Mark Louie D. LopezCollege of SciencePolytechnic University of the Philippines
NERVE PHYSIOLOGY
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FUNCTIONS OF NERVOUS SYSTEM
Sensory input or detection
Integration processing
transmission of information
perception of sensory information
learning and memory
thought processes and conscious awareness
planning and implementation of motor commands
Expression of behavior - responses to environment
ANIMAL PHYSIOLOGY
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CELLS OF NERVOUS SYSTEM
ANIMAL PHYSIOLOGY
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NEURON VS GLIAL CELLS
ANIMAL PHYSIOLOGY
NE
UR
ON
SN
EU
RO
GL
IA
• electrically excitable cell th
at processes and transmits
information through
electrical and chemical
signals.
• To surround neurons and
hold them in place,
• Supply nutrients and oxyg
en to neurons,
• To insulate one neuron
from another,
• To destroy pathogens and
remove dead neurons.
NERVOUS SYSTEM
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TYPES OF GLIAL CELLS
ANIMAL PHYSIOLOGY
Microglia act as the first and main form of active immune defense in
the central nervous system
Oligodendrocytes provide support and to insulate the axons in
the central nervous system
Astroglia perform many functions, including biochemical support
of endothelial cells that form the blood–brain barrier, provision of
nutrients to the nervous tissue, maintenance of extracellular ion
balance, and a role in the repair and scarring process of the brain and
spinal cord following traumatic injuries
Ependymal cells are a type of Glial cell and are also CSF producing
cells.
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ANIMAL PHYSIOLOGY
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FUNCTIONAL ORGANIZATION OF NEURONS
Receptive segment: Dendrites
Initial segment: Action Potential
Conductive segment: Axon
Transmissive segment: Axon Terminals
Integration segment: Soma
ANIMAL PHYSIOLOGY
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NEURONS ACCORDING TO FUNCTION
ANIMAL PHYSIOLOGY
Afferent/Sensory Neuron – receives and
transmits impulses to the CNS for
processing
Efferent/Motor Neuron – originates in the
CNS and transmits impulses to effector
organs throughout the body
Interneuron – only in CNS; integrators
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NEURONS ACCORDING TO FUNCTION
ANIMAL PHYSIOLOGY
Afferent Neuron
Efferent Neuron
Inte
rneuro
ns
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NEURONS ACCORDING TO MORPHOLOGY
ANIMAL PHYSIOLOGY
Unipolar – one process from cell body
Bipolar – 2 processes from the cell body and
the presence of axon hillock opposite the
body
Multipolar - 1 axon, several dendrites;
presence of axon hillock continuous to the
initial segment
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NEURONS ACCORDING TO MORPHOLOGY
ANIMAL PHYSIOLOGY
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NEURONS ACCORDING TO MORPHOLOGY
ANIMAL PHYSIOLOGY
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POTENTIAL DIFFERENCE
ANIMAL PHYSIOLOGY
Separated electric charges of opposite sign have the
potential of doing work if they are allowed to come
together. This potential is called an electric potential
or, because it is determined by the difference in the
amount of charge between two points, a potential
difference
Negatively Charged
Positively Charged
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RESTING MEMBRANE POTENTIAL
ANIMAL PHYSIOLOGY
All cells under resting
conditions have a potential
difference across their
plasma membranes oriented
with the inside of the cell
negatively charged with
respect to the outside. This
potential is the resting
membrane potential.
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Concentration gradient
Membrane permeability K+ > Na +
Negatively charged protein A-
ANIMAL PHYSIOLOGY
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Non-gated ion channels
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IONS INVOLVED IN MEMBRANE POTENTIAL
ANIMAL PHYSIOLOGY
• Potassium (K+) Located inside the membrane
Diffuses outside and at a faster rate since the
membrane is more permeable to K+ than to Na+
the diffusion of K+ out makes the membrane
negative, resulting to RMP (-70mV) o
• Sodium (Na+) Located outside the membrane and
moves inwards . Na-K Pump: restores the balance
of ions and maintains the -70mV RMP
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IONS INVOLVED IN MEMBRANE POTENTIAL
ANIMAL PHYSIOLOGY
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CHANGES IN MEMBRANE POTENTIAL
ANIMAL PHYSIOLOGY
Graded potential
Action potential
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ACTION POTENTIAL
ANIMAL PHYSIOLOGY
Transient changes in the membrane potential from its
resting level produce electric signals. Such changes
are the most important way that nerve cells process
and transmit information.
