Nervous System
First Lecture
Prof. Dr. S. Kattan
Arab International University
Faculty of Pharmacy
Physiology
• Can be defined as the scientific
discipline that deals with the processes
or functions of living things.
• The major goals of physiology are:
• 1- To understand and predict the body’s
responses to stimuli.
• 2- To understand how the body maintains
conditions within a narrow range of values
in the presence of a continually changing
environment.
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Homeostasis
• Homeostasis is the maintenance of a relatively
constant environment within the body.
• Most cells of the body are surrounded by a
small amount of fluid, and normal cell functions
depend on the maintenance of its fluid
environment within a narrow range of conditions,
including temperature, volume, and chemical
content.
• These conditions are called variables because
their values can change .
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• For example, body temperature
is a variable that can increase in
a hot environment or decrease
in a cold environment.
• Homeostatic mechanisms,
such as sweating or shivering,
normally maintain body
temperature near an ideal
normal value, or set point.
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Homeostasis
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Negative feedback
• Most systems of the body are regulated by
negative- feedback mechanisms, which
function to maintain homeostasis.
• Negative means that any deviation from
the set point is made smaller or is resisted.
• Negative feedback dose not prevent
variation but maintains variation within a
normal range.
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• The maintenance of normal blood pressure
is an example of a Negative- feedback
mechanism.
• Normal blood pressure is important
because it is responsible for moving blood
from the heart to tissues.
• The blood supplies the tissues with oxygen
and nutrients and removes waste products.
• Thus normal blood pressure is required to
ensure that tissue homeostasis is
maintained.
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Many NFM such as the one maintaining NBP
have three components:
• 1-a receptor monitors the value of a variable such as
blood pressure.
• 2-a control center, such as part of the brain, establishes
the set point around which the variable is maintained.
• 3-an effector such as the heart, can change the value
of the variable.
• Blood pressure depends in part on contraction of the
heart: as heart rate increases, blood pressure
increases, and as heart rate decreases, blood pressure
decreases.
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Example of Negative feedback
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Positive feedback
• Positive- feedback mechanisms are not
homeostatic and are rare in healthy individuals.
• Positive implies that when a deviation from a
normal value occurs, the response of the system
is to make the deviation even greater.
• Positive feedback therefore usually creates a
cycle leading away from homeostasis and in
some cases results in death.
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Positive feedback
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Nervous System
functions of the nervous system
• 1-Sensory input.
• Sensory receptors monitor numerous external and
internal stimuli that may be interpreted as touch,
temperature, taste, smell, sound, blood pressure, and
body position.
• Action potentials from the sensory receptors travel along
nerves to the spinal cord and brain, where they are
interpreted.
• 2-Integration.
• The brain and spinal cord are the major organs for
processing sensory input and initiating responses. the
input may produce an immediate response, may be
stored as memory, or may be ignored.
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Nervous System Continue
• 3-Homeostasis.
• The nervous system plays an important role in the
maintenance of homeostasis. The NS can stimulate or
inhibit the activities of other systems to help maintain a
constant internal environment.
• 4-Mental activity.
• The brain is the center of mental activity, including
consciousness, memory, and thinking.
• 5-Control of muscles and glands.
• Skeletal muscles normally contract only when stimulated
by the N.S.(major movements of the body).
• The N.S. also participates in controlling cardiac muscle,
smooth muscle, and many glands.
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Divisions of the N.S.
• The N.S. can be divided into the central and the
peripheral N.S.
• The C.N.S. consists of the brain and spinal cord.
• The P.N.S. consists of nerves and ganglia.
• The P.N.S. has tow subdivisions:
• 1-The sensory division conducts action potentials
from sensory receptors to the C.N.S. The neurons
that transmit action potentials from the periphery to
the C.N.S. are sensory neurons.
• 2-The motor division conducts action potentials from
the C.N.S. to effecter organs such as muscles and
glands. the neurons that transmit action potentials
from the C.N.S. toward the periphery are motor
neurons.
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• The motor division can be further
subdivided into the :
• a-Somatic motor N.S., which transmits
action potentials from the CNS to skeletal
muscles.
•
b-Autonomic NS (ANS),which
transmits action potentials from the CNS
to cardiac muscle, smooth muscle, and
glands.
• The ANS ,in turn, is divided into
sympathetic, parasympathetic, and enteric
portions.
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Cells of the NS
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• 1-Neurons,or nerve cells ,receive stimuli and
transmit action potentials to other neurons or to
effector organs.
