lecture 7

Question 1

what affects the shape of APs and neuronal firing

Answer 1

channels- Na drives the front end and Ca drives back

Question 2

properties of channels

Answer 2

phosphorylation, subunits, modifying subunits that associate w/ channel forming units

Question 3

K channels composition

Answer 3

5 separate subunits combined

large scope of diversity - each formed by a different gene

Question 4

voltage gated K channel

Answer 4

delayed rectifier, slowly inactivating or non-inactivating
located within the membrane, a part of sequence has a number of fixed charges
change in charge provides force to physically alter change of position of pore

Question 5

selectivity filter in K ion

Answer 5

selective for permeation of K

big molecules water come off easily which filter depends onNa is larger than K

Question 6

transient K channels

Answer 6

fast inactivation

Question 7

ligand gated K channels

Answer 7

Ca dependant K
some combined with V dependant
some respond to chemical changes

Question 8

apamin

Answer 8

component of bee venom- blocks KCa2 channels
SK Ca activated K channels
affects the afterhyperpolarization which in turn can affect firing rate of a neuron
increases firing rate of a cell because it doesn’t have as much of a hyperpolarization

Question 9

3 categories of calcium activated K channels

Answer 9

Bk channel (big g)
SK channel (small g)
IK channel (intermediate g)

Question 10

formation of Cl Na and Ca

Answer 10

1 subunit - very long protein with different domains

Question 11

CL pore

Answer 11

2 pores conduct ions

Question 12

2 types of ligand gated ion channels

Answer 12

• external ligand
  ex. NT receptor
• internal ligand
  ex. Ca activated K channel

Question 13

statocyst hair cells

Answer 13

channel properties create complex electrical properties
- vibration sensing at a low frequency
- sensory neutron with cilia, when bind they open channels and don’t need AP (short distances)
hair goes back and forth and gets depolarized and opens V gated Ca channels

Question 14

statocyst properties

Answer 14

sits in membrane
requires a high concentration to open Ca channels cuz it has a low affinity
once hyper polarized, Ca channels close and influx stops
having a low affinity means only Ca able to open is the cloud of calcium and once it drops the K channel will open
ALLOWS IT TO CLOSE AGAIN

Question 15

gene classes for voltage gated calcium channel families

Answer 15

L type
P type
N type- blocked by conotoxin
R type

Question 16

3 components of a bursting neuron

Answer 16

1. persistent Na current- bring in depolarization and don’t inactivate (stay open)
2. voltage gated Ca
3. Ca dependant K
   inject buffer and it will grab calcium preventing K from turning on and cell will fire faster

Question 17

sleep wake system

Answer 17

channel properties create firing properties that affect circuit and brain region function
- transition from being sleep to awake by switching from being bursting

Question 18

Na channel toxins

Answer 18

tetrodotoxin- pufferfish
saxitotoxin=- dinoflagellates 
batrachotoxin- frog
charybdotoxin- scorpion
K channel toxin:
dendrotoxoin- snake

Question 19

leiurus scorpion

Answer 19

a-toxin delays Na channel inactivation therefor causing a longer AP
blocks some conductance

Question 20

toxins

Answer 20

toxins from venoms can block channels, lock them open or alter their activation or inactivation kinetics
can alter voltage dependant properties by blocking directly or in pore

Question 21

channelopathies

Answer 21

diseases caused by point mutations in voltage gated channels

Question 22

GEPS

Answer 22

generalized epilepsy with febrile seizures

Na channel B subunit mutation

Question 23

episodic ataxia and benign familial neonatal convulsions -

Answer 23

frequent seizures within first week of life which disappear after a few months
K channel mutation

Question 24

myotonia

Answer 24

muscle weakness

Cl channel mutation