ANIMAL PHYSIOLOGY LECTURE
2ND SEMESTER | A.Y. 2022-2023
LESSON 1: NEURON STRUCTURE AND nasa central nervous
FUNCTION (PART 2) system)
Asynchronous Session o They transmit the action
potential
Conduction Velocity: Summary Slide o Axons that are myelinated
(wrapped with a myelin
sheath) DO NOT participate
in the transmission of action
potential
Internodes: the myelinated region
Transmission of the action
potential throughout the axon is
Conduction Velocity: Tells us NOT Continuous; action potential
how fast the signals are being jumps from one node of Ranvier to
transmitted by the axon; based on: another node of Ranvier and so on
o Axon diameter (surface o Action potential leaps from
area) node to node
o Myelination This action of transmission from
o Type of Conduction node of Ranvier to the next is
o To be answered: Saltatory conduction
o It makes the transmission of
action potential very fast
Myelination and rapid
Especially along very
large axons like the
sciatic nerve (Giant
axons = giant squid)
Myelination (cont.)
Vertebrate Neurons are usually
myelinated
o Not all are myelinated
(unmyelinated)
o There’s a variety of
neurons:
Myelinated and
unmyelinated (A) depicts a myelinated axon
Large and small o If there is a myelin sheath,
diameter neurons action potential will travel
Myelin: insulating layer of lipid- from the axon hillock to one
rich process of Schwann cells, in node of Ranvier to another
the peripheral nervous system, or node of Ranvier and so on
oligodendrocytes, in the central o Basically, the function of the
nervous system myelin sheath is to insulate
o Schwann cells and the axon, making that
oligodendrocytes: Types of covered area incapable of
glial cells, or supporting participating in action
cells, to the neuron potential: Saltatory
o Wraps around the axon conduction
o Function: Reduce the So mas mabilis pag-
leakage of charge across transmit niya
the membrane basically
Myelin sheaths wrap around the (B) depicts a unmyelinated axon
neuron but there are portions in o Can be seen that the action
the axon that are unmyelinated = potential, or depolarization,
Nodes of Ranvier happens throughout the
o Nodes of Ranvier: exposed axon
axonal membrane between o Due to this long
Schwann cells (kapag depolarization, or
located sa peripheral transmission, of action
nervous system) or potential:
oligodendrocytes (kapag The transmission of
, from the axon hillock
to the axonal
terminal is very
long/lengthy
(matagal)
Summary Slide: Answer and
Explanation
Remember: Neuron is the cell;
nerve fiber is a collection of axons
Many different kinds of axons
Axon Diameter: helps in
Remember: A-alpha fiber are
conduction velocity since it allows
large diameter nerve and is
for greater surface area
myelinated
o Larger surface area =
o C fiber nerve are small
higher conduction velocity
diameter nerve with no
(conduction is more rapid)
myelination
Myelinated: Allows for saltatory
o Can be seen na big ang
conduction
o Helps in increasing difference nila sa
conduction velocity
conduction velocity
Synaptic Transmission at Terminal
Comparison in the Conduction
Buttons
Velocity
So bottom row is the saphenous
nerve of the cat (C fiber); smallest After propagation of the action
nerve in the table potential:
o Small diameter and o Once the action potential
unmyelinated = conduction reaches the axon
velocity is very slow (2 button/terminal, it will
m/sec lang) trigger another voltage-
Comparing to the squid/giant axon gated channel
(50 – 1000 um) o This is the voltage-gated
o large diameter and Calcium channel
unmyelinated Electrical Synapse: Connected
o Despite being via the gap junctions
unmyelinated, since it’s o Conducts very rapidly
very large, it is still quite o Abundant in the brain of
rapid in conducting signals embryo
(30 m/sec) o Once embryo is born and
In frog sciatic nerve (18 um), even matures into adulthood,
if it’s smaller in diameter, since it is electrical synapse will turn
myelinated, it is much faster in into chemical synapse
propagating action potential Chemical Synapse: Utilizes
compared to the squid axon neurotransmitters that are
In the saphenous nerve of the cat excreted extracellularly
(A fiber), with 22 um in diameter o Does not use gap junctions
and is myelinated, it can transmit a anymore
speed of 120 m/sec o Abundant in brain of adult
Basically, game-changer ang human
myelination o Slower than the Electrical
o mas mabilis talaga kapag Synapse, but only a delay
myelinated of 0.3 ms – 5.0 ms
Human Nerve Fiber Classifications
2ND SEMESTER | A.Y. 2022-2023
LESSON 1: NEURON STRUCTURE AND nasa central nervous
FUNCTION (PART 2) system)
Asynchronous Session o They transmit the action
potential
Conduction Velocity: Summary Slide o Axons that are myelinated
(wrapped with a myelin
sheath) DO NOT participate
in the transmission of action
potential
Internodes: the myelinated region
Transmission of the action
potential throughout the axon is
Conduction Velocity: Tells us NOT Continuous; action potential
how fast the signals are being jumps from one node of Ranvier to
transmitted by the axon; based on: another node of Ranvier and so on
o Axon diameter (surface o Action potential leaps from
area) node to node
o Myelination This action of transmission from
o Type of Conduction node of Ranvier to the next is
o To be answered: Saltatory conduction
o It makes the transmission of
action potential very fast
Myelination and rapid
Especially along very
large axons like the
sciatic nerve (Giant
axons = giant squid)
Myelination (cont.)
