Lecture on the nervous system

1. Drugs Affecting
the Nervous
System

2. Hello!
I am your teacher –
Nelia B Perez
I hope to have a productive time
with you. 😉😉😉
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3. INTRODUCTION
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4. “ “Live as if you were to die
tomorrow. Learn as if you
were to live forever.” –
Mahatma Gandhi
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5. The
Nervous
System
The nervous system is the master
controlling and communicating
system of the body. Every
thought, action, and emotion
reflects its activity. Its signaling
device, or means of
communicating with body cells,
is electrical impulses, which are
rapid and specific and cause
almost immediate responses.
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6. Physiology
of the
Nervous
System
The physiology of the
nervous system involves a
complex journey of
impulses.
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7. Physiology
of the
Nervous
System
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Nerve Impulse
Neurons have two major functional
properties: irritability, the ability to
respond to a stimulus and convert it
into a nerve impulse, and
conductivity, the ability to transmit
the impulse to other neurons,
muscles, or glands.

8. Physiology
of the
Nervous
System
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Nerve Impulse
•Electrical conditions of a resting
neuron’s membrane. The plasma
membrane of a resting, or inactive,
neuron is polarized, which means that
there are fewer positive ions sitting on
the inner face of the neuron’s plasma
membrane than there are on its outer
surface; as long as the inside remains
more negative than the outside, the
neuron will stay inactive.

9. Physiology
of the
Nervous
System
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Nerve Impulse
•Action potential initiation and
generation. Most neuron in the body
are excited by neurotransmitters
released by other neurons; regardless
what the stimulus is, the result is
always the same- the permeability
properties of the cell’s plasma
membrane change for a very brief
period.

10. Physiology
of the
Nervous
System
10
Nerve Impulse
•Depolarization. The inward rush of
sodium ions changes the polarity of
the neuron’s membrane at that site,
an event called depolarization.
•Graded potential. Locally, the
inside is now more positive, and the
outside is less positive, a situation
called graded potential.

11. Physiology
of the
Nervous
System
11
Nerve Impulse
Nerve impulse. If the stimulus is strong
enough, the local depolarization activates
the neuron to initiate and transmit a long-
distance signal called action potential, also
called a nerve impulse; the nerve impulse is
an all-or-none response; it is either
propagated over the entire axon, or it
doesn’t happen at all;it never goes partway
along an axon’s length, nor does it die out
with distance as do graded potential.

12. Physiology
of the
Nervous
System
12
Nerve Impulse
Repolarization. The outflow of
positive ions from the cell restores
the electrical conditions at the
membrane to the polarized or
resting, state, an event called
repolarization; until a repolarization
occurs, a neuron cannot conduct
another impulse.

13. Physiology
of the
Nervous
System
13
Nerve Impulse
Saltatory conduction. Fibers that
have myelin sheaths conduct
impulses much faster because the
nerve impulse literally jumps, or
leaps, from node to node along the
length of the fiber; this occurs
because no electrical current can
flow across the axon membrane
where there is fatty myelin
insulation.

14. The Nerve
Impulse
Pathway
Resting membrane electrical
conditions. The external face of
the membrane is slightly positive;
its internal face is slightly
negative; the chief extracellular
ion is sodium, whereas the chief
intracellular ion is potassium; the
membrane is relatively
permeable to both ions.
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15. The Nerve
Impulse
Pathway
Stimulus initiates local
depolarization. A stimulus
changes the permeability of a
“patch” of the membrane, and
sodium ions diffuse rapidly into
the cell; this changes the polarity
of the membrane (the inside
becomes more positive; the
outside becomes more negative)
at that site.
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16. The Nerve
Impulse
Pathway
Depolarization and generation of
an action potential. If the
stimulus is strong enough,
depolarization causes membrane
polarity to be completely
reversed and an action potential
is initiated.
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17. The Nerve
Impulse
Pathway
Propagation of the action
potential. Depolarization of the
first membrane patch causes
permeability changes in the
adjacent membrane, and the
events described in (b) are
repeated; thus, the action
potential propagates rapidly
along the entire length of the
membrane.
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18. The Nerve
Impulse
Pathway
Repolarization. Potassium ions
diffuse out of the cell as the
membrane permeability changes
again, restoring the negative
charge on the inside of the
membrane and the positive
charge on the outside surface;
repolarization occurs in the same
direction as depolarization.
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19. Communication
of Neurons at
Synapses
The events occurring at the synapse are
arranged below.
 Arrival. The action potential arrives at the
axon terminal.
 Fusion. The vesicle fuses with plasma
membrane.
 Release. Neurotransmitter is released into
synaptic cleft.
 Binding. Neurotransmitter binds to
receptor on receiving neuron’s end.
 Opening. The ion channel opens.
 Closing. Once the neurotransmitter is
broken down and released, the ion channel
close. 19

20. Autonomic
Functioning
Body organs served by the autonomic nervous system
receive fibers from both divisions.
▫ Antagonistic effect. When both divisions serve the
same organ, they cause antagonistic effects, mainly
because their post ganglionic axons release different
transmitters.
▫ Cholinergic fibers. The parasympathetic fibers
called cholinergic fibers, release acetylcholine.
▫ Adrenergic fibers. The sympathetic postganglionic
fibers, called adrenergic fibers, release norepinephrine.
▫ Preganglionic axons. The preganglionic axons of
both divisions release acetylcholine.
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21. Sympathetic
Division
The sympathetic division is often referred to as the “fight-
or-flight” system.
▫ Signs of sympathetic nervous system activities. A
pounding heart; rapid, deep breathing; cold, sweaty
skin; a prickly scalp, and dilated pupils are sure signs
sympathetic nervous system activities.
▫ Effects. Under such conditions, the sympathetic
nervous system increases heart rate, blood pressure,
and blood glucose levels; dilates the bronchioles of
the lungs; and brings about many other effects that
help the individual cope with the stressor.
▫ Duration of the effect. The effects of sympathetic
nervous system activation continue for several
minutes until its hormones are destroyed by the liver.
▫ Function. Its function is to provide the best conditions
for responding to some threat, whether the best
response is to run, to see better, or to think more
clearly.
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22. Parasympathetic
Division
The parasympathetic division is most active when the
body is at rest and not threatened in any way.
▫ Function. This division, sometimes called the “resting-
and-digesting” system, is chiefly concerned with
promoting normal digestion, with elimination
of feces and urine, and with conserving body energy,
particularly by decreasing demands on
the cardiovascular system.
▫ Relaxed state. Blood pressure and heart and
respiratory rates rate being regulated at normal
levels, the digestive tract is actively digesting food,
and the skin is warm (indicating that there is no need
to divert blood to skeletal muscles or vital organs.
▫ Optical state. The eye pupils are constricted to
protect the retinas from excessive damaging light,
and the lenses of the eye are “set” for close vision.
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23. STILL
AWAKE??
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24. https://drive.google.com/file/d/1MdlYeXD0-
nbcUiy7vOcEIGsZ25rF_uGW/view?usp=sharing
https://drive.google.com/file/d/1VpPNSGCEILCx1RSpj
CSWYwdig8LpjsJ4/view?usp=sharing
Journal
Reading
Read the
Articles!
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25. Thanks!
Any questions?
You can find me at
nelia.perez@pcu.edu.ph
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