MODULE 3 REGULATION AND
INTEGRATION
UNIT 1 – THE NERVOUS SYSTEM
REGULATION AND INTEGRATION
The nervous system and the endocrine system together perform a vital function
for the body – communication. Homeostasis and therefore survival depend on
this function.
Because communication provides the means for controlling and integrating the
many different functions performed by organs, tissues, and cells. Integrating
means unifying. Unifying body functions means controlling them in ways that
make them work together like parts of one machine to accomplish homeostasis
and thus survival.
Communications makes possible control; control makes possible integration;
integration makes possible homeostasis; homeostasis makes possible survival.
NERVOUS SYSTEM
• Made up of the brain, spinal
cord and nerves
• Organized to detect changes
(stimuli) in the internal and
external environment, evaluate
that information, and possibly
respond by initiating changes in
muscles or glands.
ORGANIZATIONS OF THE NERVOUS SYSTEM
CENTRAL AND PERIPHERAL
NERVOUS SYSTEMS
- the classical manner of
subdividing the nervous system
based on the gross dissections of
early anatomists
- Categorizes all nervous system
tissues according to their relative
positions in the body: central or
peripheral
ORGANIZATIONS OF THE NERVOUS SYSTEM
Central nervous system
- The structural and functional center of the
entire nervous system
- Consists of the brain and spinal cord
- Integrates incoming pieces of sensory
information, evaluates the information, and
initiates an outgoing response
- Cells that begin in the brain or cord but
extend out through a nerve are not included
in the CNS
ORGANIZATIONS OF THE NERVOUS SYSTEM
Peripheral nervous system
- Consists of the nerve tissues that lie in the
periphery, or “outer regions”, of the nervous
system
- Nerves that originate from the brain are
called cranial nerves, and nerves that
originate from the spinal cord are called
spinal nerves
ORGANIZATIONS OF THE NERVOUS SYSTEM
SENSORY AND MOTOR DIVISIONS
- The categorization of nervous
pathways into divisions according
to the direction in which they carry
information
ORGANIZATIONS OF THE NERVOUS SYSTEM
Sensory division
- “afferent division”
(carry toward)
- conveys input into the CNS
from sensory receptors in the
body
- provides the CNS with sensory
information about the
• somatic senses (tactile,
thermal, pain, and
proprioceptive sensations);
and
• special senses (smell, taste,
vision, hearing, and
equilibrium).
ORGANIZATIONS OF THE NERVOUS SYSTEM
Motor division
- “efferent division”
carry away
- Consists of all the outgoing
motor or efferent pathways
- conveys output from the CNS
to effectors (muscles and
glands)
- Divided further into the
somatic and autonomic
nervous system
ORGANIZATIONS OF THE NERVOUS SYSTEM
SOMATIC AND AUTONOMIC
NERVOUS SYTEMS
- The categorization according to the
type of effectors they regulate
ORGANIZATIONS OF THE NERVOUS SYSTEM
SOMATIC NERVOUS SYSTEM
- Carry information to the somatic
effectors, which are the skeletal
muscles. These motor pathways
make up the somatic motor
division.
- The somatic nervous system also
includes the afferent pathways,
making up the somatic sensory
division, that provide feedback
from the somatic effectors
- Also includes the integrating
centers that receive the sensory
information and generate the
efferent response signal
ORGANIZATIONS OF THE NERVOUS SYSTEM
AUTONOMIC NERVOUS SYSTEM
- Carry information to the
autonomic, or visceral, effectors
• Smooth muscles
• Cardiac muscles
• glands
- Seems autonomous of voluntary
control, appears to govern itself
without our conscious knowledge
ORGANIZATIONS OF THE NERVOUS SYSTEM
SYMPATHETIC DIVISION
- made up of pathways that exit the
middle portions of the spinal cord
- involved in preparing the body to
deal with immediate threats to the
internal environment
- Produces the “fight-or-flight”
response
PARASYMPATHETIC DIVISION
- Exits at the brain or lower portions
of the spinal cord and coordinate
the body’s normal resting activities
- “rest-and-repair”or “rest-and-digest”
FUNCTIONS OF THE NERVOUS SYSTEM
1. SENSORY INPUT
- Most activities of the nervous system are
initiated by sensory experiences that
excite sensory receptors, whether visual
receptors in the eyes, auditory receptors
in the ears, tactile receptors on the
surface of the body, or other kinds of
receptors
- These sensory experiences can either
cause immediate reactions from the
brain, or memories of the experiences can
be stored in the brain for minutes, weeks,
or years and determine bodily reactions
at some future date
FUNCTIONS OF THE NERVOUS SYSTEM
1. SENSORY INPUT
- The figure to the right shows the somatic
portion of the sensory system, which
transmits sensory information from the
receptors of the entire body surface and
from some deep structures.
