Transcript Power point action potential

Hole’s Human A&P
Hole’s Text : pp. 364-370
Chapter 10
- The Nervous System, Part II
 Resting Membrane Potential
 Graded Potentials
 Action Potential
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4-1
Resting Membrane Potential
• membrane is polarized in a resting neuron
• charge difference on either side of membrane
Outside cell
Inside cell
Outside cell
10-14
Resting potential:

http://bcs.whfreeman.com/thelifewire/content/
chp44/4401s.swf
Resting Membrane Potential
; high concentration inside
cell
Inside or the
outside
+; high concentration
Inside or outside
outside
the cell
Inside or outside
charged proteins are
inside
the cell
hich way is K+ leaking?
hich side of the membrane is more (-)?
Outside cell
Inside cell
Outside cell
10-14
Potential Changes
•polarized resting
membrane potential =
-70mV
•depolarization
•event that makes
the interior less Predict what could make
the interior more positive.
negative
•repolarization
•return to -70mV
(can hyperpolarize)
10-15
Gated Channels

Different types of gates…
some open due to:
- binding of chemicals
- sensory changes (temperature, light, pressure)
- voltage
Local Potential Changes
• chemical gates
•“chemical” that opens the gate = neurotransmitter (nt)
• opens Na+ channels  depolarization
or out of ? cell 
• Na+ ions flow Intointo
( + or -?)
inside of cell becomes more positive
•enough (+) change in charge  opens voltage gates
•See animation of a chemical gated channel:
10-16
Local Potential Changes
•chemical gate opening leads to graded depolarization
•more nt 
more Na+ channels open 
more depolarization
• summation
• combined effect of nt  greater depolarization
until it reaches threshold  action potential
10-16
chemical gates -local potential changes- graded response
voltage gates – action potential
1. Compare location of
chemical gates and
voltage gates.
2. What opens chemical
gates? Voltage gates?
3. To open voltage gates the
interior of the neuron must
reach “threshold”. Explain.
4. When threshold is reached
there is an _____ potential.
Action Potentials – continues
down entire axon
10-17

Axon Returns to Resting State
Repolarization
 Na+ channels close
 K+ channels open
 Is K+ flowing into
or out of the cell?
 Are ions now in their
proper place?
 Na+/K+ pump
restores:
 ion balance
 resting membrane
potential.
Action potential

http://bcs.whfreeman.com/thelifewire/content/
chp44/4402s.swf
Action Potential and Refractory Period


all-or-none
– AP continue along the entire length of axon
after AP brief refractory period
 absolute – new stimulus can’t start another AP
 relative – new, stronger stimulus can start another AP
Conduction along Axons

unmyelinated axons
 AP depolarizes axon segment by segment
 depolarization of 1st segment causes voltage changes
that depolarize the adjoining segment and so on

myelinated axons
 saltatory conduction
 much faster
 AP jumps from node to node
Saltatory Conduction Along Myelinated Fibers

Rate depends on:
 myelination
 axon diameter (wider the axon, the faster)
10-20
Animations – conduction along
unmyelinated and myelinated axons


http://www.brainviews.com/abFiles/AniSal
t.htm
http://www.blackwellpublishing.com/matth
ews/actionp.html