• Each neuron consists of a:
• 1-Cell body.
• 2-Two types of processes: dendrites and
axons.
• Each neuron cell body contains a single
nucleus. As with any other cell, the nucleus of
the neuron is the source of information for
protein synthesis. If an axon, which is one of the
neuron cell processes, is separated from the cell
body, it dies because it has no connection to the
nucleus, and no protein synthesis occurs in the
axon.
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• Extensive rough endoplasmic reticulum(rough
ER), Golgi apparatus, and mitochondria
surround the nucleus. Large numbers of
neurofilaments and microtubules course
through the cytoplasm in all directions and
separate the rough ER into distinct areas in the
cell body. The areas of rough ER
concentration, when stained with a specific dye
appear as microscopic granules called Nissl
bodies.
• Dendrites are short, often highly branching
cytoplasmic extensions that are tapered from
their bases at the neuron cell body to their tips.
• Dendrites usually function to receive
information from other neurons or sensory
receptors and transmit the information toward
the neuron cell body.
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• An axon is a long cell process extending from the neuron
cell body.
• Each axon has a constant diameter and may vary in
length from a few millimeters to more than a meter.
• Axons of motor neurons conduct action potentials away
from the CNS and axons of sensory neurons conduct
action potentials toward the CNS.
• Axons also conduct action potentials from one part of the
brain or spinal cord to another part.
• Each motor neuron has a single axon that extends from
the CNS toward a target tissue.
• An axon may remain unbranched or may branch to form
collateral axons.
• Axons are surrounded by neuroglia called Schwann
cells, which form a highly specialized insulating layer of
cells called the myelin sheath.
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Types of Neuron
• 1-Multipolar neurons have many dendrites and a single
axon. Most of the neurons within the CNS ,including nearly
all motor neurons, are multipolar
• 2-Bipolar neurons have two processes: one dendrite and
one axon. Bipolar neurons are located in some sensory
organs, such as in the retina of the eye and in the nasal
cavity .Most other sensory neurons are unipolar .
• 3-Unipolar neurons have a single process extending from
the cell body. This process divides into two processes a
short distance from the cell body. One process extends to
the periphery, and the other process extends to the CNS.
The two extensions functions as a single axon with small
dendritelike sensory receptors at the periphery. The axon
receives information at the periphery and transmits that
information in the form of action potentials to the CNS.
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Neuroglia or Glial cells.
• There are five types of neuroglia:
1- Astrocytes.
2- Ependymal.
3- Microglia.
4- Oligodendrocytes.
5- Schwann cells in the PNS surround axons.
• Most neuroglia retain ability to divide.
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Neuroglia or Glial cells
• Functions of neuroglia
1- Form myelin sheet , which wrap
around axons to speed up electric
impulse conduction .
2- Provide a support function for nervous
components .
3- Provide nutrient to the neurons ,
including oxygen.
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Organization of the N Tissue
• Groups of neuron cell bodies and their dendrites, where
there is very little myelin, form gray matter. Gray matter
on the surface of the brain is called the cortex, and
clusters of gray matter located deeper within the brain
are called nuclei. In the PNS, a cluster of neuron cell
bodies is called a ganglion.
• Bundles of parallel axons with their myelin sheaths are
whitish in color and are called white matter. White
matter of the CNS forms conduction pathways, or nerve
tracts, which propagate action potentials from one area
in the CNS to another. In the PNS, bundles of axons and
their connective tissue sheaths are called nerves.
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Electrical Signals and Neuronal
Pathways
• The Resting Membrane Potential (RMP)
• All cells exhibit electrical properties.
• The outside of most cell membrane is positively charged
compared with the inside of the cell membrane, which is
negatively charged.
• This charge difference across the membrane of an
unstimulated cell is called the RMP.
• The cell is said to be polarized. The outside of the cell
membrane can be thought of as the positive pole of a
battery, and the inside as the negative pole.
• Thus a small voltage difference, or potential, can be
measured across the resting cell membrane.
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• The RMP results from differences in the
concentration of ions across the cell
membrane and the permeability characteristics
of the cell membrane.
• There is a higher concentration of Na+ ions
immediately outside the cell membrane than
inside and a higher concentration of potassium
ions immediately inside the cell membrane than
outside.
• The concentration of Na+ outside the cell
membrane and of K+ inside is maintained by the
sodium-potassium exchange pump, which
actively transports K+ into and Na+ out of the cell.
