L5:/L7 A LEVEL PREP; Excitable cells, AP, and ANS

Question 1

action potential

Answer 1

a REGENERATING depolarization that PROPAGATES along an EXCITABLE cell
REGENERATING; uses energy to move along the membrane at a constant size\amplitude
PROPAGATES; moves along membrane as an active event
EXCITABLE; capable of generating an action potential

Question 2

Steps involved in AP formation or process

Answer 2

stimulus 
depolarization - threshold- depolarization 
repolarization
hyperpolarization 
Resting MP

Question 3

detailed description of AP formation

Answer 3

stimulus excites the cell- Na channels open and Na follow electrochemical gradient -inside cell

depolarization of membrane occurs to -55mV
THRESHOLD
further depolarization

repolarization- Na channels close, K channels open
occurs at 30mV

hyperpolarization- K channels dont close fast enough

Resting MP achieved -70mV

Question 4

What terminates the Na depolarization process

Answer 4

once its gets to 30mV all Na channels are inactivated ie they close

Question 5

How are ion channels deactivated ie Na and K

Answer 5

by an INACTIVATION GATE

Question 6

How do Na and K ion channels differ

Answer 6

Na- open/close v fast

K- open/close much slower

Question 7

Refactory period

Answer 7

occurs when a second stimulus is applied to neuron/muscle fibre .0001 sec after first one

absolute RP- no AP occurs so no response
neuron or muscle fibre will not be ready to fire again until it reaches RMP; 70mV

relative RP- AP could occur if stimulus is v strong

Question 8

saltatory conduction

Answer 8

Axons are sometimes myelinated - meaning some parts are insulated
gaps in insulation; Nodes of Ranvier
The AP can only jump in nodes
This increases conduction velocity of AP an save energy

Question 9

Schwanns cells

Answer 9

responsible for myelination of peripheral nerves

Question 10

Loss of myelin results in

Answer 10

diseases such as MULTIPLE SCLEROSIS

Question 11

Oligodendrocyres

Answer 11

Responsible for myelibation of axons in CNS