lecture 2 (ch2) 2009
Post on 06-Apr-2018
214 Views
Preview:
TRANSCRIPT
-
8/3/2019 Lecture 2 (Ch2) 2009
1/29
Unit 1 Opener
-
8/3/2019 Lecture 2 (Ch2) 2009
2/29
Video 1: multi-electrode recording onan oscilloscope
Video 2: multi-electrode recordings of motor cortex during tracking task
Video 3: implications for rehabilitationfor stroke and spinal cord injury
-
8/3/2019 Lecture 2 (Ch2) 2009
3/29
Mo to r C o rtex, Spike Rec o rdings, Cyberkinetics
July 2006
http://www.cyberkineticsinc.c om /c o ntent/index.jsp
-
8/3/2019 Lecture 2 (Ch2) 2009
4/29
Intr o ducti o n t o Electrical Signaling of Nerve Cells
A m icr o electr o de m ade of glass and f illedwith a salt s o lutio n (c o nductive) can rec o rd
the transm
em
brane vo
ltageof
a nerve cell
The f irst event that happens when them icr o electr o de is inserted is that a verys m all negative v o ltage is rec o rded, calledthe resting m e m brane p o tential
-
8/3/2019 Lecture 2 (Ch2) 2009
5/29
Intr o ducti o n t o Electrical Signaling of Nerve Cells
Neur o ns generate a negative p o tential at rest,called the resting m e m brane p o tential Can be rec o rded inside and o utside of nerve cells T ypically between -40 t o -90 mV
Neur o ns generate electrical signals based o nthe f lo w of io ns acr o ss their plas m a m e m brane
Recept o r p o tentials are due t o activati o n of sens o ry neur o ns by external sti m uli Light, heat, s o und
-
8/3/2019 Lecture 2 (Ch2) 2009
6/29
Electrical Signals C o ntinued
Synaptic p o tentials the electrical p o tentialgenerated f r om comm unicati o n f r om o ne neur o nto an o ther Used in central and peripheral nerv o us syste m
W hen neur o ns send signals acr o ss a l o ngdistance d o wn the ax o n, acti o n p o tentials aregenerated.
Are the ax o ns g oo d c o nduct o rs of electricity? Ho w d o es the nerv o us syste m acc ommo date?
-
8/3/2019 Lecture 2 (Ch2) 2009
7/29
F igure 2.1 T ypes of neur o nal electrical signals (Part 1)
P acinian Corpuscle
-
8/3/2019 Lecture 2 (Ch2) 2009
8/29
F igure 2.1 T ypes of neur o nal electrical signals (Part 2)
Hippocampal P yramidal neuron
-
8/3/2019 Lecture 2 (Ch2) 2009
9/29
F igure 2.1 T ypes of neur o nal electrical signals (Part 3)
S pinal motor neuron
-
8/3/2019 Lecture 2 (Ch2) 2009
10/29
H yperp o larizati o n and Dep o larizati o n
Hyperp o larizati o n is when the m e m branepo tential bec om es mo re negative
Dep o larizati o n is when the restingm e m brane p o tential bec om es mo repo sitive A ctio n p o tential o ccurs when the thresh o ld
po tential is reached
-
8/3/2019 Lecture 2 (Ch2) 2009
11/29
F igure 2.2 Rec o rding passive and active electrical signals in a nerve cell (Part 1)
Micr o leo ctr o de
co nnected t o battery
Negative current
applied, what w o uld
happen?
P o sitive currentapplied, what w o uld
happen?
-
8/3/2019 Lecture 2 (Ch2) 2009
12/29
F igure 2.2 Rec o rding passive and active electrical signals in a nerve cell (Part 2)
-
8/3/2019 Lecture 2 (Ch2) 2009
13/29
Speci f ics of acti o n p o tentials
Speci f ics of acti o n p o tentials Independent of current used t o ev o ke it
A
llo
r no
ne M ultiple acti o n p o tentials can o ccur i f thecurrent intensities are su ff iciently l o ng anda m plitude is great en o ugh
Leads t o f requency enc o ding Am plitude of synaptic p o tentials and recept o r
po tentials can be graded
-
8/3/2019 Lecture 2 (Ch2) 2009
14/29
Io nic Mo ve m ents Pr o duce Electrical Signals
Electrical signals generated acr o ssm e m branes
Diff
erences in co
ncentratio
ns M e m branes are selectively per m eable Exchange of io ns acr o ss io nic channels
Pr o teins that all o w o nly certain kinds of io ns t o
cr o ss the m e m brane in the directi o n of their co ncentrati o n gradient
-
8/3/2019 Lecture 2 (Ch2) 2009
15/29
F igure 2.3 T ransp o rters and channels mo ve i o ns acr o ss neur o nal m e m branes
- F riends at the Bears ga m e getsyo u t o a seat that is n o t yo ur ticket.
