Nerve Tissue Part 2

121 slides
11.44 MB
717 views

Similar Presentations

Presentation Transcript

1

NERVE TISSUE Part 2Instructor Terry Wiseth ANATOMY & PHYSIOLOGY

2

MEMBRANE POTENTIAL AND NERVE IMPULSE TRANSMISSIONResting neurons maintain a difference in electrical charge across their cell membranes++++++++++++++++++++++++++++++++++----------------------------------

3

MEMBRANE POTENTIAL AND NERVE IMPULSE TRANSMISSIONThe inside of the resting neuron is negatively charged, the outside is positively charged++++++++++++++++++++++++++++++++++----------------------------------

4

MEMBRANE POTENTIAL AND NERVE IMPULSE TRANSMISSIONWhen a neuron is stimulated this polarity is reversed, these reversals are called action potentials+++++---++++++++++++++++++---+++++-----+++------------------+++-----

5

ACTION POTENTIALNerve impulses are conducted along the neuron by a wave of membrane polarity reversals (action potentials)

6

ACTION POTENTIALChemical messengers (neurotransmitters) carry nervous impulses from one neuron to another across the synapse

7

THE NEURON MEMBRANE AT RESTNeuron maintains a resting membrane potential of about -70 millivolts across the cell membrane Sodium (Na+) and potassium (K+) are the main ions involved

8

THE NEURON MEMBRANE AT RESTNa+ and K+ cannot pass through the lipid bilayer membrane Move through the membrane by using membrane proteins (pumps)

9

MEMBRANE PROTEINSMembrane proteins do several things: Some "leak" ions all the time Some "leak" ions only when the cell has been stimulated (ion "gates") Some "pump" ions by active transport

10

Na+ / K+ PUMPMembrane proteins actively transport Sodium out of the cell Potassium into the cellClick Here to See Next ImageClick Here to See Next ImageClick Here to See Next ImageClick Here to See Next Image

11

Na+ / K+ PUMPThree Na+ are pumped out for every two K+ pumped in Result is the cell has more Na+ on the outside and more K+ on the insideNa+Na+Na+Na+Na+Na+Na+Na+Na+Na+Na+Na+Na+Na+Na+Na+Na+Na+K+K+K+K+K+K+K+K+K+K+K+K+K+K+K+K+K+K+18+18+17+19+Cell MembraneNa+ / K+ Pump

12

Na+ / K+ PUMPThe pumping of Na+ out makes the outside more positive and the inside of the cell more negative

13

STIMULATED NEURONNerve cells are unique in their ability to carry a signal using membrane potential changes

14

STIMULATED NEURONStimulation of a neuron opens some of the membrane proteins (a.k.a. Na+ gates) Allows Na+ to pass freely into the cells

15

STIMULATED NEURONFree flow of Na+ into the cell causes a reversal of membrane polarity Polarity reversal is called the action potential

16

ACTION POTENTIALReversal of polarity (action potential) moves along the cell like a wave The membrane restores the resting potential very quickly In less than 7 milliseconds the cell can be stimulated again

17

ALL-OR-NONE RESPONSEOnce a threshold limit is reached any stronger stimulus will not increase the cell's response A stimulus below the threshold also will not stimulate the neuron

18

SYNAPSENeurons communicate across the synapse by using chemical messengers called neurotransmitters

19

SYNAPSENeurotransmitters may act to inhibit neurons or to excite neurons

20

SYNAPSEAttachment of the neurotransmitters to presynaptic membrane receptors causes ion channels to open Generate an action potential

21

MEMBRANE POTENTIALPlasma membrane exhibits membrane potential Resting potential Electrical voltage difference across the membrane

22

ACTION POTENTIALWith stimulation resting potential can produce responses called action potentials

23

ACTION POTENTIALResting potential is like voltage stored in a battery Electric current produced by flow of electrons from negative to positive current

24

ACTION POTENTIALAction potentials occur because plasma membrane contains ion channels that open or close in response to stimuli

25

ION CHANNELSNon-gated channels Always open Gated channels Open or close in response to stimuli

26

ION CHANNELSPlasma membrane has many more K+ non-gated channels than Na+ non-gated channels Thus membrane permeability to K+ is higher

Browse More Presentations

Last Updated: 8th March 2018

Recommended PPTs