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• When a cell is at rest, some K+ channels are open and
Na+ channels are not.
• The cell membrane is therefore more permeable to K+
than to Na+.
• This allows a few K+ to diffuse down their concentration
gradient out of the cell ,carrying their positive charges
with them.
• Larger molecules, such as proteins, which are
negatively charged, are too large to diffuse out of the
cell.
• As positive K+ leave the cell, the charge inside the cell
becomes more negative. The molecules inside the cell
with negative charges tend to attract the positive K+
back into the cell .
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• A point of equilibrium is reached at which the
tendency for K+ to move down their
concentration gradient out of the cell is balanced
by the negative charge within the cell, which
tends to attracts the K+ back into the cell.
• This point of K+ equilibrium is the point at which
the RMP is established and there is no more net
K+ movement.
• At equilibrium, there is a net positive charge
outside the cell and a net negative charge inside
the cell.
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Action potentials
• Muscle and nerve cells are excitable.
• When a stimulus is applied to a muscle cell or nerve cell,
some Na+ channels open for a very brief time, and Na+
diffuse quickly into the cell.
• The movement of Na+ into a cell is called a local current.
The positively charged Na+ entering the cell cause the
inside of the cell membrane to become more positive, a
change called depolarization.
• This depolarization results in a local potential. If
threshold is not reached, the Na+ channels close again,
and the local potential disappears without being
conducted along the nerve cell membrane.
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• If enough Na+ enter the cell so that the local
potential reaches a threshold value, this threshold
depolarization causes many more Na+ channels
to open.
• As more Na+ enter the cell, depolarization
occurs until there is a brief reversal of charge
across the membrane, and the inside of the cell
membrane becomes positive relative to the
outside of the cell membrane.
• The charge reversal causes Na+ channels to
close and K+ channels to open. Na+ then stop
entering the cell, and K+ leave the cell.
• This repolarizes the cell membrane to its resting
membrane potential. Depolarization and
repolarization constitute an action potential .
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• Action potentials occur in an all-or none fashion, that
is, if threshold is reached, the charge reversal is
complete; if the threshold is not reached, no action
potential occurs.
• Action potentials in a given cell type are all of the
same magnitude, that is, the amount of charge reversal
is always the same.
• Stronger stimuli produce frequency of action
potentials but do not increase the size of each action
potential.
• Action potential are conducted slowly in unmyelinated
axons and more rapidly in myelinated axons
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•
In unmyelinated axons, an action potential in one part
of a cell membrane stimulates local currents in adjacent
parts of the cell membrane.
• The local currents in the adjacent membrane produce
an action potential .By this means, the action potential is
conducted along the entire axon cell membrane.
• In myelinated axons, an action potential at one node of
Ranvier causes a local current to flow through the
surrounding extracellular fluid and through the cytoplasm
of the axon to the next node, stimulating an action
potential at that node of Ranvier.
• By this means action potentials jump from one node of
Ranvier to the next along the length of the axon .
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• This type of action potential conduction is called
saltatory conduction.
• Saltatory conduction greatly increases the
conduction velocity because the nodes of
Ranvier make it unnecessary for action
potentials to travel along the entire cell
membrane.
• Action potential conduction in myelinated fiber is
like a grasshopper jumping, whereas in an
unmyelinated axon it is like a grasshopper
walking.
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•
Medium-diameter, lightly myelinated axons,
characteristic of autonomic neurons, conduct action
potentials at the rate of about 3-15 m/s, whereas largediameter, heavily myelinated axons conduct action
potentials at the rate of 15-120 m/s.
• These rapidly conducted action potentials ,carried by
sensory and motor neurons, allow for rapid responses to
changes in the external environment.
• In addition, several hundred times fewer ions cross the
cell membrane during conduction in myelinated cells
than in unmyelinated cells.
• Much less energy is therefore required for the sodiumpotassium exchange pump maintain the ion
distributions.
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The Synapse
• A synapse is a junction where the axon of one neuron
interacts with another neuron or an effector organ such
as a muscle or gland.
• The end of the axon forms a presynaptic terminal. The
membrane of the dendrite or effector cell is the
postsynaptic membrane, and the space separating the
presynaptic and postsynaptic membranes is the synaptic
cleft.
• Chemical substances called neurotransmitters are
stored in synaptic vesicles in the presynaptic terminal.
• Those neurotransmitters are released by exocytosis
from the presynaptic terminal in response to each action
potential.