- This information enters the central
nervous system through peripheral nerves
and is conducted immediately to multiple
sensory areas in:
a)
b)
c)
d)
e)
the spinal cord at all levels
the reticular substance of the medulla,
pons, and mesencephalon of the brain
the cerebellum
the thalamus
areas of the cerebral cortex.
FUNCTIONS OF THE NERVOUS SYSTEM
2. MOTOR OUTPUT
- The most important eventual role of the
nervous system is to control the various
bodily activities
- This is achieved by controlling
a)
b)
c)
contraction of appropriate skeletal muscles
throughout the body
contraction of smooth muscle in the
internal organs
secretion of active chemical substances by
both exocrine and endocrine glands in
many parts of the body.
- These activities are collectively called
motor functions of the nervous system,
and the muscles and glands are called
effectors because they are the actual
anatomical structures that perform the
functions dictated by the nerve signals.
FUNCTIONS OF THE NERVOUS SYSTEM
2. MOTOR OUTPUT
- The figure shows the “skeletal” motor
nerve axis of the nervous system for
controlling skeletal muscle contraction.
- Operating parallel to this axis is another
system, called the autonomic nervous
system, for controlling smooth muscles,
glands, and other internal bodily systems
FUNCTIONS OF THE NERVOUS SYSTEM
2.
MOTOR OUTPUT
- Note that the skeletal muscles can be controlled
from many levels of the central nervous system,
including:
a)
b)
c)
d)
e)
the spinal cord
(2) the reticular substance of the medulla,
pons, and mesencephalon
the basal ganglia
the cerebellum
the motor cortex
- Each of these areas plays its own specific role,
the lower regions concerned primarily with
automatic, instantaneous muscle responses to
sensory stimuli, and the higher regions with
deliberate complex muscle movements
controlled by the thought processes of the brain.
FUNCTIONS OF THE NERVOUS SYSTEM
3. INTEGRATION
- One of the most important functions of
the nervous system is to process incoming
information in such a way that
appropriate mental and motor responses
will occur
- More than 99 percent of all sensory
information is discarded by the brain as
irrelevant and unimportant.
- For instance, one is ordinarily unaware of the
parts of the body that are in contact with
clothing, as well as of the seat pressure when
sitting.
- Likewise, attention is drawn only to an
occasional object in one’s field of vision, and
even the perpetual noise of our surroundings
is usually relegated to the subconscious.
FUNCTIONS OF THE NERVOUS SYSTEM
3. INTEGRATION
- But, when important sensory information
excites the mind, it is immediately
channeled into proper integrative and
motor regions of the brain to cause
desired responses.
- This channeling and processing of
information is called the integrative
function of the nervous system.
- Thus, if a person places a hand on a hot
stove, the desired instantaneous response
is to lift the hand. And other associated
responses follow, such as moving the
entire body away from the stove and
perhaps even shouting with pain.
