Make Up Neuro Blok 3 Juli 2014
dr I Njoman Widajadnja, M.Kes (Fis Olahraga)
Excitable Tissues:
• Nerves
• Muscle
• Cardiac muscle
• Skeletal muscle
• Smooth muscle
• Neuron: Functional unit of nervous system, with
excitability and conductivity characteristics
• The number of neurons in the CNS = 1011 = 10 billion
• Glial cells (neuroglia): Non conductive cells which protect,
maintain, and support the nervous system
• The number of glial cells = 10 – 50 x of neurons
THE HISTOLOGY OF NEURON
• Dendrite
• Cell body/ soma
• Axon hillock
• Axon
• Myelin sheath
• Synaptic knobs/
terminal buttons/
axon telodendria
Pyramidal
(pseudounipolar)
• Dendrites & soma  receptive segment
• Axon closest to axon hillock  initial
segment
• Axon  conductive segment
• Axon terminal  transmissive segment
• Stimulus: Any change in the environment that is strong enough to
initiate an action potential
• Action potential: An electrical signal that propagates along the
surface of the membrane of a neuron
• Graded potential: A small deviation from the resting membrane
potential that occurs caused by the different ion channels of all
neuron, ligand-gated or mechanically gated channels open or close
• hyperpolarizing or depolarizing graded potential
hyperpolarizing graded potential inside more negatif
Depolarizing graded potential  inside less negatif
• Receptor potential (sensory receptors)
• Post-synaptic potential (mainly in dendrites & soma):
• Excitatory post-synaptic potential (EPSP)
• Inhibitory post-synaptic potential (IPS
• Action potential  generator potential/ receptor potential
• “Receptor”  - sensory receptor
- proteins bind to hormones/ neurotransmitters
• Sensory receptors: Transducers which alter various energy in the
environment changed into action potentials in neurons
• Sensory organs = receptor + non neural cells
• Mechanism:
Stimulus  receptor/ generator potential (EPSP like; does not
spread, graded, local)  if are reach firing level/ neuronal
threshold  action potential
Characteristics
Origin
Channels
Graded Potential Action Potential
Dendrites/ Soma
Trigger zone of an
axon
Ligand-gated/
Voltage-gated (Na+
mechanically gated and K+)
Conduction
Local, not
propagated
Amplitude
 Stimulus intensity All-or-none (100
Duration
Polarity
Refractory period
(1 mV – 50 mV)
Longer (msec –
min)
Hyperpolarizing/
Depolarizing
Not present
Propagated
mV)
Shorter (0.5 – 2
msec)
Depolarizing 
Polarizing
Present
Ion Channels, macam dan gradien timbulnya
1. Leakage (bocor) channels  K+ leakage channels > Na+ leakage
channels
2. Voltage-gated channels  open/ close in response to a change
in membrane potential  Na+, K+, Ca+
3. Ligand-gated channels  open/ close in response to a specific
chemical stimulus (neurotransmitter, hormones, ions) directly or
indirectly (second messenger system)  Na+, Ca+ inward, K+
outward
4. Mechanically gated channel  open/ close in response to
mechanical stimulation (vibration, pressure, stretching) 
auditory receptors, stretch receptors of internal organs, touch
receptors of skin
THE PHYSIOLOGY OF NEURON in Rest
• Recording with an electrode inside an axon  resting membrane
potential/ polarization  typically -70 mV
(the potential difference between the inside and outside of the axon,
the inside being more negative than the extra-cellular fluid)
• Resting membrane potential  small build-up of negative ions
along the inside of membrane, and positive ions along the outside
• Neurons  range: -40 to -90 mV (ranges of membrane potential
of cells: +5mV to -100 mV)
Resting
membrane
potential
• ECF  Na+ and Cl• ICF (cytosol)  K+ and phosphates (attached to ATP and amino
acids)
• Factors causing the negativity inside neurons:
1. Leakage (bocor) of K+ to ECF
2. Negative ions inside neurons cannot leave cells (attached to
proteins/ larger molecules)
3. Na+/K+ ATPase pumps (3 Na+ out for 2 K+ in)  contributes
only -3 mV
• Synapses
• Axodendritic
• Axosomatic
• Axoaxonic
• Synapses
• Electrical synapses  gap junctions  connexons
• Chemical synapses  neurotransmitters
Excitatory Post-Synaptic Potentials (EPSP)
• Partial depolarization which decreases membrane potential/
increases neuronal excitability
• Cation channels open (Na+, K+, Ca+2)
• Na+ enters cells > Ca+2 inflow or K+ outflow
• Local depolarization  action potential, but facilitating action
potential
Inhibitory Post-Synaptic Potentials (IPSP)
• The increase of negative potential inside cells  -90 mV
(hyperpolarizing post-synaptic potential)
• Opening of Cl- or K+ channels (Cl- enter to the cells and K+ exit
from the cells), or
• Na+ and Ca+2 channels are closed
• Cells body/ soma integrates EPSP and IPSP
• An example of excitatory and inhibitory system  skeletal
muscles motor neuron
• Examples of inhibitory system organization:
• Negative feedback (Renshaw cell), spinal motor neuron
• Cerebral cortex, limbic system, cerebellum
Spatial summation
Temporal summation
Repeated stimulation of one
pre-synaptic neuron on a postSimultaneous stimulation of
many pre-synaptic neurons
on one post-synaptic neurons
synaptic neuron
References
1. Ganong WF (2005). Review of Medical Physiology, 22nd ed.
Chapter 2, Pages: 51-60; Chapter 4, Pages: 85-94.
2. Guyton AC & Hall JE (2006). Textbook of Medical
Physiology, 11th ed. Chapter 5, Pages: 57-71; Chapter 45,
Pages: 555-571
3. Carola R, Harley JP, Noback CR (1990). Human Anatomy &
Physiology. Chapter 11, Pages: 309-327
4. Tortora GJ & Derrickson BD (2006). Principles of Anatomy
and Physiology. Chapter 12, Pages: 406-427