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• The neurotransmitters diffuse across the synaptic cleft
and bind to receptor molecules on the postsynaptic
membrane.
• The binding of neurotransmitters to these membrane
receptors causes channels for Na+, K+, or Cl- to open
or close in the postsynaptic membrane, depending on
the type of neurotransmitter in the presynaptic terminal
and the type of receptors on the postsynaptic
membrane.
• The response may be either stimulation or an
inhibition of an action potential in the postsynaptic cell.
for example,. if Na+ channels open, the postsynaptic cell
becomes depolarized, and an action potential will result
if threshold is reached. If K+ or Cl- channels open, the
inside of the postsynaptic cell tends to become more
negative, or hyperpolarized, and an action potential is
inhibited from occurring.
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• Of the many neurotransmitter substances , the best
known are acetylcholine and NE .
• Other neurotransmitters include ,serotonin, dopamine,
GABA, glycin, and endorphins. Neurotransmitter
substances are rapidly broken down by enzymes within
the synaptic cleft or are transported back into the
presynaptic terminal.
• Consequently, they are removed from the synaptic cleft
so their effects on the postsynaptic membrane are very
short term. In synapses where acetylcholine is the
neurotransmitter, such as in the neuromuscular junction,
an enzyme called acetyl cholinesterase breaks down the
acetylcholine.
• The breakdown products are then returned to the
presynaptic terminal for reuse. NE is either actively
transported back into the presynaptic terminal or it is
broken down by enzymes.
• The release and breakdown or removal of
neurotransmitters occurs so rapidly that a postsynaptic
cell can be stimulated many times a second.
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Types of Synaptic
Transmission:
1-Electric transmission : where
the neurons are communicated at
the cell membrane by lowresistance gap-channel pathway
which allows passage of the
electric current from one neuron
to the other directly. In this type
the impulse can pass from one
neuron to the other in tow
directions. Electric transmission
is very rare in human N.S.
2-Chemical transmission:
occurs by release of a chemical
substance from the presynaptic
neuron to act on the membrane
of the postsynaptic neuron.
This type is the present in
human N.S.
Mechanism of Synaptic
Transmission:
1-release of chemical transmitter.
Once the action potential in the presynaptic nerve
reaches the terminal knob, it opens voltage-gated Ca++
channels predominant in this area: Ca++ enters the knob
according to concentration and electric gradients.
Entrance of Ca++ leads to migration of synaptic vesicles
to the active zone. The vesicles fuse with the
presynaptic membrane ,open and release their chemical
transmitter content into the synaptic cleft. The amount
of the transmitter released is proportional to amount of
Ca++ entered.
2-Union of chemical transmitter with its receptors.
3-Development of postsynaptic potential.
4-Removal of neurotransmitters from the synaptic cleft.
Characters of Synaptic
Transmission.
1-Forward direction.
2-Synaptic delay.
3-Fatique.
4-Synaptic plasticity.
Reflexes
• Reflexes are the functional units of the nervous system.
• A reflex is an involuntary reaction in response to a
stimulus applied to the periphery and transmitted to the
CNS.
• Reflexes allow a person to react to stimuli more quickly
than is possible if conscious though is involved.
• A reflex arc is the neuronal pathway by which a reflex
occurs.
• The reflex arc is the basic functional unit of the NS
because it is the smallest, simplest pathway capable of
receiving a stimulus and yielding a response.
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• A reflex arc has five basic components:
• 1-a sensory receptor.
• 2-a sensory neuron.
• 3-interneurons.which are neurons located
between and communicating with tow
other neurons.
• 4-a motor neuron.
• 5-an effectors organ.
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• Most reflexes occur in the spinal cord or brainstem and
not the higher brain centers.
• The result of a reflex can be seen when a person’s finger
touches a hot stove.
• pain receptors in the skin are stimulated by the hot
stove, and action potential’s are produced. Sensory
neurons conduct the action potential’s to the spinal cord,
where they synapse with interneuron's. The
interneuron's , in turn, synapse with motor neurons in the
spinal cord that conduct action potential’s along their
axons to flexor muscles in the upper limb.
• These muscles contact and pull the finger away from the
stove. No conscious thought is required for this reflex,
and withdrawal of the finger from the stimulus begins
before the person is consciously aware of any pain.
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Neuronal Pathways
• Neurons are organized within the CNS to form pathways
ranging from relatively simple to extremely complex.
• The two simplest pathways are converging and diverging
pathways.
• Converging pathways have two or more neurons that
synapse with the same neuron.