Vertebrate Neurons are usually
myelinated
o Not all are myelinated
(unmyelinated)
o There’s a variety of
neurons:
Myelinated and
unmyelinated (A) depicts a myelinated axon
Large and small o If there is a myelin sheath,
diameter neurons action potential will travel
Myelin: insulating layer of lipid- from the axon hillock to one
rich process of Schwann cells, in node of Ranvier to another
the peripheral nervous system, or node of Ranvier and so on
oligodendrocytes, in the central o Basically, the function of the
nervous system myelin sheath is to insulate
o Schwann cells and the axon, making that
oligodendrocytes: Types of covered area incapable of
glial cells, or supporting participating in action
cells, to the neuron potential: Saltatory
o Wraps around the axon conduction
o Function: Reduce the So mas mabilis pag-
leakage of charge across transmit niya
the membrane basically
Myelin sheaths wrap around the (B) depicts a unmyelinated axon
neuron but there are portions in o Can be seen that the action
the axon that are unmyelinated = potential, or depolarization,
Nodes of Ranvier happens throughout the
o Nodes of Ranvier: exposed axon
axonal membrane between o Due to this long
Schwann cells (kapag depolarization, or
located sa peripheral transmission, of action
nervous system) or potential:
oligodendrocytes (kapag The transmission of
, from the axon hillock
to the axonal
terminal is very
long/lengthy
(matagal)
Summary Slide: Answer and
Explanation
Remember: Neuron is the cell;
nerve fiber is a collection of axons
Many different kinds of axons
Axon Diameter: helps in
Remember: A-alpha fiber are
conduction velocity since it allows
large diameter nerve and is
for greater surface area
myelinated
o Larger surface area =
o C fiber nerve are small
higher conduction velocity
diameter nerve with no
(conduction is more rapid)
myelination
Myelinated: Allows for saltatory
o Can be seen na big ang
conduction
o Helps in increasing difference nila sa
conduction velocity
conduction velocity
Synaptic Transmission at Terminal
Comparison in the Conduction
Buttons
Velocity
So bottom row is the saphenous
nerve of the cat (C fiber); smallest After propagation of the action
nerve in the table potential:
o Small diameter and o Once the action potential
unmyelinated = conduction reaches the axon
velocity is very slow (2 button/terminal, it will
m/sec lang) trigger another voltage-
Comparing to the squid/giant axon gated channel
(50 – 1000 um) o This is the voltage-gated
o large diameter and Calcium channel
unmyelinated Electrical Synapse: Connected
o Despite being via the gap junctions
unmyelinated, since it’s o Conducts very rapidly
very large, it is still quite o Abundant in the brain of
rapid in conducting signals embryo
(30 m/sec) o Once embryo is born and
In frog sciatic nerve (18 um), even matures into adulthood,
if it’s smaller in diameter, since it is electrical synapse will turn
myelinated, it is much faster in into chemical synapse
propagating action potential Chemical Synapse: Utilizes
compared to the squid axon neurotransmitters that are
In the saphenous nerve of the cat excreted extracellularly
(A fiber), with 22 um in diameter o Does not use gap junctions
and is myelinated, it can transmit a anymore
speed of 120 m/sec o Abundant in brain of adult
Basically, game-changer ang human
myelination o Slower than the Electrical
o mas mabilis talaga kapag Synapse, but only a delay
myelinated of 0.3 ms – 5.0 ms
Human Nerve Fiber Classifications