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ACTION POTENTIAL
ANIMAL PHYSIOLOGY
Action potential - reversal of polarity
normal polarity: negative inside, positive outside
reversed: positive inside, negative outside
Initiated when threshold potential is with explosive opening
of the remaining voltage-gated Na+ channels
Opening voltage-gated ion channels Na+ and K +
successively
Electrical signal that propagate along a long distance
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ACTION POTENTIAL
ANIMAL PHYSIOLOGY
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MEMBRANE ION CHANNELS
ANIMAL PHYSIOLOGY
a. Leak Channels
responsible for the mov’t of ions
non gated ion channels - the resting
potential of the axon is -70mV
b. Gated Ion Channels/Voltage-Gated Channels
sensitive to voltage difference across the
membrane
closed at resting state
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MEMBRANE ION CHANNELS
ANIMAL PHYSIOLOGY
Na Channel – 2 gates
- Activation Gate (M Gate)
– close at rest
- Inactivation Gate (H
Gate) – open at rest
K Channel – (N Gate) -
closing gate
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THRESHOLD POTENTIAL
ANIMAL PHYSIOLOGY
Critical membrane potential o a change of at least 15mV
will elicit an action potential. Otherwise, a local event is
produced. And once the threshold is reached, more
explosive depolarization occurs (reversal of polarity, turned
to positive
70mV to -55mV: caused by the influx of Na+, hence the
membrane potential will lose its positivity resulting to
depolarization
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ACTION POTENTIAL
ANIMAL PHYSIOLOGY
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DEPOLARIZATION
ANIMAL PHYSIOLOGY
Voltage gated Na+ ions open (M, H gates)
Membrane suddenly becomes permeable to sodium ions.
o The rapid influx of Na+ ions causes the membrane
potential to become less negative.
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ACTION POTENTIAL
ANIMAL PHYSIOLOGY
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OVERSHOOT
ANIMAL PHYSIOLOGY
Inactivation gate (H) will close, no entry of
Na+
The rapid influx of Na+ ions causes the
membrane potential to become too positive
o more than 0mV
Reversal of polarity
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ACTION POTENTIAL
ANIMAL PHYSIOLOGY
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REPOLARIZATION
ANIMAL PHYSIOLOGY
The Na+ channels become inactivated,
while voltage-gated K+ channels open.
The efflux of K+ ions gradually restores the
negative membrane potential
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ACTION POTENTIAL
ANIMAL PHYSIOLOGY
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HYPERPOLARIZATION
ANIMAL PHYSIOLOGY
More negative point than the normal RMP
due to the slow closing of K+ channels
and an excess if K+ ions go out of the
cell.
After hyperpolarization, the polarity of the
membrane returns to the resting potential
due to the Na-K electrogenic pump
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ACTION POTENTIAL
ANIMAL PHYSIOLOGY
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ACTION POTENTIAL
ANIMAL PHYSIOLOGY
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CONDUCTION OF IMPULSES
ANIMAL PHYSIOLOGY
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CONDUCTION OF IMPULSES
ANIMAL PHYSIOLOGY
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REFRACTORY PERIODS
ANIMAL PHYSIOLOGY
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REFRACTORY PERIODS
ANIMAL PHYSIOLOGY
Absolute Refractory Period - the period during
which a second action potential cannot be elicited
even with a strong stimulus (because the ion-
gated channels are closed).
no second response no matter how strong the
second stimulus is.
after depolarization, absolute since Na channel is
closed
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REFRACTORY PERIODS
ANIMAL PHYSIOLOGY
Relative Refractory Period - The period wherein
a response may be elicited provided that the
second stimulus is greater than the threshold.
Na+ is slowly returning to resting, from closed H
gate it will open, activation gate will slowly close,
inactivation gate closed –
Technically open Na channel (M closing, H open)
o if the Na gate is open -> returning to resting
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GRADED VS ACTION POTENTIAL
ANIMAL PHYSIOLOGY
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NEUROTOXINSToxin Source Effects
Tetrodotoxin Puffer fish Blocks voltage gated Na+
channels
Saxitoxin Marine dinoflag-gelates, Fresh
water cyanobacterium
Blocks voltage gated Na+
channels
Apamin Honeybee Blocks voltage gated K+
channels
Batrachotoxin Poison arrow frog Keeps Na+ channel from
closing
Calciseptin Black mamba Blocks Ca++ channels
Iberiotoxin Indian red scorpion Blocks K+ channels
Phoneutriatoxin Banana spider Slows closing of Na+ channel
Stichodactylatoxin Sea anemone Blocks voltage gated
K+ channels
ANIMAL PHYSIOLOGY
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3rd review
ANIMAL PHYSIOLOGY
Prepare a powerpoint presentation of the review
Limit your presentation to 10 slides
Must be presentable within 15 minutes given time
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ANIMAL PHYSIOLOGY
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