1. MEMBRANEMEMBRANE
PHYSIOLOGYPHYSIOLOGY
Anita Ocampo-So, MD, FPSP, DPBA, MHA
Professor

2. Nervous SystemNervous System
A complex array of specialized
structures which serve to:
• Receive
• Store
• Transmit information
• Consist of the CNS and the PNS
• Neuron- basic unit of the NS
– 1 trillion neurons

3. NeuronsNeurons
• Made up of dendrites
• Soma
• Axon- axon terminal
• Has different organelles but no
centromere
• Classification according to
1. structure
2. Form
3. covering – Schwann cells

4. NeuronsNeurons

5. NeuronsNeurons
• structures aside from organelles
1. astrocytes
2. microglia
3. oligodendroglia – apoptosis

6. NeuronsNeurons
• Bell-Magendie Law
• Afferent – sensory
• Efferent – motor
• Afferent  200,000 interneuron 
10 efferent

7. NeuronsNeurons

8. Classification of NerveClassification of Nerve
FibersFibers
Class Conduction
Velocity
(m/sec)
Size
( μm)
Functions
A α 70-120 12-20 Proprioception
Somatic motor
β 30-70 5-12 Touch pressure
γ 15-30 3-6 Motor to muscle
spindle
δ 12-30 2-5 Pain,touch, cold
temp
B 3-5 <3 Preganglionic,
Autonomic
C 0.5-2 0.4-1.2 pain, temperature,
mechanoreception

9. Classification of NerveClassification of Nerve
FibersFibers

10. Coverings of NerveCoverings of Nerve
FibersFibers
1. endoneurium
2. perineurium
3. epineurium

11. Coverings of NerveCoverings of Nerve
FibersFibers

12. Properties of NerveProperties of Nerve
FibersFibers
1. Excitability
2. Conductivity

13. Myelinated FibersMyelinated Fibers
• Schwann cells
• Nodes of Ranvier
• Saltatory Conduction
–Advantages
• faster conduction
• saves energy
• less loss of ions

14. Myelinated FibersMyelinated Fibers

15. Resting MembraneResting Membrane
PotentialPotential
• Cells under resting conditions have an
electrical potential difference across
their plasma membrane. This potential
is the Resting Membrane Potential
(RMP)
• The cytoplasm is electrically (-) relative
to the ECF
• The RMP plays a vital role in the
excitability of nerve and muscle cells
and in other cellular responses

16. Genesis of the RMPGenesis of the RMP
1.Distribution of ions
• movement of ions depend on:
a. Concentration
b. Electrical potential difference
• if forces are equal = no movement
– Nernst equation
– Nernst equilibrium
EMF (mo) = (-)61log conc 1/conc 0
= (+)61

17. Genesis of the RMPGenesis of the RMP
– Gibbs-Donnan equilibrium
– Goldman-Hodgkin-Katz
2. Selective Permeability of the Membrane
3. Na+
- K+
pump
• RMP
– skeletal muscle (-)90mV
– nerve (-) 70 mV

18. Action PotentialAction Potential

19. Action PotentialAction Potential
• All-or-Nothing Principle
• Strength – duration curve
–Rheobase
–Utilization time
–Chronaxie

20. Refractory PeriodsRefractory Periods
• Absolute Refractory Period
• Relative Refractory Period
–nerve fibers are not
susceptible to fatigue
• Accommodation

21. Refractory PeriodsRefractory Periods
Local Excitatory States
• subthreshold stimulus
• inadequate duration of applications
According to their location
• receptor potential
• synaptic potential
• pacemaker potential
• end-plate potential
In general, moves the RMP closer to the
threshold potential

22. Synapse and SynapticSynapse and Synaptic
TransmissionTransmission
Synapse
• an anatomically specialized junction
between two neurons
• important in the transport of nerve
signals from one neuron (presynaptic) to
the next neuron (postsynaptic)
– 100 quadrillon synapses in the CNS
– 2 types
a. Electrical
b. Chemical

23. Presynaptic andPresynaptic and
Postsynaptic NeuronPostsynaptic Neuron
Presynaptic neuron
• has lots of mitochondria
• has NTs inside vesicles
• usual forms are ; round, dense, flat and
sphenoid
• intertwining – cerebellum
• basket and climbing – midbrain
Postsynaptic neuron
• contains the receptor proteins

24. Presynaptic andPresynaptic and
Postsynaptic NeuronPostsynaptic Neuron
Presynaptic
Postsynaptic

25. Presynaptic andPresynaptic and
Postsynaptic TransmissionPostsynaptic Transmission
1. axo-axonic
2. axo-dendritic
3. axo-somatic

26. Characteristics ofCharacteristics of
SynapsesSynapses
1.convergence
2.divergence
3.facilitation
4.post-tetanic potentiation
5.fatigue
6.after discharge

27. Characteristics ofCharacteristics of
SynapsesSynapses
7. subliminal fringe
8. occlusion
9. reverberation
10.inhibition
11.summation
– temporal
– spatial

28. Synaptic ResponsesSynaptic Responses
1. excitatory postsynaptic
potential
– can be graded response
which will bring the RMP
closer to the TP
2. inhibitory postsynaptic potential
– makes the membrane
hyperpolarized

29. Classes ofClasses of
NeurotransmittersNeurotransmitters
1. Acetylcholine
2. Biogenic amines – catecholamines,
serotonin, histamine
3. Amino acids – glutamate, GABA
4. Neuropeptides – endogenous opioids
5. Miscellaneous – nitric acid,
adenosine

30. Factors Affecting SynapticFactors Affecting Synaptic
EffectivenessEffectiveness
1. Presynaptic factors
2. Postsynaptic factors
3. General factors

31. ModulatorsModulators
Chemical messengers that elicit
complex responses that cannot
be described as either IPSPs
or EPSPs

32. Factors Affecting SynapticFactors Affecting Synaptic
TransmissionTransmission
1. acid-base states
a. alkalosis
b. acidosis
2. oxygen and CO2 concentrations
• Drugs
– those that excite
– those that inhibit

33. Neuromuscular JunctionNeuromuscular Junction
and N-M Transmissionand N-M Transmission

34. NeurotransmitterNeurotransmitter
ReceptorsReceptors
• metabotropic receptors
• ionophore

35. Acetylcholine SynthesisAcetylcholine Synthesis
and Metabolismand Metabolism
• Acetyl choline cholinesterase
acetate + choline

36. Events during N-MEvents during N-M
TransmissionTransmission
Action potential in Presynaptic Motor axon terminal
Increase in Ca++
ion permeability and influx of Ca++
into the Axon Terminal
Release of Ach from the Synaptic Vesicles into the
Synaptic Cleft
Diffusion of Ach to Postjunctional membrane

37. Events during N-MEvents during N-M
TransmissionTransmission
Combination of Ach with specific receptors on
postjunctional membrane
Increase in permeability of postjunctional
membrane to Na++ and K+ causes EPP
Depolarization of areas of Muscle membrane
adjacent to end plate and initiation of AP

38. Factors affecting NMFactors affecting NM
TransmissionTransmission
1. Ions
2. Drugs – curare, antibiotics
3. Acid – base conditions
4. Temperature

39. Clinical ApplicationsClinical Applications
• Hemicholiniums
• Curare
• Myasthenia Gravis
• Denervation supersensitivity
• Eaton-Lambert Myasthenia
Syndrome

40. Thank YouThank You
andand
Good DayGood Day