NERVOUS TISSUE
Detects changes in a variety of conditions inside and outside the body and
responds by generating electrical signals called nerve action potentials (nerve
impulses) that activate muscular contractions and glandular secretions
NERVOUS TISSUE
Consists of:
1. neuron (nerve cell), which consist of cell body and processes from cell body
(one to multiple dendrites and a single axon)
2. neuroglia, which do not generate or conduct nerve impulses but have other
important supporting functions
Neuron
• Excitable cells that conduct that impulses that
make possible all nervous system functions
• Form the “wiring” of the nervous system’s
information circuits
• All neurons consist of a cell body
(soma/perikaryon), and at least two processes:
one axon and one or more dendrites
• Because dendrites and axons are threadlike
extensions from a neuron’s cell body, they are
often called nerve fibers
Neuroglia
“glia” – glue
• Do not usually conduct information themselves but support the function of
neurons in various ways
• Retain their capacity for cell division throughout adulthood, unlike neurons
1. Astrocytes
- Attached outside of a capillary blood vessel in the
brain
- Star-shaped
- “feed” neurons by picking up glucose from the blood,
converting it to lactic acid, and passing it along the
neurons to which they are connected
- Help form the blood-brain barrier (BBB)
Neuroglia
2. Microglia
- small, usually stationary cells found in
the central nervous system
- Engulf and destroy microorganisms and
cellular debris
- Although classified as neuroglia,
microglia are functionally and
developmentally unrelated to other
nervous system cells
3. Ependymal cells
- Resemble epithelial cells, forming thin
sheets that line fluid-filled cavities in the
brain and spinal cord
- Some take part in producing the fluid
that fills these spaces
- Others have cilia that helps keep the
fluid circulating within the cavities
Neuroglia
4. Oligodendrocytes
- Smaller than astrocytes and have fewer
processes
- Help hold nerve fibers together and
produce the fatty myelin sheath around
nerve fibers in the central nervous
system
5. Schwann cells
- Found only in the PNS; Functional
equivalent of the oligodendrocytes
- Schwann cells wrap themselves around a
single nerve fiber. As each Schwann cell
wraps around the fiber, its nucleus and
cytoplasm are squeezed to the perimeter
to form the neurilemma, or sheath of
Schwann
GRAY AND WHITE MATTER
Gray matter
White matter
- Contains neuronal cell bodies, dendrites,
unmyelinated axons, axon terminals, and
neuroglia.
- Appears grayish rather than white because
the Nissl bodies impart a gray color and
there is little to no myelin in these areas.
- Composed primarily of myelinated axons
- The whitish color of myelin gives white
matter its name
GRAY AND WHITE MATTER
Gray matter
White matter
- Contains neuronal cell bodies, dendrites,
unmyelinated axons, axon terminals, and
neuroglia.
- Appears grayish rather than white because
the Nissl bodies impart a gray color and
there is little to no myelin in these areas.
- Composed primarily of myelinated axons
- The whitish color of myelin gives white
matter its name
CENTRAL NERVOUS SYSTEM
- The center of the regulatory process
- Comprises of both the brain and the spinal
cord
- The principal integrator of sensory input and
motor output
- Capable of evaluating incoming information
and formulating responses to changes that
threaten our homeostatic balance
COVERINGS OF THE BRAIN
AND SPINAL CORD
Because the brain and spinal cord are both delicate and vital, nature has
provided them with two protective coverings.
Because the brain and spinal cord are
both delicate and vital, nature has
provided them with two protective
coverings.
The outer covering consists of bone:
- cranial bones encase the brain,
vertebrae encase the spinal cord
The inner covering consists of
membranes known as meninges.