• In diverging pathways, the axon from one neuron divides
and synapses with more than one other neuron.
• This allows information transmitted in one neuronal
pathway to diverge into two or more pathways.
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Spinal Cord
Reflexes.
1-Knee-Jerk
reflex.
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• 1.Sensory receptors in the muscle detect
stretch of the muscle.
• 2.Sensory neurons conduct APs to the spinal
cord.
• 3. Sensory neurons synapse with motor
neurons. Descending neurons(red) within the
spinal cord also synapse with neurons of the
stretch reflex and modulate their activity.
• 4.Stimulation of the motor neurons causes
the muscle to contract and resist being
stretched.
•
• The simplest reflex is the stretch reflex, a reflex
in which muscles contract in response to a
stretching force applied to them. The Knee-Jerk
reflex is a classic example of the stretch reflex.
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2Withdrawal
Reflex.
The function of the
withdrawal is to
remove a limb or
other body part
from a painful
stimulus.
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The central nerves system
• The CNS comprises the brain lying within the skull, and the
spinal cord lying within the vertebral column.
The spinal cord
• The spinal cord consists of segments, each of which has a
pair of nerve roots, on each side.
• The dorsal roots carry impulses from peripheral receptors
into the spinal cord, while the ventral roots carry impulses to
the periphery (i.e. muscles).
• Grey matter forms the core of the spinal cord and appears
like the letter H in cross section. It contains the cell bodies of
neurons.
• White matter surrounds the grey matter. It is made up of
ascending (sensory) and descending (motor) tracts.
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The spinal cord functions
1-Transmission of sensory (afferent) impulses coming from
peripheral receptors to the brain, and of motor (efferent) impulses
from the brain to motor neurons, which supply effector organs
(muscles and glands).
2-Serving as a center for some reflexes, some of which are the
basis of the movement and posture.
– The spinal nerves:
– The spinal nerves exit the vertebral column at the cervical,
thoracic, lumbar, and sacral regions. The verves are grouped into
plexuses.
A- The phrenic nerve, which supplies the diaphragm, is the most
important branch of the cervical plexuses.
B- The branchial plexuses supplies nerves to the upper limb.
C- The lumbosacral plexuses supplies nerves to the lower limb.
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The Brain
• The major regions of the brain are the brainstem, the
diencephalon, the cerebrum, and the cerebellum.
• Brainstem
• The Brainstem connects the spinal cord to the remainder
of the brain. It consists of the medulla oblongata, the
pons, and the midbrain, and it contains several nuclei
involved iv vital body function
• The medulla ablongata is the most inferior portion of the
brainstem. In addition to ascending and descending
nerve tracts, the medulla contains nuclei with specific
function, such as control of respiration, cardiovascular
functions, swallowing, equilibrium, coughing, sneezing,
and vomiting.
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• The pons contains relay nuclei between the cerebrum
and cerebellum
• Several nuclei of The medulla oblongata, extend into the
lower part of the pons so functions such as breathing
,swallowing and balance are controlled in the lower pons
as well as in the medulla oblongata. Other nuclei in the
Pons control functions such ad chewing and salivation
• The midbrain is involved in hearing and in visual reflexes
• The reticular formation is scattered throughout the
brainstem and important in regulating consciousness
and in the sleep-wake cycle.
• Nuclei for all ,but the two first cranial nerves are also
located in the brainstem.
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The Diencephalon
• The diencephalon is composed of the two thalamic
laterally and the hypothalamus ventrally.
• Thalamic nuclei are functionally divided into several
groups. The most important of these are:
– One group that relays all types of sensation to the
sensory context except olfaction.
– Another group relays signals from the cerebellum
and basal nuclei to the motor cortex.
– The third group controls the general level of
activity of the whole cerebral cortex and is
therefore
responsible
for
the
level
of
consciousness.
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The hypothalamus
is a higher autonomic center which participates
– in controlling blood pressure, heart rate, and
body temperature.
– Also, secretes hormones that control the
release of other hormones from the pituitary
gland.
– Being part of the limbic system, the
hypothalamus plays a role in generation of
emotions.
– There are also centers for control of appetite
and water intake.
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The Cerebrum
• The cerebrum consists of the right and
left cerebral hemispheres, connected in
the midline by the corpus callosum.
• The superficial layer of each hemisphere
is composed of grey matter called the
cerebral cortex.
• The cerebral cortex has elevations (gyri)
and depressions (sulci), which greatly
increase its surface area.