- T icket checker at Bears ga m eallo wing pe o ple t o go where theyare supp o sed t o go .
-
8/3/2019 Lecture 2 (Ch2) 2009
16/29
Io n transp o rters and Io n channelsbasically w o rk against each o ther
To gether, they help t o generate the restingm e m brane p o tential, acti o n p o tentials,synaptic p o tentials, recept o r p o tentials
-
8/3/2019 Lecture 2 (Ch2) 2009
17/29
F igure 2.4 Electr o che m ical equilibriu m (Part 1)
No electricalpo tential
F loo d le f t side with K+, and i o ns will f lo w d o wn c o ncentrati o n gradient
-
8/3/2019 Lecture 2 (Ch2) 2009
18/29
F igure 2.4 Electr o che m ical equilibriu m (Part 2)
Greater the c o ncentrati o n ino ne side of the m e m brane of K+, then the mo re negative them e m brane p o tential
T his is part of theNernst equati o n
-
8/3/2019 Lecture 2 (Ch2) 2009
19/29
Basic F eatures of the A ctio n P o tential
Nernst equati o n describes a m e m brane p o tentialper m eable t o o nly o ne i o nIf yo u wanted t o calculate the equilibriu m po tentials fo r an i o n use Nernst
Ho wever, David G o ldm an rec o gnized thatm e m branes are per m eable t o mo re than o ne i o n
Go ldm an equati o n describes h o w changingper m eability f r om o ne i o n t o an o ther generatesacti o n p o tentials
-
8/3/2019 Lecture 2 (Ch2) 2009
20/29
T hree Im po rtant Io ns
S o diu m : Na +P o tassiu m : K+Chl o ride: Cl -
Equilibriu m po tentials fo r each i o n are devel o ped byusing the Nernst equati o nEx = R T /zF * ln [X1]/[X2] R is the gas c o nstant T is the abs o lute
te m perature
z is the valence F is the F araday c o nstantS o diu m -po tassiu m pu m p Receives energy f r om AT P
st o red in m ito ch o ndria Breaks AT P d o wn t o A DP
-
8/3/2019 Lecture 2 (Ch2) 2009
21/29
Sh o w Resting P o tential A nim ati o n
-
8/3/2019 Lecture 2 (Ch2) 2009
22/29
F igure 2.6 Resting and acti o n p o tentials arise f r om diff erential per m eability t o io ns
-
8/3/2019 Lecture 2 (Ch2) 2009
23/29
Na resp o nds quickly playing an i m po rtant r o le in acti o n p o tential generati o n
-
8/3/2019 Lecture 2 (Ch2) 2009
24/29
Na increases quickly but K changes mo re sl o wly during an acti o n p o tential
Rec o very ti m eneeded fo r Na to rec o ver Called re f ract o ry
peri o d
Na takes ti m e t o rec o ver but there isno re f ract o ry peri o dfo r p o tassiu mchannels
-
8/3/2019 Lecture 2 (Ch2) 2009
25/29
F igure 2.7 Resting m e m brane p o tential is deter m ined by the K + co ncentrati o n gradient
-
8/3/2019 Lecture 2 (Ch2) 2009
26/29
F igure 2.8 T he r o le of Na + in the generati o n of an acti o n p o tential in a squid giant ax o n (Part 1)
a) A n acti o n p o tential ev o ked under
no r m al c o nditi o ns
b) Na reduced by 1/3 n o tice that
rate of rise and a m plitude of acti o n
po tential is reduced
Na rest o red t o no r m al levels
acti o n p o tential shape is rest o red
-
8/3/2019 Lecture 2 (Ch2) 2009
27/29
F igure 2.8 T he r o le of Na + in the generati o n of an acti o n p o tential in a squid giant ax o n (Part 2)
(D) Na is important in action potential generation
(E) Na is not that important for the resting membrane potential
-
8/3/2019 Lecture 2 (Ch2) 2009
28/29
Sh o w A ctio n P o tential A nim ati o n
-
8/3/2019 Lecture 2 (Ch2) 2009
29/29
Assign m ent fo r W eek 2Read
V ilis 7. To uch GO T Ohttp://www.physphar m .fm d.uw o .ca/undergrad/sensesweb/ W atch M acr om edia F lash Player
Print o ut PD F fo r class fo r T uesday.
Read Chapter 9 of Purves
top related