MENINGES
Dura mater
- Made of strong white fibrous
tissue, serves as the outer layer
of the meninges, and also the
inner periosteum of the cranial
bones
Arachnoid mater
- A delicate, cobweb-like layer
- Lies between the dura and pia
mater
Pia mater
- Transparent layer adhering to
the outer surface of the brain
and spinal cord and contains
blood vessels
MENINGITIS
▪ Infection or inflammation of the
meninges
▪ Most often involves the arachnoid and
pia mater, or the leptomeninges (thin
meninges)
▪ Commonly caused by bacteria such as
Neisseria meningitides, Streptococcus
pneumonia, or Haemophilus influenza
▪ If only the spinal meninges are
involved, the condition is called spinal
meningitis
CEREBROSPINAL FLUID
- A cushion of fluid both around the organs and within the brain and spinal cord
- A reservoir of circulating fluid that, along with blood, the brain monitors for
changes in the internal environment
For example, changes in the carbon dioxide (CO2) content of CSF trigger homeostatic
responses in the respiratory control centers of the brainstem that help regulate the overall
CO2 content and pH of the body
Ventricles
- Large, fluid-filled spaces within the
brain
FORMATION OF CSF
Choroid plexus
- Separation of fluid from blood in
here causes formation of CSF
- Networks of capillaries that
project from the pia mater into
the lateral ventricles and into the
roofts of the third and fourth
ventricle
- Each choroid plexus is covered
with a special type of ependymal
cell that releases the CSF into the
fluid spaces
CIRCULATION OF CSF
1. Choroid plexus
(lateral ventricles)
2. Interventricular
foramen (of Monro)
3. Third ventricle
4. Cerebral aqueduct
(aqueduct of Sylvius)
5. Fourth ventricle
6. Cisterna magna
7. Subarachnoid space
8. Arachnoid villi
CIRCULATION OF CSF
Summary
CSF is formed by separation of fluid
from blood in the choroid plexuses
into the ventricles of the brain,
circulates through the ventricles and
into the central canal and
subarachnoid spaces, and is absorbed
back into the blood (arachnoid villi)
CEREBROSPINAL FLUID
- The amount of cerebrospinal fluid in the average adult is about 140-150mL,
continually replaced. Roughly 500mL is formed daily.
- Mainly collected through lumbar puncture
Lumbar puncture
- Withdrawal of some of the CSF from
the subarachnoid space in the
lumbar region of the spinal cord
- 22 or 24 gauge
- Above or below the fourth lumbar
vertebrae
- 1st vial: Chemistry
2nd vial: Microbiology
3rd vial: Hematology
HYDROCEPHALUS
- Accumulation of cerebrospinal fluid due
to blockage of its drainage
- When internal hydrocephalus occurs in
an infant whose skull has not completely
ossified, the increasing fluid pressure in
the ventricles causes the cranium to
swell
HYDROCEPHALUS
- This condition can be treated by surgical
placement of a shunt or tube, to drain
the excess CSF.
- When this condition occurs in an older
child or adult, the skull will not yield to
the increased fluid pressure. The
pressure instead compresses the soft
nervous tissue of the brain, potentially
leading to coma or even death
BLOOD-BRAIN BARRIER
Helps maintain the very stable environment
required for normal functioning of the brain. The
BBB is formed as astrocytes wrap their “feet”
around capillaries in the brain.
The tight junctions between epithelial cells in the
capillary wall, along with the covering formed by
footlike extensions of the astrocytes, form a
barrier that regulates the passage of most ions
between the blood and the brain tissue.
If they crossed to and from the brain freely, ions
such as sodium (Na+) and potassium (K+) could
disrupt the transmission of nerve impulses
BLOOD-BRAIN BARRIER
Water, oxygen, carbon dioxide and glucose can
cross the barrier easily.
Small, lipid-soluble molecules such as alcohol can
also diffuse easily across the barrier.
The blood-brain barrier must be taken into
consideration by researchers trying to develop
new drug treatments for brain disorders. Many
drugs and other chemicals simply will not pass
through the barrier, although they might have
therapeutic effects if they could get to the cells of
the brain.
BLOOD-BRAIN BARRIER
Parkinson disease
Involuntary skeletal muscle contractions interfere with voluntary movement. Due to
degeneration of neurons that release dopamine.
Parkinson disease can often be
alleviated by the substance dopamine,
which is deficient in the brains of
Parkinson victims. However, dopamine
cannot cross the blood-brain barrier, so
dopamine injections or tablets are
ineffective.
Levodopa (L-DOPA), however, can cross
the barrier. Levodopa is the chemical
used by brain cells to make dopamine.
PERIPHERAL NERVOUS SYSTEM
Topic 3: Cranial and Spinal nerves
Pages 35 - 38