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The Cerebrum
• Each hemispheres is divided into four lobes.
– Frontal lobe: lies in front of the central sulcus, is
important in the control of voluntary motor movement
functions, motivations, aggression, mood, and olfactory
reception.
– Parietal lobe: is the principal center for receiving and
consciously perceiving most sensory information, such
as pain, temperature, balance and taste.
– Temporal lobe: lies on the lateral surface of the
hemisphere below the lateral fissure, and contains the
primary auditory area, which is the center of hearing.
The temporal lobe plays an important role in memory,
and its anterior and inferior portions called the psychic
66 cortex.
The Cerebrum
• Occipital lobe: lies most posterior in the
cerebral hemisphere. In it is located the
primary visual cortex, the center of vision.
• The parietal, temporal and occipital lobes
meet in the angular gyrus. Just in the front
of this gyrus is an area of cortex called
Wernicke’s area This area plays a crucial
role in higher functions of the brain, such as
thinking, speech and language.
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Cerebellum
The functions of the cerebellum
• The cerebellum is concerned with:
– Control of muscle tone.
– Control balance and posture.
– Control of rate, range and direction of movement.
– Control of eye movement
– Coordination and planning of skilled voluntary muscle
activity
– A major function of the cerebellum is that a
comparator. Through its comparator function, the
cerebellum compares the intended action to what is
occurring, and modifies the action to eliminate
differences.
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Limbic system
• The olfactory cortex and certain deep cortical
region and nuclei of the cerebrum and the
diencephalon are grouped together under the
title limbic system.
• the limbic system is involved with memory,
motivation, mood, emotions, and visceral
responses to emotions.
• Since the limbic system contains the olfactory
cortex, it is considered an important part of
the olfactory center.
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Basal nuclei
• There are two primary nuclei :
1-The corpus striatum, located deep within the
cerebrum.
2-The substantial nigra, located in the midbrain.
• The basal nuclei are important in planning,
organizing, and coordinating motor movement
and posture.
• Parkinson disease, caused by lesion in basal
nuclei, and characterized by muscular rigidity,
resting, tremor, general lack of movement, and
shuffling gait.
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Cranial nerves and their
functions
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Number
Name
Function
I
Olfactory
smell
II
Optic
Vision
III
oculomotor
IV
Trochlear
V
Trigeminal
VI
Abducens

Motor to four of six
extrinsic eye muscles
and upper eyelid
 Parasympathetic
:constrict pupil, thickens
lens
Motor to one extrinsic eye
muscle
 Sensory of face and
teeth
 Motor to muscles
mastication
Motor to one extrinsic
eye
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muscle
Number
Name
VII
facial
Function


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VIII
Vestibulocochlear
IX
Glossopharyngeal
X
Vagus
XI
Accessory
XII
Hypoglossal
 Sensory: taste
Motor to muscles of facial
expression
Parasympathetic to salivary
tear glands
Hearing and balance

Sensory: taste and touch to
back of tongue
 Motor to pharyngeal
muscles
 Parasympathetic to salivary
glands
 Sensory to pharynx, larynx
and viscera
 Motor to pharynx and larynx
 Parasympathetic to viscera
of thorax and ab
 domen
Motor to neck and upper back
muscles
Motor to tongue muscle
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Ascending Tracts (Dorsal Column)
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Descending Tracts(Direct tract
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Divisions of Autonomic
Sympathetic:
- activated during times of stress
- part of fight or flight response
- prepares you for physical activity by:
↑ HR
↑ BP
↑ BR
sending more blood to skeletal muscles
inhibiting digestive tract
Para sympathetic:
- « housekeeper »
- activated under normal conditions
- involved in digestion, urine production, and
dilation/constriction of pupils,
etc.
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■ Preganglionic sympathetic neurons are
located in the IML of the thoracolumbar
spinal cord and project to postganglionic
neurons in the paravertebral or
prevertebral ganglia or the adrenal
medulla.
Preganglionic parasympathetic neurons
are located in motor nuclei of cranial
nerves III, VII, IX, and X
and the sacral IML.
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Comparison of peripheral organization and transmitters released by somatomotor and
autonomic nervous systems (NS)
ACh, acetylcholine; DA, dopamine; NE, norepinephrine; Epi, epinephrine.
(From Widmaier EP, Raff H, Strang KT:Vander’s Human Physiology. McGraw-Hill, 2008.)
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Lecture Is Finished on
Nervous System
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