tropomyosin move

g actin active site is exposed, myosin bind to g actin

form cross bridge that causes muscular contraction

Question 17

state the calcium effect on smooth muscles

Answer 17

when there is a increase in free intracellular calcium

increase in calcium influx into the cell
or by release of calcukm from internal stores

free calcium bind to the calmodulin

calcium calmodulin activates myosin light chain kinase
this phosphorylates the myosin light chains in the presence of ATP

myosin light chains are found on the myosin heads

myosin light chains phsophorylation leads to smooth muscle contraction

Question 18

what is the effect of the L type calcium blockade in the heart

Answer 18

reduced in contractility
decreases sinus node pacemaker rate
decrease atrioventricular node condition velocity
use In the treatment of angina and supraventricular tachyarrhythamias

Question 19

what is the effect of the L type calcium blockade in the smooth muscles

Answer 19

losg lasting relaxation
dilate peripheral arterioles and reduce blood pressure
use in the treatment of hypertension

Question 20

list other ligand gated channels

Answer 20

glutamate
acetylcholine
GAB
5HT
ATP

Question 21

List the calcium channel blockers

Answer 21

amiodpine
verapamil

Question 22

what are the molecules for GABA receptor

Answer 22

benzoidiazepines and zolpidem

Question 23

what do GABA regualte

Answer 23

it is a gab RECEPTOR CHOLORIDE CHANNEL COMPLEX

Question 24

what does GABA do ?

Answer 24

postsynaptic
increse the cl- influx from outside

Question 25

what are the selective agnoist and antagosit of GABA

Answer 25

agonist : isoguvacine and antagonist :biuculline

Question 26

what are the regulatory sites on the GABA

Answer 26

benzodiazepine and barbiturate sites

Question 27

what do benzodiazepines do ?

Answer 27

potentiate GABA action by increasing the frequency of GABA induced channel opening

Question 28

what does phenobarbital do?

Answer 28

increases the frequence and duration of opening

Question 29

what are the clincial application of benzodiazepines

Answer 29

anti anxity agenst
sedative agents
anti-epileptic drugs
general anaesthetic agents

Question 30

what are nicotinic acetylcholine receptors

Answer 30

extensive projection out of the membrane
chaneel pore with a narrow spot
closed intracellular end of the channel with laterally places outlets for ions

• subtype found in the skeletal muscles, neurons and autonomic ganglia

Question 31

what are the seletive agonist and antagonist of nicotinic acetylcholine receptors

Answer 31

nicotine is the agonist
a bengartoxin is the antagonist

Question 32

what do neuromuscular blocking drugs

Answer 32

block nitonic receptors function resulting in skeletal muscle paralysis
- used during surgical procedures as muscles relaxants

Question 33

how are neuromuschlar blocking drugs divided?

Answer 33

non depolarising drugs - act as antagonist at the nicotinic receptors

depolarising drugs- act as agnosit at the nicotinic receptors : causing persisten depolarising following by desensitization of the nictonic receptors

Question 34

what are non depolarizing neuromuscular blocking drugs

Answer 34

pancuronium, atracurium and tubocurarine

Question 35

what are depolarizing neuromuscular blocking drugs

Answer 35

succinylcholine

Question 36

name 2 dieases due to defective ino channel functions

Answer 36

function 1: cystic fibrosis
function 2: long qt syndrome

Question 37

what is cyctsic fibrosis

Answer 37

mutation in the epithelial chloride channel cftr(transmembrane conductance regulator)
- deletion of the phenylalanine at position 508, the defective protein cannot reach the surface membrane
- causes impaired cl, conductance in the membrane of the secretory epithelial cells
— in the lungs, this loss of CFTR activity leads to the dehydration in the airway epithelia, thickening mucus, build up of thick mucus promotes bacterial growth and potentially serious lunch infection

Question 38

what is long qt syndrome

Answer 38

mutation in the cardiac potassium channels(HERG, KCNQ1, KCNE1, KCNE2)
loss of function and reduced potassium currents
long AT intervals in the electrocardiogram, reflecting the delayed repolarization of the caridia action potential

– results in irregular heart beat — and muscle weakness